Isolation of Metronidazole-Resistant
            <i>Bacteroides fragilis</i>
            Carrying the
            <i>nimA</i>
            Nitroreductase Gene from a Patient in Washington State

Schapiro, Jeffrey M.; Gupta, Rachna; Stefansson, Eric; Fang, Ferric C.; Limaye, Ajit P.

doi:10.1128/jcm.42.9.4127-4129.2004

Cited by 45 publications

(30 citation statements)

References 25 publications

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“…For example, reported resistance rates vary widely for clindamycin (15 to 44%), cefotetan (13 to 94%), and cefoxitin (3.5 to 41.5%) (63). Resistance to even the most active drugs, such as imipenem, piperacillin-tazobactam, ampicillin-sulbactam, and metronidazole, is found in occasional strains (201,236,290). Frequently, the other species in the B. fragilis group are more resistant than B. fragilis to many antibiotics.…”

Section: Susceptibility Patterns Of Bacteroidesmentioning

confidence: 99%

Bacteroides: the Good, the Bad, and the Nitty-Gritty

2007

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SUMMARY Summary: Bacteroides species are significant clinical pathogens and are found in most anaerobic infections, with an associated mortality of more than 19%. The bacteria maintain a complex and generally beneficial relationship with the host when retained in the gut, but when they escape this environment they can cause significant pathology, including bacteremia and abscess formation in multiple body sites. Genomic and proteomic analyses have vastly added to our understanding of the manner in which Bacteroides species adapt to, and thrive in, the human gut. A few examples are (i) complex systems to sense and adapt to nutrient availability, (ii) multiple pump systems to expel toxic substances, and (iii) the ability to influence the host immune system so that it controls other (competing) pathogens. B. fragilis, which accounts for only 0.5% of the human colonic flora, is the most commonly isolated anaerobic pathogen due, in part, to its potent virulence factors. Species of the genus Bacteroides have the most antibiotic resistance mechanisms and the highest resistance rates of all anaerobic pathogens. Clinically, Bacteroides species have exhibited increasing resistance to many antibiotics, including cefoxitin, clindamycin, metronidazole, carbapenems, and fluoroquinolones (e.g., gatifloxacin, levofloxacin, and moxifloxacin).

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Section: Susceptibility Patterns Of Bacteroidesmentioning

confidence: 99%

Bacteroides: the Good, the Bad, and the Nitty-Gritty

2007

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“…Resistance to even the most active drugs, such as imipenem, piperacillin-tazobactam, ampicillin-sulbactam, and metronidazole, has been reported (23,25,26). Furthermore, there are clear differences in the geographic patterns of resistance and even differences in resistance patterns in different hospitals in a single city, perhaps due in part to the variability in prescribing patterns (27).…”

Section: Susceptibilty Testing Of Anaerobic Bacteriamentioning

confidence: 99%

Antianaerobic Antimicrobials: Spectrum and Susceptibility Testing

2013

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SUMMARY Susceptibility testing of anaerobic bacteria recovered from selected cases can influence the choice of antimicrobial therapy. The Clinical and Laboratory Standards Institute (CLSI) has standardized many laboratory procedures, including anaerobic susceptibility testing (AST), and has published documents for AST. The standardization of testing methods by the CLSI allows comparisons of resistance trends among various laboratories. Susceptibility testing should be performed on organisms recovered from sterile body sites, those that are isolated in pure culture, or those that are clinically important and have variable or unique susceptibility patterns. Organisms that should be considered for individual isolate testing include highly virulent pathogens for which susceptibility cannot be predicted, such as Bacteroides , Prevotella , Fusobacterium , and Clostridium spp.; Bilophila wadsworthia ; and Sutterella wadsworthensis . This review describes the current methods for AST in research and reference laboratories. These methods include the use of agar dilution, broth microdilution, Etest, and the spiral gradient endpoint system. The antimicrobials potentially effective against anaerobic bacteria include beta-lactams, combinations of beta-lactams and beta-lactamase inhibitors, metronidazole, chloramphenicol, clindamycin, macrolides, tetracyclines, and fluoroquinolones. The spectrum of efficacy, antimicrobial resistance mechanisms, and resistance patterns against these agents are described.

