Acquisition of endemic Pseudomonas aeruginosa on an intensive therapy unit.

During a 9-month period, patients, staff and environment were monitored in order to trace the source of endemic Pseudomonas aeruginosa on our intensive therapy unit (ITU). Of 81 patients studied, 14 (17%) acquired 15 different pyocin types while on the ITU. The most frequent site of colonization was the rectum (11 patients). Rectal strains subsequently appeared in urine (two patients), wound (one) and sputum (four) of six patients. Three episodes of cross-infection (wound (two), urine (one] occurred without development of rectal colonization. Strains isolated from the environment and staff were not implicated. While gastrointestinal carriage of P. aeruginosa may not be detected on admission to the ITU, excessive use of antibiotics may be responsible for apparent acquisition of the organism followed by endogenous transfer of the rectal strains to other sites of the body.