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In vitro antibacterial activity of moxifloxacin against hospital isolates: a multicentre study
ORIGINAL ARTICLE In vitro antibacterial activity of moxi¯oxacin against hospital isolates: a multicentre study C.-J. Soussy1, J. Nguyen2, F. Goldstein3, H. Dabernat4, A. Andremont5, R. Leclercq6, H. Drugeon7, P. Cavallo8, H. Chardon9, J. Etienne10, Y. Rio11 and P. Courvalin12 1
Service de BacteÂriologie-Virologie-HygieÁne, Henri Mondor University Hospital 94010 Creteil cedex, Laboratoire de BacteÂriologie & HygieÁne, Pitie±SalpeÃtrieÁre University Hospital, 75651 Paris cedex 13, 3 Service de Microbiologie MeÂdicale, Saint Joseph University Hospital, 75674 Paris cedex 14, 4Laboratoire de Microbiologie, Purpan University Hospital, 31059 Toulouse cedex, 5Laboratoire de BacteÂriologie et Virologie, Bichat University Hospital, 75018 Paris, 6Laboratoire de Microbiologie, CoÃte de Nacre Regional Hospital, 14033 Caen cedex, 7Laboratoire de BacteÂriologie, Guillaume et Rene Laennec University Hospital, 44035 Nantes cedex 1, 8Laboratoire de Biologie MeÂdicale, Army Hospital Begin, 94160 Saint ± Mande cedex, 9Laboratoire de BacteÂriologie et HygieÁne hospitalieÁre, City General Hospital, 13616 Aix±en-Provence cedex 1, 10 Laboratoire Central de Microbiologie, Edouard Herriot Hospital, 69437, Lyon cedex 03, 11Laboratoire de Microbiologie ± HeÂmatologie, Metz-Thionville Regional Hospital 57038 Metz Cedex, and 12 Unite des Agents AntibacteÂriens, Pasteur Institute, 75724 Paris cedex 15, France 2
Objective To evaluate the in vitro antibacterial activity of moxi¯oxacinin in comparison to that of other ¯uoroquinolones (cipro¯oxacin, o¯oxacin and trova¯oxacin). Methods A total of 2196 strains was collected in 11 French hospitals in 1998. Minimum
inhibitory concentrations (MICs) (mg/L) were determined by agar dilution and agar diffusion was performed with 5-mg discs. Internal quality control was carried out with genetically de®ned strains.
Results MIC50s and MIC90s of moxi¯oxacin against nalidixic acid (NAL)-susceptible
Enterobacteriaceae (n 663) were 0.12 and 0.5. As for other quinolones, the activity of moxi¯oxacin (4±32) was reduced against NAL-intermediate and NAL-resistant strains (n 222). MIC50s and MIC90s of moxi¯oxacin were 2 and 4 for cipro¯oxacin-susceptible P. aeruginosa (n 128); moxi¯oxacin had no activity against cipro¯oxacin-resistant strains (n 56). The activity of moxi¯oxacin was maintained against NAL-susceptible A. baumannii (n 11; 0.032±0.125), but reduced against NAL-resistant strains (n 30; 16±32). H. in¯uenzae (n 97) and M. catarrhalis (n 40) were inhibited by low concentrations (0.03±0.06 and 0.06±0.25, respectively). Moxi¯oxacin had better activity (0.06±0.12) than other tested quinolones against methicillin-susceptible S. aureus strains (n 110); cipro¯oxacin-resistant strains (n 85) (2±8) were usually methicillin-resistant. Moxi¯oxacin was moderately active against enterococci (n 149) (E. faecalis: 0.5±16; E. faecium: 2±4). Streptococci (n 194) and pneumococci (n 136), including 70 penicillin G-intermediate or G-resistant strains, were inhibited by low concentrations (0.25±0.5 for each species). Based on the regression curve, tentative zone diameter breakpoints could be 21 and <18 mm for MIC breakpoints of 1 and >2 mg/L, respectively.
Conclusions While retaining activity against Enterobacteriaceae, moxi¯oxacin was moderately active against P. aeruginosa. Its activity was inferior to that of cipro¯oxacin for these species. This study con®rmed the comparatively high in vitro activity of
Corresponding author and request for reprints: Prof C.-J. Soussy, Service de BacteÂriologie-Virologie-HygieÁne, HoÃpital Henry Mondor, 51 avenue du MareÂchal de Lattre de Tassigny, 94010 CreÂteil Cedex, France E-mail: [email protected]
ß 2003 Copyright by the European Society of Clinical Microbiology and Infectious Diseases
998 Clinical Microbiology and Infection, Volume 9 Number 10, October 2003 moxi¯oxacin against Gram-positive cocci and other pathogens isolated from communityacquired respiratory tract infections. Keywords Moxi¯oxacin, antibacterial activity, hospital clinical isolates, breakpoints
Clin Microbiol Infect 2003; 9: 997±1005
INTRODUCTION Moxi¯oxacin is a broad spectrum 8-methoxyquinolone which interacts preferentially with DNA gyrase in Gram-negative and with topoisomerase IV in Gram-positive bacteria [1]. It has enhanced activity against Gram-positive cocci but retains activity against Gram-negative bacteria [2,3]. Moxi¯oxacin also has good activity against atypical respiratory pathogens (Legionella pneumophila, Chlamydia pneumoniae and Mycoplasma pneumoniae) [4]. The aim of this study was to assess the in vitro activity of moxi¯oxacin on a large number of bacterial strains encountered in daily hospital practice in French hospitals. In addition, tentative inhibition zone diameter breakpoints were determined for moxi¯oxacin using the regression curve. MATERIALS AND METHODS Eleven French hospital laboratories (nine teaching and two general hospitals) collected all clinical isolates, except repetitive strains from the same patient, from March to May 1998. Out of this collection, 20 strains per species, were randomly selected in each center; for the most rarely isolated species, the totality of strains were studied. Clinical isolates were collected from the main types of pathological specimens from in-patients in hospital departments representing the different medical and surgical specialties. In all centers the minimum inhibitory concentrations (MIC) of moxi¯oxacin were determined for all strains by agar dilution using same batch of medium (i.e. Mueller-Hinton bioMeÂrieux, Marcy L'Etoile, France for aerobic bacteria, enriched with 5% horse blood for streptococci and with hemoglobin and polyvitex for Neisseria; HTM based Oxoid Medium enriched with HTM Oxoid supplement for Haemophilus; Wilkins-Chalgren Oxoid for anaerobic bacteria) and with an inoculum of 104 bacteria per `spot'. MICs of moxi¯oxacin, cipro¯oxacin, o¯oxacin, and trova¯oxacin were also determined (in all centers) by the E-test method (AB Biodisk, Solna,
Sweden) using the following reactive strips: moxi¯oxacin, cipro¯oxacin, o¯oxacin and trova¯oxacin. In order to determine the correlation between MICs and the inhibition zone diameters, antibiotic susceptibility testing by agar diffusion [6] was performed, according to the recommendations of the Comite de l'Antibiogramme de la SocieÂte FrancËaise de Microbiologie [5], with 5-mg moxi¯oxacin discs (supplied by Bayer-Pharma, Puteaux, France) and with discs impregnated with 30 mg of nalidixic acid, 5 mg of o¯oxacin and 5 mg of cipro¯oxacin. Analysis of moxi¯oxacin MICs and inhibition zone diameters against ®ve reference strains: S. aureus UA 531, S. aureus UA 532, E. faecalis UA 163, E.coli UA 200, P. aeruginosa UA 110, provided by the National Reference Center for Mechanisms of Resistance to Antibiotics, Institut Pasteur, Paris, indicated intercenter variabilities similar to those usually observed for these techniques. All centers provided results which were not signi®cantly different from those of the reference center (with a 5% risk of error), except data for one center regarding P. aeruginosa strains, which were excluded from the analysis. RESULTS In vitro activity of moxifloxacin: determination of MICs by agar dilution and the E-test method MIC50s, MIC90s and MIC ranges of moxi¯oxacin against Gram-negative, Gram-positive and anaerobic bacteria are shown in Tables 1, 2 and 3, respectively. Activity of moxifloxacin against Enterobacteriaceae MICs of moxi¯oxacin against Enterobacteriaceae ranged from 0.008 to >128 mg/L. MICs were 1 mg/L for 733 of the 885 tested strains (82.8%). Shigella spp., Citrobacter diversus, Hafnia alvei, Salmonella spp. and Proteus vulgaris were the most susceptible organisms with MIC90s 0.5 mg/L, whereas moxi¯oxacin had the highest MIC90 values against Citrobacter freundii and Providencia stuartii (32 mg/L). With respect to the
ß 2003 Copyright by the European Society of Clinical Microbiology and Infectious Diseases, CMI, 9, 997±1005
Soussy et al In vitro activity of moxifloxacin 999 Table 1 Minimum inhibitory concentrations (MIC)50s and MIC90s and MIC ranges (mg/L) of moxi¯oxacin by agar dilution and E-test against Gram-negative micro-organisms (n 1320) MIC50 Micro-organisms
(n)
All Enterobacteriaceae Escherichia coli Citrobacter freundii Citrobacter diversus Salmonella spp. Hafnia alvei Shigella spp. Klebsiella pneumoniae Klebsiella oxytoca Enterobacter cloacae Other Enterobacter Serratia marcescens Proteus mirabilis Morganella morganii Proteus vulgaris Providencia rettgeri Providencia stuartii Pseudomonas aeruginosa Acinetobacter baumannii Acinetobacter iwoffi Other Acinetobacter Stenotrophomonas maltophilia Haemophilus influenzae Haemophilus parainfluenzae Moraxella catarrhalis Neisseria spp.
