A recent article in Frontier Microbiology featured in their Food Microbiology section titled “Campylobacter fetus Foodborne Illness Outbreak in the Elderly” is part of an ongoing series called From Farm Gate to Food Plate: Current Challenges In Foodborne Microorganism Detection, Epidemiology, and Genetic Diversity. The purpose of this study was to raise awareness of this infectious disease among physicians working with at-risk patients, such as the elderly or immunocompromised patients. It also brought to light a rare type of Campylobacter strain.

Here, researchers looked at a Campylobacter outbreak with a rare strain, Campylobacter fetus, that sickened 7 elderly patients at a rehabilitation center in Southeast France in June 2021.

According to the study, the outbreak was linked to unpasteurized, raw cow’s milk cheese.

French Institute of Public Health Notified of Outbreak Cluster

The French Institute of Public Health was notified of the occurrence of cluster of digestive illness with fever among hospitalized patients in a rehabilitation center, prompting an outbreak investigation. Why? This is usually a sign of foodborne illness or some other kind of “stomach flu,” which is pretty much the same thing.

The age range of the patients was 70 to 90 years old. This places all of them in the “higher risk” category when it comes to foodborne illness, meaning they are more likely to experience complications and longer recover.  Five of the patients were at the facility for post-orthopedic surgery reeducation, one of which was also recovering from post-acute heart failure. The final patient was recovering from acute myeloid leukemia chemotherapy. Age and health status places them at the top of the high-risk category.

Patient Symptoms

The patients had similar symptoms. Mild watery diarrhea with a maximum of five stools a day over the course of five days. There were no reports of nausea or vomiting. Five of the patients had a fever. All common symptoms of Campylobacter infection. No patient developed sepsis. Of the six patients with implanted medical devices, two had infections (hip prosthesis and shoulder prosthesis).

Lab Tests Revealed Rare Campylobacter Strain

A variety of laboratory tests were preformed to identify what was making these elderly women sick. Both blood and stool samples were analyzed for nearly all patients and synovial fluid (fluid in the joints) was available for testing for one patient. The results were conclusive.

Three of the five patients with blood culture analysis resulted in positive Campylobacter fetus isolation. Two of the patients had the rare bacteria in both their blood and stool samples. A type of genetic identification called Polymerase Chain Reaction (PCR) identified Campylobacter fetus in two of the patient stool samples and in the one patient whose synovial fluid (joint fluid) was tested.

No other intestinal bacteria were found in the stools except for one patient who was also infected with Listeria monocytogenes. Fortunately, antibiotic resistant testing revealed that all of the patients should respond to common antibiotics, such as ampicillin, amoxicillin + clavulanic acid, gentamicin, erythromycin, ciprofloxacin, and tetracycline.

Raw Milk Cheese Implicated

Extenuating circumstances prevent definitive conclusions, however raw milk cheese has been strongly implicated in this outbreak. The majority of patients indicated consuming unpasteurized cow’s milk cheese of the Tomme des Pyrénées variety. Some patients also consumed another raw milk cheese variety, Camembert, prior to becoming sick.

The presence of Listeria monocytogenes in a patient sample also strengthens this conclusion, as Listeria is a common contaminant in raw milk cheese.

These cheeses were served as part of a recently implemented “farm-to-fork strategy” though unpasteurized dairy products should have been avoided.

Hygiene Issues in the Kitchens

Hygiene issues in the rehabilitation center’s kitchens may have been a contributing factor in the Campylobacter outbreak.

A traceback investigation was initiated by French public health authorities, revealing “serious hygiene issues” in the facility’s kitchens. In fact, the kitchen was shut down due to “disrespect of ‘cold-chain’ guidelines” on June 14, 2021.

The presence of harmful bacteria in the raw milk cheese and deviations in temperatures may have allowed harmful bacteria to grow in infectious numbers sufficient to cause harm in the at-risk population of the rehabilitation center.

Cheese Samples Not Tested

Ideally a traceback investigation would involve testing foods that were consumed by the outbreak patients. Unfortunately, it was not possible to clearly incriminate either for the raw milk cheeses in the outbreak due to the absence of microbiological analysis of the suspected food samples.

The Dangers of Raw Milk Cheese

You may have heard from different sources that raw milk cheese is dangerous. And it is. Specifically for higher risk populations such as the elderly, those with a compromised immune system, and pregnant women. But what makes it so dangerous? It is made from raw milk.

What is Raw Milk

Raw milk is milk that has not been pasteurized. The process of pasteurization is designed to kill harmful bacteria that may be lurking in the milk. Milk coming directly from the animal is not innately harmful in most cases. But a lot happens between milk being produced by the animal, to consumption.

Dairy animals, no matter how well maintained, live in unsterile environments. Their utters must be sufficiently sanitized so ensure potential bacteria or contaminants do not transfer into the milk. Equipment, transportation, containers, and so many other steps in the production process leave milk vulnerable to contamination. The milk itself provides an excellent medium for bacterial growth, if left to its own devices.

How Dangerous is It?

According to a study published by the Center for Disease Control and Prevention and Prevention (CDC), unpasteurized dairy products are 840 times more likely to cause illness and 45 times more likely to result in hospitalization than pasteurized dairy products. The study suggests that as the popularity of raw dairy products grow, so will the incidence of illness where “the consumption of unpasteurized milk or cheese could increase outbreak-related illnesses by 96%.”

Aging Reduces Risk

The aging process should reduce the risk of harmful bacteria, but it isn’t absolute. In 1949, the FDA enacted a 60-day rule that required raw milk cheese to be aged a minimum of 60 days. At the time, there were no known disease-causing pathogens that could survive the acidifying process of aging cheese. New studies show that this isn’t necessarily the case, but the rule persists.

In some cases, the 60 days rule works. In others it doesn’t. For this reason, it is recommended that those in high-risk categories avoid all things unpasteurized.

Conclusion of Study

The investigation into this Raw French Cheese Campylobacter Outbreak brings to light some important factors when it comes to high-risk populations.

“This highlights the importance of routine hygienic measures to prevent transmission within facilities housing people at risk. Even if the source of infection was only suspected and not confirmed, consumption of unpasteurized dairy products should also be avoided in these specific populations.”

Even in France.

By: Heather Van Tassell