To elucidate the epidemiology of widespread ciprofloxacin resistance in our Veterans Affairs medical center using whole cell DNA analysis.

In vitro study of ciprofloxacin resistant and susceptible Enterobacteriaceae isolated during the course of a clinical epidemiologic study of quinolone resistance.

Veterans Affairs Medical Center with acute care and long-term care divisions.

We examined 40 ciprofloxacin-resistant strains of Serratia marcescens, Proteus mirabilis, and Providencia stuartii using restriction endonuclease analysis of whole cell DNA and compared them with concomitantly isolated ciprofloxacin sensitive strains. We sought to determine whether resistant strains were identical to susceptible strains, indicating in vivo emergence of resistant strains from susceptible strains, and whether resistant strains were shared among patients. All 26 ciprofloxacin-resistant S marcestens isolates shared a single ecoRI restriction pattern. Multiple patterns were seen in the ciprofloxacin-susceptible S marcescens isolates; however, several isolates had a pattern matching that of the resistant isolates. Similar results were seen among the P mirabilis isolates. Three different ecoRI patterns were found among the ciprofloxacin-resistant P stuartii isolates; none matched those found among the susceptible isolates. The frequency of spontaneous emergence of ciprofloxacin resistance in susceptible S marcescens strains with restriction pattern matching that of the resistant strains was significantly higher than that of nonmatching strains.

Ciprofloxacin-resistant strains of Enterobacteriaceae became widespread within a short period of time. Resistant strains of S marcestens and P mirabilis arose from endemic susceptible strains. The resistant strain of S marcescens appeared to arise from a susceptible strain with a relatively high frequency of spontaneous ciprofloxacin resistance.

A computer virus outbreak was recognized, verified, defined, investigated, and controlled using an infection control approach. The pathogenesis and epidemiology of computer virus infection are reviewed.

Case-control study.

Pharmacy of a tertiary care teaching institution.

On October 28, 1991, 2 personal computers in the drug information center manifested symptoms consistent with the “Jerusalem” virus infection. The same day, a departmental personal computer began playing ‘Yankee Doodle,” a sign of “Doodle” virus infection. An investigation of all departmental personal computers identified the “Stoned” virus in an additional personal computer. Controls were functioning virus-free personal computers within the department. Cases were associated with users who brought diskettes from outside the department (5/5 cases versus 5/13 controls, p = .04) and with College of Pharmacy student users (3/5 cases versus 0/13 controls, p = .012). The detection of a virus-infected diskette or personal computer was associated with the number of 5 1/4-inch diskettes in the files of personal computers, a surrogate for rate of media exchange (mean= 17.4 versus 152.5, p = .018, Wilcoxon rank sum test). After education of departmental personal computer users regarding appropriate computer hygiene and installation of virus protection software, no further spread of personal computer viruses occurred, although 2 additional Stoned-infected and 1 Jerusalem-infected diskettes were detected.

We recommend that virus detection software be installed on personal computers where the interchange of diskettes among computers is necessary, that write-protect tabs be placed on all program master diskettes and data diskettes where data are being read and not written, that in the event of a computer virus outbreak, all available diskettes be quarantined and scanned by virus detection software, and to facilitate quarantine and scanning in an outbreak, that diskettes be stored in organized files.

Examination of suspended macroscopic debris that was noted in hospital cafeteria drinking water over a prolonged period of time.

A tertiary care hospital.

A retrospective description of events.

Conventional medical microbiology techniques were employed to determine if contamination of drinking water had occurred.

Microscopic examinations of the debris showed live nematodes similar to Strongyloides stercoralis rhabditiform larvae and amoebic trophozoites. A culture of an ice container in the cafeteria yielded coliform bacteria. Hospital employees lost work because of a diarrheal illness thought to be contracted from drinking cafeteria water. Further investigation revealed that the debris contained numerous ciliated organisms, nematodes, fresh water amoebae, bacterial mats, flagellated fungi, and unidentified cysts suggesting that the debris was of a freshwater origin rather than fecal contamination. Another hospital served by a collateral city water line experienced a similar problem. The debris was observed in November when lake water in the reservoir undergoes inversion.

Nonpathogenic freshwater microbiota probably originating from the city reservoir were the cause of pseudocontamination of hospital drinking water.

Describe an outbreak of surgical wound infections associated with total hip arthroplasty; identify risk factors for surgical wound infection during the pre-outbreak and outbreak periods.

A 100-bed hospital. From May 1 to September 30, 1988, 7 of 15 patients who underwent total hip arthroplasty developed surgical wound infections from Staphylococcus aureus (5), Enterobacter cloacae (1), b-hemolytic streptococci (1), enterococci (1), coagulase-negative staphylococci (1), and Escherichia coli (1) (attack rate = 46.7%).

Retrospective cohort studies comparing surgical wound infection rates by patient-and procedure-related risk factors during the pre-outbreak and outbreak periods were conducted. Drop plate quantitative air culturing was conducted in 10 consecutive total hip artbroplasties in the subsequent 6 months.

