Pseudomonas aeruginosa antibiogram profiles are poor indicators of genetic relatedness

Pseudomonas aeruginosa is a significant nosocomial pathogen responsible for severe and life threatening infections particularly in immunocompromised patients. This organism is ubiquitous in healthcare environments particularly water systems which act as a reservoir of infection. Recognition of a potential outbreak and having the ability to quickly identify and mitigate sources of exposure is critical for effective infection control. Historically analysis of P. aeruginosa antibiogram profiles represents a convenient and frequently used ‘first line’ indicator of strain relatedness. Reported here is a comparison of P. aeruginosa antibiogram profiles with those obtained using rapid Variable Number Tandem Repeat (VNTR) for patient and environmental isolates in in three separate local nosocomial outbreaks. The results demonstrate that antibiogram profiles from P. aeruginosa should not be employed as presumptive indicators of relatedness, doing so can falsely re-assure clinicians. Use of rapid molecular typing method VNTR allows genotypically identical strains to be unambiguously identified within 48 h.