Contact isolation has been recommended by the Centers for Disease Control and Prevention for the prevention of nosocomial transmission of methicillin-resistant Staphylococcus aureus (MRSA), but there are few data which prospectively quantitate the effectiveness of contact isolation for this purpose. During an outbreak of MRSA in a neonatal intensive care unit between July 18, 1991 and January 30, 1992, weekly surveillance cultures were performed on all patients. Sixteen of 331 admissions became colonized with MRSA, and 3 (19%) developed infections: bacteremia, conjunctivitis, and dialysis catheter site infection. The isolates from all 16 patients were submitted to plasmid profile analysis and restriction enzyme analysis of whole cell DNA. All of the patients had identical chromosomal patterns and plasmid profiles, which differed from control isolates from other wards, indicating that the outbreak resulted from spread of a unique strain. None of 144 personnel who were cultured after recent contact with newly colonized patients during the outbreak were found to carry MRSA, which suggests that patients were the reservoir for transmission rather than caregivers. The most probable source for each individual transmission was determined based on proximity in time and space and shared exposure to caregivers. The rate of transmission of MRSA from patients on contact isolation was significantly lower (0.009 transmissions per day on isolation) than the rate for patients not on isolation (0.140 transmissions per day unisolated, relative risk = 15.6, 95% confidence interval 5.3-45.6, p < 0.0001). The authors conclude that the risk of nosocomial transmission of MRSA was reduced 16-fold by contact isolation during the outbreak in this neonatal intensive care unit. These data confirm the results of previous studies which have suggested that contact isolation was effective in controlling the epidemic spread of methicillin-resistant Staphylococcus aureus.

To assess the role of slime in the pathogenesis of nosocomial bloodstream infections caused by coagulase-negative staphylococci, we compared the characteristics of 27 nosocomial bloodstream isolates with those of 27 skin isolates from non-hospital personnel. Of 27 bloodstream isolates, 14 were judged to be significant by a clinical index, and 13 were contaminants. Slime production was observed in 13 of 14 significant isolates but in only 3 of 13 contaminants (P = 0.0003) and 4 of 27 skin isolates (P = 0.0001). The 14 pathogens were identified as Staphylococcus epidermidis. Only 7 of 13 contaminants and 9 of 27 skin isolates belonged to the same species (P less than 0.006). Slime-producing strains of S. epidermidis represented 13 of 14 pathogens but only 2 of 13 contaminants (P less than 0.0003). Neither adherence to Teflon catheters nor phagocytosis and killing of coagulase-negative staphylococci by polymorphonuclear leukocytes was significantly influenced by slime production. Nevertheless, the identity of the organism and the slime production test predicted the clinical significance of blood isolates of coagulase-negative staphylococci with an overall accuracy of 89%.

A modified oxidase reagent, 1% tetramethyl-p-phenylenediamine in dimethyl sulfoxide, proved superior to the routinely used 1% aqueous tetramethyl-p-phenylenediamine dihydrochloride in detecting weakly oxidase-positive gram-negative bacteria after 24 h of growth on agar media (40 of 40 positive versus 22 of 40 positive). The bacterial inoculum was obtained with a cotton-tipped swab instead of a loop or wooden applicator, and the reaction required less than 15 s.

Environmental surface and personnel hand impression cultures were obtained during 13 sampling periods in the University of Virginia Pediatric Intensive Care Unit to document potential reservoirs of nosocomial pathogens. In 78 environmental cultures Staphylococcus aureus was found eight times and gram-negative bacilli ten times. The patient chart cover was the most commonly contaminated surface. Acinetobacter calcoaceticus was found in five of ten cultures positive for gram-negative bacilli. Thirty of 59 hand cultures were positive for S aureus and gram-negative bacilli; nurses and residents had both, respiratory therapists only gram-negative bacilli, and A calcoaceticus was the most commonly isolated bacterium of potentially nosocomial significance (14/30). Laboratory investigation of bacterial survival revealed that gram-negative bacilli survived on a dry formica surface from a few hours up to three days but Acinetobacter survived up to 13 days. Since A calcoaceticus has been implicated in many nosocomial infections, its long survival on a dry surface may be an additional factor in its transmission in hospitals and suggests that more attention be paid to environmental surfaces as a source of significant nosocomial pathogens.

Epidemic keratoconjunctivitis (EKC) due to adenovirus type 8 affected 126 (7%) of 1870 ophthalmology clinic patients during an outbreak. Risk factors and mode of transmission were studied by comparing cases (n = 58) and controls (n = 200) for exposure to risk factors. Pneumotonometry (odds ratio [OR], 10.5; 95% confidence interval [CI], 4.0-27.7), multiple clinic visits (OR, 5.9; 95% CI, 3.3-10.6), and contact with an infected physician (OR, 3.3; 95% CI, 1.2-9.0) were significant risk factors for infection. The hands of 3 patients and 3 physicians with EKC were cultured before and after hand washing to assess adenovirus removal; 3 had hand cultures positive for adenovirus after hand washing. In conclusion, this outbreak appeared to be due to inadequate disinfection of instruments, especially pneumotonometers, and finger-to-eye transmission by health care workers. Hand washing did not reliably remove adenovirus from contaminated fingers. Gloving for exam of eyes with EKC may help prevent transmission. Ophthalmologists with EKC were a significant risk factor for patients and should be furloughed for the duration of communicability.