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Interstate Common-Source Outbreaks of Staphylococcal Food Poisoning -- North Carolina, Pennsylvania

From July 21 to August 4, 1982, three outbreaks of acute gastroenteritis associated with a single Pennsylvania caterer and caused by Staphylococcus aureus phage type 53 were reported to CDC. Two outbreaks were linked to a specialty ham product, which had been produced in Brooklyn, New York, and distributed to five states, and one was associated with a stuffed chicken-breast product.

North Carolina: On July 21, 14 cases of acute gastrointestinal illness occurred among 41 persons traveling by bus from Allegheny County, Pennsylvania, through Iredell County, North Carolina. Box lunches, containing ham-and-cheese sandwiches prepared by an Allegheny County caterer, had been served to the passengers after more than 5H hours without refrigeration. Symptoms included vomiting (86%), abdominal cramps (86%), nausea (79%), diarrhea (69%), dizziness or weakness (69%), and fever (14%). The incubation period was 2H-5 hours (mean 3T hours). All affected persons sought medical aid at a hospital in Iredell County; nine were hospitalized.

Food histories obtained from 39 passengers implicated the ham-and-cheese sandwiches as the vehicle of transmission. Fourteen (38%) of 37 persons who ate the sandwiches became ill, and none (0/2) of those who had not eaten them became ill, (p 0.05). Stool cultures from four of nine hospitalized persons were positive for S. aureus phage type 53, which was also isolated from the ham-and-cheese sandwiches; enterotoxin tests of the sandwiches revealed preformed enterotoxin type A.

Pennsylvania, Outbreak 1: On July 22, an outbreak of gastrointestinal illness occurred in Grove City, Pennsylvania, following a picnic attended by 600 people and catered by the same Allegheny County caterer. Of 49 persons interviewed, 33 reported illness, with symptoms that included diarrhea (76%), vomiting (61%), abdominal cramps (36%), and nausea (24%). The incubation period was 4-8 hours (mean 5 hours). Three persons were hospitalized.

Food histories showed that stuffed chicken breast was the probable vehicle of transmission. Thirty-three (69%) of 48 persons who ate the stuffed chicken breasts became ill; the one person who did not eat the chicken did not become ill. Although ham had been served at the picnic, it was not implicated. Isolates from the stuffed chicken breasts and from stool cultures from two ill persons were positive for S. aureus phage type 53. The Allegheny County Health Department found S. aureus in two previously unopened cryovac-packaged hams taken from the caterer on July 27. It was postulated that the lunches had been cross-contaminated at the caterer's work area. When specimens from a new shipment of hams were culture-negative, the caterer was allowed to continue operation.

Outbreak 2: On August 4, at least 51 cases of acute gastrointestinal illness occurred among 248 passengers on an Ohio River boat trip from Pittsburgh, Pennsylvania, to Waterford Park, West Virginia. Food had been provided by the same Allegheny County caterer. Symptoms included diarrhea (86%), nausea (81%), vomiting (77%), and abdominal cramps (61%). The incubation period was 1H-7H hours (mean 6 hours). Twenty-six of those affected sought medical aid at an Ohio hospital; three were hospitalized. Food histories of 199 persons interviewed implicated sliced ham as the vehicle of transmission. The attack rate was 30% (51/171) for those who ate ham and 0% (0/28, p 0.001) for those who did not eat ham. S. aureus phage type 53 was isolated from stool specimens from eight patients treated at the hospital. Allegheny County Health Department tests on specimens from a previously unopened cryovac-packaged ham obtained August 5 showed S. aureus phage type 53.

After the third outbreak, the U.S. Department of Agriculture (USDA) tested previously unopened cryovac-packaged hams and found 12 of 21 hams culture-positive for S. aureus. The isolates from nine of these hams were phage type 53; none had preformed enterotoxin, but the isolates were enterotoxin type A-producing. On August 17, the USDA formally recalled 36,000 pounds of ham distributed by the Brooklyn, New York, processor to five states, (Connecticut, Maryland, New York, Pennsylvania, and Virginia). USDA inspection implicated a "cold smoke" method of processing the specialty ham, allowing exposure to bacterial growth temperatures for over 6 hours. The processor has now discontinued this method. Reported by L Cox, East Liverpool City Hospital, East Liverpool, R Campbell, TJ Halpin, MD, State Epidemiologist, Ohio State Dept of Health; SM Freedman, MD, New York City Dept of Health; P Silverman, DrPH, G Christy, NM Richards, MD, S Steingart, Allegheny County Health Dept, T DeMelfi, C Tyger, E Witte, VDM, CW Hays, MD, State Epidemiologist, Pennsylvania State Dept of Health; JN MacCormack, MD, MP Hines, DVM, State Epidemiologist, North Carolina State Dept of Human Resources; Epidemiology Br, United States Dept of Agriculture; Minneapolis Center for Microbiological Investigations, Food and Drug Administration; Div of Field Svcs, Epidemiology Program Office, Staphylococcus Laboratory, Hospital Infections Program, Enteric Diseases Br, Div of Bacterial Diseases, Center for Infectious Diseases, CDC; WD Mashburn, MPH, Iredell County Health Dept, North Carolina.

Editorial Note

Editorial Note: In 1981, S. aureus was responsible for 18% of all reported food-borne disease outbreaks in the United States, making it the second most commonly reported food-borne pathogen. Ham was the vehicle in 18% of S. aureus outbreaks; outbreaks involving ham have almost always been caused by S. aureus. In 1981, eight of nine ham-associated outbreaks were caused by this organism. (The etiologic agent of the ninth outbreak was unknown.)

The effect of USDA intervention cannot be assessed, since production of the specialty ham product was discontinued after investigation of these outbreaks.

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