Salmonella Enteritidis Infections Associated with a Contaminated Immersion Blender at a CampFoodborne Pathogens and Disease

About

Authors
Elizabeth R. Daly, Colleen M. Smith, Peter Wikoff, John Seiferth, Jayne Finnigan, Alisha M. Nadeau, Joyce J. Welch
Year
2010
DOI
10.1089/fpd.2010.0537
Subject
Applied Microbiology and Biotechnology / Microbiology / Animal Science and Zoology / Food Science

Text

Salmonella Enteritidis Infections Associated with a Contaminated Immersion Blender at a Camp

Elizabeth R. Daly,1 Colleen M. Smith,2 Peter Wikoff,3 John Seiferth,2 Jayne Finnigan,3

Alisha M. Nadeau,3 and Joyce J. Welch2

Abstract

More than 100 foodborne salmonellosis outbreaks occur each year in the United States. Contaminated food preparation equipment is implicated in approximately 32% of Salmonella outbreaks with a known source. In

April 2009, we investigated reported Salmonella infections at a camp in New Hampshire. Camp attendees were contacted to complete a standard questionnaire. The questionnaire asked about foods eaten while at the camp, symptoms of gastrointestinal illness, visits to healthcare providers, and specimen submission for pathogen testing. Laboratory and environmental investigations were conducted, including testing of foods and food preparation equipment. A total of 133 ill persons, including 47 laboratory-confirmed Salmonella Enteritidis infections, were identified during this investigation. A total of 142 (80%) of 178 camp attendees completed a standard questionnaire and 109 cases of gastrointestinal illness and 33 healthy individuals were identified.

Statistical analysis of survey data indicated that people who ate pudding were 15 times more likely to become ill with salmonellosis than those who did not eat pudding (risk ratio, 15.2; 95% confidence interval, 2.3–102.3).

Salmonella Enteritidis was identified in leftover pudding and in the internal mixing components of the blender used to mix the pudding. All patient, food, and blender isolates exhibited the same pulsed-field gel electrophoresis pattern. This outbreak of Salmonella Enteritidis was caused by a Salmonella-contaminated hand-held immersion blender used to prepare pudding at a camp. A malfunctioning blender shaft seal is suspected to have resulted in contamination of the blender and subsequently pudding prepared using the blender.

Introduction

Salmonella is a Gram-negative bacterium, typicallytransmitted through contaminated food via the fecal–oral route, that causes an estimated 1.4 million illnesses and 400 deaths annually in the United States (Voetsch et al., 2004).

There are more than 2500 Salmonella serotypes. Of more than 40,000 human clinical isolates of Salmonella reported in 2006, 6740 (16.6%) were serotype Enteritidis, making it the second most common serotype causing human illness (CDC, 2008).

More than 100 foodborne salmonellosis outbreaks occur each year in the United States, with serotype Enteritidis accounting for more than any other serotype (CDC, 2006a). Implication of contaminated food preparation equipment is reported in approximately 32% of Salmonella outbreakswith a known source (CDC, 2006a).

We describe an outbreak of Salmonella Enteritidis infections at a camp in New Hampshire attributed to pudding contaminated by a Salmonella-contaminated hand-held immersion blender. This outbreak investigation is noteworthy in that the outbreak strain of Salmonellawas identified in patient, food, and blender isolates; laboratory confirmation of an outbreak’s source occurs infrequently in outbreak investigations and a vehicle is implicated in only 37% of reported foodborne outbreaks in the United States (CDC, 2006a). Further, an unlikely food vehicle was implicated as the pudding contained only two ingredients (pasteurized milk and dry pudding mix) and preparation involved little food service worker hand contact. Ultimate implication of the immersion blender required extensive specimen collection and laboratory testing.

Methods

Detection of the outbreak

On April 19, 2009, an emergency room physician called the

New Hampshire Department of Health and Human Services (DHHS) to report gastrointestinal illness in three students 1Communicable Disease Surveillance Section, 2Food Protection Section, and 3Public Health Laboratories, New Hampshire Department of Health and Human Services, Concord, New Hampshire.

FOODBORNE PATHOGENS AND DISEASE

Volume 7, Number 9, 2010 ª Mary Ann Liebert, Inc.

DOI: 10.1089=fpd.2010.0537 1083 who had recently returned from a school trip to a camp. The students had stayed at the camp from April 14 to April 17.

Initial laboratory testing of stool specimens from ill students at the emergency department indicated infection with Salmonella enterica serogroup D, which was later confirmed at the New

Hampshire Public Health Laboratories (PHL) as S. enterica serotype Enteritidis. A second student group from a different school arrived at the camp on April 20 as the outbreak investigation was beginning, and a group of students from a third school arrived onApril 22. By themorning of April 24, campers from the second and third school groupswere reporting illness.

DHHS also learned of gastrointestinal illness in a private nonschool group that stayed at the property from April 17 to

April 19 (groups and timeline outlined in Table 1).

Case finding and cohort study

Confirmed, probable, and suspect case definitions were developed. A confirmed case was defined as vomiting or diarrhea (3 loose stools in 24 hours)within 7 days of consuming foods from the camp in a person whose stool tested positive for Salmonella. A probable case was vomiting or diarrhea within 7 days of consuming foods from the camp in a person whose stool was not tested for Salmonella. A suspect case was any gastrointestinal symptoms (such as nausea) without vomiting or diarrhea within 7 days of consuming foods from the camp in a person whose stool was not tested for Salmonella.

Students and staff from three school groups that attended the camp were enrolled in a retrospective cohort study.

Contact information for camp attendees was obtained from school nursing staff, and camp attendees were contacted to complete a standard questionnaire approximately 6 days after onset of illness of the first case. The questionnaire asked about more than 70 food items served and other potential exposures while at the camp, symptoms of gastrointestinal illness in the week before and after arrival at the camp, visits to healthcare providers, and specimen submission for pathogen testing.