Both clades of the epidemic KPC-producing Klebsiella pneumoniae clone ST258 share a modified galactan O-antigen type.
After the first report in May 2008, the National Reference Center for Susceptibility Testing confirmed 113 cases of infection or colonization by KPC-producing members of the family Enterobacteriaceae in Poland by the end of 2009. The vast majority of patients were found in 18 hospitals; three patients were diagnosed at outpatient clinics. Most of the institutions were in the Warsaw area, including three hospitals with the highest numbers of cases. When available, the data on previous hospitalizations often indicated that these hospitals were the probable acquisition sites; one patient arrived from New York. The group of 119 unique isolates consisted of Klebsiella pneumoniae (n = 114), followed by Klebsiella oxytoca (n = 3), and Escherichia coli (n = 2). The K. pneumoniae isolates were dominated by the clone sequence type 258 (ST258) (n = 111); others were ST11 and ST23. The ST258 group was heterogeneous, with 28 pulsed-field gel electrophoresis (PFGE) subtypes, ∼25 plasmid profiles, and nine β-lactamase patterns differing by KPC variants (KPC-2 mainly), and SHV-12, CTX-M-3, and TEM-1-like enzymes. Plasmids carrying bla(KPC) genes varied in size (~48 to 250 kb), structure, and conjugation potential. Transferable IncFII(K) plasmids of ~110 to 160 kb, probably pKpQIL or its derivatives, were observed in all K. pneumoniae clones and in K. oxytoca. Also prevalent were nontypeable pETKp50-like plasmids of ~50 kb, found in K. pneumoniae ST258 and E. coli isolates (ST93 and ST224). Two K. pneumoniae-E. coli pairs from single patients might represent the in vivo transfer of such plasmids. The striking diversity of KPC producers at the early stage of dissemination could result from several introductions of these bacteria into the country, their multidirectional evolution during clonal spread, and transfer of the plasmids.