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In vitro activity of loracarbef against common respiratory pathogens compared with amoxicillin-clavulanic acid: a multi-centre study in The Netherlands
IRI‘BRNITI,,Y~L,UORLAI.O~
Antimicrobial Agents International Journal of Antimicrobial Agents 5 (1995) 183-186
In vitro activity of loracarbef against common respiratory pathogens compared with amoxicillin-clavulanic acid: a multi-centre study in The Netherlands Anthony J.A. van Griethuysen”,“, Anhonius J.H.M. Janssena, Max van Noortb, Henri A. Verbrugh”, Rob J.A. Diepersloot” “Reg.ional Laboratory of Health, Canisius Wilhelmina Hospital, Nijmegen, The Netherlands bEli Lilly Nederland B. V., Nieuwegein, The Netherlands ‘Laboratory for Public Health, Diakonessen Hospital, Utrecht, The Netherlands
Received 19 October 1993; revised 24 June 1994; accepted 12 October 1994
Abstract Loracarbef (LC) is the first clinically available carbacephem. In order to evaluate the antimicrobial activity of LC, a total of 593 clinical strains of H. injluenzae, M catarrhalis, S. pneumoniae and S. pyogenes were collected by seven participating study centres. Minimal inhibitory concentrations for loracarbef and amoxycillin-clavulanic acid combination (AC) were determined by a microdilution method. The MIC-90 of/Hactamase-negative strains of H. infuenzae was 2.0 (LC) and 0.5 (AC), and for/?-lactamase-positive strains 4.0 (LC) and 2.0 (AC) mg/l. For B-lactamase-negative and j%lactamase-positive strains of M. catarrhalis, the MIC-90 results were 0.5 and 2.0 (LC) and 0.13 and 0.5 (AC) mgll. The MIC-90 for AC was ~0.03 for both S. pneumoniae and S. pyogenes, while the LC results were 0.5 and 0.25 mg/l, respectively. Of all strains tested, only one /3-lactamase-positive isolate of H. injluenzae was shown to be resistant to LC and another one to be resistant to AC. The MICs for both AC and LC were significantly higher in H. injkenzae and M. catarrhalis strains isolated in the centre and in the south-east of The Netherlands.In conclusion, the results of this study indicate that loracarbef can be used in the initial therapy of community acquired respiratory infections. Keywords:
Loracarbef
1. Introduction
The carbacephems are a new class of /Alactam antibiotics structurally resembling the cephalosporins [l]. In the carbacephems the sulphur atom at position I in the dihydrothiazine ring has been replaced. This synthetic manipulation increases the chemical stability and has no detrimental effect on the pharmacokinetic properties of the new drug [2, 31. Loracarbef is the first carbacephem to undergo clinical development. It has been shown to have in-vitro activity against both ,8-lactamase-positive and /3-lactamase-negative strains of Haemophilus influenzae and Moraxella catarrhalis and streptococci [4]. Loracarbef may, there-
*Corresponding author. Tel. (+31-80) 657 514; Fax (+31-80) 657 516. 0924-8579/95/$29.00 0 1995 Elsevier Science B.V. All rights reserved SSDI 0924-8579(94)00062-X
fore, be useful in the treatment of community acquired respiratory tract infections. In a multi-centre study we compared the in-vitro activity of loracarbef with that of the amoxicillin-clavulanic acid combination and evaluated the influence of previous antibiotic usage, specialism of the attending physician and the location of the laboratory on the MICs.
2. Materials and methods Patients attending outpatient clinics and hospitalized for upper respiratory tract infections (URI: otitis, sinusitis, tonsillitis and epiglottitis) and lower respiratory tract infections (LRI: tracheitis, bronchitis, pneumonia) over a six month period were included in the study. For each patient age, gender, the use of antibiotics in the two
A.J.A.
