First published in Food Technology Magazine, July 2004. (Download PDF version)
An estimated 76 million cases of foodborne illness occur each year in the United States, costing between $6.5 billion and $34.9 billion in medical care and lost productivity (Mead et al., 1999; Buzby and Roberts, 1997). Of the estimated 13.8 million cases of foodborne illness due to known agents, roughly 30% are due to bacteria. The remaining cases of known etiology are due to parasites in 3% of the cases and viruses in 67% of the cases; bacteria are the causative agents of foodborne illness in 60% of cases requiring hospitalization (Mead et al., 1999).
The Institute of Food Technologists previously published Scientific Status Summaries on parasites (www.ift.org/pdfs/sss/parasites.pdf) and viruses (www.ift.org/pdfs/sss/virus-transmission-via-food.pdf) and has recently updated its Scientific Status Summary, “Bacteria Associated with Foodborne Disease,” originally published in the April 1988 issue of Food Technology.
The updated document (available at www.ift.org/pdfs/sss/bacteria.pdf) provides information on the pathogenic significance, association with foods, and control measures for Salmonella, Shigella, Campylobacter, Yersinia enterocolitica, Listeria, Vibrio, Staphylococcus aureus, Clostridium perfringens, Clostridium botulinum, Bacillus cereus, and Enterobacter sakazakii. Enterohemorrhagic Escherichia coli is omitted from the summary, as an entire separate Scientific Status Summary is dedicated to it (www.ift.org/pdfs/sss/ecoli.pdf).
Highlights of the revision include new regulatory information pertaining to performance standards for Salmonella in poultry and C. perfringens in cooked meats, and National Shellfish Sanitation Program guidelines for harvesting shellfish to limit Vibrio contamination and growth.
To provide the association with foods, recent outbreaks implicating each pathogen have been included. In many cases, these foods represent new vehicles for foodborne illness, such as the association of Salmonella with cantaloupe and sprouts. For some pathogens, advances in technology have provided the microorganism with a new niche. For example, packaging innovations caused foods such as clam chowder and bean dip to be implicated in C. botulinum outbreaks, since consumers mistakenly thought the foods did not require refrigeration when in fact they did.
Additionally, our scientific knowledge and understanding of many of the pathogens has increased greatly over the past 16 years. A new inclusion in this summary is E. sakazakii, a pathogen of increasing concern in infant formula. Listeria monocytogenes was an emerging pathogen and the focus of much research when the first version of this Scientific Status Summary was written. The susceptibility of the organism to pasteurization is now known, and the current document summarizes these research conclusions. The online document also incorporates the results of recently conducted risk assessments of L. monocytogenes in ready-to-eat (RTE) foods and Vibrio parahaemolyticus in raw molluscan shellfish.
The presence of potentially life-threatening pathogens in our environment, the ability of some of them to survive and/or proliferate under refrigeration and in reduced oxygen atmospheres, and, for some pathogens, the low number necessary for disease production indicate the seriousness of the potential hazards with which we are faced. The food industry utilizes a variety of effective control measures to limit potential hazards. While all food manufacturers utilize control measures to ensure food safety, some food industries are required to create and follow a HACCP plan.
It is impossible, however, to create a risk-free food supply. While food manufacturers and distributors employ necessary control measures to ensure the safety of food until it reaches the consumer, all food handlers and consumers have the responsibility upon purchase of the food to maintain these control measures until consumption. While outbreaks associated with a particular commercially processed food receive widespread public attention, a much greater number of individual cases of foodborne illness occurring in restaurants and in the home are not reported. Between 1993 and 1997, approximately 19% of outbreaks of foodborne illness occurred in private residences; delicatessens, cafeterias, and restaurants were responsible for 33% of outbreaks (CDC, 2000a). Only one of more than 1,300 outbreaks, including bacterial and viral, with known or unknown etiology was attributed to a “commercial product” in 2000 (CDC, 2000b). Proper handling, cooking, and storage practices in foodservice operations and in the home can prevent the majority of foodborne illnesses.
The principal control measures for prevention of foodborne disease continue to be use of adequate time–temperature heat treatments or cooking procedures; avoidance of cross-contamination of cooked or RTE foods by utensils, equipment, or cutting surfaces that are not properly cleaned and disinfected after contact with fresh, uncooked raw foods; avoidance of consumption of undercooked or contaminated raw foods; and avoidance of contamination of raw foods during handling by infected food handlers.
When the first version of this Scientific Status Summary was published, E. coli O157:H7 and L. monocytogenes were emerging pathogens that were not yet “household names.” Campylo-bacteriosis was just being recognized as the cause of illnesses previously identified as salmonellosis, and, although one report isolated E. sakazakii from powdered milk, the cause of infection in neonates was largely unknown. Strides have since been made to improve food safety, and fortunately some of the pathogens discussed are currently recognized as minimal contributors to foodborne illness, while others have increased in significance. Certain characteristics of the bacteria have been known for decades, while others have appeared more recently in somewhat unexpected situations.
Undoubtedly, new pathogens will continue to emerge, and our understanding of current pathogens will change. However, this Scientific Status Summary contains some of the fundamental information relating to these bacterial pathogens and can serve as a resource for undergraduates and food scientists seeking an overview of today’s pathogens of concern.