Genome sequencing and characterization of an XDR ST111 serotype O12 hospital outbreak strain of Pseudomonas aeruginosa

A series of extensively drug-resistant (XDR) isolates of Pseudomonas aeruginosa from two outbreaks in UK hospitals were characterized by whole genome sequencing (WGS). Although these isolates were resistant to antibiotics other than colistin, we confirmed that they are still sensitive to disinfectants. The sequencing confirmed that isolates in the larger outbreak were serotype O12 and further revealed that they belonged to the ST111 sequence type which is a major epidemic strain of P. aeruginosa throughout Europe. As this is the first reported sequence of an ST111 strain, the genome was examined in depth, focusing particularly on antibiotic resistance and potential virulence genes, and on the reported regions of genome plasticity. High degrees of sequence similarity were discovered between outbreak isolates collected from recently infected patients, sinks, an isolate from the sewer and an historical isolate, suggesting that the ST111 strain has been endemic in the hospital for many years. The ability to translate easily from outbreak investigation to detailed genome biology using the same data demonstrates the flexibility of WGS application in a clinical setting.