184
van Griethuysen et al. IInternational Journal of Antimicrobial Agents 5 (1995)
Escherichia coli ATCC 25922. The production of p-lactamase by strains of H. influenzae and M. catarrhalis was
weeks prior to the study, diagnosis and specialty of the attending physician was recorded. Seven centres, both hospital and public health laboratories, located in various parts of The Netherlands cooperated in this study. They are designated by the major city in their region (Goes, Leeuwarden, Utrecht, Nijmegen, Breda, Eindhoven and Amsterdam). Each laboratory received frozen microtitre testpanels together with a comprehensive protocol, that was prepared by one of the participating centres (Nijmegen). First isolates of Huemophilus injluenzae Q-lactamasepositive and -negative: HIN’ and HIN-), Moraxellu catarrhaiis @-lactamase-positive and -negative: MCA’ and MCA-), Streptococcuspneumoniae (SPN) and Streptococcus pyogenes (SPY) were collected. Each strain was stored in glycerol-broth at -70°C. The participating laboratory was asked to collect about twenty strains of each species. Loracarbef was obtained from Eli Lilly and Company (Indianapolis, Indiana, USA) and the combination of amoxicillin/clavulanic acid (AC) from Smith Kline Beecham Biologicals (Rixensart, Belgium). Dilutions of both antibiotics were prepared in Isosensi-test broth (Oxoid Ltd, Basingstoke, Harts, United Kingdom) supplemented with 1% lysed horse blood and 0.5% isovitalex (BBL Microbiology systems, Cockeysville, MD, USA). 0.05 ml of doubling dilutions, from 32 to 0.03 mg/l for loracarbef and 64132 to 0.06/0.03 mg/l for AC, were delivered to cup 2 through 12 of alternating rows of microtitre plates (Greiner, Frickenhausen, BRD). Cup 1 was reserved for growth control. The AC combination was used in a fixed 2: 1 ratio according to NCCLS recommendations. After transport to the various laboratories the microtitre plates were kept frozen at -70°C. All plates were used within six weeks after preparation. The plates were inoculated according to guidelines published by the National Committee for Clinical Laboratory Standards (NCCLS) [5]. Cultures were read after 18-20 h. The MIC results were validated by concomitantly testing of Staphylococcus aweus ATCC 29213 and Table 1 In-vitro activity
of loracarbef
against
593 isolates
of respiratory
pathogens
183-186
confirmed by adding one drop of nitrocefin solution (Oxoid Ltd, Basingstoke, Harts., UK) to growth control cup that was free of antibiotics, and checking for colour change to read after 30 min. A strain was considered sensitive if the MIC for loracarbef was 58 mg/l and if the MIC for AC was 14/2 (for H.injIuenzae only) or 5814 mg/l (all other strains).
3. Statistics. Log-transformed MIC-values were analyzed by means of multiple linear regression. As possible determinants of these log-transformed MIC-values we considered: production of /?-lactamase, gender, diagnosis, the use of antibiotics in the two weeks prior to the study and specialty of the attending physician and centre of isolation. Contingency tables were analyzed by means of chisquare tests.
4. Results A total of 593 strains were collected, 370 from male and 223 female patients. Patients had either upper (n = 210) or lower (n = 383) respiratory tract infection and presented themselves to pulmonary physicians (n = 239), pediatricians (n = 173), specialists in internal medicine (n = 77), ear-nose and throat specialists (n = 32), or physicians with other speciatties (n = 52). Ninety-nine patients had used antibiotics in the two weeks preceding this study. A summary of the MIC determinations is presented in Table 1. The MICs for all control strains tested in the various laboratories were within quality control limits [5]. Loracarbef as well as the combination of AC were highly active against both/?-lactamase-positive and -neg-
compared
with amoxicillin/clavulanic
acid (2: 1)
Organism
n
Antibiotic
MIC-50
MIC-90
Range
% Susceptibility
Haemophilus injuenzae j3-lactamase-negative Haemophilus in@enzae /I-lactamase-positive Moraxella catarrhalis /3-lactamase-negative Moraxella catarrhalis /?-lactamase-positive Streptococcus pneumoniae
157
loracarbef amoxklav loracarbef amoxklav loracarbef amoxklav loracarbef amoxklav loracarbef amoxklav loracarbef amoxklav loracarbef amoxklav
1 0.5 2 1 0.25 SO.03 0.5 0.13 0.5 SO.03 0.13 SO.03 0.5 0.06
2 0.5 4 2 0.5 0.13 2 0.5 0.5 5 0.03 0.25 5 0.03 2 0.5
0.03316 0.12-2 0.5-16 0.25-8 0.03-l 5 0.03-0.5 0.25-16 5 0.03-l 5 0.01558 5 0.03-0.25 0.064 5 0.0330.5 ~O.lL16 S 0.03-8
99 100 98 98 100 100 99 100 100 100 100 100 99 99
Streptococcus pyogenes All
42 63 98 143 90 593
A.J.A.
