Sequence-Based Epidemiology of an OXA-48 Plasmid during Hospital Outbreak

Abstract

A large OXA-48 outbreak in The Netherlands involved the spread of OXA-48-producing Enterobacteriaceae among at least 118 patients, suggesting horizontal transfer of this resistance gene through one or more plasmids. Elucidating transmission dynamics of resistance plasmids is hampered by the low resolution of classic typing methods. This study aimed to investigate the molecular epidemiology of plasmids carrying the OXA-48 carbapenemase using a next-generation sequencing approach. A total of 68 OXA-48-producing Enterobacteriaceae isolates collected from the hospital outbreak, as well as 22 non-outbreak-related OXA-48-producing Enterobacteriaceae isolates from The Netherlands, Libya, and Turkey were selected. Plasmids were sequenced using the Illumina MiSeq platform, and read sets were assembled and analyzed. In all plasmids, bla OXA-48 was embedded in transposon Tn1999.2 and located on a ca. 62-kb IncL/M conjugative plasmid in 14 different species. There were a maximum of 2 single nucleotide polymorphisms (SNPs) between the core sequence alignment of all plasmids. Closely related sequence variants of this plasmid were detected in nonoutbreak isolates from The Netherlands and other countries. Thirty-one of 89 OXA-48producing isolates also harbored bla CTX-M-15, which was not located on the bla OXA-48carrying plasmid. Sequencing of four plasmids harboring bla CTX-M-15 revealed extensive plasmid heterogeneity. A ca. 62-kb plasmid was responsible for the OXA-48 outbreak in a Dutch hospital. Our findings provide strong evidence for both within-host interspecies and between-host dissemination of plasmid-based OXA-48 during a nosocomial outbreak. These findings exemplify the complex epidemiology of carbapenemase-producing Enterobacteriaceae (CPE).