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Apparent plateau in β-lactamase production among clinical isolates of Haemophilus influenzae and Moraxella catarrhalis in the United States: results from the LIBRA Surveillance initiative
International Journal of Antimicrobial Agents 19 (2002) 119– 123 www.ischemo.org
Original article
Apparent plateau in b-lactamase production among clinical isolates of Haemophilus influenzae and Moraxella catarrhalis in the United States: results from the LIBRA Surveillance initiative Mark E. Jones a,*, James A. Karlowsky b, Rene´e Blosser-Middleton b, Ian A. Critchley b, Clyde Thornsberry c, Daniel F. Sahm b a
Focus Technologies, Koninginneweg 11, Hil6ersum, 1217 KP, The Netherlands b 13665 Technology Dri6e, Herndon, VA 20171, USA c 7003 Chadwick Dri6e, Brentwood, TN 37027, USA Received 6 July 2001; accepted 25 October 2001
Abstract Haemophilus influenzae (n= 2791) and Moraxella catarrhalis (n= 1249) isolated from patient specimens during 1999 were collected from 290 laboratories participating in a moxifloxacin surveillance study as part of the LIBRA Surveillance intitiative. Isolates were tested for in vitro susceptibility to a panel of agents suitable for the treatment of respiratory tract infections. b-Lactamase production was identified in 32.2% of H. influenzae and 94.2% of M. catarrhalis. These percentages differed by less than 1.5% from results of a study conducted in 1997–1998 and were similar to results from other recent US surveillance studies. Resistance among H. influenzae to trimethoprim-sulphamethoxazole increased considerably, from 2% in the 1997– 1998 study (n= 6588 H. influenzae) to 15.5% in the current study. One isolate of H. influenzae had an MIC of 8 mg/l to both levofloxacin and moxifloxacin; all other isolates had MICs of 5 0.5 mg/l and 5 0.25 mg/l, respectively. b-Lactamase production was found to confer ampicillin resistance in nearly all isolates. For M. catarrhalis, b-lactamase-negative isolates had MICs 5 0.12– 0.25 mg/l for ampicillin and 50.03–0.12 mg/l for ceftriaxone. In contrast, b-lactamase production resulted in MICs of 5 0.12– \16 mg/l for ampicillin and 50.03–4 mg/l for ceftriaxone. All M. catarrhalis had MICs 5 0.12 mg/l for moxifloxacin and 51 mg/l for levofloxacin. In summary, antimicrobial susceptibilities and the prevalence of b-lactamase production in H. influenzae and M. catarrhalis in the United States has remained essentially unchanged from 1997– 1998 to 1999. © 2002 Elsevier Science B.V. and the International Society of Chemotherapy. All rights reserved. Keywords: Antimicrobial susceptibility; Haemophilus influenzae; Moraxella catarrhalis; Longitudinal surveillance study; b-Lactamase; Fluoroquinolones
1. Introduction Haemophilus influenzae and Moraxella catarrhalis are significant aetiological agents in community-acquired respiratory tract infections (CA-RTI) [1]. Until the late 1970s, isolates of both species were highly susceptible to ampicillin and amoxycillin, as they had not yet ac* Correspondent author. Tel.: + 31-35-625-7290; fax: +31-35-6257287. E-mail address: [email protected] (M.E. Jones).
quired b-lactamases [2]. The near ubiquitous acquisition of BRO b-lactamases by M. catarrhalis [3] and the widespread dissemination of TEM-1 [2] and, less commonly, ROB-1 b-lactamases [4] among H. influenzae have effectively removed the aminopenicillins without a combined b-lactamase inhibitor, as an empirical therapeutic option for infections in which these species are suspected pathogens. The production of b-lactamase may also compromise the activity of some cephalosporin classes.
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M.E. Jones et al. / International Journal of Antimicrobial Agents 19 (2002) 119–123
In the United States, acquired resistance to b-lactams among H. influenzae and M. catarrhalis and increases in penicillin non-susceptible Streptococcus pneumoniae and associated resistance to macrolides and trimethoprimsulphamethoxazole (TMP-SMX) [5,6] have created a need for alternative compounds for empirical treatment of CA-RTI. In response, a number of newer fluoroquinolones such as levofloxacin and moxifloxacin have been developed to provide first-line or alternative antimicrobials with activity against S. pneumoniae, H. influenzae and M. catarrhalis. The first moxifloxacin USA surveillance study was initiated in the 1997– 1998 winter season as part of the ongoing LIBRA Surveillance initiative to provide comprehensive longitudinal surveillance of resistance in clinical isolates of S. pneumoniae, M. catarrhalis, and H. influenzae. Data from the 1997– 1998 study has been previously published [5]. Here, we report the susceptibility of H. influenzae and M. catarrhalis from 1999.
presence or absence of b-lactamase, are shown in Table 1. Predictably, b-lactamase production conferred ampicillin resistance in nearly all isolates (98.8%). Ten isolates with a confirmed b-lactamase negative ampicillin resistant (BLNAR) phenotype were detected from seven of the nine USA bureau of census regions, a prevalence of 0.5% among b-lactamase-negative isolates and 0.4% among all H. influenzae tested. One of these also tested as resistant (MIC, 8 mg/l) to amoxycillinclavulanate. Inhibition of b-lactamase by the clavulanate component of amoxycillin-clavulanate conferred susceptibility to 99.9% of all H. influenzae. b-Lactamase production had no effect on susceptibility to cephalosporins to which 100% of b-lactamase-positive isolates were susceptible. Azithromycin non-susceptibility was detected in five (0.2%) of isolates. All H. influenzae isolates, irrespective of b-lactamase production, were susceptible to moxifloxacin and levofloxacin except one, which had an MIC of 8 mg/l for both agents, all other isolates had MICs of \ 0.5 mg/l for levofloxacin or 5 0.25 mg/l for moxifloxacin.
