Nosocomial Outbreak of Extensively Drug-Resistant Acinetobacter baumannii Isolates Containing Carried on a Plasmid.

Carbapenem antibiotics are among the mainstays for treating infections caused by , especially in the Northwest United States, where carbapenem-resistant remains relatively rare. However, between June 2012 and October 2014, an outbreak of carbapenem-resistant occurred in 16 patients from five health care facilities in the state of Oregon. All isolates were defined as extensively drug resistant. Multilocus sequence typing revealed that the isolates belonged to sequence type 2 (international clone 2 [IC2]) and were >95% similar as determined by repetitive-sequence-based PCR analysis. Multiplex PCR revealed the presence of a carbapenemase gene, later identified as Whole-genome sequencing of all isolates revealed a well-supported separate branch within a global phylogeny. Pacific Biosciences (PacBio) SMRT sequencing was also performed on one isolate to gain insight into the genetic location of the carbapenem resistance gene. We discovered that , flanked on either side by IS elements in opposite orientations, was carried on a 15,198-bp plasmid designated pORAB01-3 and was present in all 16 isolates. The plasmid also contained genes encoding a TonB-dependent receptor, septicolysin, a type IV secretory pathway (VirD4 component, TraG/TraD family) ATPase, an integrase, a RepB family plasmid DNA replication initiator protein, an alpha/beta hydrolase, and a BrnT/BrnA type II toxin-antitoxin system. This is the first reported outbreak in the northwestern United States associated with this carbapenemase. Particularly worrisome is that was carried on a plasmid and found in the most prominent worldwide clonal group IC2, potentially giving pORAB01-3 great capacity for future widespread dissemination.