Shigella in the trenches
Why Shigella? One reason is that few bacteria are needed for a person to become ill. Another reason is that the Shigella bacteria are present in the diarrheal stools of infected persons while they are sick and for up to two weeks after they’ve been sick. Most Shigella infections are the result of the bacterium passing from stools or soiled fingers of one person to the mouth of another person because the person handling the food didn’t wash hands with soap after using the bathroom. Publicity about handwashing exists because Shigella bacteria is estimated to cause 450,000 cases of gastroenteritis each year (infections usually result in acute diarrhea), mostly among children under the age of 5. Raw vegetables can become contaminated if they are harvested from a field with sewage in it. Flies can breed in infected feces and then contaminate food as they land on it. Water may become contaminated with Shigella bacteria if sewage or fecal matter runs into it.
During the past two decades, numerous outbreaks of Shigella sonnei have been associated with day-care centers. This makes sense as toddlers aren’t always fully toilet-trained, and their family members and playmates are put at risk of infection. This is also a concern as children under the age of 9 don’t have the immune system development to fight infections easily, so they are harder hit and at greater risk of complications.
Day-care centers aren’t the only venue heavily affected by Shigella. Other foodservice operations have been the source of outbreaks. In one Centers for Disease Control (CDC) investigation, the ubiquitous garnish of parsley was found to be the food vehicle for a multi-state outbreak. Seven outbreaks linked by Pulsed-field gel electrophoresis (PFGE, a multi-state “finger-printing” of suspected pathogens) of stool samples from those who were ill found chopped, uncooked curly parsley to be the common food. Traceback investigations found one farm to be a possible source for the parsley served in six of the seven outbreaks. The municipal water that supplied this farm’s packing shed hydro-cooler and used in making ice for packing prior to transport was not chlorinated. The investigation also showed many of the farm workers had limited training in hygiene and there were few sanitary facilities available.
In many instances of contamination, water has been called a stealth player, and this example illustrates that. It also illustrates the need for farm workers to be considered food handlers. Should regulations in place for retail foodservices (as per Food Code) also be in place for farm workers?
Once the contaminated parsley arrived at the restaurants, it was washed, chopped and left at room temperature. This holding time and temperature, along with additional moisture, was conducive for growth of the bacteria, which led to this multi-state outbreak affecting more than 500 people.