2. Materials and methods
3.2. M. catarrhalis 2.1. Bacterial isolates and susceptibility testing Isolates of H. influenzae (n =2791) and M. catarrhalis (n=1249) were prospectively gathered during February through October 1999 from 290 participant laboratories distributed throughout the United States. Isolates were limited to one per patient. Of the 290 laboratories, 253 (87.3%) also participated in a previous 1997– 1998 surveillance study [5]. The 1997– 1998 study tested 6583 isolates of H. influenzae and 3648 isolates of M. catarrhalis from 377 laboratories [5]. The methodologies followed for organism collection, re-identification, b-lactamase testing and antimicrobial susceptibility testing were identical to those described in the previous surveillance study [5]. NCCLS guidelines for antimicrobial susceptibility testing, MIC interpretation and quality control were followed [7]. Moxifloxacin MICs for H. influenzae were interpreted using more recently published NCCLS guidelines [8] because those available in 1999 [7] did not include breakpoints for moxifloxacin. As in previous studies [5,9], for comparative purposes only, NCCLS breakpoint definitions for Staphylococcus aureus were used to interpret M. catarrhalis quantitative susceptibility data [7].
3. Results
3.1. H. influenzae Overall susceptibility data for all antimicrobials tested against H. influenzae, grouped according to the
Susceptibility data for all antimicrobials tested against the 1249 isolates of M. catarrhalis, listed by b-lactamase status, are shown in Table 2. Applying NCCLS-defined breakpoints for S. aureus [7] as a guide for interpreting M. catarrhalis data, b-lactamase production conferred ampicillin resistance in 86.8% of b-lactamase-positive isolates (resistance was 81.7% for all isolates). All other antimicrobials tested maintained consistent activity independent of b-lactamase status, against the M. catarrhalis study set, with the exception of one isolate (b-lactamase-positive) with an MIC of 8 mg/l for cefuroxime and four isolates with MICs of ]4 mg/l for TMP-SMX. For M. catarrhalis, next to ampicillin, ceftriaxone activity appeared to be the most influenced by b-lactamase status, as the ceftriaxone MIC90 increased from 5 0.03 mg/l for b-lactamase-negative isolates to 1 mg/l for b-lactamase-positive isolates. No isolate had an MIC of \ 0.12 mg/l for moxifloxacin (MIC90, 0.06 mg/l) or \1 mg/l for levofloxacin (MIC90, 0.03 mg/l).
4. Discussion For H. influenzae the 32.2% of isolates producing b-lactamase remains essentially unchanged from the 33.3% recorded in the previous 1997–1998 study [5]. Since the first reports of b-lactamase production in H. influenzae in the mid-1970s, a number of surveillance studies undertaken in the United States have documented increases in this phenotype, primarily through acquisition of TEM-1 [10–15], to a peak prevalence of
M.E. Jones et al. / International Journal of Antimicrobial Agents 19 (2002) 119–123
36% recorded in 1994– 1995 [16]. The 33% reported in 1997–1998 studies [5,6,17] and the prevalence identified in the current study (32.2%) strongly suggest that for now at least, the prevalence of TEM-1 and ROB-1 carriage in this species in the USA, has leveled off. Recent data from outside of the USA, show the incidence of b-lactamase production in H. influenzae is very variable by country and often remains comparatively low [18], although whether or not the incidence has stabilised is less clear. Careful surveillance in this species will be necessary to track further increases in
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TEM-1 or ROB-1 carriage, evolution of these b-lactamases toward extended-spectrum activity, or acquisition of other extended-spectrum TEM or SHV b-lactamases, as has occurred in members of the Enterobacteriaceae. Bearing in mind the capacity of bacterial species to evolve further antibiotic resistance, this seems likely to occur [2]. Speculation that changes in b-lactam selective pressure may underlie the stabilization or reduction (in some locales) in the prevalence of b-lactamase in H. influenzae has yet to be substantiated. Although no BLNAR isolates were identified in our
Table 1 In vitro activity of tested antimicrobials against 2791 isolates of H. influenzae, according to the presence (n = 898) or absence (n =1893) of b-lactamase production Antimicrobial/ b-lactamase status
MIC range
MIC50
MIC90
Modal MIC
0.25 \16 0.25
\16 \16 1
0.12 \16 50.12
1 2 1
0.5 0.5 0.25
%Sa
%Ia
%Ra
67.5 0.4b 99.3
0.4 0.8 0.2
32.1 98.8 0.5c
99.9 99.8 99.9
– – –
0.1 0.2d 0.1
100 100 100
– – –
– – –
0 0 0.1
0 0 0 0.2e 0.1 0.2
(mg/l) Ampicillin All isolates b-Lactamase-positive b-Lactamase-negative
50.12–\16 50.12–\16 50.12–\16
Amoxycillin-cla6ulanate All isolates b-Lactamase-positive b-Lactamase-negative
50.03–8 50.03–8 50.03–8
0.5 1 0.25
Ceftriaxone All isolates b-Lactamase-positive b-Lactamase-negative
50.03–2 50.03–2 50.03–2
50.03 50.03 50.03
50.03 50.03 50.03
50.03 50.03 50.03
Cefuroxime All isolates b-Lactamase-positive b-Lactamase-negative
50.25–8 50.25–4 50.25–8
1 1 1
2 2 2
1 1 0.5
100 100 99.9
Azithromycin All isolates b-Lactamase-positive b-Lactamase-negative
50.06–\32 50.06–\32 50.06–\32
0.5 0.5 0.5
1 1 1
0.5 0.5 0.5
99.8 99.9 99.8
– – –
TMP-SMX All isolates b-Lactamase-positive b-Lactamase-negative
50.03–\4 50.03–\4 50.03–\4
0.25 0.25 0.25
0.25 0.25 0.25
76.7 73.4 78.3
7.7 7.1 8.0
Le6ofloxacin All isolates b-Lactamase-positive b-Lactamase-negative
50.008–8 50.008–0.5 50.008–8
0.015 0.015 0.015
0.015 0.015 0.015