(885) (213) (38) (19) (31) (3) (4) (117) (44) (101) (44) (61) (113) (47) (17) (2) (31) (189) (41) (9) (3) (38) (97) (11) (40) (7)
MIC90
Dilution
E-test
MIC ranges
Dilution
E-test
Dilution
E-test
0.008->128 0.008->128 0.032±64 0.032±8 0.063±1 0.125±0.25 0.032±0.063 0.032±128 0.032±16 0.032±128 0.032±32 0.063±16 0.063±64 0.063±128 0.125±1 0.5±4 0.063±128 0.25->128 0.032±64 0.032±0.5 0.063 0.032±16 0.008±0.063 0.008±0.25 0.016±0.25 0.016±0.125
0.002->32 0.002->32 0.047->32 0.032->32 0.023±2 0.032±0.19 0.008±0.043 0.023->32 0.023±8 0.023->32 0.047->32 0.047->32 0.047->32 0.016->32 0.125±0.75 0.094->32 0.094->32 0.125->32 0.016->32 0.016±0.19 0.032 0.016±12 0.003±0.094 <0.002±0.25 0.008±0.19 0.003±0.064
0.125 0.063 0.125 0.063 0.125
0.125 0.047 0.125 0.047 0.125
8 1 32 0.125 0.5
8 0.5 >32 0.25 1
0.125 0.125 0.125 0.25 0.5 0.5 0.25 0.25
0.125 0.094 0.064 0.125 0.25 0.25 0.094 0.19
1 1 8 16 4 16 16 0.5
0.75 0.5 8 >32 4 12 16 0.25
32 4 16
12 4 >32
0.5 0.032 0.063 0.063
128 128 32
0.38 0.016 0.032 0.047
>32 >32 >32
2 0.063 0.125 0.25
1 0.032 0.094 0.125
MIC50s and MIC90s are not calculated for groups with fewer than 10 isolates. N. gonorrhoeae: 2; N. meningitidis: 5.
Table 2 MIC50s and MIC90s and MIC ranges of moxi¯oxacin by agar dilution and E-test against Gram-positive microorganisms (n 815) MIC50 Micro-organisms Staphylococcus aureus Coag. negative staphylococci Enterococcus faecalis Enterococcus faecium Other enterococci Streptococci A, C & G Streptococci B Other streptococci Streptococcus pneumoniae
(n) Oxa Oxa Oxa Oxa
a
S Ra Sa Ra
Pen Sb Pen Ib Pen Rb
(122) (84) (60) (70) (125) (19) (5) (90) (84) (20) (66) (54) (16)
MIC90
MIC ranges
Dilution
E-test
Dilution
E-test
Dilution
E-test
0.063 1 0.063 1 0.5 2
0.032 1 0.064 0.75 0.25 1.5
0.25 8 0.25 4 16 4
0.125 6 0.38 4 16 4
0.25 0.25 0.25 0.25 0.25 0.125
0.19 0.19 0.125 0.125 0.125 0.125
0.5 0.5 0.5 0.5 0.5 0.5
0.38 0.38 0.5 0.19 0.19 0.38
0.016±8 0.032±32 0.032±4 0.063±32 0.125±32 0.5±64 0.25±0.5 0.063±1 0.008±1 0.032±1 0.032±0.5 0.063±2 0.063±2
0.008->32 0.006->32 0.008±3 0.016->32 0.064->32 0.25->32 0.19±0.5 0.047±0.75 0.064±0.5 0.047±12 0.047±0.25 0.032±0.75 0.094±0.75
MIC50s and MIC90s are not calculated for groups with fewer than 10 isolates. Oxa: oxacillin ± oxa S (susceptible): CMI 2 mg/L; oxa R: CMI > 2 mg/L. b Pen: penicillin G ± Pen S (susceptible): CMI < 0.1 mg/L; Pen I (intermediate): 0.1 CMI 1 mg/L; Pen R (resistant): CMI > 1 mg/L. a
ß 2003 Copyright by the European Society of Clinical Microbiology and Infectious Diseases, CMI, 9, 997±1005
1000 Clinical Microbiology and Infection, Volume 9 Number 10, October 2003 Table 3 MIC50s and MIC90s and MIC ranges (mg/L) of moxi¯oxacin by agar dilution and E-test against anaerobic microorganisms (n 61) MIC50
MIC90
MIC ranges
Micro-organisms
(n)
Dilution
E-test
Dilution
E-test
Dilution
E-test
Clostridium perfringens Bacteroides fragilis Other Bacteroides Peptostreptococcus
(8) (28) (12) (13)
0.25 1 0.125
0.125 0.094 0.38
4 4 4
1.5 4 4
0.125±1 0.125±4 0.125±8 0.063±4
0.032±3 0.064±16 0.094->32 0.016->32
MIC50s and MIC90s are not calculated for groups with fewer than 10 isolates.
susceptibility to nalidixic acid (NAL) (susceptible 74.9%, intermediate and resistant 25.1%), the MIC50s and MIC90s of moxi¯oxacin were 0.125 and 0.5 mg/L, and 4 and 32 mg/L against NAL-susceptible and NAL-intermediate-resistant strains, respectively. Against strains which were susceptible (MIC 1 mg/L) to cipro¯oxacin (85.0%), MIC50s and MIC90s were 0.125 and 0.5 mg/L, whereas they were 2 and 8 mg/L, 16 and 64 mg/L against CIP-intermediate and CIP-resistant (MIC> 2 mg/L) isolates, respectively (Table 4). Activity of moxifloxacin against other Gram-negative bacteria Moxi¯oxacin had an intermediate activity against P. aeruginosa with MICs between 0.25 and >128 mg/L (MIC50 ± MIC90, 4±128 mg/L) (Table 1). Moxi¯oxacin displayed poor activity against A. baumannii whereas it was more active against A. lwof® and other Acinetobacter species (MICs between 0.032 and 0.5 mg/L). Moxi¯oxacin also demonstrated good in vitro activity against S. maltophilia with MIC50s and MIC90s of 0.5 and 2 mg/L, respectively. MICs against H. in¯uenzae and H. parain¯uenzae ranged from 0.008 to
0.25 mg/L and in vitro activity of moxi¯oxacin was not affected by ampicillin-resistance. Of the 40 M. catarrhalis strains tested, 38 were beta-lactamase producers and moxi¯oxacin MICs ranged from 0.016 to 0.25 mg/L. The few strains of Neisseria spp. were also highly susceptible to moxi¯oxacin with MICs 0.125 mg/L. Activity of moxifloxacin against Gram-positive cocci Most of the 122 oxacillin-susceptible S. aureus strains, susceptible or not to penicillin G, were very sensitive (MICs between 0.016 and 0.5 mg/ L). Twelve out of these 122 clinical isolates (9.8%) were resistant to cipro¯oxacin and were inhibited by 0.25±8 mg/L of moxi¯oxacin concentrations (except one at 0.06). Oxacillin-resistant strains could be divided into two populations: one (13.1%) with low MICs (0.03±0.12 mg/L), which was susceptible to cipro¯oxacin and the other (86.9%) with higher MICs of 0.25±32 mg/L, which was resistant to cipro¯oxacin. The moxi¯oxacin activity against coagulasenegative staphylococci was similar: MICs ranged from 0.03 to 0.25 mg/L (except for one strain at 1 mg/L) for oxacillin- and cipro¯oxacin-suscep-
Table 4 Activity of moxi¯oxacin against Enterobacteriaceae and P. aeruginosa according to nalidixic acid (Nal) and cipro¯oxacin (Cip) susceptibility MIC (mg/L)
Nal Cip 0.008 0.016 0.032 0.063 0.125 0.25 0.5
EnteroSa bacteriacesae Ra Ra Ra No of strains
Sb
Ra Ra Ra
Sb Ib Rb
P. aeruginosa No of strains
Sb Ib Rb
2
6
43
219 2
2
6
43
221
201 2 203
104 7 1
77
1
2 7
2
112
26 26 10 4 5 6 1 2 107 39 20
1
11 35 40
1
4
8
16 32 64 128 >128 Total
2
663
8 4 3 1 6 4 2 1 8 14 28 29 13 8 24 22 33 31 13
89 29 104 885
15 11 10 4 1 2 2 8 8 15 17 11 35 40 16 13 20 12 15 18
1 81 1 8 8
128 5 56 189
a
S (susceptible): CMI 8 mg/L; I; R (resistant): CMI > 16 mg/L. S (susceptible): CMI 1 mg/L; I (intermediate): 1 < CMI 2 mg/L; R (resistant): CMI > 2 mg/L.