Rates of surgical wound infection were significantly higher for arthroplasties in which no intraoperative prophylactic antimicrobials were given (44% versus 8%, relative risk [RR] = 5.4, p= .01), or in which the posterior approach (20% versus 3%, RR= 6.7, p = .04) or a specific prosthesis (39% versus 5%, RR=6.3, p = 0.01) was used. The surgical wound infection rate was highest when one circulating nurse, Nurse A, assisted (47% versus 4%, RR= 12.8, p<.001). Logistic regression analysis identified use of the posterior approach (RR= 1.8, p= .04) and Nurse A's participation (RR= 5.0, p <.001) as independent risk factors for surgical wound infection. Interviews of the nursing supervisor indicated that Nurse A had recurrent dermatitis on her bands. During 6 months following Nurse A's reassignment, the rate declined significantly (from 7/15 to 0/10, p=.01). Drop plate culturing yielded 2 to 10 colonies per plate of organisms that did not match outbreak organisms.

Outbreaks associated with personnel generally involve only 1 species. In this outbreak, Nurse A (possibly because of her dermatitis), technique, the posterior approach, and/or other undetermined factors were the primary predictors of surgical wound infection.

To describe the characteristics of home healthcare clients with respect to infection risks and the presence of infections.

Descriptive survey of client charts using a point prevalence design.

A private San Francisco, California, Bay area home care agency.

A random sample of 175 clients (28%) was taken from the active client list for a single day; demographic data and clinical data from the last visit prior to the selection day were collected from each chart.

The clients were predominantly elderly (mean= 68.6) with an average of 3.6 comorbid conditions; 12% had an invasive device. Over 20% had an infection on the day surveyed. Five percent had an infection that occurred during home care delivery

A substantial proportion of home health clients have infections, and they represent persons with a number of the risks associated with infections. Guidelines for defining and monitoring infections in home care need to be developed. Hospital-based surveillance methods are not altogether appropriate in this setting; redesigning methods such as targeted surveillance, monitoring rehospitalization, or immunization practices are discussed as potential ways to measure quality of care in the home setting.

To determine the frequency of recognition of methicillin-resistant Staphylococcus aureus (MRSA) as an infection control problem and its prevalence among long-term care facilities, and to evaluate whether certain long-term care facility characteristics such as bed size, ownership, level of infection control activity, and frequency of resident transfers to acute care hospitals are related to the recognition or prevalence of MRSA in this setting.

Questionnaire survey.

Seventy-five long-term care facilities in the 8 counties of western New York.

Seventy-five of 81 (92.6%) long-term care facilities returned a completed questionnaire. Seventy-nine percent were considered to have a “limited” level of infection control activity (part-time infection control practitioner who spent less than 10 hours a week on infection control activities). The larger the long-term care facility, the more time was spent on infection control activities (p = .01). Seventy-two percent of the long-term care facilities screened new admissions for MRSA by reviewing culture reports; 69% of the long-term care facilities had a specific infection control policy for MRSA. Sixteen of the 75 (21%) facilities felt they had an infection control problem with MRSA. By univariate analysis, the only characteristic significantly associated with this recognition was use of nurse practitioners or physician assistants by a facility (p<.05). Eighty-one percent of the 75 long-term care facilities had identified one or more patients with MRSA in the year prior to the survey. By univariate analysis, the only characteristics that were significantly associated with the number of residents with MRSA were the monthly average number of residents transferred to acute care facilities (p = .034) and facility bed size (p= .022); there was also a trend toward increasing intensity of infection control activities (p= .085). However, facility bed size and the average number of resident transfers per month to acute care facilities were strongly associated (p = .0002). By stepwise logistic regression analysis, only bed size was an independent predictor of the number of residents with MRSA. Many long-term care facilities had tried to eradicate MRSA; ciprofloxacin was most commonly used to eradicate MRSA.

The vast majority of the 75 long-term care facilities in the 8 counties of western New York have identified patients with MRSA, although only a minority (21%) of them actually believed that an infection control problem existed. Facility size (a surrogate for the monthly average number of resident transfers to acute care facilities) seems to be an important factor in determining the number of residents with MRSA in long-term care facilities in our geographic region. The major longitudinal studies of MRSA in such facilities have so far been done only in Veterans Affairs facilities. Further studies are needed in freestanding long-term care facilities, the largest group of long-term care facilities in the United States, to determine the epidemiology of MRSA in this setting and to develop practical and valid infection control methods for residents with MRSA.

To determine the clinical significance and source of fungemia following a cluster of positive blood cultures during a 3-day period.

Chart review was used to determine the clinical significance of positive blood cultures. Microbiologic sampling of the laboratory environment was used to determine potential sources of fungal contamination.

A large, tertiary care, community teaching hospital.

All patients with blood cultures positive for Aspergillusspecies, Penicillium species, or both during the outbreak period.

Thirteen patients, all children, were reported to have positive blood cultures for fungus during a 3-day period in early 1990. None had clinical features consistent with fungemia. Investigation of specimen processing procedures revealed that microbiologic plates were not processed-as per protocol-under the biologic hood but inadvertently were left open to air on the work bench by laboratory technicians. Settling plates left at the workbench, at door entry sites, and at sites of renovation immediately adjacent to the laboratory were positive forAspergillus and/or Penicillium; control plates placed elsewhere were negative. Airflow patterns suggested spread into the microbiologic laboratory through an open door located near the implicated workbench station and a false ceiling above the workbench area.

Our investigation demonstrates that faulty technique in the laboratory coupled with a change in environmental conditions can result in false-positive cultures and an outbreak of pseudofungemia.