0.015 0.015 0.015
100 100 99.9
– – –
– – 0.1f
Moxifloxacin All isolates b-Lactamase-positive b-Lactamase-negative
50.008–8 50.008–0.25 50.008–8
0.015 0.015 0.015
0.03 0.03 0.03
0.015 0.015 0.015
100 100 99.9
– – –
0 0 0.1f
a
\4 \4 \4
15.5 19.5 13.6
MICs interpreted using NCCLS M100-S9 breakpoints as susceptible (S), intermediate (I), or resistant (R) [7]. Four isolates (0.4%) were b-lactamase-positive and ampicillin-susceptible. c Ten isolates (0.5%) were b-lactamase-negative and ampicillin-resistant. d Two isolates (0.2%) were b-lactamase-positive and amoxycillin-clavulanate-resistant. e I or R breakpoints are not published for azithromycin [7]. Five isolates (0.2%) were nonsusceptible to azithromycin; one was b-lactamase-positive and four were b-lactamase-negative. f One isolate (0.04%) was nonsusceptible to both levofloxacin and moxifloxacin. Moxifloxacin MICs were interpreted using the recently defined 2001 NCCLS breakpoints for this compound (S, 51 mg/l) [8]. b
M.E. Jones et al. / International Journal of Antimicrobial Agents 19 (2002) 119–123
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Table 2 In vitro activity of test antimicrobials against 1249 isolates of M. catarrhalis, according to the presence (n = 1176) or absence (n= 73) of b-lactamase productiona Antimicrobial/b-lactamase status
MIC range
MIC50
MIC90
Modal MIC
(mg/l) Ampicillin All isolates b-Lactamase-positive b-Lactamase-negative
50.12–\16 50.12–\16 50.12–0.25
2 2 50.12
8 8 50.12
4 4 50.12
Amoxycillin-cla6ulanate All isolates b-Lactamase-positive b-Lactamase-negative
50.03–4 50.03–4 50.03–0.12
0.12 0.12 B = 0.03
0.25 0.25 B =0.03
0.25 0.25 50.03
Ceftriaxone All isolates b-Lactamase-positive b-Lactamase-negative
50.03–4 50.03–4 50.03–0.12
0.25 0.25 50.03
1 1 50.03
0.5 0.5 50.03
Cefuroxime All isolates b-Lactamase-positive b-Lactamase-negative
50.25–8 50.25–8 50.25–2
1 1 0.5
2 2 0.5
1 1 0.5
Azithromycin All isolates b-Lactamase-positive b-Lactamase-negative
50.06–2 50.06–2 50.06–50.12
50.06 50.06 50.06
50.06 50.06 50.06
50.06 50.06 50.06
TMP-SMX All isolates b-Lactamase-positive b-Lactamase-negative
50.03–\4 50.03–\4 50.03–2
0.12 0.12 0.12
0.5 0.5 0.25
0.12 0.25 0.12
Le6ofloxacin All isolates b-Lactamase-positive b-Lactamase-negative
50.008–1 50.008–1 50.008–0.06
0.03 0.03 0.03
0.03 0.03 0.06
0.03 0.03 0.03
Moxifloxacin All isolates b-Lactamase-positive b-Lactamase-negative
50.008–0.12 50.008–0.12 50.008–0.06
0.06 0.06 0.06
0.06 0.06 0.06
0.06 0.06 0.06
a
No NCCLS-defined breakpoints are available for M. catarrhalis [7,8].
preceding 1997– 1998 study [5], the 10 isolates detected here represent a similar prevalence rate to that reported in the United States in the 1994– 1995 respiratory season (0.5%) [16]. Three BLNARs were derived from the same laboratory in the state of Wisconsin and two isolates were from the same laboratory in New Jersey; these may represent clonal types in each setting, similar to a previous report [16]. Together these data suggests no increasing trend, but rather sporadic isolation of such organisms. Resistance to TMP-SMX was the only upward trend detected, increasing from 13.5% in 1997– 1998 to 15.5% in the current study. TMP-SMX nonsusceptibility (intermediate plus resistant isolates) also increased from 20.9% in the 1997–1998 study to 23.2% in the current study, which agrees with data from a contemporary surveillance study [17]. b-Lactamase-positive isolates
(73.4% susceptible) were also more likely to demonstrate TMP-SMX nonsusceptibility than b-lactamasenegative isolates (78.3% susceptible). Although there are few data describing this phenomenon directly in the published literature, a previous 1997–1998 surveillance study showed 75.3% susceptibility among b-lactamasepositive isolates and 81.0% susceptibility among b-lactamase-negative isolates, suggesting that this association had also not changed greatly. Similarly the 0.2% azithromycin resistance does not represent any increase over the three azithromycin-nonsusceptible isolates (all b-lactamase-negative) detected in our previous 1997–1998 study [5] or the two azithromycin-nonsusceptible isolates reported in the SENTRY study for 1997–1998 (b-lactamase status unknown) [17]. Although recent reports have identified isolates of M. catarrhalis and H. influenzae with reduced susceptibili-
M.E. Jones et al. / International Journal of Antimicrobial Agents 19 (2002) 119–123
ties to fluoroquinolones [19,20], the fluoroquinolone resistant isolate reported here is the first such isolate identified in our testing of more than 10 000 H. influenzae referred to our laboratory during the last three years from Europe and the United States (data not shown). Thus elevated MICs to moxifloxacin and levofloxacin in H. influenzae or M. catarrhalis represent extremely rare events. The 94.2% of M. catarrahlis b-lactamase-positive, were similar to the 92.4% reported in the 1997–1998 study [5] and in other US studies since 1996 [5,6,15,17] indicating that in this species also the incidence of b-lactamase has leveled off, albeit at \ 90%. Moxifloxacin showed little differentiation in vitro from levofloxacin against M. catarrhalis, the compounds having at most a two-fold difference in MIC90. For H. influenzae and M. catarrhalis in the USA at least, there seems to be no upward trend in resistance. The longitudinal aspect of this surveillance programme will play an important role in detecting changes in the susceptibility of important respiratory tract pathogens to fluoroquinolones and other antimicrobial agents.