b
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Soussy et al
In vitro activity of moxifloxacin 1001
Table 5 Susceptibility and resistance rates, based on MIC breakpoints for moxi¯oxacin (MIC by agar dilution, n 2, 196)
Enterobacteriaceae (n 885) P. aeruginosa (n 189) A. baumannii (n 41) Other Acinetobacter (n 12) S. maltophilia (n 38) H. influenzae (n 97) H. parainfluenzae (n 11) M. catarrhalis (n 40) Neisseria spp. (n 7) S. aureus (n 206) Coag. neg staphylococci (n 130) E. faecalis (n 125) E. faecium (n 19) Other enterococci (n 5) S. pneumoniae (n 136) Other streptococci (n 194) Clostridium perfringens (n 8) Bacteroides fragilis (n 28) Other Bacteroides (n 13) Peptostreptococcus (n 12)
S n (%)
I n (%)
R n (%)
733 47 12 12 27 97 11 40 7 162 94 105 6 5 134 194 8 23 6 10
22 (2.5) 40 (21.1) 1 (2.4)
130 (14.7) 102 (54.0) 28 (68.3)
9 (23.7)
2 (5.2)
(82.8) (24.9) (29.3) (100.0) (71.1) (100.0) (100.0) (100.0) (100.0) (78.6) (72.3) (84.0) (31.6) (100.0) (98.5) (100.0) (100.0) (82.1) (46.2) (83.3)
15 (7.3) 21 (16.2) 7 (36.8)
29 15 20 6
(14.1) (11.5) (16.0) (31.6)
2 (1.5) 1 (3.6) 4 (30.8)
4 (14.3) 3 (23.0) 2 (16.7)
S (susceptible): MIC 1 mg/L; I (intermediate): 1 < MIC 2 mg/L; R (resistant)>2 mg/L. Clinical efficacy has not yet been demonstrated for Cip R strains.
tible strains. Five strains, susceptible to oxacillin and resistant to cipro¯oxacin were inhibited by 0.06, 1, 2 or 4 mg/L of moxi¯oxacin. Out of the 70 strains resistant to oxacillin, 22 were susceptible to cipro¯oxacin with moxi¯oxacin MICs between 0.06 and 0.25 mg/L. The remaining 48 isolates were resistant to cipro¯oxacin and had moxi¯oxacin MICs between 0.5 and 32 mg/L. Moxi¯oxacin MICs against enterococci ranged from 0.12 to 64 mg/L. Cipro¯oxacin-resistant strains had generally higher MICs than the susceptible strains. Streptococci were inhibited by lower concentrations, between 0.008 and 1 mg/L, including pneumococci (MICs: 0.03±2 mg/L), whether susceptible, intermediate or resistant to penicillin G. Out of the 41 cipro¯oxacin-intermediate or cipro¯oxacinresistant strains, 39 were inhibited by concentrations 0.5 mg/L and the remaining two by 2 mg/L of moxi¯oxacin. Activity of moxifloxacin against anaerobes Moxi¯oxacin MICs against C. perfringens ranged from 0.2 to 1 mg/L; MICs for B. fragilis and other Bacteroides spp. were slightly higher, ranging from 0.12 to 8 mg/L; those for Peptostreptococcus spp. were relatively spread out, comprised between 0.06 and 4 mg/L.
In vitro activity of moxifloxacin expressed as percentages of susceptible and resistant strains Considering MIC breakpoints for moxi¯oxacin which have been de®ned as 1 mg/L and >2 mg/L, susceptibility and resistances rates for the 2196 isolates are given in Table 5. Comparative activity of moxifloxacin vs. ciprofloxacin, ofloxacin and trovafloxacin (E tests) The activity of moxi¯oxacin was compared to those of other ¯uoroquinolones (Table 6). Moxi¯oxacin was less active against Enterobacteriaceae than cipro¯oxacin, similar to trova¯oxacin and more active than o¯oxacin. However, MIC50s of moxi¯oxacin were slightly higher than those of trova¯oxacin against S. marcescens, M. morganii and P. stuartii whereas the reverse was observed against C. diversus, Salmonella spp., and Klebsiella spp. Moxi¯oxacin activity against P. aeruginosa (MIC50±MIC90: 4->32 mg/L) was similar to that of o¯oxacin (4->32 mg/L) and lower than that of trova¯oxacin (1->32 mg/L) and cipro¯oxacin (0.38->32 mg/L). MIC50s and MIC90s of moxi¯oxacin were 2 and 4 for cipro¯oxacin-susceptible
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1002 Clinical Microbiology and Infection, Volume 9 Number 10, October 2003 Table 6 Comparative activity of moxi¯oxacin against most common respiratory pathogens and Enterobacteriaceae (MIC by Etest in mg/L) Micro-organism
Phenotypea
Enterobacteriaceae
S. pneumoniae
S. aureus
Quinoloneb
MIC50
Ofl Tro Cip Mxf
0.19 0.125 0.003 0.125 2 2 2 0.125 0.094 0.094 0.75 0.5 0.5 0.125 0.125 0.19
Pen Pen Pen Pen Pen Pen Pen Pen Pen Pen Pen Pen
S I R S I R S I R S I R
Ofl
Oxa Oxa Oxa Oxa Oxa Oxa Oxa Oxa
S R S R S R S R
Ofl
Tro Cip Mxf
Tro Cip Mxf
MIC90 >32 32 4 8 4 4 4 0.19 0.19 0.19 1 1.5 1 0.19 0.19 0.19
0.38 >32 0.023 0.75 0.125 16 0.032 1
2 >32 0.125 >32 1 >32 0.125 6
H. influenzae
Ofl Trov Cip Mxf
0.032 0.008 0.006 0.016
0.064 0.016 0.012 0.032
M. catarrhalis
Ofl Tro Cip Mxf
0.094 0.016 0.023 0.047
0.125 0.032 0.032 0.125
a
Oxa: Oxacillin; Pen: penicillin; S: susceptible; I: intermediate; R: resistant Pen S: MIC < 0.1 mg/L; Pen I: 0.1 MIC 1 mg/L; Pen R: MIC > 1 mg/L Oxa S: MIC 2 mg/L; Oxa R: MIC > 2 mg/L. b Ofl: ofloxacin; Tro: trovafloxacin; Cip: ciprofloxacin; Mxf: moxifloxacin.
Figure 1 Correlation between the inhibition zone diameters (mm) obtained with a 5-mg moxi¯oxacin disc (y-axis) and the log2 of the MIC (mg/L) of moxi¯oxacin determined by agar dilution (x-axis) for 1815 strains.
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Soussy et al
In vitro activity of moxifloxacin 1003
Figure 2 Distribution of the clinical isolates as being susceptible, intermediate, and resistant according to the MICs (S.I.R) and inhibition zone diameters (s.i.r) obtained with 5-mg moxi¯oxacin disc.
