Methicillin-resistant Staphylococcus aureus outbreak at a Veterans' Affairs Medical Center: importance of carriage of the organism by hospital personnel.

The reported prevalence of nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) by hospital personnel averages 2.5%. From August 1985 to September 1987, 155 patients at our Veterans' Affairs Medical Center (VAMC) were colonized or infected with MRSA. In December 1986, only two (2.1%) of 94 healthcare workers were identified as nasal carriers. Prompted by a sharp increase in the number of patients with MRSA in early 1987, contact tracing identified 450 employees, of whom 36 (8%) were nasal carriers. Thirty-five percent of surgical residents (7 of 20) were nasal carriers. Prior to being identified as a nasal carrier, one surgical resident was associated with the inter-hospital spread of the VAMC MRSA strain to the burn unit of the affiliated university hospital. Three family members of two employee carriers were also found to harbor the epidemic strain. All 36 carriers were decolonized with various antimicrobial combinations. Vigorous infection control measures were effective in controlling the epidemic. The frequency of MRSA carriage by hospital personnel at our medical center during the epidemic proved higher than previously appreciated. Thus, healthcare workers may comprise a sizable MRSA reservoir. During an MRSA epidemic, infection control should attempt to identify and decolonize this hospital reservoir, as these individuals can disseminate MRSA both within the hospital as well as into the community.

Widespread colonization of personnel at a Veterans Affairs medical center by methicillin-resistant, coagulase-negative Staphylococcus.

A serial prospective survey of nasal colonization of hospital personnel by methicillin-resistant coagulase-negative staphylococci (MRCNS) was conducted at a Veterans Affairs medical center on three occasions over a 16-month period. The epidemiological typing systems used to assess relatedness included antimicrobial susceptibility profiles; biotyping; phage typing; plasmid profiles; restriction fragment length polymorphism (RFLP) analysis with ribosomal RNA; and plasmid hybridization with a 1.68-MD plasmid as the DNA probe. Forty-three percent of all personnel and 62% of all nurses were colonized with MRCNS. Nurses on the wards (72%) and in the intensive care unit (73%) were significantly more likely to be colonized with MRCNS than nurses who had less contact with patients or those who worked in the operating room. The molecular epidemiological typing systems indicated some degree of relatedness among the strains. Specifically, riboprobe analysis revealed a Dice coefficient of > 90%. However, each typing system detected dissimilarity among strains. Further studies are needed to determine the role that such human reservoirs of MRCNS serve in horizontal transmission to and subsequent infection of hospitalized patients.