nim gene-independent metronidazole-resistant Bacteroides fragilis in surgical site infections

Abstract

Background: is the most common anaerobic pathogen isolated from surgical site infections (SSIs). Metronidazole resistance is increasing and the mechanisms of resistance are not clear in some isolates. The aim of the present study was to investigate the metronidazole susceptibility prevalence, and detect genes in isolates from SSIs. Methods: This study included 100 surgery patients with signs and symptoms indicative of SSIs. Syringe aspiration of the infected site was used to collect specimens. All specimens were cultured on BBA (Brucella blood agar), KVLB (kanamycin-vancomycin laked blood), and BBE (Bacteroides bile esculin) agar. The MIC (minimum inhibitory concentration) of metronidazole was determined by the agar dilution method according to the Clinical and Laboratory Standard Institute (CLSI). Then the PCR method was used to determine the presence of the gene.Results: In the present study, 26 were isolated from 100 SSIs specimens. Eight isolates were metronidazole resistant; the metronidazole MIC was 32 µg/mL for 7 isolates and 64 µg/mL for one isolate. All isolates were gene negative. Conclusion: The emergence of metronidazole-resistant limits the application of this drug for treatment and prophylaxis of SSIs. Thus, rapid identification of metronidazole-resistant is essential to restrict inappropriate, superfluous administration. In spite of various metronidazole resistance mechanisms other than that depending on the gene, detection of by PCR is unsuitable for identifying res isolates. Therefore, phenotypic methods are better to screen for and identify metronidazole-resistant .

Keywords

• Bacteroides fragilis
• surgical site infections
• metronidazole
• minimum inhibitory concentration
• nim gene