P. aeruginosa; moxi¯oxacin had no activity against cipro¯oxacin-resistant strains (Table 4). Regarding Acinetobacter spp., moxi¯oxacin and trova¯oxacin were the most active against ¯uoroquinolonessusceptible strains. Against S. maltophilia, moxi¯oxacin had a higher activity (0.38±1 mg/L) than trova¯oxacin (0.5±3 mg/L), cipro¯oxacin (1.5± 16 mg/L) and o¯oxacin (3->32 mg/L). The four antibiotics had excellent activity against Haemophilus spp. and Neisseria spp. but o¯oxacin MICs were higher than those of moxi¯oxacin, trova¯oxacin and cipro¯oxacin. O¯oxacin and moxi¯oxacin MICs against M. catarrhalis appeared to be slightly higher than those of trova¯oxacin and cipro¯oxacin. Against oxacillin-susceptible S. aureus strains, moxi¯oxacin had an activity similar to that of trova¯oxacin (0.023±0.125 mg/L) and greater than that of cipro¯oxacin (0.125±1 mg/L) and o¯oxacin (0.38±2 mg/L). Against oxacillin-resistant S. aureus strains, the activity of moxi¯oxacin and trova¯oxacin were nearly similar; however, moxi¯oxacin MIC90s appeared lower than those of trova¯oxacin. The same holds true for coagulasenegative staphylococci for both oxacillin-susceptible and oxacillin-resistant strains. Against the various species of enterococci, the activity of moxi¯oxacin and trova¯oxacin appeared to be identical and greater than that of cipro¯oxacin and o¯oxacin. MIC50s for E. faecalis (moxi¯oxacin and trova¯oxacin, 0.25; cipro¯oxacin, 1; o¯oxacin, 4 mg/L) were lower than those against E. faecium (moxi¯oxacin and trova¯oxacin, 1.5; cipro¯oxacin, 2; o¯oxacin, 8 mg/L). Moxi¯oxacin and trova¯oxacin also appeared to be more active than cipro¯oxacin and o¯oxacin against streptococci. Moxi¯oxacin and trova¯oxacin had distinctly higher activity against S. pneumoniae than cipro¯oxacin. This increased activity was not affected by the penicillin G susceptibility. Against C. per-
fringens, o¯oxacin was the least active (MIC50 and MIC90, 0.5±32 mg/L) followed by cipro¯oxacin (0.19->32 mg/L), moxi¯oxacin (0.19±3 mg/L) and trova¯oxacin (0.094±0.19 mg/L). The last two drugs also had the best activity against B. fragilis and other Bacteroides spp. with MIC50s± MIC90s of 0.12±1.5 mg/L and 0.38±1.5 mg/L for moxi¯oxacin and 0.12±0.38 and 0.12±0.75 g/L for trova¯oxacin. The same was true against Peptostreptococcus (MIC 50±MIC90, 0.09±4 mg/L for moxi¯oxacin and 0.19±4 mg/L for trova¯oxacin). Correlation between inhibition zone diameters and MICs For this correlation, only strains with exact MIC and inhibition zone diameter determinations, were selected. The regression curve between the MIC values (logarithm to the base 2) on the x-axis and the inhibition diameters (arithmetic scale) in the y-axis was determined by the least-square method on 1815 strains whose distribution is depicted in Figure 1, where the width of the lines is proportional to the number of strains with the same coordinates [7]. The critical diameters can then be deduced from the critical concentrations. Using a zone diameter breakpoint of 21 mm to denote sensitivity, a false sensitivity (Rs) and false resistant (Sr) rate of 0.55% (12strains)wasseenineachcase(Figure2).Tentative zone diameter breakpoints with a 5-mg moxi¯oxacin disc content could thus be 21 and 18 mm (21, sensitive; 18±20, intermediate and <18, resistant) for all species, including P. aeruginosa. DISCUSSION The in vitro activity of moxi¯oxacin has been extensively studied in several countries, but to
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1004 Clinical Microbiology and Infection, Volume 9 Number 10, October 2003 our knowledge this was the ®rst large survey to be conducted in France, covering most of the pathogens routinely involved in human infections. Moxi¯oxacin, while maintaining activity against Gram negative bacilli, exhibited an increased activity against Gram-positive cocci (i.e. staphylococci, streptococci including pneumococci, and enterococci) as compared to cipro¯oxacin, o¯oxacin and trova¯oxacin [1]. E-test and agar dilution methods provided similar MIC values for all species tested. As far as staphylococci were concerned, moxi¯oxacin-resistant strains, in this study, were found mainly among the methicillin-resistant isolates. Almost all S. pneumoniae (134 out of 136 strains) were inhibited by moxi¯oxacin concentrations of 0.032±0.5 mg/L, irrespective of their susceptibility to penicillin G. Only two strains were inhibited by 2 mg/L, one of intermediate susceptibility and the other resistant to penicillin G. Moxi¯oxacin was very active against Haemophilus spp. and Moraxella catarrhalis with MICs ranging from 0.008 to less than 0.25 mg/L. These results are in line with those previously presented in other countries [8,9]. As most isolates were inhibited by concentrations 1 mg/L, this study con®rms that moxi¯oxacin exerts a signi®cant inhibitory activity against the micro-organisms isolated in France and considered to be responsible for community-acquired respiratory tract infections, whether or not they are resistant to antibiotics commonly prescribed for these infections. Its activity is comparable or superior to that of other recently developed ¯uoroquinolones [10,11]. In addition, the activity of moxi¯oxacin against Enterobacteriaceae was greater than that of o¯oxacin, similar to that of trova¯oxacin, but was inferior to that of cipro¯oxacin. As expected, its activity was reduced against nalidixic acid, as is also the case for other ¯uoroquinolones [12]. While having an intermediate level of activity against P. aeruginosa, moxi¯oxacin showed relatively good activity against nalidixic acid-susceptible Acinetobacter spp.; for the species, MICs were always higher when considering nalidixic acid-resistant isolates. Against anaerobic bacteria, moxi¯oxacin was slightly more active against C. perfringens than against B. fragilis, as previously demonstrated [13]. Using pharmacokinetic and MIC distribution data for the organisms to be targeted by the antibiotic, tentative in vitro breakpoint MICs for moxi¯oxacin were produced to assist interpretation of sensitivity. From in vitro activity against strains
considered to be part of the wild-sensitive population, an MIC breakpoint of 1 mg/L was suggested for all the species studied with the exception of Pseudomonas spp. [14]. An MIC breakpoint of 1 mg/L for respiratory pathogens was endorsed by Grimm et al [15], and results of clinical trials presented by Krasemann et al suggested that 89±97% of causative pathogens could be expected to be eradicated following the treatment of respiratory infections, when MICs of causative strains are 2 mg/L [16]. As P. aeruginosa strains were less susceptible, two MIC breakpoints were suggested for this species: 4 mg/L and 1 mg/L, allowing for a category of intermediate sensitivity. Finally, the MIC breakpoints which were adopted for all species in Europe, were 1 mg/L and >2 mg/L [17], and these breakpoints are supported by the MIC distribution data that are observed in the present study. Proposed zone diameter breakpoints using BSAC [14] or NCCLS criteria [18], differ from those used in the present study. One explanation is the use of different types of the moxi¯oxacin disc. In the present study, disc diffusion tests were performed with a single disc of 5 mg regardless of the species tested, whereas BSAC recommended the use of 1 mg discs for all organisms except Pseudomonas spp.; acceptable zone ranges were obtained only with the 5 mg disc for this last species. Considering the critical concentration of 1 mg/L, a zone diameter breakpoint of 21 mm to denote sensitivity provided very low false sensitivity and false resistant rates (<1%) and the rare cases of false resistance were mainly observed for nonrespiratory pathogens in the present study. While retaining activity against Enterobacteriaceae, moxi¯oxacin was moderately active against P. aeruginosa. Its activity was inferior to that of cipro¯oxacin for these species. In addition this study con®rmed the comparatively high in vitro activity of moxi¯oxacin against Gram-positive cocci and other pathogens isolated from community-acquired respiratory tract infections. ACKNOWLEDGEMENTS This work was supported by Bayer Pharma, France. REFERENCES 1. Zhanel GC, Walkty A, Vercaigne L et al. The new fluoroquinolones: a critical review. Can J Infect Dis 1999; 10 (3): 207±38.
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Soussy et al
2. Siefert HM, Domdey-Bette A, Henninger K, Hucke F, Kohlsdorfer C, Stass HH. Pharmacokinetics of the 8-methoxyquinolone, moxifloxacin: a comparison in humans and other mammalian species. J Antimicrob Chemother 1999; 43 (Suppl. B): 69±76. 3. Fass RJ. In vitro activity of Bay 12±8039, a new 8-methoxyquinolone. Antimicrob Agents Chemother 1997; 41: 1818±24. 4. Dalhoff A, Petersen U, Endermann R. In vitro activity of BAY 12±8039, a new 8-methoxyquinolone. Chemother 1996; 42: 410±25. 5. Bauer AW, Kirby WMM, Sherris JC, Turck M. Antibiotic susceptibility testing by standardized single disk method. Am J Clin Pathol 1966; 45: 493±6. 6. Comite de l'Antibiogramme de la SocieÂte FrancËaise de Microbiologie: Communique 2000±2001. SocieÂte FrancËaise de Microbiologie. URL: http://www.sfm. asso.fr/no. speÂcial 7. Sirot J, Courvalin P, Soussy C-J. Definition and determination of in vitro antibiotic susceptibility breakpoints for bacteria. Clin Microbiol Infect 1996; 2 (Suppl. 1): S5±10. 8. Piddock LJ, Johnson M, Ricci V, Hill SL. Activities of new fluoroquinolones against fluoroquinoloneresistant pathogens of the lower respiratory tract. Antimicrob Agents Chemother 1998; 42 (11): 2956±60. 9. Souli M, Wennersten CB, Eliopoulos GM. In vitro activity of BAY 12±8039, a new fluoroquinolone, against species representative of respiratory tract pathogens. Intern J Antimicrob Agents 1998; 10: 23±30. 10. Brueggemann AB, Kugler KC, Doern GV. In vitro activity of BAY 12±8039, a new 8-methoxyquinolone, compared to activities of six fluoroquinolones against Streptococcus pneumoniae, Haemophilus influ-
11.
12.
13.
14.
15.
16.
17. 18.
In vitro activity of moxifloxacin 1005
enzae and Moraxella catarrhalis. Antimicrob Agents Chemother 1997; 41: 1594±7. Woodcock JM, Andrews JM, Boswell FJ, Brenwald NP, Wise R. In vitro activity of BAY 12±8039, a new 8-methoxyquinolone. Antimicrob Agents Chemother 1997; 41: 101±6. Bachoual R, Tankovic J, Soussy C-J. Analysis of mutations involved in fluoroquinolone resistance of in vivo mutants of Escherichia coli. Microb Drug Res 1998; 4 (4): 271±5. Aldridge KE, Ashcroft DS. Comparison of the in vitro activities of Bay 12±8039, a new quinolone, and other antimicrobials against clinically important anaerobes. Antimicrob Agents Chemother 1997; 41: 709±11. Andrews JM, Ashby JP, Jevons GM, Wise R. Tentative minimum inhibitory concentrations and zone diameter breakpoints for moxifloxacin using BSAC criteria. J Antimicrob Chemother 1999; 44: 819±22. Grimm H. Moxifloxacin: Tentative interpretative criteria for the disc susceptibility testing using the German DIN 58940 method. In: Abstracts Ninth European Congress of Clinical Microbiology and Infectious Diseases, Berlin, Germany. Abstract P220. Clin Microb Infect 1999; 5 (Suppl. 3): 143. Krasemann C, Meyer JM, Springsklee M. Suggested breakpoints for moxifloxacin. In: Abstracts Ninth European Congress of Clinical and Microbiology Infectious Diseases, Berlin, Germany. Abstract P206. Clin Microb Infect 1999; 5 (Suppl. 3): 139. Avelox. Summary of Product Characteristics. Leverkusen, Germany: Bayer Vital GmbH, 1999, 1±17. Avelox. Summary of Product Characteristics. West Haven, CT: Bayer Corporation, 2000, 1±17.
