Molecular characterisation of multidrug-resistant Bacteroides isolates from Hungarian clinical samples

Abstract

Objectives: Members of the Bacteroides fragilis group are the most important components of the normal human gut microbiota, however these bacteria can also cause severe infections. Due to frequent use of antibiotics, the spread of multidrug-resistant (MDR) strains is a real threat worldwide.

Methods: In a multicentre study, 400 Bacteroides isolates from five Hungarian microbiology laboratories were cultured and were identified by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). Minimum inhibitory concentrations (MICs) of ten antibiotics were determined by the agar dilution method and were evaluated according to EUCAST or CLSI breakpoints.

Results: Six MDR strains were found and their antibiotic resistance genes were investigated by molecular methods The DNA amplicon of B. fragilis SZ38 was sequenced to search for a mutation in the gyrA gene. Among the six MDR isolates, one cfiA-, two cepA-, three cfxA-, two ermG-, six tetQ-, three tetX- and two bexA-positive strains were found. None of the MDR isolates harboured cepA, nim, ermB or tetX1 genes.

Conclusions: In the past 12 years, only a few cases of MDR Bacteroides infections have been reported. Within a comprehensive multicentre survey, we demonstrated the relatively high prevalence of MDR strains isolated in one centre with five isolates as well as one isolate from another centre during a relatively short period of time. This study highlights the importance of antimicrobial susceptibility testing and surveillance among B. fragilis group isolates.

Keywords: Agar dilution; Antibiotic resistance genes; Bacteroides; Multidrug resistance; RT-PCR; Sequencing.