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Healthcare Infection Prevention - SHEA coverage: ICPs unload drug payload after strep outbreak

SHEA coverage

ICPs unload drug payload after strep outbreak

We would have seen . . . additional deaths’

Healthcare Infection Prevention

When caught in the middle of a highly virulent, rapidly progressing nursing home outbreak, there comes a time to forget shoe-leather epidemiology and pick up a sledgehammer. Such was the case for epidemiologists who were looking at three deaths in five days with no clear lines of transmission. As a result, they decided to "carpet bomb" a long-term care facility with antibiotics. "Your first obligation is to make the outbreak stop," said David Fisman, MD, an epidemiologist at McMaster University in Hamilton, Ontario. "Given the pace of the outbreak . . . we would have seen a number of additional deaths," he reported recently in Salt Lake City at the annual conference of the Society for Healthcare Epidemiology of America.

The pathogen was a nasty one: a Group A streptococcus M1T1 strain that killed two people in the first 48 hours of an outbreak in a nursing home in Hamilton in late November 2001. One resident died of pneumonia and the other of necrotizing fascitis.

Public health investigators went to the site to conduct interviews and begin culturing staff and residents. Throat, nose, perianal, vaginal, and wound cultures were obtained from a total of 245 residents and staff, he said. "There had been a large holiday party at the institution four days prior. This party had been attended by residents and family members, staff, and merchants from the community. There was a lot of mixing going on in a rather small common area on the first floor."

Interviews revealed that a staff member had been diagnosed with scarlet fever in early November, when she developed streptococcal pharyngitis complicated by a rash. The institution seemed slow in picking up this link to the outbreak, as the worker was allowed to handle food after developing the illness, he said. But a firm link between that case and the subsequent outbreak could not be established. However, chart review identified no cases of invasive strep disease in residents in the two-month period prior to the first two index cases. Persistent asymptomatic carriage of strep was identified in two staff and five residents. "[But] there was no apparent epidemiologic link that we could determine between cases, noncases, and carriers," he said.

On the second day of the investigation, a third resident became ill and rapidly died of Group A streptococcal bacteremia. Given the highly virulent nature of the known cases and the muddied epidemiologic picture, the decision was made to provide empiric antibiotic treatment (azithromycin 250 mg for five days) to all staff and residents. The explosive nature of this outbreak — with three fatalities in a five-day period — keyed the decision. "The downstream impact of wide-scale [antibiotic] use on bacterial-resistant pathogens in this institution remains a concern," Fisman said.

Still, the method was effective, as no new cases of invasive disease were seen during the six weeks following mass-antibiotic treatment. Antibiotic prophylaxis was offered for family members of the fatal cases. The mass-prescription approach worked, but it is difficult to recommend as any kind of general rule, he concluded. "There is no clear threshold for the use of mass antibiotics," Fisman said. "It is very difficult to come up with hard-and-fast rules because streptococcal isolates are so heterogeneous in terms of their virulence. It is very difficult to make any sort of sweeping recommendation on the basis of single outbreaks like this and probably even on the basis of an aggregate experience."

Reference

1. Smith A, McGeer A, Tolomeo O, et al. Virulent Group A streptococcus outbreak in a long-term care institution: Efficacy of mass antibiotic treatment. Abstract 254. Presented at the Society for Health Care Epidemiology of America. Salt Lake City; April 6-9, 2002.