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Service de BacteÂriologie-Virologie-HygieÁne, Henri Mondor University Hospital 94010 Creteil cedex, Laboratoire de BacteÂriologie & HygieÁne, Pitie±SalpeÃtrieÁre University Hospital, 75651 Paris cedex 13, 3 Service de Microbiologie MeÂdicale, Saint Joseph University Hospital, 75674 Paris cedex 14, 4Laboratoire de Microbiologie, Purpan University Hospital, 31059 Toulouse cedex, 5Laboratoire de BacteÂriologie et Virologie, Bichat University Hospital, 75018 Paris, 6Laboratoire de Microbiologie, CoÃte de Nacre Regional Hospital, 14033 Caen cedex, 7Laboratoire de BacteÂriologie, Guillaume et Rene Laennec University Hospital, 44035 Nantes cedex 1, 8Laboratoire de Biologie MeÂdicale, Army Hospital Begin, 94160 Saint ± Mande cedex, 9Laboratoire de BacteÂriologie et HygieÁne hospitalieÁre, City General Hospital, 13616 Aix±en-Provence cedex 1, 10 Laboratoire Central de Microbiologie, Edouard Herriot Hospital, 69437, Lyon cedex 03, 11Laboratoire de Microbiologie ± HeÂmatologie, Metz-Thionville Regional Hospital 57038 Metz Cedex, and 12 Unite des Agents AntibacteÂriens, Pasteur Institute, 75724 Paris cedex 15, France 2
Objective To evaluate the in vitro antibacterial activity of moxi¯oxacinin in comparison to that of other ¯uoroquinolones (cipro¯oxacin, o¯oxacin and trova¯oxacin). Methods A total of 2196 strains was collected in 11 French hospitals in 1998. Minimum
inhibitory concentrations (MICs) (mg/L) were determined by agar dilution and agar diffusion was performed with 5-mg discs. Internal quality control was carried out with genetically de®ned strains.
Results MIC50s and MIC90s of moxi¯oxacin against nalidixic acid (NAL)-susceptible
Enterobacteriaceae (n 663) were 0.12 and 0.5. As for other quinolones, the activity of moxi¯oxacin (4±32) was reduced against NAL-intermediate and NAL-resistant strains (n 222). MIC50s and MIC90s of moxi¯oxacin were 2 and 4 for cipro¯oxacin-susceptible P. aeruginosa (n 128); moxi¯oxacin had no activity against cipro¯oxacin-resistant strains (n 56). The activity of moxi¯oxacin was maintained against NAL-susceptible A. baumannii (n 11; 0.032±0.125), but reduced against NAL-resistant strains (n 30; 16±32). H. in¯uenzae (n 97) and M. catarrhalis (n 40) were inhibited by low concentrations (0.03±0.06 and 0.06±0.25, respectively). Moxi¯oxacin had better activity (0.06±0.12) than other tested quinolones against methicillin-susceptible S. aureus strains (n 110); cipro¯oxacin-resistant strains (n 85) (2±8) were usually methicillin-resistant. Moxi¯oxacin was moderately active against enterococci (n 149) (E. faecalis: 0.5±16; E. faecium: 2±4). Streptococci (n 194) and pneumococci (n 136), including 70 penicillin G-intermediate or G-resistant strains, were inhibited by low concentrations (0.25±0.5 for each species). Based on the regression curve, tentative zone diameter breakpoints could be 21 and <18 mm for MIC breakpoints of 1 and >2 mg/L, respectively.
Conclusions While retaining activity against Enterobacteriaceae, moxi¯oxacin was moderately active against P. aeruginosa. Its activity was inferior to that of cipro¯oxacin for these species. This study con®rmed the comparatively high in vitro activity of
Corresponding author and request for reprints: Prof C.-J. Soussy, Service de BacteÂriologie-Virologie-HygieÁne, HoÃpital Henry Mondor, 51 avenue du MareÂchal de Lattre de Tassigny, 94010 CreÂteil Cedex, France E-mail: [email protected]
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998 Clinical Microbiology and Infection, Volume 9 Number 10, October 2003 moxi¯oxacin against Gram-positive cocci and other pathogens isolated from communityacquired respiratory tract infections. Keywords Moxi¯oxacin, antibacterial activity, hospital clinical isolates, breakpoints
Clin Microbiol Infect 2003; 9: 997±1005
INTRODUCTION Moxi¯oxacin is a broad spectrum 8-methoxyquinolone which interacts preferentially with DNA gyrase in Gram-negative and with topoisomerase IV in Gram-positive bacteria [1]. It has enhanced activity against Gram-positive cocci but retains activity against Gram-negative bacteria [2,3]. Moxi¯oxacin also has good activity against atypical respiratory pathogens (Legionella pneumophila, Chlamydia pneumoniae and Mycoplasma pneumoniae) [4]. The aim of this study was to assess the in vitro activity of moxi¯oxacin on a large number of bacterial strains encountered in daily hospital practice in French hospitals. In addition, tentative inhibition zone diameter breakpoints were determined for moxi¯oxacin using the regression curve. MATERIALS AND METHODS Eleven French hospital laboratories (nine teaching and two general hospitals) collected all clinical isolates, except repetitive strains from the same patient, from March to May 1998. Out of this collection, 20 strains per species, were randomly selected in each center; for the most rarely isolated species, the totality of strains were studied. Clinical isolates were collected from the main types of pathological specimens from in-patients in hospital departments representing the different medical and surgical specialties. In all centers the minimum inhibitory concentrations (MIC) of moxi¯oxacin were determined for all strains by agar dilution using same batch of medium (i.e. Mueller-Hinton bioMeÂrieux, Marcy L'Etoile, France for aerobic bacteria, enriched with 5% horse blood for streptococci and with hemoglobin and polyvitex for Neisseria; HTM based Oxoid Medium enriched with HTM Oxoid supplement for Haemophilus; Wilkins-Chalgren Oxoid for anaerobic bacteria) and with an inoculum of 104 bacteria per `spot'. MICs of moxi¯oxacin, cipro¯oxacin, o¯oxacin, and trova¯oxacin were also determined (in all centers) by the E-test method (AB Biodisk, Solna,
Sweden) using the following reactive strips: moxi¯oxacin, cipro¯oxacin, o¯oxacin and trova¯oxacin. In order to determine the correlation between MICs and the inhibition zone diameters, antibiotic susceptibility testing by agar diffusion [6] was performed, according to the recommendations of the Comite de l'Antibiogramme de la SocieÂte FrancËaise de Microbiologie [5], with 5-mg moxi¯oxacin discs (supplied by Bayer-Pharma, Puteaux, France) and with discs impregnated with 30 mg of nalidixic acid, 5 mg of o¯oxacin and 5 mg of cipro¯oxacin. Analysis of moxi¯oxacin MICs and inhibition zone diameters against ®ve reference strains: S. aureus UA 531, S. aureus UA 532, E. faecalis UA 163, E.coli UA 200, P. aeruginosa UA 110, provided by the National Reference Center for Mechanisms of Resistance to Antibiotics, Institut Pasteur, Paris, indicated intercenter variabilities similar to those usually observed for these techniques. All centers provided results which were not signi®cantly different from those of the reference center (with a 5% risk of error), except data for one center regarding P. aeruginosa strains, which were excluded from the analysis. RESULTS In vitro activity of moxifloxacin: determination of MICs by agar dilution and the E-test method MIC50s, MIC90s and MIC ranges of moxi¯oxacin against Gram-negative, Gram-positive and anaerobic bacteria are shown in Tables 1, 2 and 3, respectively. Activity of moxifloxacin against Enterobacteriaceae MICs of moxi¯oxacin against Enterobacteriaceae ranged from 0.008 to >128 mg/L. MICs were 1 mg/L for 733 of the 885 tested strains (82.8%). Shigella spp., Citrobacter diversus, Hafnia alvei, Salmonella spp. and Proteus vulgaris were the most susceptible organisms with MIC90s 0.5 mg/L, whereas moxi¯oxacin had the highest MIC90 values against Citrobacter freundii and Providencia stuartii (32 mg/L). With respect to the
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Soussy et al In vitro activity of moxifloxacin 999 Table 1 Minimum inhibitory concentrations (MIC)50s and MIC90s and MIC ranges (mg/L) of moxi¯oxacin by agar dilution and E-test against Gram-negative micro-organisms (n 1320) MIC50 Micro-organisms
(n)
All Enterobacteriaceae Escherichia coli Citrobacter freundii Citrobacter diversus Salmonella spp. Hafnia alvei Shigella spp. Klebsiella pneumoniae Klebsiella oxytoca Enterobacter cloacae Other Enterobacter Serratia marcescens Proteus mirabilis Morganella morganii Proteus vulgaris Providencia rettgeri Providencia stuartii Pseudomonas aeruginosa Acinetobacter baumannii Acinetobacter iwoffi Other Acinetobacter Stenotrophomonas maltophilia Haemophilus influenzae Haemophilus parainfluenzae Moraxella catarrhalis Neisseria spp.
