Bacteroides fragilisis 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 ofB. fragilis cfiA-positive isolates. The second purpose was to investigate the carbapenemase activity inB. fragilisstrains by Carba NP test. In the study, 5.2% ofB. fragilisisolates are phenotypically resistant to meropenem. ThecfiAgene was identified in 6.1% ofB. fragilisisolates. The MICs of meropenem were significantly higher incfiA-positive strains. The presence of thecfiA gene along with the IS1186was detected in oneB. fragilisstrain which was resistant to meropenem (MIC 1.5 mg/L). The Carba NP test results were positive for all thecfiA-positive strains, including those susceptible to carbapenems based on their MIC values. A review of the literature revealed that the rate ofB. fragiliswith thecfiA 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 thecfiA gene detection inB. fragilisisolates. The positive result obtained is of greater clinical importance than the detection of the genecfiA.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00430-023-00765-w.