Two Sporadic Cases of Erysipelothrix rhusiopathiae Infection, Minnesota 2024

Erysipelothrix rhusiopathiae is a gram-positive, rod-shaped bacterium that can cause infections in livestock, marine mammals and humans. Human infections are traditionally affiliated with occupational exposures to E. rhusiopathiae through farming, butchering, or cooking. In July 2024, the Minnesota Department of Health was notified of two E. rhusiopathiae infections in the Minneapolis-St. Paul metropolitan area. Concerned about a possible outbreak, an investigation was initiated to determine the possible source(s) of infection.

Epidemiologists conducted reiterative, semi-structured interviews with the families of each case-patient. Cultures were forwarded to the MDH Public Health Laboratory for next-generation sequencing to determine the relatedness of the two samples, and additional queries of electronic health records (EHRs) were utilised to detect any additional cases of E. rhusiopathiae occurring in the Minneapolis-St. Paul area.

Both case-patients were adults from the Hmong community with underlying health conditions that presented to emergency care on two separate occasions. Interviews with the case-patients' families elucidated that they may have had direct or indirect exposures to raw or undercooked meat, possibly from a live animal market, but otherwise had no similar exposures. At MDH-PHL, the isolates were confirmed as E. rhusiopathiae and were noted to be 23,328 single nucleotide polymorphisms different. No additional case-patients were identified through a query of EHRs.

Given the lack of an epidemiological linkage and no apparent genetic relatedness of these two samples, epidemiologists considered these cases to likely not be part of an outbreak. While the true source of infection for these cases could not be determined, interviews helped elucidate possible exposure routes of infection, including contact with undercooked meat or environmental exposure to surfaces contaminated by raw meat. Given its rarity, E. rhusiopathiae cases should be studied when they occur to establish greater epidemiological and molecular evidence to support future outbreak investigations of the pathogen.