To summarize the results of an investigation of increased rates of tuberculin skin test conversion in employees at a university hospital.

The results of annual tuberculin skin tests performed on all 1,845 hospital employees from 1986 to 1991 were reviewed.

A 450-bed acute tertiary care university hospital.

The rate of tuberculin skin test conversion was 0.35% (standard deviation ± 0.15) from 1986 to 1989 and increased to 1.7% during 1991. Investigation revealed deviations from the Centers for Disease Control (CDC) guidelines for tuberculosis control, which included the failure to consider tuberculosis as a probable cause of community-acquired pneumonia and the failure to initiate isolation precautions when tuberculosis was suspected.

The epidemic appeared to be secondary to delays in diagnosis and isolation of patients with pulmonary tuberculosis. Future control measures should include isolation of all hospital patients admitted with pneumonia until tuberculosis has been excluded.

Analyze changes that have occurred among U.S. hospitals over a 17-year period, 1975 through 1991, in the percentage of Staphylococcus aureus resistant to b-lactam antibiotics and associated with nosocomial infections.

Retrospective review. The percentage of methicillin-resistant S aureus (MRSA) was defined as the number of S aureus isolates resistant to either methicillin, oxacillin, or nafcillin divided by the total number of S aureus isolates for which methicillin, oxacillin, or nafcillin susceptibility test results were reported to the National Nosocomial Infections Surveillance (NNIS) System.

NNIS System hospitals.

Of the 66,132 S aureus isolates that were tested for susceptibility to methicillin, oxacillin, or nafcillin during 1975 through 1991, 6,986 (11%) were resistant to methicillin, oxacillin, or nafcillin. The percentage MRSA among all hospitals rose from 2.4% in 1975 to 29% in 1991, but the rate of increase differed significantly among 3 bed-size categories: <200 beds, 200 to 499 beds, and 2500 beds. In 1991, for hospitals with <200 beds, 14.9% of S aureus isolates were MRSA, for hospitals with 200 to 499 beds, 20.3% were MRSA; and for hospitals with >500 beds, 38.3% were MRSA. The percentage MRSA in each of the bed-size categories rose above 5% at different times: in 1983, for hospitals with 2500 beds; in 1985, for hospitals with 200 to 499 beds; and in 1987, for hospitals with <200 beds.

This study suggests that hospitals of all sizes are facing the problem of MRSA, the problem appears to be increasing regardless of hospital size, and control measures advocated for MRSA appear to require re-evaluation. Further study of MRSA in hospitals would benefit our understanding of this costly pathogen.

To compare the clinical virulence of nosocomially acquired methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S aureus (MSSA) infections in 1989.

A retrospective comparison of host factors, in-hospital exposures, sites of infections, and outcomes of patients with nosocomial MRSA and MSSA infections.

University of Illinois Hospital, Chicago, Illinois.

Forty-four adult patients with nosocomial S aureus infections.

The 22 MRSA-infected and 22 MSSA-infected persons were similar regarding mean age, gender, underlying diseases, and exposure to surgery. Before developing infection, MRSA-infected persons were more likely to have received antibiotics (73% compared with 27%, odds ratio = 7.1, 95% confidence interval [CI95] = 2.0-25.8 p = .003) and to have stayed in the hospital >2 weeks (64% compared with 18%, odds ratio = 7.9, CI95 = 2.0-31.6, p = .002). Bacteremia was the most common presentation in the MRSA and MSSA groups (55% and 59%, respectively). Infectious complications and death were infrequent in both groups.

MRSA and MSSA strains infect patients with similar demographic features and underlying diseases, but MRSA infections are significantly more common among patients with previous antibiotic therapy and a prolonged preinfection hospital stay. Clinical presentations and outcomes did not differ significantly between the 2 groups. Thus, similar to studies in the early 1980s, our findings do not suggest greater intrinsic virulence of MRSA.

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.