van Griethuysen
et al. IInternational
Journal of Antimicrobial
ative strains of H. influenzae and A4. catarrhalis. Only one out of 42 /3-lactamase-positive H. influenzae strains had a MIC of 16 mg/l for loracarbef and was classified as being resistant according to NCCLS guidelines [5]. All /I-lactamase-negative strains of H. influenzae were susceptible to AC and of the B-lactamase-positive strains only one strain showed an MIC of 8 mg/l and was therefore considered to be resistant [5]. All /3-lactamase-negative strains of A4. catarrhalis were susceptible to both loracarbef and the amoxycillin clavulanate combination. Among the /3-lactamase-positive strains resistance to loracarbef was noted in one strain. Overall, a two- to fourfold increase in MIC-50 and MIC-90 was found for loracarbef and AC alike when /I-lactamase-positive strain’s were compared with/3-lactamase-negative strains of Al. catarrhalis and H. injiuenzue. All pneumococci and S. pyogenes strains were shown to be susceptible to both loracarbef and AC. For Streptococcus pyogenes cultured from females the MIC results for AC were significantly lower than for isolates from men (p < 0.05). No statistically significant differences related to gender could be demonstrated for the other species. As shown in Table 2 there were considerable differences (p c 0.05) in log transformed MICs between the various centres for H. inzuenzae and M. catarrhalis. The results of each centre are presented as a species specific MIC ratio relative to the results of the laboratory in Goes which was arbitrarily given the MIC-value 1.0 (Table 2). For pneumococci there were no statistically significant differences between the various centres. Even after correction for the number of &lactamase producing strains the MIC results tended to be higher in Utrecht (centre of The Netherlands) and in Eindhoven (south-east of The Netherlands) for H. inzuenzae and for M. catarrhalis (p c 0.05) (Table 2). No influence on MIC results could be demonstrated for diagnosis or specialty of the attending physician, or previous antibiotic usage. Validation data with ATCC strains showed centres not
Table 2 Regional differences in The Netherlands in sensitivity of H. influenzae and S. pyogenes to loracarbef and amoxillin-clavulanate acid (2: 1) H. influenzae
M. catarrhalis
Centre
Loracarbef
AC
Loracarbef
AC
Goes Leeuwarden Nijmegen Breda Amsterdam Utrecht Eindhoven
1.0 1.7* 0.7 0.8 0.6 1.5* 2.1*
1.0 l.‘!/ 1.o 0.8 OX 1.:;*
1.0 0.9 1.2 0.7 0.7 1.3* 1.4*
1.0 0.7 0.7 0.4 0.6 1.1 0.7
2.Y
*Significant differences in comparison with Goes p < 0.05. Log-transformed MICs from Goes were given the value of one. No significant differences were seen for S. pneunzoniue.
Agents 5 (1995)
183-186
to differ on the basis of laboratory the study.