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“…This either indicates the presence of an unknown IS element not detected by the primers used or puts into question the notion It is important to acknowledge the emerging resistance to metronidazole within the B. fragilis group. Clinical failures following metronidazole treatment due to Bacteroides strains with reduced susceptibility have been reported (7,18,20). Different mechanisms of resistance have been proposed (4,6), and the importance of nim genes has been reported by several groups (3,10,25).…”

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confidence: 99%

Inducible Metronidazole Resistance and nim Genes in Clinical Bacteroides fragilis Group Isolates

Löfmark

Fang

Hedberg

et al. 2005

Antimicrob Agents Chemother

109

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Nitroimidazole resistance (nim) genes were detected in 2% of 1,502 clinical Bacteroides fragilis group strains isolated from 19 European countries, and a novel nim gene was identified. High metronidazole resistance could be induced in nim-positive strains, which emphasizes the importance of acknowledging metronidazole resistance in the clinical setting.Anaerobic infections are common and can cause diseases associated with severe morbidity but are easily overlooked in the clinical setting. Bacteroides fragilis group species are opportunistic pathogens that constitute a dominating bacterial group in the normal intestinal microflora. In particular, B. fragilis is among the most clinically relevant anaerobic species. Interspecies lateral transfer of resistance genes among anaerobes has been shown for several clinically important antimicrobial agents such as beta-lactam agents, clindamycin, tetracycline, and metronidazole (3,17,19,22,24). Metronidazole, a 5-nitroimidazole agent, is particularly useful against Bacteroides spp. that tend to be resistant to a wide range of antimicrobial agents (1, 2). Although the rate of resistance remains low, at Ͻ1%, metronidazole-resistant organisms are beginning to emerge (8,11,15,16,21). Five nitroimidazole resistance genes, nimA to -E, have been identified that confer reduced susceptibility to 5-nitroimidazole antibiotics on species of the B. fragilis group (10,23,26). The proposed resistance mechanism conferred by the nim genes is that they encode a 5-nitroimidazole reductase (4). Four of the nim genes have been shown to be associated with different mobile insertion sequence (IS) elements flanked by inverted repeats (10, 25). There is strong evidence that these IS elements carry regulatory signals for expression of certain resistance genes, including the nim genes (10,13,15,21,25).A total number of 1,502 clinical B. fragilis group isolates were surveyed for the prevalence and distribution of various nim genes. The strains, originating from a previous surveillance study of antimicrobial susceptibility including 19 European countries (11), were collected during 1999 to 2001. The different Bacteroides species had previously been identified by conventional biochemical tests, and the MIC of metronidazole was determined by the agar dilution method as recommended by the National Committee for Clinical Laboratory Standards (NCCLS) (14).The strains were screened for nim genes by PCR with specific primers (26) and cleaved with the restriction enzyme Hsp92II for determination of the nim type. In addition, HpaII and TacI were used for selected strains. One strain (HUN19) was sequenced after it was found to have unique and novel restriction fragment length polymorphism (RFLP) patterns. All nim-positive strains were further investigated by PCR for associated IS elements and the locations of the elements with respect to the nim gene (17) with specific primers newly designed or previously described (10).Twelve nim-positive clinical strains for which the initial MICs were relatively low (0.25 to...

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Isolation of Metronidazole-Resistant Bacteroides fragilis Carrying the nimA Nitroreductase Gene from a Patient in Washington State

Abstract: Members of the

Cited by 45 publications

References 25 publications

Bacteroides: the Good, the Bad, and the Nitty-Gritty

Bacteroides: the Good, the Bad, and the Nitty-Gritty

Antianaerobic Antimicrobials: Spectrum and Susceptibility Testing

Inducible Metronidazole Resistance and nim Genes in Clinical Bacteroides fragilis Group Isolates

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