Acknowledgements We thank Bayer Corporation for providing funding for this study under the auspices of the LIBRA Surveillance initiative. We express our appreciation to the many microbiologists and other personnel in each of the participating laboratories, without whose commitment these studies would not be possible.
References [1] Bartlett JG, Mundy LM. Community-acquired pneumonia. New Engl J Med 1995;333:1619 –24. [2] Livermore DM. b-Lactamases in laboratory and clinical practice. Clin Micro Rev 1995;8:557 – 84. [3] Bootsma HJ, van Dijk H, Verhoef J, Fleer A, Mooi FR. Molecular characterization of the BRO b-lactamase of Moraxella (Branhamella) catarrhalis. Antimicrob Agents Chemother 1996;40:966 –72. [4] Daum RS, Murphey-Corb M, Shapira E, Dipp S. Epidemiology of rob b-lactamase among ampicillin-resistant Haemophilus influenzae isolates in the United States. J Infect Dis 1988;157:450 – 5. [5] Jones ME, Staples AM, Critchley I, et al. Benchmarking the in vitro activity of moxifloxacin and comparator agents against recent respiratory isolates from 377 medical centers throughout the United States. Antimicrob Agents Chemother 2000;44:2645 – 52. [6] Thornsberry C, Jones ME, Hickey M, Mauriz Y, Kahn J, Sahm DF. Resistance surveillance of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the United States, 1997 –1998. J Antimicrob Chemother 1999;44:749 – 59.
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[7] National Committee for Clinical Laboratory Standards. Performance Standards for Antimicrobial Susceptibility Testing, Ninth Informational Supplement. Document M100-S9 NCCLS. Wayne, PA, 1999. [8] National Committee for Clinical Laboratory Standards. Performance Standards for Antimicrobial Susceptibility Testing, Eleventh Informational Supplement. Document M100-S11 NCCLS. Wayne, PA, 2001. [9] Jones ME, Staples AM, Critchley I, et al. Benchmarking the in vitro activity of moxifloxacin against recent clinical isolates of Streptococcus pneumoniae, Moraxella catarrhalis and H. influenzae: a European multi-center study. Diagn Microbiol Infect Dis 2000;37:201 – 11. [10] Barry AL, Pfaller MA, Fuchs PC, Packer RR. In vitro activities of 12 orally administered antimicrobial agents against four species of bacterial respiratory pathogens from US medical centers in 1992 and 1993. Antimicrob Agents Chemother 1994;38:2419 – 25. [11] Doern GV, Jorgensen JH, Thornsberry C, Preston DA. The Haemophilus Surveillance Group Prevalence of the antimicrobial resistance among clinical isolates of Haemophilus influenzae: a collaborative study. Diagn Microbiol Infect Dis. 1986; 4: 95 – 107. [12] Doern GV, Jorgensen JH, Thornsberry C, et al. National collaborative study of the prevalence of antimicrobial resistance among clinical isolates of Haemophilus influenzae. Antimicrob Agents Chemother 1998;32:180 – 5. [13] Jorgenson JH. Update on the mechanisms and prevalence of antimicrobial resistance in Haemophilus influenzae. Clin Infect Dis 1992;14:1119 – 23. [14] Rittenhouse SP, Miller L, Kaplan RL, Mosely GH, Poupard JA. A survey of b-lactamase-producing Haemophilus influenzae: an evaluation of 5750 isolates. Diagn Microbiol Infect Dis 1995;21:223 – 5. [15] Thornsberry C, Ogilvie P, Kahn J, Mauriz Y, the Laboratory Investigator Group. Surveillance of antimicrobial resistance in Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the United States in the 1996 – 1997 respiratory season. Diagn Microbiol Infect Dis 1997;29: 249 – 257. [16] Jones RN, Jacobs MR, Washington JA, Pfaller MA. A 1994 –95 surveillance of Haemophilus influenzae susceptibility to ten orally administered agents. Diagn Microbiol Infect Dis 1997;27:75 –83. [17] Doern GV, Jones RN, Pfaller MA, Kugler K, the SENTRY Participants Group. Haemophilus influenzae and Moraxella catarrhalis from patients with community-acquired respiratory tract infections: antimicrobial susceptibility patterns from the SENTRY Antimicrobial Surveillance Program (United States and Canada, 1997), Antimicrob Agents Chemother 2000;43: 385 – 389 [18] Sahm DF, Jones ME, Hickey ML, Diakun DR, Mani S, Thornsberry C. Resistance surveillance of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis isolated in Asia and Europe, 1997 – 1998. J Antimicrob Chemother 2000;45:457 – 66. [19] Biedenbach DJ, Jones RN. Fluoroquinolone-resistant Haemophilus influenzae: frequency of occurrence and analysis of confirmed strains in the SENTRY Antimicrobial Surveillance Program (North and Latin America). Diagn Microbiol Infect Dis 2000;36:255 – 9. [20] DiPersio JR, Jones RN, Barrett T, Doern GV, Pfaller MA. Fluoroquinolone-resistant Moraxella catarrhalis in a patient with pneumonia: report from the SENTRY Antimicrobial Surveillance Program (1998). Diagn Microbiol Infect Dis 1998;32:131 – 5.