185
performance
during
5. Discussion The results of this study demonstrate that loracarbef has good antibacterial activity against several common respiratory pathogens. Our investigations therefore confirm the outcome of some previous studies [6,7]. Based on the MIC-50 and MIC-90 results the combination of amoxicillin-clavulanic acid was more active than loracarbef for all the pathogens tested in this study. However, using a MIC of 58.0 mg/l to define susceptibility for loracarbef, 99% of all strains were susceptible to both AC and loracarbef. Loracarbef was active against ACresistant pneumococci that may become increasingly prevailing in the near future. When the drug is administered orally using standard 400 mg doses peak concentrations of 12.0-16.0 mg/l are readily achieved. If 200 mg capsules are used, the mean peak concentrations will not exceed 8.0 mg/l [3]. The mean plasma elimination halflife (T,,,) in normal patients is 1.3 h; however, one study of skin-blister fluid suggests that the elimination half-life of loracarbef may be prolonged in interstitial fluids, a finding with potential implications for drug efficacy [9]. The MIC results in our study indicate that a twice daily dosage scheme of 200 mg loracarbef is sufficient for most infections; the higher dosage of 400 mg may be advisable in Haemophilus infections. Clinical trials are necessary to assess these suggestions. The MIC results of p-lactamase producing isolates of both H. influenzae and M. catarrhalis indicate that loracarbef has a considerable stability against /3-lactamase enzymes commonly encountered in these pathogens. The MIC results of /?-lactamase producing strains were two or fourfold higher in comparison with P-lactamase-negative strains. These results generally resemble those of loracarbef as reported by Cao and Neu [lo]. For H. injluenzae, M. catarrhalis and S. pyogenes there were considerable differences in the outcome of MIC testing between the various centres. Geographical variation in resistance to antibiotics has been documented in other European countries. These differences may in part be explained by local prescribing habits [l l] or, as in the case of the Eindhoven laboratory, by the geographical location which is close to Belgium where MICs for respiratory pathogens are known to be higher than in The Netherlands [12]. Knowledge of the geographical variation in resistance of bacteria is important for the initial choice of antibiotic therapy. Most studies on this subject, however, rely on the MIC determinations in a reference laboratory performed [ 131.The use of centrally prepared microtitre plates and a uniform protocol, as in this study would greatly facilitate the insight in the geographical variation of resistance patterns.
186
A.J.A.
vun Griethuysen
et al. IInternational
In conclusion, the results of this study indicate that loracarbef can be used in the initial therapy of community acquired respiratory infections. The antibacterial activity of loracarbef is quite similar to that of the older cephalosporins cefaclor and cefuroxime-axetil [B]. Its enhanced chemical stability and better pharmacokinetic profile makes it a potential successor of the older oral cephalosporins.
Acknowledgment The authors thank F.T.C. Willems+, P.H.J. van Keulen (Breda), M.J. Haverkorn (Eindhoven), J.E. Degener (Leeuwarden), L.J.M. Sabbe (Goes) and P.G.H. Peerbooms, all medical microbiologists from the participating laboratories for their cooperation and Moniek Elsendoorn for the preparation of the manuscript. Statistical analysis was performed by J. Nauta of the Free University, Amsterdam. This study was funded by a grant from Eli Lilly Nederland.
References [1] Mochida K, Shiraki C, Yamasaki M et al. Aminothiazolylglycyl derivatives of carbacephems. I. Synthesis and antibacterial activity of novel carbacephems with substituted aminothiazolyl groups. J. Antibiotics 1987;40:14-21. [2] Gray G, Ramotar K, Krulicki W et al. Stability and in vitro activity of LY 163892 and cefaclor. Abstract 1200, 27th Interscience Conf. Antimicrobial Agents and Chemotherapy, New York, October 1987.
