621. Cracking the Case: Salmonella Enteritidis and the 2010 Egg Recall
Session: Poster Abstract Session: Outbreak Investigation
Friday, October 21, 2011
Room: Poster Hall B1
Background: Salmonella Enteritidis (SE) causes 6,000 to 7,000 laboratory confirmed illnesses annually in the United States. Shell eggs and poultry are foods commonly linked to human SE infections. SE can silently infect the ovaries of healthy hens, resulting in internally contaminated eggs. In July 2010, a nationwide increase in SE infections with pulsed-field gel electrophoresis (PFGE) pattern JEGX01.0004 was identified.

Methods: A case was defined as a clinical infection yielding an SE isolate indistinguishable from the outbreak strain (JEGX01.0004). Since this pattern is commonly reported (30-40% of SE isolates), investigations focused on restaurant or event clusters where more than one case had eaten. Surplus incidence by state was determined by calculating the ratio of reported cases during the outbreak period to the average during the previous five year period. Tracebacks were conducted for suspect food items.

Results: In 2010, a surplus of 1,939 isolates of the outbreak strain were reported that were likely to be associated with this outbreak. Adjusting for under-reporting and under-diagnosis, it is estimated that more than 56,000 people may have become ill.  Twenty-nine restaurant or event clusters were identified in 11 states. States with surplus incidence ≥7.0 per million were significantly more likely to have identified a cluster than those <7.0 per million (p<0.001). Egg suppliers were identified for 16 of the clusters. A single producer in Iowa (Producer A) was identified as a supplier of shell eggs in 94% (15/16) of clusters. Traceback identified a second Iowa producer (Producer B) as another potential source of contaminated shell eggs.  Producer A was found to sell feed to Producer B; both producers shared the same source of pullets (young chickens).  Inspection of these producers identified 13 environmental samples matching the outbreak strain and found substantial potential for egg contamination. These producers recalled over 550 million shell eggs in August, 2010.

Conclusion: This large outbreak of SE infections was associated with shell eggs. Shell eggs remain an important vehicle for SE infection.  Continued efforts are needed to ensure safe preparation of foods containing shell eggs.

Subject Category: C. Clinical studies of bacterial infections and antibacterials including sexually transmitted diseases and mycobacterial infections (surveys, epidemiology, and clinical trials)

Joanna Gaines, PhD, MPH, Centers for Disease Control and Prevention, Atlanta, GA, Thai-An Nguyen, MPH, CDC, Atlanta, GA, Charlotte Wheeler, MD MPH, California Department of Public Health, Richmond, CA, Jeffrey Higa, MPH, California Department of Health Services, Gardena, CA, Jan Lidgard, AB, PHM, CLS, Microbial Diseases Laboratory, California Department of Public Health, Richmond, CA, Joshua Rounds, MPH, Acute Disease Investigation & Control Section, Minnesota Department of Health, St. Paul, MN and Ian Williams, PhD, Centers for Disease Control & Prevention, Atlanta, GA


J. Gaines, None

T. A. Nguyen, None

C. Wheeler, None

J. Higa, None

J. Lidgard, None

J. Rounds, None

I. Williams, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.