(885) (213) (38) (19) (31) (3) (4) (117) (44) (101) (44) (61) (113) (47) (17) (2) (31) (189) (41) (9) (3) (38) (97) (11) (40) (7)
MIC90
Dilution
E-test
MIC ranges
Dilution
E-test
Dilution
E-test
0.008->128 0.008->128 0.032±64 0.032±8 0.063±1 0.125±0.25 0.032±0.063 0.032±128 0.032±16 0.032±128 0.032±32 0.063±16 0.063±64 0.063±128 0.125±1 0.5±4 0.063±128 0.25->128 0.032±64 0.032±0.5 0.063 0.032±16 0.008±0.063 0.008±0.25 0.016±0.25 0.016±0.125
0.002->32 0.002->32 0.047->32 0.032->32 0.023±2 0.032±0.19 0.008±0.043 0.023->32 0.023±8 0.023->32 0.047->32 0.047->32 0.047->32 0.016->32 0.125±0.75 0.094->32 0.094->32 0.125->32 0.016->32 0.016±0.19 0.032 0.016±12 0.003±0.094 <0.002±0.25 0.008±0.19 0.003±0.064
0.125 0.063 0.125 0.063 0.125
0.125 0.047 0.125 0.047 0.125
8 1 32 0.125 0.5
8 0.5 >32 0.25 1
0.125 0.125 0.125 0.25 0.5 0.5 0.25 0.25
0.125 0.094 0.064 0.125 0.25 0.25 0.094 0.19
1 1 8 16 4 16 16 0.5
0.75 0.5 8 >32 4 12 16 0.25
32 4 16
12 4 >32
0.5 0.032 0.063 0.063
128 128 32
0.38 0.016 0.032 0.047
>32 >32 >32
2 0.063 0.125 0.25
1 0.032 0.094 0.125
MIC50s and MIC90s are not calculated for groups with fewer than 10 isolates. N. gonorrhoeae: 2; N. meningitidis: 5.
Table 2 MIC50s and MIC90s and MIC ranges of moxi¯oxacin by agar dilution and E-test against Gram-positive microorganisms (n 815) MIC50 Micro-organisms Staphylococcus aureus Coag. negative staphylococci Enterococcus faecalis Enterococcus faecium Other enterococci Streptococci A, C & G Streptococci B Other streptococci Streptococcus pneumoniae
(n) Oxa Oxa Oxa Oxa
a
S Ra Sa Ra
Pen Sb Pen Ib Pen Rb
(122) (84) (60) (70) (125) (19) (5) (90) (84) (20) (66) (54) (16)
MIC90
MIC ranges
Dilution
E-test
Dilution
E-test
Dilution
E-test
0.063 1 0.063 1 0.5 2
0.032 1 0.064 0.75 0.25 1.5
0.25 8 0.25 4 16 4
0.125 6 0.38 4 16 4
0.25 0.25 0.25 0.25 0.25 0.125
0.19 0.19 0.125 0.125 0.125 0.125
0.5 0.5 0.5 0.5 0.5 0.5
0.38 0.38 0.5 0.19 0.19 0.38
0.016±8 0.032±32 0.032±4 0.063±32 0.125±32 0.5±64 0.25±0.5 0.063±1 0.008±1 0.032±1 0.032±0.5 0.063±2 0.063±2
0.008->32 0.006->32 0.008±3 0.016->32 0.064->32 0.25->32 0.19±0.5 0.047±0.75 0.064±0.5 0.047±12 0.047±0.25 0.032±0.75 0.094±0.75
MIC50s and MIC90s are not calculated for groups with fewer than 10 isolates. Oxa: oxacillin ± oxa S (susceptible): CMI 2 mg/L; oxa R: CMI > 2 mg/L. b Pen: penicillin G ± Pen S (susceptible): CMI < 0.1 mg/L; Pen I (intermediate): 0.1 CMI 1 mg/L; Pen R (resistant): CMI > 1 mg/L. a
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1000 Clinical Microbiology and Infection, Volume 9 Number 10, October 2003 Table 3 MIC50s and MIC90s and MIC ranges (mg/L) of moxi¯oxacin by agar dilution and E-test against anaerobic microorganisms (n 61) MIC50
MIC90
MIC ranges
Micro-organisms
(n)
Dilution
E-test
Dilution
E-test
Dilution
E-test
Clostridium perfringens Bacteroides fragilis Other Bacteroides Peptostreptococcus
(8) (28) (12) (13)
0.25 1 0.125
0.125 0.094 0.38
4 4 4
1.5 4 4
0.125±1 0.125±4 0.125±8 0.063±4
0.032±3 0.064±16 0.094->32 0.016->32
MIC50s and MIC90s are not calculated for groups with fewer than 10 isolates.
susceptibility to nalidixic acid (NAL) (susceptible 74.9%, intermediate and resistant 25.1%), the MIC50s and MIC90s of moxi¯oxacin were 0.125 and 0.5 mg/L, and 4 and 32 mg/L against NAL-susceptible and NAL-intermediate-resistant strains, respectively. Against strains which were susceptible (MIC 1 mg/L) to cipro¯oxacin (85.0%), MIC50s and MIC90s were 0.125 and 0.5 mg/L, whereas they were 2 and 8 mg/L, 16 and 64 mg/L against CIP-intermediate and CIP-resistant (MIC> 2 mg/L) isolates, respectively (Table 4). Activity of moxifloxacin against other Gram-negative bacteria Moxi¯oxacin had an intermediate activity against P. aeruginosa with MICs between 0.25 and >128 mg/L (MIC50 ± MIC90, 4±128 mg/L) (Table 1). Moxi¯oxacin displayed poor activity against A. baumannii whereas it was more active against A. lwof® and other Acinetobacter species (MICs between 0.032 and 0.5 mg/L). Moxi¯oxacin also demonstrated good in vitro activity against S. maltophilia with MIC50s and MIC90s of 0.5 and 2 mg/L, respectively. MICs against H. in¯uenzae and H. parain¯uenzae ranged from 0.008 to
0.25 mg/L and in vitro activity of moxi¯oxacin was not affected by ampicillin-resistance. Of the 40 M. catarrhalis strains tested, 38 were beta-lactamase producers and moxi¯oxacin MICs ranged from 0.016 to 0.25 mg/L. The few strains of Neisseria spp. were also highly susceptible to moxi¯oxacin with MICs 0.125 mg/L. Activity of moxifloxacin against Gram-positive cocci Most of the 122 oxacillin-susceptible S. aureus strains, susceptible or not to penicillin G, were very sensitive (MICs between 0.016 and 0.5 mg/ L). Twelve out of these 122 clinical isolates (9.8%) were resistant to cipro¯oxacin and were inhibited by 0.25±8 mg/L of moxi¯oxacin concentrations (except one at 0.06). Oxacillin-resistant strains could be divided into two populations: one (13.1%) with low MICs (0.03±0.12 mg/L), which was susceptible to cipro¯oxacin and the other (86.9%) with higher MICs of 0.25±32 mg/L, which was resistant to cipro¯oxacin. The moxi¯oxacin activity against coagulasenegative staphylococci was similar: MICs ranged from 0.03 to 0.25 mg/L (except for one strain at 1 mg/L) for oxacillin- and cipro¯oxacin-suscep-
Table 4 Activity of moxi¯oxacin against Enterobacteriaceae and P. aeruginosa according to nalidixic acid (Nal) and cipro¯oxacin (Cip) susceptibility MIC (mg/L)
Nal Cip 0.008 0.016 0.032 0.063 0.125 0.25 0.5
EnteroSa bacteriacesae Ra Ra Ra No of strains
Sb
Ra Ra Ra
Sb Ib Rb
P. aeruginosa No of strains
Sb Ib Rb
2
6
43
219 2
2
6
43
221
201 2 203
104 7 1
77
1
2 7
2
112
26 26 10 4 5 6 1 2 107 39 20
1
11 35 40
1
4
8
16 32 64 128 >128 Total
2
663
8 4 3 1 6 4 2 1 8 14 28 29 13 8 24 22 33 31 13
89 29 104 885
15 11 10 4 1 2 2 8 8 15 17 11 35 40 16 13 20 12 15 18
1 81 1 8 8
128 5 56 189
a
S (susceptible): CMI 8 mg/L; I; R (resistant): CMI > 16 mg/L. S (susceptible): CMI 1 mg/L; I (intermediate): 1 < CMI 2 mg/L; R (resistant): CMI > 2 mg/L.