Journal of Antimicrobial
Agents 5 (1995)
183-186
[3] DeSante KA, Zeckel M. Pharmacokinetic profile of loracarbef. Am J Med 1992;92(suppl 6A):l619. [4] Doern G. In vitro activity of loracarbef and effects of susceptibility test methods. Am J Med 1992;92(suppl. 6A):7-15. [5] National Committee for Clinical Laboratorv Standards. Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically, 2nd ed. NCCLS Document M7-A2, Villanova, PA, 1990. in-vitro activity of a 161Howard AJ, Dunkin KT. Comparative new oral carbacephem. LY163892. J Antimicrob Chemother 1988;22:445456. activity of LY163892, an [71 Jones RN, Barry AL. Antimicrobial orally administered I-carbacephem. J Antimicrob Chemother 1988;22:315-320. PI Doern GV, Vautour R, Parker D et al. In vitro activity of loracarbef (LYl63892) a new oral carbacephem antimicrobial agent, against respiratory isolates of Haemophilus infuenzae and Moraxella catarrhalis. Antimicrob. Agents Chemother 1991;35:1504-1507. tissue 191Lees AS, Andrews JM, Wise R. The pharmacokinetics, penetration and in-vitro activity of loracarbef, a /J-lactam antibiotic of the carbacephem class. J. Antimicrob Chemother 1993;32:853-859. stability of LY163892. Abstract VOI Cao C, Neu HC. Beta-lactamase 1202, Interscience Conf. Antimicrobial Agents and Chemotherapy, New York, October 1987. 1111Chugh TD, Neil L. Mahboob AG et al. In vitro activity of antibacterial agents on Haemophilus injuenzae isolates. Trop Geogr. Med 1986;38:404407. and resisWI Machka K. Braveny I, Dabernat H et al. Distribution tance patterns of H. injkenzae: a European cooperative study. Eur J Clin Microbial Inf Dis 1988;7: 1424. [I31 Howard AJ, Williams HM. The prevalence of antibiotic resistance in Haemophilus influenzae in Ireland. J. Antimicrob Chemother 1989;24:963-971.
Antimicrobial Agents International Journal of Antimicrobial Agents 5 (1995) 183-186
In vitro activity of loracarbef against common respiratory pathogens compared with amoxicillin-clavulanic acid: a multi-centre study in The Netherlands Anthony J.A. van Griethuysen”,“, Anhonius J.H.M. Janssena, Max van Noortb, Henri A. Verbrugh”, Rob J.A. Diepersloot” “Reg.ional Laboratory of Health, Canisius Wilhelmina Hospital, Nijmegen, The Netherlands bEli Lilly Nederland B. V., Nieuwegein, The Netherlands ‘Laboratory for Public Health, Diakonessen Hospital, Utrecht, The Netherlands
Received 19 October 1993; revised 24 June 1994; accepted 12 October 1994
Abstract Loracarbef (LC) is the first clinically available carbacephem. In order to evaluate the antimicrobial activity of LC, a total of 593 clinical strains of H. injluenzae, M catarrhalis, S. pneumoniae and S. pyogenes were collected by seven participating study centres. Minimal inhibitory concentrations for loracarbef and amoxycillin-clavulanic acid combination (AC) were determined by a microdilution method. The MIC-90 of/Hactamase-negative strains of H. infuenzae was 2.0 (LC) and 0.5 (AC), and for/?-lactamase-positive strains 4.0 (LC) and 2.0 (AC) mg/l. For B-lactamase-negative and j%lactamase-positive strains of M. catarrhalis, the MIC-90 results were 0.5 and 2.0 (LC) and 0.13 and 0.5 (AC) mgll. The MIC-90 for AC was ~0.03 for both S. pneumoniae and S. pyogenes, while the LC results were 0.5 and 0.25 mg/l, respectively. Of all strains tested, only one /3-lactamase-positive isolate of H. injluenzae was shown to be resistant to LC and another one to be resistant to AC. The MICs for both AC and LC were significantly higher in H. injkenzae and M. catarrhalis strains isolated in the centre and in the south-east of The Netherlands.In conclusion, the results of this study indicate that loracarbef can be used in the initial therapy of community acquired respiratory infections. Keywords:
Loracarbef
1. Introduction
The carbacephems are a new class of /Alactam antibiotics structurally resembling the cephalosporins [l]. In the carbacephems the sulphur atom at position I in the dihydrothiazine ring has been replaced. This synthetic manipulation increases the chemical stability and has no detrimental effect on the pharmacokinetic properties of the new drug [2, 31. Loracarbef is the first carbacephem to undergo clinical development. It has been shown to have in-vitro activity against both ,8-lactamase-positive and /3-lactamase-negative strains of Haemophilus influenzae and Moraxella catarrhalis and streptococci [4]. Loracarbef may, there-
*Corresponding author. Tel. (+31-80) 657 514; Fax (+31-80) 657 516. 0924-8579/95/$29.00 0 1995 Elsevier Science B.V. All rights reserved SSDI 0924-8579(94)00062-X
fore, be useful in the treatment of community acquired respiratory tract infections. In a multi-centre study we compared the in-vitro activity of loracarbef with that of the amoxicillin-clavulanic acid combination and evaluated the influence of previous antibiotic usage, specialism of the attending physician and the location of the laboratory on the MICs.
