Phenotypic and genotypic identification of carbapenem resistance in Bacteroides fragilis clinical strains

Bacteroides fragilis is an important etiological agent of serious infections in humans. Rapid methods, readily adaptable to use in medical laboratories, are needed to detect antibiotic resistance and decrease the likelihood of therapy failure. The aim of this study was to determine the prevalence of B. fragilis cfi A-positive isolates. The second purpose was to investigate the carbapenemase activity in B. fragilis strains by Carba NP test. In the study, 5.2% of B. fragilis isolates are phenotypically resistant to meropenem. The cfiA gene was identified in 6.1% of B. fragilis isolates. The MICs of meropenem were significantly higher in cfi A-positive strains. The presence of the cfi A gene along with the IS 1186 was detected in one B. fragilis strain which was resistant to meropenem (MIC 1.5 mg/L). The Carba NP test results were positive for all the cfi A-positive strains, including those susceptible to carbapenems based on their MIC values. A review of the literature revealed that the rate of B. fragilis with the cfi A gene varies from 7.6 to 38.9% worldwide. Presented results are in line with the other European studies. Phenotypic testing with the Carba NP test, it seems to be a viable alternative for the cfi A gene detection in B. fragilis isolates. The positive result obtained is of greater clinical importance than the detection of the gene cfi A.