The molecular epidemiology of Pseudomonas aeruginosa bloodstream infection isolates in a non-outbreak setting.

The molecular epidemiology of Pseudomonas aeruginosa bloodstream infection (BSI) isolates has received limited attention. This study aims to characterise the molecular relationship of P. aeruginosa bloodstream infection isolates in the non-outbreak setting at a single tertiary healthcare facility. P. aeruginosa BSI isolates from patients who were admitted to the Royal Brisbane and Women's Hospital over a 13 month period from November 2009 were identified retrospectively from the Pathology Queensland Clinical and Scientific Information System. The isolates were typed by iPLEX MassARRAY MALDI-TOF MS genotyping. The Diversilab® automated rapid strain typing platform (bioMérieux Australia Pty Ltd) was used to assess the genotypic relationships between study isolates that showed indistinguishable iPLEX20SNP profiles. Clinical data was also collected retrospectively from patient notes. Fifty three P. aeruginosa BSI episodes were available for study. Thirty five different clones or clonal complexes were identified by iPLEX MassARRAY MALDI-TOF MS genotyping. Seventeen BSI isolates with indistinguishable iPLEX20SNP profiles underwent further Diversilab® genotyping and were found to belong to a further 13 different genotypes. There was no relationship between clonality and acquisition type, source of infection or length of stay in the setting of hospital acquired infection. The non-clonal population structure suggests that there is ongoing environmental exposure of inpatients to P. aeruginosa. In clinical areas dealing with the at risk patient, routine attention to mechanism of environmental colonisation is important and should be addressed even in the non-outbreak setting.