2. Materials and methods Patients attending outpatient clinics and hospitalized for upper respiratory tract infections (URI: otitis, sinusitis, tonsillitis and epiglottitis) and lower respiratory tract infections (LRI: tracheitis, bronchitis, pneumonia) over a six month period were included in the study. For each patient age, gender, the use of antibiotics in the two
A.J.A.
184
van Griethuysen et al. IInternational Journal of Antimicrobial Agents 5 (1995)
Escherichia coli ATCC 25922. The production of p-lactamase by strains of H. influenzae and M. catarrhalis was
weeks prior to the study, diagnosis and specialty of the attending physician was recorded. Seven centres, both hospital and public health laboratories, located in various parts of The Netherlands cooperated in this study. They are designated by the major city in their region (Goes, Leeuwarden, Utrecht, Nijmegen, Breda, Eindhoven and Amsterdam). Each laboratory received frozen microtitre testpanels together with a comprehensive protocol, that was prepared by one of the participating centres (Nijmegen). First isolates of Huemophilus injluenzae Q-lactamasepositive and -negative: HIN’ and HIN-), Moraxellu catarrhaiis @-lactamase-positive and -negative: MCA’ and MCA-), Streptococcuspneumoniae (SPN) and Streptococcus pyogenes (SPY) were collected. Each strain was stored in glycerol-broth at -70°C. The participating laboratory was asked to collect about twenty strains of each species. Loracarbef was obtained from Eli Lilly and Company (Indianapolis, Indiana, USA) and the combination of amoxicillin/clavulanic acid (AC) from Smith Kline Beecham Biologicals (Rixensart, Belgium). Dilutions of both antibiotics were prepared in Isosensi-test broth (Oxoid Ltd, Basingstoke, Harts, United Kingdom) supplemented with 1% lysed horse blood and 0.5% isovitalex (BBL Microbiology systems, Cockeysville, MD, USA). 0.05 ml of doubling dilutions, from 32 to 0.03 mg/l for loracarbef and 64132 to 0.06/0.03 mg/l for AC, were delivered to cup 2 through 12 of alternating rows of microtitre plates (Greiner, Frickenhausen, BRD). Cup 1 was reserved for growth control. The AC combination was used in a fixed 2: 1 ratio according to NCCLS recommendations. After transport to the various laboratories the microtitre plates were kept frozen at -70°C. All plates were used within six weeks after preparation. The plates were inoculated according to guidelines published by the National Committee for Clinical Laboratory Standards (NCCLS) [5]. Cultures were read after 18-20 h. The MIC results were validated by concomitantly testing of Staphylococcus aweus ATCC 29213 and Table 1 In-vitro activity
of loracarbef
against
593 isolates
of respiratory
pathogens
183-186
confirmed by adding one drop of nitrocefin solution (Oxoid Ltd, Basingstoke, Harts., UK) to growth control cup that was free of antibiotics, and checking for colour change to read after 30 min. A strain was considered sensitive if the MIC for loracarbef was 58 mg/l and if the MIC for AC was 14/2 (for H.injIuenzae only) or 5814 mg/l (all other strains).
3. Statistics. Log-transformed MIC-values were analyzed by means of multiple linear regression. As possible determinants of these log-transformed MIC-values we considered: production of /?-lactamase, gender, diagnosis, the use of antibiotics in the two weeks prior to the study and specialty of the attending physician and centre of isolation. Contingency tables were analyzed by means of chisquare tests.
