The epidemiology of gentamicin-resistant Pseudomonas aeruginosa on an intermediate care unit

The authors conducted a prospective six-month study of colonization by gentamicin-resistant Pseudomonas aeruginosa on an intermediate care unit at a Cleveland, Ohio hospital with the use of selective culture techniques, serotyping, and plasmid analysis. Thirty-five of 163 patients (21%) were culture positive at least once for gentamicin-resistant Pseudomonas aeruginosa. Patient samples, environmental cultures, and personnel hand cultures revealed no common source for the organisms. Plasmid profiling added little to the serotyping data. Only nonambulation and length of stay on the unit were significant independent risk factors for colonization with gentamicin-resistant Pseudomonas aeruginosa by multiple logistic regression analysis. Age, use of urinary catheters, exposure to antibiotics, and duration of antibiotic use were correlated with one or both of the independent risk factors, but were not themselves independently associated with colonization by these resistant organisms. Cross-colonization apparently was not an important mode of dissemination of gentamicin-resistant Pseudomonas aeruginosa on this intermediate care unit. The identified risk factors appear to be more important than cross-colonization, and control strategies should address these issues.