Original article
Apparent plateau in b-lactamase production among clinical isolates of Haemophilus influenzae and Moraxella catarrhalis in the United States: results from the LIBRA Surveillance initiative Mark E. Jones a,*, James A. Karlowsky b, Rene´e Blosser-Middleton b, Ian A. Critchley b, Clyde Thornsberry c, Daniel F. Sahm b a
Focus Technologies, Koninginneweg 11, Hil6ersum, 1217 KP, The Netherlands b 13665 Technology Dri6e, Herndon, VA 20171, USA c 7003 Chadwick Dri6e, Brentwood, TN 37027, USA Received 6 July 2001; accepted 25 October 2001
Abstract Haemophilus influenzae (n= 2791) and Moraxella catarrhalis (n= 1249) isolated from patient specimens during 1999 were collected from 290 laboratories participating in a moxifloxacin surveillance study as part of the LIBRA Surveillance intitiative. Isolates were tested for in vitro susceptibility to a panel of agents suitable for the treatment of respiratory tract infections. b-Lactamase production was identified in 32.2% of H. influenzae and 94.2% of M. catarrhalis. These percentages differed by less than 1.5% from results of a study conducted in 1997–1998 and were similar to results from other recent US surveillance studies. Resistance among H. influenzae to trimethoprim-sulphamethoxazole increased considerably, from 2% in the 1997– 1998 study (n= 6588 H. influenzae) to 15.5% in the current study. One isolate of H. influenzae had an MIC of 8 mg/l to both levofloxacin and moxifloxacin; all other isolates had MICs of 5 0.5 mg/l and 5 0.25 mg/l, respectively. b-Lactamase production was found to confer ampicillin resistance in nearly all isolates. For M. catarrhalis, b-lactamase-negative isolates had MICs 5 0.12– 0.25 mg/l for ampicillin and 50.03–0.12 mg/l for ceftriaxone. In contrast, b-lactamase production resulted in MICs of 5 0.12– \16 mg/l for ampicillin and 50.03–4 mg/l for ceftriaxone. All M. catarrhalis had MICs 5 0.12 mg/l for moxifloxacin and 51 mg/l for levofloxacin. In summary, antimicrobial susceptibilities and the prevalence of b-lactamase production in H. influenzae and M. catarrhalis in the United States has remained essentially unchanged from 1997– 1998 to 1999. © 2002 Elsevier Science B.V. and the International Society of Chemotherapy. All rights reserved. Keywords: Antimicrobial susceptibility; Haemophilus influenzae; Moraxella catarrhalis; Longitudinal surveillance study; b-Lactamase; Fluoroquinolones
1. Introduction Haemophilus influenzae and Moraxella catarrhalis are significant aetiological agents in community-acquired respiratory tract infections (CA-RTI) [1]. Until the late 1970s, isolates of both species were highly susceptible to ampicillin and amoxycillin, as they had not yet ac* Correspondent author. Tel.: + 31-35-625-7290; fax: +31-35-6257287. E-mail address: [email protected] (M.E. Jones).
quired b-lactamases [2]. The near ubiquitous acquisition of BRO b-lactamases by M. catarrhalis [3] and the widespread dissemination of TEM-1 [2] and, less commonly, ROB-1 b-lactamases [4] among H. influenzae have effectively removed the aminopenicillins without a combined b-lactamase inhibitor, as an empirical therapeutic option for infections in which these species are suspected pathogens. The production of b-lactamase may also compromise the activity of some cephalosporin classes.
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In the United States, acquired resistance to b-lactams among H. influenzae and M. catarrhalis and increases in penicillin non-susceptible Streptococcus pneumoniae and associated resistance to macrolides and trimethoprimsulphamethoxazole (TMP-SMX) [5,6] have created a need for alternative compounds for empirical treatment of CA-RTI. In response, a number of newer fluoroquinolones such as levofloxacin and moxifloxacin have been developed to provide first-line or alternative antimicrobials with activity against S. pneumoniae, H. influenzae and M. catarrhalis. The first moxifloxacin USA surveillance study was initiated in the 1997– 1998 winter season as part of the ongoing LIBRA Surveillance initiative to provide comprehensive longitudinal surveillance of resistance in clinical isolates of S. pneumoniae, M. catarrhalis, and H. influenzae. Data from the 1997– 1998 study has been previously published [5]. Here, we report the susceptibility of H. influenzae and M. catarrhalis from 1999.
presence or absence of b-lactamase, are shown in Table 1. Predictably, b-lactamase production conferred ampicillin resistance in nearly all isolates (98.8%). Ten isolates with a confirmed b-lactamase negative ampicillin resistant (BLNAR) phenotype were detected from seven of the nine USA bureau of census regions, a prevalence of 0.5% among b-lactamase-negative isolates and 0.4% among all H. influenzae tested. One of these also tested as resistant (MIC, 8 mg/l) to amoxycillinclavulanate. Inhibition of b-lactamase by the clavulanate component of amoxycillin-clavulanate conferred susceptibility to 99.9% of all H. influenzae. b-Lactamase production had no effect on susceptibility to cephalosporins to which 100% of b-lactamase-positive isolates were susceptible. Azithromycin non-susceptibility was detected in five (0.2%) of isolates. All H. influenzae isolates, irrespective of b-lactamase production, were susceptible to moxifloxacin and levofloxacin except one, which had an MIC of 8 mg/l for both agents, all other isolates had MICs of \ 0.5 mg/l for levofloxacin or 5 0.25 mg/l for moxifloxacin.