4. Results A total of 593 strains were collected, 370 from male and 223 female patients. Patients had either upper (n = 210) or lower (n = 383) respiratory tract infection and presented themselves to pulmonary physicians (n = 239), pediatricians (n = 173), specialists in internal medicine (n = 77), ear-nose and throat specialists (n = 32), or physicians with other speciatties (n = 52). Ninety-nine patients had used antibiotics in the two weeks preceding this study. A summary of the MIC determinations is presented in Table 1. The MICs for all control strains tested in the various laboratories were within quality control limits [5]. Loracarbef as well as the combination of AC were highly active against both/?-lactamase-positive and -neg-
compared
with amoxicillin/clavulanic
acid (2: 1)
Organism
n
Antibiotic
MIC-50
MIC-90
Range
% Susceptibility
Haemophilus injuenzae j3-lactamase-negative Haemophilus in@enzae /I-lactamase-positive Moraxella catarrhalis /3-lactamase-negative Moraxella catarrhalis /?-lactamase-positive Streptococcus pneumoniae
157
loracarbef amoxklav loracarbef amoxklav loracarbef amoxklav loracarbef amoxklav loracarbef amoxklav loracarbef amoxklav loracarbef amoxklav
1 0.5 2 1 0.25 SO.03 0.5 0.13 0.5 SO.03 0.13 SO.03 0.5 0.06
2 0.5 4 2 0.5 0.13 2 0.5 0.5 5 0.03 0.25 5 0.03 2 0.5
0.03316 0.12-2 0.5-16 0.25-8 0.03-l 5 0.03-0.5 0.25-16 5 0.03-l 5 0.01558 5 0.03-0.25 0.064 5 0.0330.5 ~O.lL16 S 0.03-8
99 100 98 98 100 100 99 100 100 100 100 100 99 99
Streptococcus pyogenes All
42 63 98 143 90 593
A.J.A.
van Griethuysen
et al. IInternational
Journal of Antimicrobial
ative strains of H. influenzae and A4. catarrhalis. Only one out of 42 /3-lactamase-positive H. influenzae strains had a MIC of 16 mg/l for loracarbef and was classified as being resistant according to NCCLS guidelines [5]. All /I-lactamase-negative strains of H. influenzae were susceptible to AC and of the B-lactamase-positive strains only one strain showed an MIC of 8 mg/l and was therefore considered to be resistant [5]. All /3-lactamase-negative strains of A4. catarrhalis were susceptible to both loracarbef and the amoxycillin clavulanate combination. Among the /3-lactamase-positive strains resistance to loracarbef was noted in one strain. Overall, a two- to fourfold increase in MIC-50 and MIC-90 was found for loracarbef and AC alike when /I-lactamase-positive strain’s were compared with/3-lactamase-negative strains of Al. catarrhalis and H. injiuenzue. All pneumococci and S. pyogenes strains were shown to be susceptible to both loracarbef and AC. For Streptococcus pyogenes cultured from females the MIC results for AC were significantly lower than for isolates from men (p < 0.05). No statistically significant differences related to gender could be demonstrated for the other species. As shown in Table 2 there were considerable differences (p c 0.05) in log transformed MICs between the various centres for H. inzuenzae and M. catarrhalis. The results of each centre are presented as a species specific MIC ratio relative to the results of the laboratory in Goes which was arbitrarily given the MIC-value 1.0 (Table 2). For pneumococci there were no statistically significant differences between the various centres. Even after correction for the number of &lactamase producing strains the MIC results tended to be higher in Utrecht (centre of The Netherlands) and in Eindhoven (south-east of The Netherlands) for H. inzuenzae and for M. catarrhalis (p c 0.05) (Table 2). No influence on MIC results could be demonstrated for diagnosis or specialty of the attending physician, or previous antibiotic usage. Validation data with ATCC strains showed centres not
Table 2 Regional differences in The Netherlands in sensitivity of H. influenzae and S. pyogenes to loracarbef and amoxillin-clavulanate acid (2: 1) H. influenzae
M. catarrhalis
Centre
Loracarbef
AC
Loracarbef
AC
Goes Leeuwarden Nijmegen Breda Amsterdam Utrecht Eindhoven
1.0 1.7* 0.7 0.8 0.6 1.5* 2.1*
1.0 l.‘!/ 1.o 0.8 OX 1.:;*
1.0 0.9 1.2 0.7 0.7 1.3* 1.4*
1.0 0.7 0.7 0.4 0.6 1.1 0.7
2.Y
*Significant differences in comparison with Goes p < 0.05. Log-transformed MICs from Goes were given the value of one. No significant differences were seen for S. pneunzoniue.
