A study in Northern Italy found that some unpasteurized milk sold from vending machines contained potentially harmful levels of pathogens and did not meet public health standards.

The Salmonella, Campylobacter jejuni, E. coli O157 and Mycobacterium avium subsp. paratuberculosis (Map) detected in the milk “pose a clear risk for consumers and could have serious public health consequences,” the researchers wrote. Results of their study appeared in the March 23 issue of the journal Foodborne Pathogens and Disease.

Vending machines are used to dispense raw milk in some European countries, and raw milk advocates in the U.S. sometimes point to this easy availability as evidence that the unpasteurized milk must be safe. The sale of raw milk — latte crudo — from self-service automatic vending machines has been allowed in Italy since 2004.

The investigation looked at 33 farms in the Emilia-Romagna region of Northern Italy that together sell about 3,500 liters of unpasteurized milk daily via 60 vending machines. From January to July 2010, researchers collected 66 samples from farm bulk tanks and 66 from vending machines in the first part of the study, and then another 99 samples from vending machines in the second part of the study.

The samples were analyzed using various test methods, from the standard culture method of detection (ISO) to polymerase chain reaction (PCR) tests and also the modified Bacteriological Analytical Manual cultural method (mBAM).

All pathogens investigated were detected in the raw milk sold from vending machines; 5 percent of the samples had at least one pathogen. However, none of the pathogens was detected using the official ISO tests — the method the area’s regulators rely on to check the safety of the milk and order recalls, if necessary, leading the researchers to suggest that such tests are not sensitive enough. The pathogens were detected using the PCR and mBAM tests.

“Given that extremely small numbers of organisms are present and that they may not be evenly distributed in the milk,” the researchers said ISO is “consequently not appropriate” as the official method for testing raw milk.

They point out that even extremely small amounts of bacteria may be infectious and pathogens may proliferate after testing to levels that pose unacceptable risks. The study notes four disease outbreaks — two due to Campylobacter and two to E. coli O157:H7 —   linked to consumption of unpasteurized milk in the Emilia-Romagna region, despite prior testing conducted at the farms.

In the study, another concern was that three samples of raw milk tested positive for Mycobacterium avium subsp. paratuberculosis, also known as Map.  Map causes Johne’s disease in cattle and other ruminants, and has been suspected as a possible cause of Crohn’s disease in humans. The researchers said the positivity of 3 percent of samples suggests that “raw milk consumption is a significant source of Map exposure for consumers.”

In comparison with milk samples collected from bulk tanks, the milk samples collected from vending machines showed a significant increase of total bacterial count “meaning that raw milk was mishandled during distribution and sale,” perhaps due to lack of consistent temperature control, “which may result in an increase of pathogenic microbial load, raising further questions on raw milk safety,” the authors wrote.

The researchers concluded that  “raw milk sold in vending machines in the considered

province does not have an optimal microbiological quality and does not meet criteria fixed by law in terms of safety for hygienic quality and for exposition to all the pathogenic

bacteria investigated in the study.”

In order to ensure consumers’ safety, the researchers advised “a new approach” to avoid mishandling raw milk being transported from farm to vending machines, and also that the milk should undergo adequate testing at the farms to determine if it is contaminated.