2. Materials and methods
3.2. M. catarrhalis 2.1. Bacterial isolates and susceptibility testing Isolates of H. influenzae (n =2791) and M. catarrhalis (n=1249) were prospectively gathered during February through October 1999 from 290 participant laboratories distributed throughout the United States. Isolates were limited to one per patient. Of the 290 laboratories, 253 (87.3%) also participated in a previous 1997– 1998 surveillance study [5]. The 1997– 1998 study tested 6583 isolates of H. influenzae and 3648 isolates of M. catarrhalis from 377 laboratories [5]. The methodologies followed for organism collection, re-identification, b-lactamase testing and antimicrobial susceptibility testing were identical to those described in the previous surveillance study [5]. NCCLS guidelines for antimicrobial susceptibility testing, MIC interpretation and quality control were followed [7]. Moxifloxacin MICs for H. influenzae were interpreted using more recently published NCCLS guidelines [8] because those available in 1999 [7] did not include breakpoints for moxifloxacin. As in previous studies [5,9], for comparative purposes only, NCCLS breakpoint definitions for Staphylococcus aureus were used to interpret M. catarrhalis quantitative susceptibility data [7].
3. Results
3.1. H. influenzae Overall susceptibility data for all antimicrobials tested against H. influenzae, grouped according to the
Susceptibility data for all antimicrobials tested against the 1249 isolates of M. catarrhalis, listed by b-lactamase status, are shown in Table 2. Applying NCCLS-defined breakpoints for S. aureus [7] as a guide for interpreting M. catarrhalis data, b-lactamase production conferred ampicillin resistance in 86.8% of b-lactamase-positive isolates (resistance was 81.7% for all isolates). All other antimicrobials tested maintained consistent activity independent of b-lactamase status, against the M. catarrhalis study set, with the exception of one isolate (b-lactamase-positive) with an MIC of 8 mg/l for cefuroxime and four isolates with MICs of ]4 mg/l for TMP-SMX. For M. catarrhalis, next to ampicillin, ceftriaxone activity appeared to be the most influenced by b-lactamase status, as the ceftriaxone MIC90 increased from 5 0.03 mg/l for b-lactamase-negative isolates to 1 mg/l for b-lactamase-positive isolates. No isolate had an MIC of \ 0.12 mg/l for moxifloxacin (MIC90, 0.06 mg/l) or \1 mg/l for levofloxacin (MIC90, 0.03 mg/l).
4. Discussion For H. influenzae the 32.2% of isolates producing b-lactamase remains essentially unchanged from the 33.3% recorded in the previous 1997–1998 study [5]. Since the first reports of b-lactamase production in H. influenzae in the mid-1970s, a number of surveillance studies undertaken in the United States have documented increases in this phenotype, primarily through acquisition of TEM-1 [10–15], to a peak prevalence of
M.E. Jones et al. / International Journal of Antimicrobial Agents 19 (2002) 119–123
36% recorded in 1994– 1995 [16]. The 33% reported in 1997–1998 studies [5,6,17] and the prevalence identified in the current study (32.2%) strongly suggest that for now at least, the prevalence of TEM-1 and ROB-1 carriage in this species in the USA, has leveled off. Recent data from outside of the USA, show the incidence of b-lactamase production in H. influenzae is very variable by country and often remains comparatively low [18], although whether or not the incidence has stabilised is less clear. Careful surveillance in this species will be necessary to track further increases in
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TEM-1 or ROB-1 carriage, evolution of these b-lactamases toward extended-spectrum activity, or acquisition of other extended-spectrum TEM or SHV b-lactamases, as has occurred in members of the Enterobacteriaceae. Bearing in mind the capacity of bacterial species to evolve further antibiotic resistance, this seems likely to occur [2]. Speculation that changes in b-lactam selective pressure may underlie the stabilization or reduction (in some locales) in the prevalence of b-lactamase in H. influenzae has yet to be substantiated. Although no BLNAR isolates were identified in our
Table 1 In vitro activity of tested antimicrobials against 2791 isolates of H. influenzae, according to the presence (n = 898) or absence (n =1893) of b-lactamase production Antimicrobial/ b-lactamase status
MIC range
MIC50
MIC90
Modal MIC
0.25 \16 0.25
\16 \16 1
0.12 \16 50.12
1 2 1
0.5 0.5 0.25
%Sa
%Ia
%Ra
67.5 0.4b 99.3
0.4 0.8 0.2
32.1 98.8 0.5c
99.9 99.8 99.9
– – –
0.1 0.2d 0.1
100 100 100
– – –
– – –
0 0 0.1
0 0 0 0.2e 0.1 0.2
(mg/l) Ampicillin All isolates b-Lactamase-positive b-Lactamase-negative
50.12–\16 50.12–\16 50.12–\16
Amoxycillin-cla6ulanate All isolates b-Lactamase-positive b-Lactamase-negative
50.03–8 50.03–8 50.03–8
0.5 1 0.25
Ceftriaxone All isolates b-Lactamase-positive b-Lactamase-negative
50.03–2 50.03–2 50.03–2
50.03 50.03 50.03
50.03 50.03 50.03
50.03 50.03 50.03
Cefuroxime All isolates b-Lactamase-positive b-Lactamase-negative
50.25–8 50.25–4 50.25–8
1 1 1
2 2 2
1 1 0.5
100 100 99.9
Azithromycin All isolates b-Lactamase-positive b-Lactamase-negative
50.06–\32 50.06–\32 50.06–\32
0.5 0.5 0.5
1 1 1
0.5 0.5 0.5
99.8 99.9 99.8
– – –
TMP-SMX All isolates b-Lactamase-positive b-Lactamase-negative
50.03–\4 50.03–\4 50.03–\4
0.25 0.25 0.25
0.25 0.25 0.25
76.7 73.4 78.3
7.7 7.1 8.0
Le6ofloxacin All isolates b-Lactamase-positive b-Lactamase-negative
50.008–8 50.008–0.5 50.008–8
0.015 0.015 0.015
0.015 0.015 0.015
