Healthcare Infection Prevention: MRSA in the community: Is family spread a factor?

Emerging data finding transmission in the home

Increasing reports of community-acquired strains of methicillin-resistant Staphylococcus aureus may be driven in part by former hospital patients spreading MRSA to family members upon returning home, epidemiologists reported recently in Washington, DC, at the annual conference of the Society for Healthcare Epidemiology of America (SHEA).

"Familial contact may be an under-recognized [source] of MRSA transmission, said Leonard Mermel, MD, hospital epidemiologist at Rhode Island Hospital in Providence. "We were able to document transmission among family members in different households."

To identify risk factors for community-acquired MRSA acquisition in children, Mermel and colleagues conducted a retrospective review of hospital medical and laboratory records of MRSA patients younger than 18 from 1997-2001. MRSA was considered health care-associated if any of the following criteria were present:

  • It was isolated more than 48 hours after admission.
  • The patient had a history of previous MRSA isolation hospitalization or surgery in the prior year.
  • An indwelling device was present at time of culture.

MRSA was considered community-acquired only if the patient had no health care associated risk factors identified and it was isolated no more than 48 hours after admission.

Of the 57 total pediatric patients with MRSA infection identified, 23 (40%) met the criteria for community-acquired infection. "All had clinically significant MRSA infections," he said, noting that most of the community cases were soft-tissue infections. Two of the community cases attended day care, and four were part of an extended family with multiple MRSA-infected members. Molecular typing revealed that all four children and one adult had the same MRSA clone. "MRSA has emerged as a community-acquired pathogen in children without traditional risk factors," Mermel said. "Recent reports suggest that less apparent risk factors may exist such as contact with household members with MRSA risk factors or day-care attendance."

In another SHEA study, Canadian researchers looking at household contacts of MRSA patients also found some tantalizing evidence that the phenomenon is occurring. Though, as with the previous study, the number of cases are too small to carry much statistical power, the findings suggest at least some strains of MRSA are moving from the hospital to the community via the household contacts of discharged patients. Data from Canadian surveillance systems find that about 5% to 7% of MRSA cases are occurring in the community.

"These are in individuals with out any of the known risk factors and no exposure to the hospital or other acute care facilities, "said Andrew Simor, MD, infectious disease consultant at Sunnybrook and Women’s College Health Sciences Centre at the University of Toronto in Ontario. To determine the risk of transmission, the researchers cultured consenting contacts of discharged MRSA patients. Cultures for detection of MRSA were obtained at baseline and then monthly for up to nine months. Seven index patients and 12 household contacts have been enrolled in the study and followed for at least three months. Contacts of three (43%) of the index patients had at least one positive culture for MRSA, representing 25% of the 12 household contacts.