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Raw milk can harbor Campylobacter even after negative tests

Raw milk can harbor dangerous bacteria, even when routine testing results show it to be uncontaminated, says a report from Utah on a 2014 outbreak of confirmed or suspected campylobacteriosis in 99 individuals. The report appears in today’s issue of Morbidity Mortality Weekly Report (MMWR).

The outbreak began in May 2014 with three patients who tested positive on pulsed field gel electrophoresis for Campylobacter jejuni. They had all consumed raw milk from an unnamed dairy in Weber County in northern Utah. The dairy’s routine testing, which is required monthly of dairies selling raw milk in Utah and consists of somatic cell and coliform counts, had yielded results within acceptable levels (<400,000 somatic cells/mL and <10 coliform colony forming units/mL).

Enhanced testing after the illnesses were identified showed C jejuni in the dairy’s milk.

Officials suspended the dairy’s permit in August and then reinstated it Oct 1 after follow-up cultures were negative. However, seven more C jejuni cases occurred by Nov 4, and the permit was permanently revoked Dec 1.

It total, 99 people in Utah, 85 (86%) of them from northern counties, were identified through lab testing and patient interviews as having confirmed (59) or probable (40) cases of campylobacteriosis from May 9 to Nov 6, 2014. Patients ranged in age from 1 to 74 years; 10 were hospitalized, and 1 died.

Of the 98 patients for whom exposure history was available, 53 reported drinking raw milk, 52 of them milk from the Weber Country dairy; 4 drank raw milk but could not name the dairy where it was purchased, and 14 bought raw milk at the dairy but did not report drinking it.

The authors point out that “Current raw milk testing standards do not readily detect contamination.” They recommend more education of consumers about the dangers associated with consuming unpasteurized milk, and they conclude, “The safest alternative is to consume pasteurized milk.”