0.015 0.015 0.015
100 100 99.9
– – –
– – 0.1f
Moxifloxacin All isolates b-Lactamase-positive b-Lactamase-negative
50.008–8 50.008–0.25 50.008–8
0.015 0.015 0.015
0.03 0.03 0.03
0.015 0.015 0.015
100 100 99.9
– – –
0 0 0.1f
a
\4 \4 \4
15.5 19.5 13.6
MICs interpreted using NCCLS M100-S9 breakpoints as susceptible (S), intermediate (I), or resistant (R) [7]. Four isolates (0.4%) were b-lactamase-positive and ampicillin-susceptible. c Ten isolates (0.5%) were b-lactamase-negative and ampicillin-resistant. d Two isolates (0.2%) were b-lactamase-positive and amoxycillin-clavulanate-resistant. e I or R breakpoints are not published for azithromycin [7]. Five isolates (0.2%) were nonsusceptible to azithromycin; one was b-lactamase-positive and four were b-lactamase-negative. f One isolate (0.04%) was nonsusceptible to both levofloxacin and moxifloxacin. Moxifloxacin MICs were interpreted using the recently defined 2001 NCCLS breakpoints for this compound (S, 51 mg/l) [8]. b
M.E. Jones et al. / International Journal of Antimicrobial Agents 19 (2002) 119–123
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Table 2 In vitro activity of test antimicrobials against 1249 isolates of M. catarrhalis, according to the presence (n = 1176) or absence (n= 73) of b-lactamase productiona Antimicrobial/b-lactamase status
MIC range
MIC50
MIC90
Modal MIC
(mg/l) Ampicillin All isolates b-Lactamase-positive b-Lactamase-negative
50.12–\16 50.12–\16 50.12–0.25
2 2 50.12
8 8 50.12
4 4 50.12
Amoxycillin-cla6ulanate All isolates b-Lactamase-positive b-Lactamase-negative
50.03–4 50.03–4 50.03–0.12
0.12 0.12 B = 0.03
0.25 0.25 B =0.03
0.25 0.25 50.03
Ceftriaxone All isolates b-Lactamase-positive b-Lactamase-negative
50.03–4 50.03–4 50.03–0.12
0.25 0.25 50.03
1 1 50.03
0.5 0.5 50.03
Cefuroxime All isolates b-Lactamase-positive b-Lactamase-negative
50.25–8 50.25–8 50.25–2
1 1 0.5
2 2 0.5
1 1 0.5
Azithromycin All isolates b-Lactamase-positive b-Lactamase-negative
50.06–2 50.06–2 50.06–50.12
50.06 50.06 50.06
50.06 50.06 50.06
50.06 50.06 50.06
TMP-SMX All isolates b-Lactamase-positive b-Lactamase-negative
50.03–\4 50.03–\4 50.03–2
0.12 0.12 0.12
0.5 0.5 0.25
0.12 0.25 0.12
Le6ofloxacin All isolates b-Lactamase-positive b-Lactamase-negative
50.008–1 50.008–1 50.008–0.06
0.03 0.03 0.03
0.03 0.03 0.06
0.03 0.03 0.03
Moxifloxacin All isolates b-Lactamase-positive b-Lactamase-negative
50.008–0.12 50.008–0.12 50.008–0.06
0.06 0.06 0.06
0.06 0.06 0.06
0.06 0.06 0.06
a
No NCCLS-defined breakpoints are available for M. catarrhalis [7,8].
preceding 1997– 1998 study [5], the 10 isolates detected here represent a similar prevalence rate to that reported in the United States in the 1994– 1995 respiratory season (0.5%) [16]. Three BLNARs were derived from the same laboratory in the state of Wisconsin and two isolates were from the same laboratory in New Jersey; these may represent clonal types in each setting, similar to a previous report [16]. Together these data suggests no increasing trend, but rather sporadic isolation of such organisms. Resistance to TMP-SMX was the only upward trend detected, increasing from 13.5% in 1997– 1998 to 15.5% in the current study. TMP-SMX nonsusceptibility (intermediate plus resistant isolates) also increased from 20.9% in the 1997–1998 study to 23.2% in the current study, which agrees with data from a contemporary surveillance study [17]. b-Lactamase-positive isolates
(73.4% susceptible) were also more likely to demonstrate TMP-SMX nonsusceptibility than b-lactamasenegative isolates (78.3% susceptible). Although there are few data describing this phenomenon directly in the published literature, a previous 1997–1998 surveillance study showed 75.3% susceptibility among b-lactamasepositive isolates and 81.0% susceptibility among b-lactamase-negative isolates, suggesting that this association had also not changed greatly. Similarly the 0.2% azithromycin resistance does not represent any increase over the three azithromycin-nonsusceptible isolates (all b-lactamase-negative) detected in our previous 1997–1998 study [5] or the two azithromycin-nonsusceptible isolates reported in the SENTRY study for 1997–1998 (b-lactamase status unknown) [17]. Although recent reports have identified isolates of M. catarrhalis and H. influenzae with reduced susceptibili-
M.E. Jones et al. / International Journal of Antimicrobial Agents 19 (2002) 119–123
ties to fluoroquinolones [19,20], the fluoroquinolone resistant isolate reported here is the first such isolate identified in our testing of more than 10 000 H. influenzae referred to our laboratory during the last three years from Europe and the United States (data not shown). Thus elevated MICs to moxifloxacin and levofloxacin in H. influenzae or M. catarrhalis represent extremely rare events. The 94.2% of M. catarrahlis b-lactamase-positive, were similar to the 92.4% reported in the 1997–1998 study [5] and in other US studies since 1996 [5,6,15,17] indicating that in this species also the incidence of b-lactamase has leveled off, albeit at \ 90%. Moxifloxacin showed little differentiation in vitro from levofloxacin against M. catarrhalis, the compounds having at most a two-fold difference in MIC90. For H. influenzae and M. catarrhalis in the USA at least, there seems to be no upward trend in resistance. The longitudinal aspect of this surveillance programme will play an important role in detecting changes in the susceptibility of important respiratory tract pathogens to fluoroquinolones and other antimicrobial agents.