Agents 5 (1995)
183-186
to differ on the basis of laboratory the study.
185
performance
during
5. Discussion The results of this study demonstrate that loracarbef has good antibacterial activity against several common respiratory pathogens. Our investigations therefore confirm the outcome of some previous studies [6,7]. Based on the MIC-50 and MIC-90 results the combination of amoxicillin-clavulanic acid was more active than loracarbef for all the pathogens tested in this study. However, using a MIC of 58.0 mg/l to define susceptibility for loracarbef, 99% of all strains were susceptible to both AC and loracarbef. Loracarbef was active against ACresistant pneumococci that may become increasingly prevailing in the near future. When the drug is administered orally using standard 400 mg doses peak concentrations of 12.0-16.0 mg/l are readily achieved. If 200 mg capsules are used, the mean peak concentrations will not exceed 8.0 mg/l [3]. The mean plasma elimination halflife (T,,,) in normal patients is 1.3 h; however, one study of skin-blister fluid suggests that the elimination half-life of loracarbef may be prolonged in interstitial fluids, a finding with potential implications for drug efficacy [9]. The MIC results in our study indicate that a twice daily dosage scheme of 200 mg loracarbef is sufficient for most infections; the higher dosage of 400 mg may be advisable in Haemophilus infections. Clinical trials are necessary to assess these suggestions. The MIC results of p-lactamase producing isolates of both H. influenzae and M. catarrhalis indicate that loracarbef has a considerable stability against /3-lactamase enzymes commonly encountered in these pathogens. The MIC results of /?-lactamase producing strains were two or fourfold higher in comparison with P-lactamase-negative strains. These results generally resemble those of loracarbef as reported by Cao and Neu [lo]. For H. injluenzae, M. catarrhalis and S. pyogenes there were considerable differences in the outcome of MIC testing between the various centres. Geographical variation in resistance to antibiotics has been documented in other European countries. These differences may in part be explained by local prescribing habits [l l] or, as in the case of the Eindhoven laboratory, by the geographical location which is close to Belgium where MICs for respiratory pathogens are known to be higher than in The Netherlands [12]. Knowledge of the geographical variation in resistance of bacteria is important for the initial choice of antibiotic therapy. Most studies on this subject, however, rely on the MIC determinations in a reference laboratory performed [ 131.The use of centrally prepared microtitre plates and a uniform protocol, as in this study would greatly facilitate the insight in the geographical variation of resistance patterns.
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In conclusion, the results of this study indicate that loracarbef can be used in the initial therapy of community acquired respiratory infections. The antibacterial activity of loracarbef is quite similar to that of the older cephalosporins cefaclor and cefuroxime-axetil [B]. Its enhanced chemical stability and better pharmacokinetic profile makes it a potential successor of the older oral cephalosporins.
Acknowledgment The authors thank F.T.C. Willems+, P.H.J. van Keulen (Breda), M.J. Haverkorn (Eindhoven), J.E. Degener (Leeuwarden), L.J.M. Sabbe (Goes) and P.G.H. Peerbooms, all medical microbiologists from the participating laboratories for their cooperation and Moniek Elsendoorn for the preparation of the manuscript. Statistical analysis was performed by J. Nauta of the Free University, Amsterdam. This study was funded by a grant from Eli Lilly Nederland.
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