Background: Carbapenems are used to treat severe infections caused by multi-drug-resistant organisms, however, the emergence of carbapenem-resistant bacterial isolates is becoming an increasing therapeutic challenge. Since the first Klebsiella (K.) pneumoniae carbapenemase (KPC)-producing K. pneumoniae was reported in 2001, KPC-producing isolates have been found increasingly, specially in Enterobacteriaceae. The aim of this study was to characterize the mechanisms of a carbapenem-resistant Proteus (P.) mirabilis.
Methods: A carbapenem-resistant P. mirabilis isolate was recovered from pleural drainage fluid of a patient admitted to surgical intensive care unit. Antimicrobial susceptibility testing of the isolate was performed by disk diffusion according to Clinical and Laboratory Standards Institute guidelines, and subsequent minimal inhibitory concentrations were determined with the E-test. Amplification of the bla(KPC) gene generated a positive band and the PCR products were sequenced subsequently. The plasmid of the isolate was extracted and was successfully transformed into Escherichia (E.) coli DH5α.
Results: The P. mirabilis isolate was resistant to all detected antimicrobial agents except tigecycline. KPC-2 was confirmed by DNA sequence analysis. The transformant E. coli was resistant to carbapenems. Further study demonstrated that upstream and downstream regions of bla(KPC-2) were identical to that observed in K. pneumoniae submitted to GenBank from China in 2007.
Conclusion: Carbapenem resistance in the P. mirabilis isolate in this study is mainly due to production of KPC-2.