Lack of association between clinical and environmental isolates of Pseudomonas aeruginosa in hospital wards.

Seventy-three environmental and clinical isolates of Pseudomonas aeruginosa recovered from a single hospital over a 6-month period were compared for epidemiological type characteristics. Environmental isolates were obtained from sinks, taps and water, in rooms where patients were treated. The strains represented only six O-antigenic types and 8.2% of them were not typable. Serotype 011 was most frequent in the environment, whereas serotypes 06, 012 and 02,5 predominated among clinical isolates. More than 60% of all isolates belonged to four pyocin types (1, 10, 33 and 45), and approximately 80% were phage typable. Environmental isolates were more sensitive to antibiotics than clinical isolates. There was little correspondence between the types of strains of P. aeruginosa isolated from patients and those isolated from the environment. However, isolates of identical type were frequently recovered from different patients within the same clinic and were found to be related in time and location. We conclude that the environment was not an important source of P. aeruginosa infection and that transfer of organisms was mainly from patient-to-patient.