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 evaluate the use of focused surveillance in following resistance patterns within an intensive care unit (ICU).

Antibiograms of 167 gram-negative isolates from ICU patients were compared to the hospitalwide antibiograms. ICU isolates were examined for the newer forms of beta-lactamase resistance. An outbreak of multiresistant Pseudomonas aeruginosa during the survey illustrated the usefulness of focused surveillance in early intervention and containment.

A 700-bed adult tertiary care hospital with a 16-bed medical and surgical ICU.

Hospitalwide and ICU antibiograms of the Enterobacteriaceae were similar. However, resistance of P aeruginosa in the ICU was underestimated by hospitalwide rates. Susceptibility of ICU isolates to ceftazidime, ciprofloxacin, and piperacillin was 54%, 54%, and 42%, compared with 81%, 77%, and 85%, respectively, in the hospital at large. Thirty-five percent of isolates exhibited one of the newer forms of beta-lactamase-mediated resistance, with 17% of isolates exhibiting Class I cephalosporinase production.

Targeted survey of high antibiotic-use hospital units should be used to study bacterial epidemiology, rather than relying on general hospital data to evaluate patterns of antimicrobial resistance. Monitoring of potential problem areas leads to prompt identification of changes in resistance and allows early intervention.

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 determine the recovery of vancomycin-resistant enterococci (VRE) on fingertips, gloved fingertips, and environmental surfaces commonly encountered in the healthcare setting, and to examine the importance of handwashing on the removal of these organisms.

Two clinical isolates of VRE (Enterococcus faecalis and Enterococcus faecium) were inoculated onto the hands of healthy human volunteers and the following environmental surfaces: countertops, bedrails, telephones, and stethoscopes. Following inoculation, samples were obtained at various time intervals to determine rates of recovery of organisms. To evaluate the effects of handwashing on enterococcal recovery, two different soap preparations were tested. Hands were washed with water alone or with one of the soaps and water. The soap and water studies were performed with a 5-second and a 30-second wash.

Both enterococcal strains survived for at least 60 minutes on gloved and ungloved fingertips. The E faecalis was recoverable from countertops for 5 days; the E faecium persisted for 7 days. For bedrails, both enterococcal species survived for 24 hours without significant reduction in colony counts. The bacteria persisted for 60 minutes on the telephone handpiece and for 30 minutes on the diaphragmatic surface of the stethoscope. A 5-second wash with water alone resulted in virtually no change in recovery of enterococci; a 30-second wash with water plus either soap was necessary to eradicate the bacteria from hands completely.

VRE are capable of prolonged survival on hands, gloves, and environmental surfaces. Hands should be washed thoroughly and gloves removed following contact with patients infected or colonized with these multidrug-resistant bacteria. Finally, environmental surfaces may serve as potential reservoirs for nosocomial transmission of VRE and need to be considered when formulating institutional infection control policies.

To determine the prevalence of and risk factors for having a positive tuberculin skin test (TST) result among employees at a medical examiner's office (MEO).

Cohort study, environmental investigation.

Several employees at a medical examiner's office were found to have positive TST results after autopsies were performed on persons with multidrug-resistant tuberculosis (MDR-TB).

Employees of the MEO.

Of 18 MEO employees, 5 (28%) had a positive TST result; 2 of these 5 had TST conversions. We observed a trend between TST conversion and participation in autopsies on persons with MDR-TB (2 of 2 converters versus 3 of 13 employees with negative TST; relative risk=4.3; 95% confidence interval 1.61 to 11.69; P=0.l0). The environmental investigation revealed that the autopsy room was at positive pressure relative to the rest of the MEO and that air from the autopsy room mixed throughout the facility.

A systematic approach to preventing transmission of Mycobacterium tuberculosis in autopsy suites should include effective environmental controls and routine tuberculin skin testing of employees.

To investigate an apparent excess of operative site infections (OSI) reported according to doctor's diagnosis (presumptive OSI) by applying objective criteria for classification (documented OSI). To examine potential consequences of habitual overdiagnosis of OSI.

A case-control design was used to examine the clinical course of 18 case patients (12 presumptive OSI, six documented OSI) and 18 matched controls. Comparisons also were made between presumptive and documented OSI patients.

A nonteaching community hospital.

Thirty-six patients having laminectomies done by the same surgeon.

Implementation of objective criteria for diagnosis of confirmed OSI and reclassification of presumptive OSI patients.

Postoperatively, the frequency of specific adverse events within the operative site (including post-operative hematoma or bleeding; wound necrosis, dehiscence, or sinus tract; and dural tear) was 83% for documented OSI patients, contrasted with 16.7% for presumptive OSI patients (P<.01) and controls (P=.007). Median days of inpatient stay were 27 for documented OSI, contrasted with 9.5 for presumptive OSI (P=.01) and 7 for controls (P<.001).

