Salmonellosis outbreaks

The Illinois outbreak in 1985 involved 16,284 cases with two deaths verified as infections from the tetracycline-resistant strain (0.012% mortality) (Final Task Force Report, Salmonellosis outbreak, Hillfarm Dairy, Melrose Park, IL, September 1985). 

Stewart DS, Reineke KF, Ulaszek JM, Tortorello ML. Growth of Salmonella during sprouting of alfalfa seeds associated with salmonellosis outbreaks. J Food Prot 2001 64(5) 618-22. 

There are many different subspecies or serotypes of Salmonella spp. capable of sickening humans (Chin and Ascher 2000), and they occur in a variety of different environments. Salmonella spp. may occur in water, soil, insects, factory and kitchen surfaces, animal feces, and raw meats, poultry, and seafood. The bacteria can be isolated from these sources and grown. Most typically, salmonellosis outbreaks in the United States occur because of improperly cooked food such as meat, poultry, seafood, and eggs improperly prepared fruits, vegetables, milk, and other food and drinks or via improperly washed hands, food contact surfaces, and utensils. There are approximately 40,000 salmonellosis cases resulting in approximately 600 deaths each year reported in the United States. Additionally, there are roughly 400 cases of typhoid fever recorded in the United States annually, but 75% of them are associated with international travel. Immediate medical attention significantly reduces mortality, but the case fatality rate is 12-30% in untreated cases (Murray et al. 2005). 

Transmission of Salmonella infection may also occur from man to man and animal to man. Salmonellosis outbreaks have been reported in person handling chicken, ducks, kittens and hedgehogs. 

Parish, M.E. 1998a. Coliforms, E. coli and Salmonella serovars associated with a citrus processing facility implicated in a salmonellosis outbreak. J. Food Prot. 61, 280-284. 

Human infection usually occurs from consuming raw or undercooked foods. The largest Salmonellosis outbreak in the United States, involved 16,0(X) cases and was caused by milk products from a Chicago dairy in 1985. Although no outbreaks associated with drinking water have been reported, recent studies found Salmonella widely distributed in Southern California surface water (2). Currently, Salmonella is one of many waterborne pathogens regularly screened by water authorities. 

If a salmonellosis outbreak occurs, a local or state health official will most likely conduct an investigation. School personnel should be prepared to address the following questions ... 

Sagoo, S.K., Little, C.L., Ward, L., Gillespie, I.A. and Mitchell, R.T. (2003) Microbiological study of ready-to-eat salad vegetables from retail establishments uncovers a national outbreak of salmonellosis . Journal of Food Protection, 66, 403-409. 

In the more recent Chicago outbreak of Salmonellosis, which has been attributed to milk contaminated with a tetracycline-resistant strain of Salmonella typhimurium. there were two deaths verified as resulting from infections with the resistant strain of Salmonel la in 16 284 confirmed cases. If one pools these cases with those cited in the NRDC petition then the incidence of mortality (0.09%) is similar or than that of persons affected by antibiotic-sensitive Salmone1 la (0.21%) also cited by NRDC. Thus the similarity of risks of human infections with resistant and sensitive strains of SaImone 11a agrees with research data obtained in controlled experiments (Smith 15). 

The most serious association of antibiotics with salmonellosis was the 1965 outbreak in England of phage type 29 Salmonella typhimurium, resistant to tetracyclines. Six human deaths were attributed to this epidemic. It was traced to "shotgun" treatment of young calves with antibiotics followed by wide dispersal of the calves ( ). Although this epidemic did not involve the use of livestock feeds containing antibiotics, the seriousness of the outbreak led to an inquiry in the UK and a report by the Swann Committee, 1969, into this use. The report of the committee called for a stop to the use of certain common antibiotics in animal feeds in the United Kingdom. 

Salmonella are a frequent cause of foodborne illness, commonly termed "food poisoning," going back long before the use of antibiotics. Salmonellosis is of unusual interest and importance to inhabitants of Chicago because of the outbreak starting in March of 1985, caused by a resistant strain of Salmonella typhimurium. 

In September 1984, Dr. S. Holmberg and co-workers of the Centers for Disease Control (CDC) reported an outbreak of salmonellosis in 18 patients, 13 of whom had consumed hamburger... 

According to Holmberg s summary of salmonellosis published in 1984 and covering the years 1971 to 1983, 17 outbreaks involved resistant organisms and affected 312 persons, 13 of whom (4.2%) died from salmonellosis. Nineteen outbreaks caused by nonresistant organisms resulted in only 4 (0.2%) fatalities in 1,912 ill persons. These percentages have been widely publicized. A fatality of 0.26% was reported in 1972 in a report to FDA by a task force (18). 

