Pseudomonas aeruginosainfection in hospital: a comparison between ‘infective’ and ‘environmental’ strains

Abstract

SUMMARYOne hundred and fifty-six infections or episodes of infection associated withPseudomonas aeruginosain six hospitals over 14 months were investigated. Pyocine typing and serotyping suggested that 145 distinct episodes had occurred, caused by 78 different strains. During this period 15 distinct strains were isolated from the environment at one of the hospitals; 12 of these were apparently un-associated with infection in the same ward during the period, and 4 were of types not encountered in infective processes at any hospital. There appeared to be a rather higher proportion of unclassifiable pyocine inhibition patterns among the environmental strains; in general these strains also produced smaller amounts of haemolysin. If failure to produce haemolysinin vitrois correlated with lack of virulencein vivo, this may partially explain the sporadic nature of hospital infection withPs. aeruginosa, despite the prevalence of strains of this species in the environment.