Virulence determinants in human and environmental Pseudomonas aeruginosa isolates from hospital wards.

Adhesiveness, cytotoxicity and synthesis of exoenzymes and pyoverdin were compared for 36 clinical and 37 environmental isolates of Pseudomonas aeruginosa isolated from infected patients and the hospital environment, respectively. Clinical strains produced higher levels of cytotoxins, proteases and phospholipase C but a lower level of elastase as compared to environmental strains. Adhesiveness and frequency of pyoverdin-producing strains did not differ significantly between the two groups. High variability in the expression of virulence determinants was observed in human and environmental isolates belonging to the same 0 serotype and in epidemiological correlates of P. aeruginosa from hospitalized patients and the environment. Because of this phenotypic heterogeneity, it is hazardous to predict the potential invasiveness of P. aeruginosa on the basis of exoenzyme level