Acknowledgements We thank Bayer Corporation for providing funding for this study under the auspices of the LIBRA Surveillance initiative. We express our appreciation to the many microbiologists and other personnel in each of the participating laboratories, without whose commitment these studies would not be possible.
References [1] Bartlett JG, Mundy LM. Community-acquired pneumonia. New Engl J Med 1995;333:1619 –24. [2] Livermore DM. b-Lactamases in laboratory and clinical practice. Clin Micro Rev 1995;8:557 – 84. [3] Bootsma HJ, van Dijk H, Verhoef J, Fleer A, Mooi FR. Molecular characterization of the BRO b-lactamase of Moraxella (Branhamella) catarrhalis. Antimicrob Agents Chemother 1996;40:966 –72. [4] Daum RS, Murphey-Corb M, Shapira E, Dipp S. Epidemiology of rob b-lactamase among ampicillin-resistant Haemophilus influenzae isolates in the United States. J Infect Dis 1988;157:450 – 5. [5] Jones ME, Staples AM, Critchley I, et al. Benchmarking the in vitro activity of moxifloxacin and comparator agents against recent respiratory isolates from 377 medical centers throughout the United States. Antimicrob Agents Chemother 2000;44:2645 – 52. [6] Thornsberry C, Jones ME, Hickey M, Mauriz Y, Kahn J, Sahm DF. Resistance surveillance of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the United States, 1997 –1998. J Antimicrob Chemother 1999;44:749 – 59.
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[7] National Committee for Clinical Laboratory Standards. Performance Standards for Antimicrobial Susceptibility Testing, Ninth Informational Supplement. Document M100-S9 NCCLS. Wayne, PA, 1999. [8] National Committee for Clinical Laboratory Standards. Performance Standards for Antimicrobial Susceptibility Testing, Eleventh Informational Supplement. Document M100-S11 NCCLS. Wayne, PA, 2001. [9] Jones ME, Staples AM, Critchley I, et al. Benchmarking the in vitro activity of moxifloxacin against recent clinical isolates of Streptococcus pneumoniae, Moraxella catarrhalis and H. influenzae: a European multi-center study. Diagn Microbiol Infect Dis 2000;37:201 – 11. [10] Barry AL, Pfaller MA, Fuchs PC, Packer RR. In vitro activities of 12 orally administered antimicrobial agents against four species of bacterial respiratory pathogens from US medical centers in 1992 and 1993. Antimicrob Agents Chemother 1994;38:2419 – 25. [11] Doern GV, Jorgensen JH, Thornsberry C, Preston DA. The Haemophilus Surveillance Group Prevalence of the antimicrobial resistance among clinical isolates of Haemophilus influenzae: a collaborative study. Diagn Microbiol Infect Dis. 1986; 4: 95 – 107. [12] Doern GV, Jorgensen JH, Thornsberry C, et al. National collaborative study of the prevalence of antimicrobial resistance among clinical isolates of Haemophilus influenzae. Antimicrob Agents Chemother 1998;32:180 – 5. [13] Jorgenson JH. Update on the mechanisms and prevalence of antimicrobial resistance in Haemophilus influenzae. Clin Infect Dis 1992;14:1119 – 23. [14] Rittenhouse SP, Miller L, Kaplan RL, Mosely GH, Poupard JA. A survey of b-lactamase-producing Haemophilus influenzae: an evaluation of 5750 isolates. Diagn Microbiol Infect Dis 1995;21:223 – 5. [15] Thornsberry C, Ogilvie P, Kahn J, Mauriz Y, the Laboratory Investigator Group. Surveillance of antimicrobial resistance in Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the United States in the 1996 – 1997 respiratory season. Diagn Microbiol Infect Dis 1997;29: 249 – 257. [16] Jones RN, Jacobs MR, Washington JA, Pfaller MA. A 1994 –95 surveillance of Haemophilus influenzae susceptibility to ten orally administered agents. Diagn Microbiol Infect Dis 1997;27:75 –83. [17] Doern GV, Jones RN, Pfaller MA, Kugler K, the SENTRY Participants Group. Haemophilus influenzae and Moraxella catarrhalis from patients with community-acquired respiratory tract infections: antimicrobial susceptibility patterns from the SENTRY Antimicrobial Surveillance Program (United States and Canada, 1997), Antimicrob Agents Chemother 2000;43: 385 – 389 [18] Sahm DF, Jones ME, Hickey ML, Diakun DR, Mani S, Thornsberry C. Resistance surveillance of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis isolated in Asia and Europe, 1997 – 1998. J Antimicrob Chemother 2000;45:457 – 66. [19] Biedenbach DJ, Jones RN. Fluoroquinolone-resistant Haemophilus influenzae: frequency of occurrence and analysis of confirmed strains in the SENTRY Antimicrobial Surveillance Program (North and Latin America). Diagn Microbiol Infect Dis 2000;36:255 – 9. [20] DiPersio JR, Jones RN, Barrett T, Doern GV, Pfaller MA. Fluoroquinolone-resistant Moraxella catarrhalis in a patient with pneumonia: report from the SENTRY Antimicrobial Surveillance Program (1998). Diagn Microbiol Infect Dis 1998;32:131 – 5.