MRSA IN ONTARIO - CAN TRANSMISSION BE CONTROLLED?

K. Green, M. Saginur, C.A. Fleming, DE. Low, A.McGeer, Mount Sinai Hospital and the Laboratory Proficiency Testing Program, Ontario.

Background: Since 1995, hospitals in Ontario have been working to control the dissemination of an epidemic strain of MRSA. The Ontario Laboratory Proficiency Testing Program has conducted annual surveys since 1996 in order to assess changes in the incidence of these pathogens in the province.

Methods: Each January, LPTP mails a questionnaire to all licensed clinical microbiology laboratories in Ont. The questionnnaire asks laboratories to provide information on the number of patients identified as colonized or infected with MRSA, and details of hospital screening programs for these organisms. Questionnaires for 1998 and 1999 also asked for the number of MRSA infections in those years.

Results: In the last two years, 100% of laboratories have responded. The number of laboratories not isolating MRSA has decreased steadily to a low of 7% (8/121) in 1999 [11% in 1998]; all such labs serve hospitals of <60 beds in northern or eastern Ontario. In 1999, all of the 224 hospitals responding reported having an MRSA screening program: 219 screen patients transferred from other countries, 220 (98%) screen those transferred from another hospital in Ontario, 204 (91%) those admitted from a nursing home, and 214 (95%) screen patients with a history of recent hospitalization in Ontario. The proportion of hospitals reporting compliance with Ontario admission screening recommendations increased from 75% to 90% from 1998 to 1999. Additional prevalence surveys are performed in 160/224 (71%) of hospitals, compared to 60% of hospitals in 1998. For screening purposes, all hospitals reported obtaining nasal swabs, 201 (90%) wounds/skin lesions swabs, and 213 (95%) at least one of groin, perirectal or rectal swabs, most commonly (159/213, 75%) rectal. Overall, the number of patients identified as colonized or infected with MRSA has been: 1992 - 471, 1993-475, 1994 -566, 1995 -1426, 1996 - 4212, 1997 - 6866, 1998 - 8016, 1999 - 8252. The number of patients with MRSA positive blood cultures remained stable between 1998 and 1999 at 135 and 133 respectively. In 1998, 111/133 labs, representing 4416 MRSA patients, were able to report colonization vs infection: 927/4416 (21%) patients were infected. In 1999, 100/121 laboratories, representing 4259 isolates reported that 1106/4259 (26%) of patients were infected (P<0.001 compared to 1998). Laboratories reporting on 4152 patients were able to provide an assessment of the source of the isolate: 58% acquired their MRSA nosocomially, 15% from a nursing home, 6% in the community, and for 24% of patients the source could not be determined.

Conclusions: MRSA remain an institutional organism in Ontario. Despite an increase in the intensity of screening programs, the number of patients infected or colonized with MRSA increased by only 3% from 1998 to 1999, and the number of reported bacteremias was stable. These data suggest that Ontario hospitals are succeeding in bringing this epidemic under control However, the small but statistically significant increase in the percentage of reported MRSA isolates associated with infection is of concern.

 

Presented at:

COMMUNITY AND HOSPITAL INFECTION CONTROL ASSOCIATION - CANADA (CHICA) Conference, The Sheraton Centre, Toronto ON, Canada, May 29-31, 2000.