b
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Soussy et al
In vitro activity of moxifloxacin 1001
Table 5 Susceptibility and resistance rates, based on MIC breakpoints for moxi¯oxacin (MIC by agar dilution, n 2, 196)
Enterobacteriaceae (n 885) P. aeruginosa (n 189) A. baumannii (n 41) Other Acinetobacter (n 12) S. maltophilia (n 38) H. influenzae (n 97) H. parainfluenzae (n 11) M. catarrhalis (n 40) Neisseria spp. (n 7) S. aureus (n 206) Coag. neg staphylococci (n 130) E. faecalis (n 125) E. faecium (n 19) Other enterococci (n 5) S. pneumoniae (n 136) Other streptococci (n 194) Clostridium perfringens (n 8) Bacteroides fragilis (n 28) Other Bacteroides (n 13) Peptostreptococcus (n 12)
S n (%)
I n (%)
R n (%)
733 47 12 12 27 97 11 40 7 162 94 105 6 5 134 194 8 23 6 10
22 (2.5) 40 (21.1) 1 (2.4)
130 (14.7) 102 (54.0) 28 (68.3)
9 (23.7)
2 (5.2)
(82.8) (24.9) (29.3) (100.0) (71.1) (100.0) (100.0) (100.0) (100.0) (78.6) (72.3) (84.0) (31.6) (100.0) (98.5) (100.0) (100.0) (82.1) (46.2) (83.3)
15 (7.3) 21 (16.2) 7 (36.8)
29 15 20 6
(14.1) (11.5) (16.0) (31.6)
2 (1.5) 1 (3.6) 4 (30.8)
4 (14.3) 3 (23.0) 2 (16.7)
S (susceptible): MIC 1 mg/L; I (intermediate): 1 < MIC 2 mg/L; R (resistant)>2 mg/L. Clinical efficacy has not yet been demonstrated for Cip R strains.
tible strains. Five strains, susceptible to oxacillin and resistant to cipro¯oxacin were inhibited by 0.06, 1, 2 or 4 mg/L of moxi¯oxacin. Out of the 70 strains resistant to oxacillin, 22 were susceptible to cipro¯oxacin with moxi¯oxacin MICs between 0.06 and 0.25 mg/L. The remaining 48 isolates were resistant to cipro¯oxacin and had moxi¯oxacin MICs between 0.5 and 32 mg/L. Moxi¯oxacin MICs against enterococci ranged from 0.12 to 64 mg/L. Cipro¯oxacin-resistant strains had generally higher MICs than the susceptible strains. Streptococci were inhibited by lower concentrations, between 0.008 and 1 mg/L, including pneumococci (MICs: 0.03±2 mg/L), whether susceptible, intermediate or resistant to penicillin G. Out of the 41 cipro¯oxacin-intermediate or cipro¯oxacinresistant strains, 39 were inhibited by concentrations 0.5 mg/L and the remaining two by 2 mg/L of moxi¯oxacin. Activity of moxifloxacin against anaerobes Moxi¯oxacin MICs against C. perfringens ranged from 0.2 to 1 mg/L; MICs for B. fragilis and other Bacteroides spp. were slightly higher, ranging from 0.12 to 8 mg/L; those for Peptostreptococcus spp. were relatively spread out, comprised between 0.06 and 4 mg/L.
In vitro activity of moxifloxacin expressed as percentages of susceptible and resistant strains Considering MIC breakpoints for moxi¯oxacin which have been de®ned as 1 mg/L and >2 mg/L, susceptibility and resistances rates for the 2196 isolates are given in Table 5. Comparative activity of moxifloxacin vs. ciprofloxacin, ofloxacin and trovafloxacin (E tests) The activity of moxi¯oxacin was compared to those of other ¯uoroquinolones (Table 6). Moxi¯oxacin was less active against Enterobacteriaceae than cipro¯oxacin, similar to trova¯oxacin and more active than o¯oxacin. However, MIC50s of moxi¯oxacin were slightly higher than those of trova¯oxacin against S. marcescens, M. morganii and P. stuartii whereas the reverse was observed against C. diversus, Salmonella spp., and Klebsiella spp. Moxi¯oxacin activity against P. aeruginosa (MIC50±MIC90: 4->32 mg/L) was similar to that of o¯oxacin (4->32 mg/L) and lower than that of trova¯oxacin (1->32 mg/L) and cipro¯oxacin (0.38->32 mg/L). MIC50s and MIC90s of moxi¯oxacin were 2 and 4 for cipro¯oxacin-susceptible
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1002 Clinical Microbiology and Infection, Volume 9 Number 10, October 2003 Table 6 Comparative activity of moxi¯oxacin against most common respiratory pathogens and Enterobacteriaceae (MIC by Etest in mg/L) Micro-organism
Phenotypea
Enterobacteriaceae
S. pneumoniae
S. aureus
Quinoloneb
MIC50
Ofl Tro Cip Mxf
0.19 0.125 0.003 0.125 2 2 2 0.125 0.094 0.094 0.75 0.5 0.5 0.125 0.125 0.19
Pen Pen Pen Pen Pen Pen Pen Pen Pen Pen Pen Pen
S I R S I R S I R S I R
Ofl
Oxa Oxa Oxa Oxa Oxa Oxa Oxa Oxa
S R S R S R S R
Ofl
Tro Cip Mxf
Tro Cip Mxf
MIC90 >32 32 4 8 4 4 4 0.19 0.19 0.19 1 1.5 1 0.19 0.19 0.19
0.38 >32 0.023 0.75 0.125 16 0.032 1
2 >32 0.125 >32 1 >32 0.125 6
H. influenzae
Ofl Trov Cip Mxf
0.032 0.008 0.006 0.016
0.064 0.016 0.012 0.032
M. catarrhalis
Ofl Tro Cip Mxf
0.094 0.016 0.023 0.047
0.125 0.032 0.032 0.125
a
Oxa: Oxacillin; Pen: penicillin; S: susceptible; I: intermediate; R: resistant Pen S: MIC < 0.1 mg/L; Pen I: 0.1 MIC 1 mg/L; Pen R: MIC > 1 mg/L Oxa S: MIC 2 mg/L; Oxa R: MIC > 2 mg/L. b Ofl: ofloxacin; Tro: trovafloxacin; Cip: ciprofloxacin; Mxf: moxifloxacin.
Figure 1 Correlation between the inhibition zone diameters (mm) obtained with a 5-mg moxi¯oxacin disc (y-axis) and the log2 of the MIC (mg/L) of moxi¯oxacin determined by agar dilution (x-axis) for 1815 strains.
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Soussy et al
In vitro activity of moxifloxacin 1003
Figure 2 Distribution of the clinical isolates as being susceptible, intermediate, and resistant according to the MICs (S.I.R) and inhibition zone diameters (s.i.r) obtained with 5-mg moxi¯oxacin disc.
P. aeruginosa; moxi¯oxacin had no activity against cipro¯oxacin-resistant strains (Table 4). Regarding Acinetobacter spp., moxi¯oxacin and trova¯oxacin were the most active against ¯uoroquinolonessusceptible strains. Against S. maltophilia, moxi¯oxacin had a higher activity (0.38±1 mg/L) than trova¯oxacin (0.5±3 mg/L), cipro¯oxacin (1.5± 16 mg/L) and o¯oxacin (3->32 mg/L). The four antibiotics had excellent activity against Haemophilus spp. and Neisseria spp. but o¯oxacin MICs were higher than those of moxi¯oxacin, trova¯oxacin and cipro¯oxacin. O¯oxacin and moxi¯oxacin MICs against M. catarrhalis appeared to be slightly higher than those of trova¯oxacin and cipro¯oxacin. Against oxacillin-susceptible S. aureus strains, moxi¯oxacin had an activity similar to that of trova¯oxacin (0.023±0.125 mg/L) and greater than that of cipro¯oxacin (0.125±1 mg/L) and o¯oxacin (0.38±2 mg/L). Against oxacillin-resistant S. aureus strains, the activity of moxi¯oxacin and trova¯oxacin were nearly similar; however, moxi¯oxacin MIC90s appeared lower than those of trova¯oxacin. The same holds true for coagulasenegative staphylococci for both oxacillin-susceptible and oxacillin-resistant strains. Against the various species of enterococci, the activity of moxi¯oxacin and trova¯oxacin appeared to be identical and greater than that of cipro¯oxacin and o¯oxacin. MIC50s for E. faecalis (moxi¯oxacin and trova¯oxacin, 0.25; cipro¯oxacin, 1; o¯oxacin, 4 mg/L) were lower than those against E. faecium (moxi¯oxacin and trova¯oxacin, 1.5; cipro¯oxacin, 2; o¯oxacin, 8 mg/L). Moxi¯oxacin and trova¯oxacin also appeared to be more active than cipro¯oxacin and o¯oxacin against streptococci. Moxi¯oxacin and trova¯oxacin had distinctly higher activity against S. pneumoniae than cipro¯oxacin. This increased activity was not affected by the penicillin G susceptibility. Against C. per-
fringens, o¯oxacin was the least active (MIC50 and MIC90, 0.5±32 mg/L) followed by cipro¯oxacin (0.19->32 mg/L), moxi¯oxacin (0.19±3 mg/L) and trova¯oxacin (0.094±0.19 mg/L). The last two drugs also had the best activity against B. fragilis and other Bacteroides spp. with MIC50s± MIC90s of 0.12±1.5 mg/L and 0.38±1.5 mg/L for moxi¯oxacin and 0.12±0.38 and 0.12±0.75 g/L for trova¯oxacin. The same was true against Peptostreptococcus (MIC 50±MIC90, 0.09±4 mg/L for moxi¯oxacin and 0.19±4 mg/L for trova¯oxacin). Correlation between inhibition zone diameters and MICs For this correlation, only strains with exact MIC and inhibition zone diameter determinations, were selected. The regression curve between the MIC values (logarithm to the base 2) on the x-axis and the inhibition diameters (arithmetic scale) in the y-axis was determined by the least-square method on 1815 strains whose distribution is depicted in Figure 1, where the width of the lines is proportional to the number of strains with the same coordinates [7]. The critical diameters can then be deduced from the critical concentrations. Using a zone diameter breakpoint of 21 mm to denote sensitivity, a false sensitivity (Rs) and false resistant (Sr) rate of 0.55% (12strains)wasseenineachcase(Figure2).Tentative zone diameter breakpoints with a 5-mg moxi¯oxacin disc content could thus be 21 and 18 mm (21, sensitive; 18±20, intermediate and <18, resistant) for all species, including P. aeruginosa. DISCUSSION The in vitro activity of moxi¯oxacin has been extensively studied in several countries, but to
