21 sickened; Yersinia enterocolitica outbreak associated with ready-to-eat salad mix, Norway, 2011

What’s Yersinia doing in salad?

In 2011, an outbreak of illness caused by Yersinia enterocolitica O:9 in Norway was linked to ready-to-eat salad mix, an unusual vehicle for this pathogen.

MacDonald et al report in Emerging Infectious Diseases the outbreak illustrates the need to characterize isolates of this organism, and reinforces the need for international traceback mechanisms for fresh produce. Excerpts below.

Yersiniosis, a notifiable disease in Norway, is the fourth most common cause of acute bacterial enteritis registered by the Norwegian Surveillance System for Communicable Diseases. Approximately 30 domestic cases are reported annually (2010 incidence rate 0.5 cases/100,000 population). In Norway, >98% of cases of Yersinia enterocolitica infection are caused by serotype O:3, which is also the dominant serotype in Europe, Japan, and parts of North America. Infection by Y. enterocolitica is often associated with ingestion of pork because pigs commonly harbor the pathogenic serotypes O:3 and O:9. Recent foodborne outbreaks have been associated with pork products (2,3) and pasteurized milk.

A confirmed case-patient was defined as a person in Norway after January 1, 2011, who had laboratory-confirmed Y. enterocolitica O:9 infection that matched the MLVA profile of the outbreak strain. By May 5, the NRL had registered 21 outbreak case-patients (median age 37 years [range 10–63 years]), of whom 15 were female. Case-patients resided in 10 geographically dispersed municipalities throughout the country. Most case-patients became ill during February 7–March 20.

We traced the suspected salad mix to a single Norwegian company. Under the auspices of the Norwegian Food Safety Authority, we conducted an environmental investigation, including a traceback investigation and a review of production and cleaning procedures at the company. The suspected salad mix contained 4 salad green types: arugula, radicchio rosso, iceberg lettuce, and endive. These ingredients came, unprocessed, from 12 suppliers in 2 European countries. After delivery to the company in Norway, the greens were washed in 2 cold water baths, cut, and packaged. We found no indications of inadequate routines for ingredient control, hygiene, or sampling within Norway. We identified radicchio rosso, a leaf chicory, as the likely source of infection because it can be stored for several months and was the only ingredient included in the suspected salad mix that had delivery, production, and storage dates consistent with the outbreak period. The company in Norway traced the radicchio rosso to 1 of 3 possible growers in 1 European country but was not able to identify the source of contamination. The Norwegian company voluntarily withdrew all salad mixes containing radicchio rosso from the market. After withdrawal of the implicated ingredients, no new outbreak cases were reported.

Reminder from German scientists: seasoned minced meat and raw minced pork are not for little children

A recent study by the Robert Koch Institute found that even small children in Germany eat raw meat more often than expected, so the Federal Institute for Risk Assessment (BfR) decided to remind Germans that raw meat for children is a bad idea.

"Raw animal foods are often contaminated with pathogens", explains Professor Dr. Dr. Andreas Hensel, president of BfR. "For this reason, especially vulnerable sections of the population, such as small children, pregnant women, the elderly and people with a weakened immune system, should as a rule not eat these foods raw."

Raw meat can transmit, among other things, salmonella, Campylo¬bacter, E. coli including EHEC, Yersinia, Listeria and also viruses and parasites.

A recent study by the Robert Koch Institute published in the Epidemiological Bulletin has shown that raw minced pork is the most important risk factor for contracting yersiniosis. Yesiniosis is a gastro-intestinal disease which is notably caused by the bacterium Yersinia enterocolitica. Yersinia are predominantly spread through food, especially raw pork. Pork, for example minced pork and seasoned minced meat, is often eaten raw in Germany. One of the surprising findings of the published study was the high number of children who had eaten raw minced pork. Even of children who were one-year-old or younger it was reported that almost 30% of those who had fallen ill (and 4 % of the control persons) had eaten raw minced pork.

In Germany and other European countries, Campylobacter is now the most prevalent bacterial pathogen for enteric infections in humans. In the year 2011, more than 70,000 human campylobacteriosis cases were reported.

Campylobacter bacteria are notably found in raw or insufficiently heated poultry meat, but also in raw meat of other animals as well as raw milk and hen’s eggs.
The number of reported salmonellosis cases in humans, especially from Salmonella Enteritidis, has fallen significantly in the last three years.

In contrast, human infections with Salmonella Typhimurium have decreased to a lesser extent. SalmonellaTyphimurium are especially common in turkey meat and pork. As part of zoonosis monitoring, salmonella, most frequently Salmonella Typhimurium, were detected in 5 % of minced meat samples in 2009. This finding confirms that raw minced meat can be a source of infection for humans.

To protect themselves against often severe cases of foodborne infections, especially vulnerable sections of the population such as children under five, pregnant women, elderly and persons with a weakened immune system should as a matter of principle refrain from eating raw foods. They should therefore avoid consuming raw mince or seasoned minced meat, raw sausage, raw milk and raw-milk cheese, raw fish (e.g. sushi) and certain fishery products (e.g. smoked and gravad salmon) as well as raw seafood (e.g. raw oysters).

All that and no mention of raw sprouts? In Germany? The risk assessors did say consumers can “protect themselves by cooking meat and poultry sufficiently and evenly” and that “such meat must be cooked until the juices run clear and the meat has a whitish (poultry), gray-pink (pork) or gray-brown (beef) color. The inside temperature of the meat should be at least 70 °C for two minutes. If in doubt, consumers can measure this temperature by means of a meat thermometer.”

Some risk assessors. Color is a lousy indicator and consumers should be using a tip-sensitive digital thermometer to erase doubt. And stop making little kids barf.

Pigs in the patch? 20 sick with yersinia linked to lettuce in Norway

Since February, the Reference Laboratory at the Norwegian Institute of Public Health has identified identical strains of Yersinia enterocolitica O:9 in 20 patients living in Norway.

Interviews with the patients with yersiniosis led to suspicion of a particular pre-packaged lettuce mix that was withdrawn from the market.

Further investigation led to suspicion of several pre-packaged lettuce mixes purchased in grocery stores. Preliminary investigations conducted at the Norwegian Veterinary Institute strengthened this suspicion. The manufacturer has therefore withdrawn a further nine lettuce mixes from the market. The Norwegian Food Safety Authority recommends that consumers should not eat these lettuce mixes. The Norwegian Institute of Public Health is continuing the investigation in co-operation with the Food Safety Authority and Veterinary Institute.

Cocktail sausages sicken kids, need to be reheated

Christchurch butchers handing out free cocktail sausages to children — a New Zealand tradition — have been linked to at least six cases of yersiniosis in kids under five-years-old.

Canterbury’s Medical Officer of Health, Dr Ramon Pink, says cocktail sausages (also known as cheerios or saveloys) should be heated before they are eaten and should not be offered cold to children at butcher’s shops or delicatessens.

The cocktail sausages were given to most of the children over the counter – a common practice which has been associated with outbreaks of salmonella and campylobacter in Christchurch in the past.

While cocktail sausages are cooked during their preparation they are not ready-to-eat foods. Further heating before eating is required to destroy any bacteria that may have contaminated them after they were made.