Characterization of carbapenem-resistant Acinetobacter baumannii ST540 and Klebsiella pneumoniae ST2237 isolates in a pneumonia case from China

Aims This study aimed to characterize the chromosome and plasmid sequences, and determine the transferability of plasmids in carbapenem-resistance Acinetobacter baumannii DD520 and Klebsiella pneumoniae DD521 isolates from the same patient who was co-infected in a hospital in China. Methods and Results Both isolates DD520 and DD521 exhibited multidrug resistance phenotype, especially the former isolate which was resistant to nine classes of antimicrobials including carbapenems, quinolones, penicillins, cephalosporins, tetracyclines, phenicols, fosfomycins, sulfanilamides and aminoglycosides. Carbapenem resistance genes of bla(OXA-23) and bla(OXA-66) were identified on the chromosome of A. baumannii DD520, and bla(KPC-2) was found in the plasmid pDD521.2 from K. pneumoniae DD521. Phylogenetic analysis revealed that A. baumannii DD520 belonged to the ST540 clone, and K. pneumoniae DD521 belonged to the ST2237 clone. Plasmid analysis suggested that bla(KPC-2) was embedded into plasmid pDD521.2, which might be resulted from IS26- and Tn1721-mediated transposition. Plasmid pDD521.2 carrying bla(KPC-2) successfully transferred from K. pneumoniae DD521 into Escherichia coli C600, and carbapenems resistance also transferred in the conjugation. Conclusions To our knowledge, it was the first report of A. baumannii ST540 and K. pneumoniae ST2237 in the same patient in China. Both these two isolates exhibited resistance to carbapenem, which was likely to have resulted from carbapenem-resistance genes bla(OXA-23)-bla(OXA-66) on the chromosome of A. baumannii ST540, and bla(KPC-2) in the plasmid of K. pneumoniae ST2237. Significance and Impact of the Study Our study highlighted that effective measures were urgent to prevent and control the co-infection caused by two or more carbapenem-resistance pathogens in the same patient.