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E. coli outbreak in Marine recruits associated with undercooked beef
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ATLANTA — An outbreak of Escherichia coli that sickened hundreds of Marine Corps recruits in San Diego last year was significantly associated with undercooked beef prepared by a civilian contractor, according to the results of an investigation.
The outbreak occurred in October and November among newly enlisted men at Marine Corps Recruit Depot, San Diego, and Camp Pendleton, a nearby base where recruits conduct weapons and field training, according to Amelia A. Keaton, MD, MS, EIS officer in the CDC’s Outbreak Response and Prevention Branch.
The outbreak involved Shiga toxin-producing E coli (STEC) — a major cause of foodborne illness in the United States each year and the pathogen responsible for the current multistate outbreak of E. coli linked to romaine lettuce. In all, 244 male recruits are suspected of being sickened, including 15 who developed a life-threatening complication of STEC infections called hemolytic uremic syndrome (HUS). Among those who developed HUS, six were deemed critically ill but none died, Keaton told Infectious Disease News during the CDC’s annual EIS conference.
She said the outbreak presented several challenges for investigators and highlighted some unique risk factors among military trainees living in close quarters.
“Nobody on our team had a military background, so we first wanted to understand what their training environment is like,” Keaton said. “Do they have any unique exposures that people in the general public don’t have? We wanted to get a sense of what day-to-day life was like for these guys and what risk factors for infection they were exposed to.”
Investigation
Keaton and colleagues interviewed 43 case patients and 135 healthy controls, plus Marine officers, food workers and staff. They observed food preparation practices and studied recruit sleeping quarters, bathroom facilities and cafeterias where meals were served to around 2,000 to 3,000 recruits at a time, Keaton said.
Although they were unable to directly test any meat, through interviews investigators found that ill recruits were 2.4 times likelier to report consuming undercooked beef than healthy controls. Moreover, Keaton said investigators directly observed beef being undercooked.
According to Keaton, most dining facilities on military bases are run by civilian contractors, including the facilities involved in this outbreak, which offered the same menu prepared by the same company. The Navy is in charge of inspecting such facilities once a month, she said.
“A lot of people reported eating meals that were visibly undercooked,” Keaton said. “When we observed food preparation, we saw that food workers were cooking a large number of hamburger patties and a large number of meals. Because such a large number of meals are being prepared, they’re only able to check foods intermittently with a meat thermometer. In some instances, we saw there were temperature abuses where they weren’t necessarily cooking to temperatures recommended by California state law.”
Risk factors
Keaton said the highly structured Marine Corps training regimen that is meant to instill a sense of teamwork among recruits also facilitates the spread of infections. During the investigation, Keaton and colleagues noted poor hygiene practices among recruits and said soap, paper towels and hand sanitizer were often unavailable.
“They’re in close contact all the time. Because they are sleeping next to each other and using the bathroom together ... it’s likely that they may come in contact with whatever germs their platoonmates have,” Keaton said.
Although beef was determined to be a risk factor, Keaton said not enough information was collected to definitively say what caused the outbreak. They identified a single unnamed beef supplier, but base records did not document which lots had been served. Looking at the timeline, the investigators believed there was likely a point-source — like contaminated beef — that led to the majority of illnesses but were unable to say how much person-to-person spread there was on top of that.
“It takes a small amount of [STEC] bacteria to get somebody sick, so if [you’re not] as hygienic as possible, it’s always possible to spread it to someone else,” Keaton said. “We were particularly worried in this setting because these guys were in such close contact, but we weren’t able to say to what degree that happened here.”
According to Keaton, the Navy instituted some sanitation practices and hygiene measures during the outbreak to help limit the spread of STEC. She said they left the Navy with some public health recommendations about sanitation practices and appropriate temperature guidelines for the kitchen.
“We would like to think that we helped stop the outbreak, but fortunately the Navy had put in a lot of measures before we even got there to help limit the spread,” Keaton said. – by Gerard Gallagher
Reference: Keaton AA, et al. Outbreak of E. coli 0157:H7 and E. coli 026 infections at a Marine Corps. recruit depot (MCRD), San Diego and Camp Pendleton, California — October-November, 2017. Presented at: Epidemic Intelligence Service conference; April 16-19, 2018; Atlanta.
Disclosures: Keaton reports no relevant financial disclosures.