Literature Review
Literature Review
Meier PA, Carter CD, Wallace SE, et al. A prolonged outbreak of methicillin-resistant Staphylococcus aureus in the burn unit of a tertiary medical center. Infect Control Hosp Epidemiol 1996; 17:798-802.
Infection control policy for methicillin-resistant Staphylococcus aureus (MRSA) at the University of Iowa Hospitals and Clinics in Iowa City requires health care workers to use barrier precautions. However, when MRSA was isolated from four patients on the burn unit in March 1993, laboratory evidence supported the hypothesis of cross-transmission, and staff were reminded to wash their hands after caring for patients.
Between the end of May and mid-June, six additional patients were identified as having the epidemic strain in their wounds. All were considered colonized and were not treated. Two of the patients subsequently developed serious MRSA infections. One patient had been an inpatient on the burn unit during the first cluster. Environmental cultures performed during the second cluster were negative for MRSA.
To determine whether burn unit personnel were a "reservoir" for the epidemic strain, nares cultures were obtained from 56 HCWs, including surgeons, nurses, physical therapists, occupational therapists, and housekeepers. Sixteen staff (29%) had methicillin-susceptible S. aureus in their nares, and three (5.4%) carried MRSA. "Antibiograms and chromosomal DNA typing confirmed that these three MRSA isolates were identical to the outbreak strain," the authors report.
Hospital epidemiologists determined that two of the three burn unit staff had cared for the affected patients. One, a surgical resident, helped perform skin grafts on six of the 10 patients. The second, a nurse, cared for five patients, including two who were not treated by the surgical resident. Although there was no documentation that the third HCW, a nursing assistant, had cared for any of the 10 patients, nursing assistants might not sign medical records when they help patients.
A hospital epidemiologist treated the three staff who carried the epidemic strain with mupirocin twice daily for five days. After three years of active surveillance, no additional patients have been detected who were colonized or infected with the epidemic MRSA strain.
MRSA can colonize numerous burn unit patients, putting them at risk for serious infections, the authors state. HCWs can contaminate their hands while caring for those patients, then transmit MRSA to other highly susceptible patients.
"In addition, because MRSA colonizes or infects extensive body surface areas in burn patients, these organisms can contaminate the air and the local environment. Consequently, on burn units, MRSA may be transmitted through the air and by environmental surfaces such as hydrotherapy equipment. Thus, once MRSA is introduced into a burn unit, this organism may cause a major outbreak of MRSA infections," the report states. Of the 10 burn unit patients who acquired MRSA, four developed serious infections that necessitated additional treatment and hospitalization.
The need to control MRSA continues to be debated. The American Hospital Association in 1994 issued a report advising hospitals to evaluate several factors before implementing control measures: incidence of nosocomial transmission, likelihood of spread to high-risk individuals, MRSA prevalence within the facility and in referring facilities, and available infection control resources.
While noting that hospital infection control personnel must decide which methods are appropriate when faced with epidemic or endemic MRSA, the authors state that aggressive measures were indicated at their facility based on the outbreak’s characteristics.
Their methods might not be appropriate in other settings, they say, but "when epidemiologic evidence indicates that healthcare workers are the most likely source for MRSA, this approach can be effective."
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