Colonization of the anterior nares by MRSA predicts the development of staphylococcal infection in long-term care patients; most infections arise from endogenously carried strains. Colonization by MRSA indicates a significantly greater risk for infection than does colonization by MSSA. The results offer a theoretic rationale for reduction in MRSA infections by interventions aimed at eliminating the carrier state.

S. aureus is a cause of urinary tract infection among patients with urinary tract catheterization. The majority of isolates are methicillin-resistant S. aureus. S. aureus bacteriuria can lead to subsequent invasive infection. The efficacy of antistaphylococcal therapy in preventing late-onset staphylococcal infection in patients with persistent staphylococcal bacteriuria should be tested in controlled trials.

The clinical features, microbiological characteristics, and outcomes of 163 episodes of bacteremia occurring at a long-term-care facility were evaluated. The rate of nosocomial bacteremia increased from 0.20 to 0.36 cases/1,000 patient-days from 1985 to 1989; there was a parallel increase in the rate of all nosocomial infections combined. Bacteremia was documented in 6.5% of all hospital-acquired infections. The majority of isolates were gram-negative, and Providencia stuartii was the most common gram-negative species. Staphylococcus aureus was the most frequent isolate; one-third of S. aureus strains were resistant to methicillin. Bacteremia was polymicrobial in 36 episodes (22%), 14 of which involved an enterococcal species. Portals of entry included the urinary tract (55%), the respiratory tract (11%), and soft tissue (9%). Overall mortality was 21.5%. Death was significantly associated with residence on the intermediate-care unit, the presence of a respiratory infection, a change in mental status, and relatively recent admission. Optimal management of bacterial infection in a long-term-care setting requires the availability of blood culture results. Initial decisions about antibiotic therapy should be made in light of the likelihood of infection with multiresistant organisms and of polymicrobial infection.

In our long-term-care facility, acquisition of multiply resistant Enterobacteriaceae was associated with the presence of decubitus ulcers and prior exposure to ampicillin. Acquisition of resistant P aeruginosa was associated with total antibiotic exposure. Molecular typing of P aeruginosa isolates implicated patient-to-patient transmission of a limited number of resistant strains.

We performed a case-control study of risk factors for the acquisition of ciprofloxacin-resistant gram-negative isolates ip a Veterans Affairs medical center. Sixty-five patients with resistant isolates and 50 control patients were identified. Prior fluoroquinolone use was significantly more frequent among patients with resistant isolates than it was among controls (58 versus 20%; P = 0.0001). The association with prior quinolone use was stronger in the long-term-care division (81 versus 32%; P = 0.0005) than it was in the acute-care division (29 versus 0%; P = 0.015). On multivariate analysis, prior receipt of a fluoroquinolone was the single most significant risk factor for isolation of a ciprofloxacin-resistant gram-negative organism (P = 0.0001).The fluoroquinolone antimicrobial agent ciprofloxacin has a broad spectrum of activity against gram-positive and gram-negative bacteria (16). High-level ciprofloxacin resistance among methicillin-resistant Staphylococcus aureus strains has been reported following the use of ciprofloxacin for eradication of staphylococcal colonization (14). Resistant isolates of Pseudomonas aeruginosa and members of the family Enterobacteriaceae can be selected in vitro (3,15) and may occur in vivo after ciprofloxacin therapy (10, 13). The epidemiology of ciprofloxacin-resistant gram-negative bacilli within a hospital has not been described previously.We found widespread resistance to ciprofloxacin among gram-negative bacilli isolated in the acute-and long-termcare divisions of a Department of Veterans Affairs medical center and demonstrated an association between the acquisition of resistant organisms and prior receipt of a fluoroquinolone. MATERIALS AND METHODSDescription of the facility. The Pittsburgh Veterans Affairs Medical Center consists of two geographically separate divisiops, a 438-bed acute-care division and a 432-bed longterm-care division. The two divisions share a common microbiology laboratory, located within the acute-care division. Ciprofloxacin was introduced in January 1988. In the third quarter of 1989 the microbiology laboratory reported an apparent increase in the frequency of ciprofloxacin resistance among gram-negative isolates. We therefore instituted a prospective study of risk factors for the acquisition of ciprofloxacin-resistant bacteria.Ciprofloxacin susceptibility. Antimicrobial susceptibility testing was performed by using the Vitek system. Susceptibilities of members of the family Enterobacteriaceae and Acinetobacter spp. were determined by using GNS-F1 and GNS-F2 cards. Testing of P. aeruginosa was performed by using the GNS-PA card. Susceptibility testing of other gram-negative bacilli was performed by a disk diffusion * Corresponding author. assay (1). The equivalent MIC breakpoints for ciprofloxacin were as follows: susceptible, less than or equal to 1 ,ug/ml; resistant, greater than or equal to 4 pug/ml. Epidemiologic study. From November 1989 through April 1990, the microbiology laboratory prospectively identified patients from whom ciprofloxacin...