Documented OSI patients were found to have significantly more adverse findings and longer lengths of stay than presumptive OSI patients or controls. The similarity of findings for presumptive OSI patients and controls suggests that the apparent excess frequency of OSI was caused by incorrect diagnosis. Whereas doctor's diagnosis may be useful as an initial screen for OSI, use of objective criteria for confirming OSI may avert the consequences of overdiagnosis, including excessive length of stay and unnecessary therapy, which lead to elevated healthcare costs and threaten a physician's practice.

To determine the validity of an active, hospital laboratory isolate-based surveillance system in estimating rates of infection and to evaluate the use of surveillance data in describing institutional risk factors for increased rates of infection. Methicillin-resistant Staphylococcus aureus (MRSA) was chosen as the prototype organism for these evaluations.

Correlation Study: linear regression analysis and Student's t test were used to evaluate the correlation between number of MRSA isolates and number of MRSA infections in acute-care hospitals. Cross-Sectional Study: Student's t test, analysis of variance, and multiple linear regression analysis were used to evaluate the association between mean annual rate of MRSA blood isolates and institutional risk factors for increased rates of infection.

Acute-care hospitals, New Jersey.

The number of MRSA blood isolates was significantly correlated with MRSA blood infections (R, 0.78; P<01) and provided a good proxy measure for number of infections. Multivariate analysis demonstrated hospital location in the inner city (P= .02) and number of occupied beds (P<.01) to be independently associated with increased mean annual rates of MRSA blood isolates in acute-care hospitals.

This surveillance system is a valid tool for the estimation of institutional rates of infection and for the determination of institutional risk factors for increased rates of infection. It is ideal for further population-based investigations of antimicrobial-resistant bacteria.

To investigate an outbreak in neonates of Enterobacter cloacae infection resistant to third-generation cephalosporins.

A retrospective study of an outbreak in the neonatal intensive care unit (NICU) and review of E cloacae isolates in pediatric wards and other intensive care units from June 1992 through March 1993.

An academic tertiary care hospital.

Six patients admitted to the NICU were colonized or infected with E cloacae resistant to third-generation cephalosporins. In the period preceding the outbreak, four E cloacae isolates were available from four patients in the pediatric surgical ward. Nine isolates from four patients in two other intensive care units (ICUs) also were collected during the outbreak. Isolates were biotyped by the API 50CH system and genotyped by polymerase chain reaction (PCR) fingerprinting.

Typing by interrepeat PCR showed that 21 isolates, which were obtained from five neonates, were identical. One neonate was colonized with a different strain. Some neonates were colonized with a single type of E cloacae for a relatively long period of time. Isolates of patients who were cared for in the pediatric surgical ward and the two other intensive care units (ICUs) showed different genotypes. One patient in an ICU was colonized with an E cloacae strain genetically identical to the outbreak strain. No predominant biotype could be established.

E cloacae can colonize neonates for a long period of time and although colonization with E cloacae initially may arise endogenously, we were able to show further transmission by cross-contamination in a neonatal intensive care unit.

To evaluate the clonality of methicillin-resistant Staphylococcus aureus (MRSA) strains among hospitalized patients.

University-affiliated, 465-bed tertiary-care teaching hospital with adjacent cancer clinic in Hamilton, Ontario, Canada.

Thirty-five colonized and 30 infected patients from January 2, 1992, through August 31, 1993, were investigated retrospectively. Analysis by restriction fragment-length polymorphisms of ribosomal RNA genes (ie, ribotyping) of 103 nosocomial isolates of MRSA from these 65 patients and of 25 selected unrelated strains was completed. Ribotyping results were compared with the phage typing data obtained prospectively during the course of prospective MRSA surveillance.

HindIII ribotyping was more discriminating than phage typing when epidemiologically unrelated strains were differentiated by these methods (19 different ribotypes versus 14 phage types; P< .005). Two early index cases were identified. Isolates from the index cases were two different strains, identified by ribotyping analysis as ribotype A (clonal group 1) and ribotype B (clonal group 2), respectively. These two ribotypes were not found when typing the unrelated control strains. Thirty-six colonized and infected patients (55%) had clonal group 1 isolates, and 20 (31%) had clonal group 2 isolates. These two clones emerged in the hospital in January and February 1992 and dominated the entire investigated period. There also were six patients with an additional clonal group (group 4) that emerged and disappeared in the second quarter of 1993.

This study highlights the utility of ribotyping in investigating nosocomial MRSA. Three MRSA clones caused nosocomial colonization or infection in patients at this hospital. Two of these MRSA clones, once introduced, were maintained among our patients throughout the study period.