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1004 Clinical Microbiology and Infection, Volume 9 Number 10, October 2003 our knowledge this was the ®rst large survey to be conducted in France, covering most of the pathogens routinely involved in human infections. Moxi¯oxacin, while maintaining activity against Gram negative bacilli, exhibited an increased activity against Gram-positive cocci (i.e. staphylococci, streptococci including pneumococci, and enterococci) as compared to cipro¯oxacin, o¯oxacin and trova¯oxacin [1]. E-test and agar dilution methods provided similar MIC values for all species tested. As far as staphylococci were concerned, moxi¯oxacin-resistant strains, in this study, were found mainly among the methicillin-resistant isolates. Almost all S. pneumoniae (134 out of 136 strains) were inhibited by moxi¯oxacin concentrations of 0.032±0.5 mg/L, irrespective of their susceptibility to penicillin G. Only two strains were inhibited by 2 mg/L, one of intermediate susceptibility and the other resistant to penicillin G. Moxi¯oxacin was very active against Haemophilus spp. and Moraxella catarrhalis with MICs ranging from 0.008 to less than 0.25 mg/L. These results are in line with those previously presented in other countries [8,9]. As most isolates were inhibited by concentrations 1 mg/L, this study con®rms that moxi¯oxacin exerts a signi®cant inhibitory activity against the micro-organisms isolated in France and considered to be responsible for community-acquired respiratory tract infections, whether or not they are resistant to antibiotics commonly prescribed for these infections. Its activity is comparable or superior to that of other recently developed ¯uoroquinolones [10,11]. In addition, the activity of moxi¯oxacin against Enterobacteriaceae was greater than that of o¯oxacin, similar to that of trova¯oxacin, but was inferior to that of cipro¯oxacin. As expected, its activity was reduced against nalidixic acid, as is also the case for other ¯uoroquinolones [12]. While having an intermediate level of activity against P. aeruginosa, moxi¯oxacin showed relatively good activity against nalidixic acid-susceptible Acinetobacter spp.; for the species, MICs were always higher when considering nalidixic acid-resistant isolates. Against anaerobic bacteria, moxi¯oxacin was slightly more active against C. perfringens than against B. fragilis, as previously demonstrated [13]. Using pharmacokinetic and MIC distribution data for the organisms to be targeted by the antibiotic, tentative in vitro breakpoint MICs for moxi¯oxacin were produced to assist interpretation of sensitivity. From in vitro activity against strains
considered to be part of the wild-sensitive population, an MIC breakpoint of 1 mg/L was suggested for all the species studied with the exception of Pseudomonas spp. [14]. An MIC breakpoint of 1 mg/L for respiratory pathogens was endorsed by Grimm et al [15], and results of clinical trials presented by Krasemann et al suggested that 89±97% of causative pathogens could be expected to be eradicated following the treatment of respiratory infections, when MICs of causative strains are 2 mg/L [16]. As P. aeruginosa strains were less susceptible, two MIC breakpoints were suggested for this species: 4 mg/L and 1 mg/L, allowing for a category of intermediate sensitivity. Finally, the MIC breakpoints which were adopted for all species in Europe, were 1 mg/L and >2 mg/L [17], and these breakpoints are supported by the MIC distribution data that are observed in the present study. Proposed zone diameter breakpoints using BSAC [14] or NCCLS criteria [18], differ from those used in the present study. One explanation is the use of different types of the moxi¯oxacin disc. In the present study, disc diffusion tests were performed with a single disc of 5 mg regardless of the species tested, whereas BSAC recommended the use of 1 mg discs for all organisms except Pseudomonas spp.; acceptable zone ranges were obtained only with the 5 mg disc for this last species. Considering the critical concentration of 1 mg/L, a zone diameter breakpoint of 21 mm to denote sensitivity provided very low false sensitivity and false resistant rates (<1%) and the rare cases of false resistance were mainly observed for nonrespiratory pathogens in the present study. While retaining activity against Enterobacteriaceae, moxi¯oxacin was moderately active against P. aeruginosa. Its activity was inferior to that of cipro¯oxacin for these species. In addition this study con®rmed the comparatively high in vitro activity of moxi¯oxacin against Gram-positive cocci and other pathogens isolated from community-acquired respiratory tract infections. ACKNOWLEDGEMENTS This work was supported by Bayer Pharma, France. REFERENCES 1. Zhanel GC, Walkty A, Vercaigne L et al. The new fluoroquinolones: a critical review. Can J Infect Dis 1999; 10 (3): 207±38.
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2. Siefert HM, Domdey-Bette A, Henninger K, Hucke F, Kohlsdorfer C, Stass HH. Pharmacokinetics of the 8-methoxyquinolone, moxifloxacin: a comparison in humans and other mammalian species. J Antimicrob Chemother 1999; 43 (Suppl. B): 69±76. 3. Fass RJ. In vitro activity of Bay 12±8039, a new 8-methoxyquinolone. Antimicrob Agents Chemother 1997; 41: 1818±24. 4. Dalhoff A, Petersen U, Endermann R. In vitro activity of BAY 12±8039, a new 8-methoxyquinolone. Chemother 1996; 42: 410±25. 5. Bauer AW, Kirby WMM, Sherris JC, Turck M. Antibiotic susceptibility testing by standardized single disk method. Am J Clin Pathol 1966; 45: 493±6. 6. Comite de l'Antibiogramme de la SocieÂte FrancËaise de Microbiologie: Communique 2000±2001. SocieÂte FrancËaise de Microbiologie. URL: http://www.sfm. asso.fr/no. speÂcial 7. Sirot J, Courvalin P, Soussy C-J. Definition and determination of in vitro antibiotic susceptibility breakpoints for bacteria. Clin Microbiol Infect 1996; 2 (Suppl. 1): S5±10. 8. Piddock LJ, Johnson M, Ricci V, Hill SL. Activities of new fluoroquinolones against fluoroquinoloneresistant pathogens of the lower respiratory tract. Antimicrob Agents Chemother 1998; 42 (11): 2956±60. 9. Souli M, Wennersten CB, Eliopoulos GM. In vitro activity of BAY 12±8039, a new fluoroquinolone, against species representative of respiratory tract pathogens. Intern J Antimicrob Agents 1998; 10: 23±30. 10. Brueggemann AB, Kugler KC, Doern GV. In vitro activity of BAY 12±8039, a new 8-methoxyquinolone, compared to activities of six fluoroquinolones against Streptococcus pneumoniae, Haemophilus influ-
11.
12.
13.
14.
15.
16.
17. 18.
In vitro activity of moxifloxacin 1005
enzae and Moraxella catarrhalis. Antimicrob Agents Chemother 1997; 41: 1594±7. Woodcock JM, Andrews JM, Boswell FJ, Brenwald NP, Wise R. In vitro activity of BAY 12±8039, a new 8-methoxyquinolone. Antimicrob Agents Chemother 1997; 41: 101±6. Bachoual R, Tankovic J, Soussy C-J. Analysis of mutations involved in fluoroquinolone resistance of in vivo mutants of Escherichia coli. Microb Drug Res 1998; 4 (4): 271±5. Aldridge KE, Ashcroft DS. Comparison of the in vitro activities of Bay 12±8039, a new quinolone, and other antimicrobials against clinically important anaerobes. Antimicrob Agents Chemother 1997; 41: 709±11. Andrews JM, Ashby JP, Jevons GM, Wise R. Tentative minimum inhibitory concentrations and zone diameter breakpoints for moxifloxacin using BSAC criteria. J Antimicrob Chemother 1999; 44: 819±22. Grimm H. Moxifloxacin: Tentative interpretative criteria for the disc susceptibility testing using the German DIN 58940 method. In: Abstracts Ninth European Congress of Clinical Microbiology and Infectious Diseases, Berlin, Germany. Abstract P220. Clin Microb Infect 1999; 5 (Suppl. 3): 143. Krasemann C, Meyer JM, Springsklee M. Suggested breakpoints for moxifloxacin. In: Abstracts Ninth European Congress of Clinical and Microbiology Infectious Diseases, Berlin, Germany. Abstract P206. Clin Microb Infect 1999; 5 (Suppl. 3): 139. Avelox. Summary of Product Characteristics. Leverkusen, Germany: Bayer Vital GmbH, 1999, 1±17. Avelox. Summary of Product Characteristics. West Haven, CT: Bayer Corporation, 2000, 1±17.
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