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Salmonella enteriditis, an organism dear to my heart (luckily not my posterior small intestine) is a common cause of food poisoning. As some of you may know, I did my PhD thesis work on Salmonella gastroenteritis (aka food poisoning) and I like to think that I am something of an expert on the topic. 

Typically, Salmonella food poisoning outbreaks are localized and rarely reach epidemic proportions. However, there have recently been two major nationwide Salmonella outbreaks in the US —one in 2007 and now in early 2009.

The current outbreak has afflicted 388 people in 42 states and may be caused by the same strain (Saint Paul) that was responsible for the 2007 outbreak. Ultimately, the 2007 outbreak was linked to contaminated tomatoes. The jury is still out on the cause of the most recent outbreak. Needless to say, CDC scientists are scurrying to quickly identify the source of the current outbreak because it took the agency over 5 months to conclusively identify the culprit in the 2007 epidemic. Not surprisingly, many grocery stores and restaurants suffered financially because of the outbreak.

Many of you may be wondering why Salmonella food poisoning is becoming such a problem in the US. I don’t believe that the strains responsible for the most recent outbreaks are more virulent than the ones that have traditionally caused more localized outbreaks. Instead, the reliance of food manufacturers and grocery store chains on one or two major food distributors (rather than multiple suppliers) is likely responsible for the severity and breadth of these nationwide outbreaks. This suggests that regulatory agencies ought to more closely scrutinize the microbiological quality of the operations of the major distributors. I believe that those efforts would greatly reduce the likelihood of future major outbreaks of food poisoning.

Until next time.

Good Luck and Good Job Hunting (avoid raw vegetables, undercooked poultry and raw eggs)
 

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This may be one of the more notable years for Salmonella food poisoning. First, there was a modest outbreak in the eating clubs at Princeton University and now a larger outbreak in Texas and New Mexico. This is the first time that I can recall in my almost 30 years as a card-carrying food microbiologist that there has been this many highly-publicized cases of Salmonella food poisoning in one year. Although I don’t wish Salmonella gastroenteritis on anybody, it is kind of rewarding that an organism that led to my PhD is making headlines once again. Typically, Salmonella outbreaks are not noteworthy and rarely receive much notice— usually taking a backseat to potentially life-threatening outbreaks of enteropathogenic Escherichia coli.

Like the Princeton outbreak, the exact source of the Salmonella infection is unclear. That said, public health and CDC officials are leaning towards large, raw tomatoes. In 2006, the Food and Drug Administration discovered that consumption of tomatoes in restaurants had caused a salmonella outbreak that affected 21 states. , “until the source of the outbreak is identified federal and local health officials in both states have recommended that infants, the elderly and anyone with an impaired immune system avoid eating Roma and red round tomatoes that are not grown at home or sold attached to the vine.” So far, 40 confirmed cases, with patients ranging in age from 3 to 82, have been reported in New Mexico and Texas since April. To date, 17 people have been hospitalized, but no deaths have been reported.

Molecular analyses indicated that all of the cases in New Mexico and Texas were caused by the same strain, a relatively rare serovar called Saint Paul (6^th most common serovar infecting humans). Federal health officials at the Centers for Disease Control in Atlanta, GA fear that this may be the beginning of a large national outbreak of Salmonella gastroenteritis. This is because about 30 cases caused by the Saint Paul strain, have also been reported this year in Arizona, Colorado, Idaho, Illinois, Indiana, Kansas and Utah. Like the New Jersey, Texas and New Mexico outbreaks, the cause of those other outbreaks is under investigation.

Salmonella gastroenteritis generally last between four and seven days, and most people are able to recover without medical (antibiotic) treatment. But, it can sometimes lead to death in immunocompromised adults or young children. Symptoms include headache, nausea, abdominal pain, diarrhea and sometimes vomiting.  Although textbook descriptions of the pathogenesis of Salmonella gastroenteritis generally portray it as a mild illness, I can tell you that people I know (lab mates of mine) who came down with the disease (gee, how did that happen?) suggest otherwise!

I suspect that fecally-contaminated water may be source of the infection. But, then again, it has been almost 30 years since I thought about Salmonella gastroenteritis. That said, I don’t think that you ever forget the essence or minutiae of your thesis work!

For those of you who are interested, the electron micrograph of Salmonella typhimurium shown with this post is from my PhD dissertation. As I recall, the electron micrograph was taken in 1980 and the bacterium shown in the micrograph was grown for 48 hours on nutrient agar . Althought I would like to take credit for the shot (nice pose eh?),  it was taken by Phil Hegge in the Department of Bacteriology at the University of Wisconsin-Madison, my alma mater. if you look closely you may be able to see fimbriae along with the flagella.

Until next time

Good Luck and Good Job Hunting (and remember to wash your tomatoes)!!!!!

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