Frequency of resistance to moxifloxacin and cefoxitin in clinical isolates of Bacteroides fragilis in Tabriz

Abstract

Bacteroides fragilis is the most common opportunistic pathogen inhabiting the human intestine. This pathogen causes severe infections. Antibiotic resistance is an important issue in the treatment of infections caused by B. fragilis. The aim of present study was to determine the frequency of resistance to moxifloxacin and cefoxitin in clinical isolates of B. fragilis and their typing by molecular method. Methods: Forty-eight B. fragilis isolates were isolated from 200 collected clinical specimens. The minimum inhibitory concentration (MIC) of moxifloxacin and cefoxitin was determined using the microbroth dilution method. The antibiotic resistance genes of gyrA, parC, and cftxA were investigated by PCR method. To investigate the possibility of mutation in gyrA and parC gene, the PCR product of moxifloxacin resistant isolates without resistance by efflux pumpe after purification was compared with the sequences in the databases. The strains of B. fragilis were analyzed by RAPD-PCR method. Results: Among 200 samples, including diabetic foot ulcers, stool, abscesses, surgical site wounds, wound secretions collected from Tabriz hospitals, 48 isolates of B. fragilis were isolated. Resistance to cefoxitin and moxifloxacin was observed in 45.8% and 60.4% of isolates, respectively. The genes of cftxA, gyrA mutation, parC mutation were detected in 31.3%, 8.3% and 4.2% respectively. RAPD-PCR results revealed, 48 B. fragilis isolates were belonged into 5 clusters. Efflux pump-mediated resistance was detected in 41.7% of cefoxitin-resistant isolates. Resistance to moxifloxacin due to the efflux pump was detected in 54.2% of isolates resistant to this antibiotic.