Numerous episodes have occurred in which humans have developed drug-resistant nontyphoid Salmonella infections that have been traced to animal sources (23). These bacteria can be transmitted to humans in food or through direct contact with animals. Antimicrobial resistance limits the tlierapeutic options available to veterinarians and physicians for the subset of clinical cases of nontyphoid Salmonella that require treatment. A recent example is a clone of Salmonella typhimurium DT 104 with chromosomally encoded resistance to ampicillin, tetracycline, streptomycin, chloramphenicol and sulfonamides, which has become increasingly common in humans in England and Wales since 1990 (24). Since 1992, only Salmonella enteritidis has accounted for more cases of human salmonellosis than Salmonella typhimurium DT 104 (25, 26). Multiresistant DT 104 has currently emerged in several European countries (27-29) outbreaks have been also reported in the United States in both cattle (30) and humans (31). 

Although most foodborne diseases are sporadic and often not reported, foodborne disease outbreaks may take on massive proportions. For example, in 1994, an outbreak of salmonellosis caused by contaminated ice cream occurred in the United States, affecting an estimated 224,000 persons. In 1988, an outbreak of hepatitis A, resulting from the consumption of contaminated clams, affected some 300,000 individuals in China. 

Likewise, the foodborne outbreak (salmonellosis) in The Dalles, Oregon, perpetrated by the Rajneeshees in September 1984, was not known to have been deliberately caused for almost a year. Were it not for a sudden and incriminating outburst by its leader that led to a full investigation by state and federal authorities, it is possible that the Oregon Salmonella typhimurium outbreak would have never been solved (Miller et al., 2001). 

Torok, T. J., Tauxe, R. V, Wise, R. R, Livengood, J. R., Sokolow, R., Mauvais, S., et al. (1997). A large community outbreak of salmonellosis caused by intentional contamination of restaurant salad bars. Journal of the American Medical Association, 278, 389-395. 

Salmonella typhimurium DT104 is usually resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline. An outbreak of 25 culture-confirmed cases of multidrug-resistant S. typhimurium DT104 has been identified in Denmark (54). The strain was resistant to the above-mentioned antibiotics and nalidixic acid and had reduced susceptibility to fluoroquinolones. A swineherd was identified as the primary source (54). The DT104 strain was also found in cases of salmonellosis in Washington State, and soft cheese made with unpasteurized milk was identified as an important vehicle of its transmission (55). 

The clinical course of human salmonellosis is usually characterized by acute onset of fever, abdominal pain, diarrhea, nausea, and sometimes vomiting. In some cases, particularly in the very young and in the elderly, dehydration can become severe and life threatening. Antibiotic treatment is necessary in less than 2% of the clinical cases. Serious complications occur in a small proportion of cases. The incidence is particularly high in children and the elderly, accounting for up to 60% of all reported laboratory confirmed cases. Studies in developed countries indicate that more than 80% of all salmonellosis cases occur individually rather than as outbreaks. 

Torok, T, Tauxe, RV, Wise, RP, Livengood, JR, Sokolow, R, Mauvais, S, Birkness, KA, Skeels, MR, Horan, JM, Foster, LR. A Large Community Outbreak of Salmonellosis Caused by Intentional Contamination of Restaurant Salad Bars. Journal of the American Medical Association, 278(5) 389-395, 1997... 

There is decreasing incidence in rates of salmonellosis in the United States. Foodborne outbreaks of enteric fever are rare, and a small number of cases often are associated with international travel, especially to developing countries. The most common Salmonella serotypes are Typhimurium and Enteritidis, accounting for approximately 50% of isolates from patients. The overall downward trend in rates of salmonellosis is believed to be due to the improved foodhandling practices and water treatment. 

Food borne diseases may effect a large number of persons in a short time from a common source. Previous outbreaks of Salmonellosis connted thousands of affected persons. Two representative examples of these ontbreaks are the following. In the USA in 1985 contamination of pasteurized milk with Salmonella typhimu-rium caused an outbreak of salmonella infection which affected 170,000 people. Another outbreak in China in 1991, contamination of hquid ice-cream with Salmonella enteritidis affected 224,000 people. 

Transmission of Salmonellosis occurs in the majority of cases by contaminated food. The most common sources are poultry, eggs, fruits, vegetables, dairy products and shellfish. Peanut butter has been also implicated in an outbreak of salmonellosis in the USA and powdered infant formula in two outbreaks with Salmonella enteric in infants in France. 

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