Features of infections due to Klebsiella pneumoniae carbapenemase-producing Escherichia coli: emergence of sequence type 131

Abstract

Background: Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae has become endemic in many US hospitals. On the other hand, KPC-producing Escherichia coli remains rare.

Methods: We studied infection or colonization due to KPC-producing E. coli identified at our hospital between September 2008 and February 2011. A case-control study was conducted to document clinical features associated with this organism. Susceptibility testing, sequencing of β-lactamase genes, pulsed-field gel electrophoresis, multilocus sequence typing, and plasmid analysis were performed for characterization of the isolates.

Results: Thirteen patients with KPC-producing E. coli were identified. The patients had multiple comorbid conditions and were in hospital for variable periods of time before KPC-producing E. coli was identified. The presence of liver diseases was independently associated with recovery of KPC-producing E. coli when compared with extended-spectrum β-lactamase-producing E. coli. The isolates showed variable susceptibility to carbapenems. Seven isolates belonged to sequence type (ST) 131, which is the international epidemic, multidrug-resistant clone, but their plasmid profiles were diverse. KPC-producing organisms other than E. coli were isolated within 1 month from 5 of the patients. The KPC-encoding plasmids were highly related in 3 of them, suggesting the occurrence of their interspecies transfer.

Conclusions: KPC-producing E. coli infections occur in severely ill patients who are admitted to the hospital. Acquisition of the KPC-encoding plasmids by the ST 131 clone, reported here for the first time to our knowledge in the United States, seems to represent multiple independent events. These plasmids are often shared between E. coli and other species.

Figure 1.

Pulsed-field gel electrophoresis profiles, phylogenetic groups, and sequence types of 13 Klebsiella pneumoniae carbapenemase–producing Escherichia coli isolates.

Figure 2.

A, Plasmid profiles of 13 Klebsiella pneumoniae carbapenemase (KPC)–producing Escherichia coli isolates using restriction enzyme EcoRI. B, DNA hybridization using a probe specific to the KPC gene.

Figure 3.

Plasmid profiles of Klebsiella pneumoniae carbapenemase–producing Escherichia coli–non–E. coli pairs from 5 cases using restriction enzyme HpaI. Lanes 1 and 2, E. coli and K. pneumoniae from case 1; lanes 3, 4, and 5, E. coli, Enterobacter cloacae, and Klebsiella oxytoca from case 4; lanes 6 and 7, E. coli and Serratia marcescens from case 9; lanes 8 and 9, E. coli and K. pneumoniae from case 12; lanes 10 and 11, E. coli and K. pneumoniae from case 13.