Prevalence of nim-genes in Bacteroides fragilis group in Belgium
Abstract number: P2039
Wybo I., Soetens O., Van Doorslaer K., Piérard D., Lauwers S.
Objectives: Metronidazole resistance among anaerobic Gram-negative bacilli remains low and below 1 percent in species of the B. fragilis group  in Belgium. This resistance has been shown to be associated with nitroimidazole (nim) resistance genes. The presence of a nim gene does not necessarily confer metronidazole resistance as nim genes have been detected in B. fragilis group isolates that have a MIC below 16 mg/L and are therefore considered susceptible. High level metronidazole resistance can however be induced in nim-gene-carrying B. fragilis group strains. The purpose of this study was to determine the prevalence of nim genes in isolates belonging to the B. fragilis group isolated in Belgium.
Methods: From October 2003 to February 2005 238 B. fragilis group strains were collected in 9 Belgian hospitals . Metronidazole susceptibility was determined by Etest®. The strains were screened for nim genes by PCR with specific primers. When positive, sequencing of the PCR product was performed.
Results: Nim genes were detected in 5/135 (3.7%) of B. fragilis strains and 1/103 (0.97%) of other B. fragilis group strains. They were not found in isolates with a MIC less than 2 mg/L. Of isolates with MIC higher than 1 mg/L 62.5% (5/8) B. fragilis strains and 20% (1/5) other B. fragilis group strains were nim gene positive. The only metronidazole resistant B. fragilis isolate (MIC=32 mg/L) carried the nimA gene. All other nim-gene carrying B. fragilis isolates (2 nimD, 1 nimB and 1 nimE) were susceptible, but with relatively high MIC values (3 with MIC=4 mg/L and 1 with MIC=2 mg/L). In the other B. fragilis group strains one B. vulgatus isolate carried the nimD gene and had a MIC of 4 mg/L. The only metronidazole resistant strain (MIC=32 mg/L) in this group was a nim gene negative B. thetaiotaomicron isolate. This either suggests the presence of another resistance mechanism in this strain or the presence of a nim gene, that was not detected with the PCR assay used.
Conclusion: Nitroimidazole (nim) resistance genes were present in 2.5%B. fragilis group clinical isolates in Belgium and associated with higher MIC values (range: 232 mg/L). The prevalence of nim-genes in B. fragilis group clinical isolates in Belgium is comparable with the prevalence other European countries.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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