High Prevalence of Metallo-β-lactamase Among Carbapenem-resistant Klebsiella Pneumoniae in a Teaching Hospital in China

The aim of this study was to characterize the carbapenemases in carbapenem-resistant Klebsiella pneumoniae (CR-KP) from a Chinese teaching hospital. A total of 40 CR-KPs were screened for the presence of carbapenemases. Minimum inhibitory concentrations were determined by agar dilution. The modified Hodge test was used for the detection of carbapenemase production. Carbapenemase, extended-spectrum β-lactamase, and AmpC genes were detected using polymerase chain reaction (PCR) and sequencing. A conjugation test was performed using a broth culture mating method, transferred plasmids were typed by PCR-based replicon typing, and clonal relatedness was investigated by enterobacterial repetitive intergenic consensus sequences PCR (ERIC-PCR) and multilocus sequence typing (MLST). The results revealed that modified Hodge test was positive for 28 CR-KPs, and CR-KPs exhibited high resistance rates against various antibiotics, except colistin (5.0%) and tigecycline (22.5%). ERIC and MLST profiles showed no clonal outbreak. PCR demonstrated a high prevalence rate (55.0%, 22/40) of metallo-β-lactamases (MBLs) in CR-KPs. IMP-4, IMP-8, NDM-1, and KPC-2 were identified in 14 (35.0%), 7 (17.5%), 2 (5.0%), and 7 (17.5%) isolates, respectively. Notably, 2 CR-KPs coproduced 2 carbapenemases simultaneously (IMP-8/NDM-1 and IMP-4/KPC-2). In vitro transfer of carbapenem resistance was successful for 11 MBL-producing CR-KPs. The extended spectrum β-lactamase genes were detected in 30 (75.0%) of these CR-KPs. To the best of our knowledge, this is the first report focusing on carbapenem resistance in K. pneumoniae due to metalloenzymes in China. Screening and surveillance of MBLs in Enterobacteriaceae is urgently needed in this region to control and prevent the spread of these resistance determinants.