German authorities have highlighted the risks of drinking unpasteurized, raw milk after tests found some of it was contaminated with Listeria, Campylobacter or Shiga toxin-producing E. coli (STEC).

The three pathogens were detected in up to 5 percent of about 360 raw milk samples examined, according to the Federal Office of Consumer Protection and Food Safety (BVL).

Results come from 2019 zoonoses monitoring. Federal and state authorities took 6,792 samples at all levels of the food chain and examined them for the most important foodborne pathogens.

In Germany, drinking milk is generally heat-treated before it is sold to consumers. Those such as small children, the elderly, immunocompromised people and pregnant women are advised to not have unpasteurized, raw milk products.

In total, 18 of 368 samples, or almost 5 percent of bulk tank milk, which is untreated milk directly from the producer, was contaminated with STEC. Bacterial isolates often had the eae gene — one of the main virulence factors.

Campylobacter was detected in nine of 360 samples of tank milk from dairy cattle farms. Listeria monocytogenes was present in 11 of 369 samples but Salmonella was not found in 370 samples.

ESBL or AmpC-producing E. coli were detected in 10.1 percent, or 37 of 368, samples of tank milk using selecive methods.

BVL recommended that milk from the farm is boiled before consumption to kill germs.

Salmonella and Campylobacter in other products
Salmonella was detected in four of 420 samples of unprocessed fish such as tilapia and pangasius. Three of 473 samples of fresh beef sold at retail was contaminated. Two of 515 samples of fresh conventional pork and two of 357 samples of fresh organic pork were positive. Retail fresh ground pork had a Salmonella contamination rate of eight of 429 samples.

A total of 79 isolates were available for typing and they belonged to 16 serovars. The most common were Salmonella Typhimurium, including its monophasic variant and Salmonella Derby.

The detection rate of Campylobacter in fresh retail chicken was 46.4 percent of 472 samples, which is about the same as previous years. Three samples had more than 100 CFU/g with the highest bacterial count being 600 CFU/g.

There has still been little progress in reducing Campylobacter on broiler carcasses. A process hygiene criterion was introduced in 2018 but the proportion of neck skin samples with Campylobacter counts of higher than 1,000 colony forming units per gram was about the same as previous years, at 23.4 percent. Currently 30 percent of samples at the slaughterhouse can exceed this level but this will dro to 20 percent by 2025.

Prevalence of other pathogens
With 31 of 420 positive samples, STEC was frequently detected in ground pork. From retail fresh beef, 21 of 472 samples were positive. STEC was only found once in 399 samples of frozen parsley and four times in 321 samples of fresh baby spinach.

In total, 241 isolates belonged to 49 different O serogroups with O55 and O2 most frequently represented. E. coli O157 was detected six times.

imported fish such as tilapia and pangasius was often contaminated with Listeria monocytogenes with 139 of 420 being positive samples. Listeria monocytogenes was also detected in five of 400 samples of frozen parsley from retail, wholesale or import points.

Yersinia enterocolitica was found in 14 of 511 samples of fresh conventional pork sold at retail or wholesale and six of 355 samples of organic pork. Vibrio was detected in nine of 399 samples of unprocessed freshwater fish from aquaculture such as tilapia and pangasius.