We attempted to determine if an increase in resistance to ciprofloxacin occurred among nosocomial pathogens, especially Pseudomonas aeruginosa and Staphylococcus aureus.

We examined 1989-1992 ciprofloxacin susceptibility results from 8,517 P aeruginosa and 9,021 S aureus isolates associated with nosocomial infections reported to the National Nosocomial Infections Surveillance System.

For S aureus, 27.1% of isolates were resistant to ciprofloxacin; of methicillin-resistant S aureus isolates, 80% also were resistant to ciprofloxacin. A logistic regression model found that ciprofloxacin resistance was more common among S aureus isolated from the urinary and respiratory tracts than from other sites of isolation, and among isolates that were methicillin resistant. After controlling for these factors, the model showed a 123% increase in the odds of ciprofloxacin resistance from 1989-1990 to 1991-1992. For P aeruginosa, 4.7% of the isolates were resistant to ciprofloxacin. Resistance varied by site of infection and rose most dramatically for respiratory tract isolates from 2.0% in 1989-1990 to 5.3% in 1991-1992.

Resistance to ciprofloxacin is more frequent among nosocomial S aureus than among P aeruginosa and is increasing rapidly among S aureus isolates and from selected sites among P aeruginosa isolates.

To describe two cases of nosocomial legionellosis and discuss the epidemiology of this infection.

Potable water was collected from multiple sites. Patient and environmental isolates were characterized by the Legionella slide agglutination test and monoclonal antibody subtyping. Concordance among isolates was confirmed by pulsed-field gel electrophoresis (PFGE).

A 713-bed university-affiliated hospital.

There was widespread contamination of potable water with Legionella pneumophila during a period of major construction; cooling towers were without growth of Legionella. One patient's isolate was the same by PFGE as the environmental isolate collected from the water faucet in his room. Control measures included superheating water used in all patient care areas to 75°C for 72 hours and flushing superheated water through faucets and showers; cleaning shower heads with a sonicator washer; and raising the hot water storage tank temperature from 43°C to 52°C. After these interventions, repeat environmental cultures over the next 6 months were without growth of Legionella, and no further cases of nosocomial legionnaires' disease were documented. An association between legionnaires' disease and construction is postulated. Heightened surveillance and preventive measures may be warranted during periods of excavation on hospital grounds or when potable water supplies are otherwise shut down and later repressurized.

A clinical, microbiological, and molecular analysis to identify the source of a cluster of pseudoinfections.

Retrospective analysis of the cases, prospective epidemiologic survey, and laboratory investigation. Molecular analysis of the isolates was performed using pulsed-field gel electrophoresis (PFGE).

A tertiary Veterans Affairs medical center.

Three patients admitted over a Z-week period with musculoskeletal complaints had one or more joint fluid specimens submitted for culture. In each case, anaerobic chopped meat-glucose broth (CMGB) tubes yielded one or more organisms not typically associated with septic arthritis (Enterobacter cloacae, Enterococcus faecium, Enterococcus casseliflavus, Enterococcus faecalis, Escherichia hermannii, and Pseudomonas diminuti). The first three organisms were isolated from specimens from multiple patients. Two patients had multiple positive cultures; for two patients, separate cultures yielded additional organisms on solid media.

Laboratory investigation yielded an isolate of E faecium from 1 of 30 sham-inoculated CMGB tubes. PFGE analysis demonstrated that a single strain of E cloacae was isolated from four CMGB tubes representing all three patients, and a single strain of E faecium was isolated from CMGB tubes representing two patients and the sham-inoculated tube.

The application of molecular typing clearly demonstrated clonality among the isolates and indicated that a common source of contamination, most likely the CMGB tubes, was responsible for these cases.

To achieve immunity to hepatitis B in healthcare workers who failed to respond to intramuscular vaccination and boosters.

An open prospective study of intradermal vaccination with recombinant hepatitis B vaccine.

A large community hospital in Connecticut.

Healthcare workers including physicians, nurses, and laboratory workers.

Immunization with high-dose intradermal recombinant hepatitis B vaccine, given in up to four doses, achieved immunity in 88% of healthcare workers who had previously been nonimmune.

We conclude that intradermal vaccination is efficacious in the majority of healthcare workers who failed to respond to intramuscular vaccine. Further studies, including randomized comparisons with intramuscular vaccine as well as studies of cell-mediated immunity, appear warranted.

To describe a nosocomial outbreak caused by multiresistant Acinetobacter baumannii.

Descriptive and case-control study. Antibiotic susceptibilities and pulsed-field gel electrophoresis (PFGE) of genomic DNA digested with Sfil and also with Apal were used as markers of strain identity.

A large medical school-affiliated hospital in the city of Houston, Texas.

During a 10-week period, A baumannii was isolated from 25 patients admitted to the intensive care unit (ICU). The attack rate was 14.3 per 100 ICU admissions. Case patients were intubated more frequently and for longer periods, and had longer ICU and hospital stays (P<0.05 for each of these characteristics). Multivariate logistic regression analysis identified the length of ICU stay and the use of third-generation cephalosporins as associated with the acquisition of A baumannii. Patients infected with A baumannii had a higher mortality rate than colonized patients and control patients [P<0.0l). Sixteen isolates recovered from these 25 patients were susceptible only to imipenem/ cilastatin, and PFGE confirmed that a single clone was the cause of this outbreak. Nine isolates of A baumannii from patients infected or colonized in two other hospitals in Houston during the same period, differed from the outbreak isolates by their susceptibility to ciprofloxacin. However, PFGE results were identical, indicating unsuspected genetic relatedness among isolates from three different hospitals.

A baumannii is an important nosocomial opportunistic pathogen and can adversely affect the outcome of ICU patients who acquire this organism. This outbreak was caused by a single clone that was isolated concurrently from three hospitals.