Milk That Was Pasteurized Believed Cause of Infection

An outbreak of a rare, fatal infection was apparently caused by bacteria in milk, indicating that pasteurization may not be effective in some instances, the Centers for Disease Control reported Wednesday.

The disease, called listeriosis, occurred across Massachusetts in August, 1983. There were 49 victims, including two fetuses and five newborns, and 14 of them died.

Bacteria Survived

In today’s New England Journal of Medicine, researchers from the Centers for Disease Control linked the outbreak to store-brand milk sold by a supermarket chain. Apparently, the bacteria in the milk were not all killed and may have multiplied during the cold-storage process.

The researchers said it is the first known instance in which bacteria apparently eluded pasteurization and caused illness in persons.

Their results suggest that, “although pasteurization is a highly effective method of eliminating bacterial pathogens (disease producers), it may not always be 100% effective,” the researchers wrote.

Raw, or unpasteurized, milk is frequently associated with outbreaks of food poisoning, and the researchers said persons should not turn against pasteurized milk on the basis of the latest finding.

“It is important to remember the potential benefits of this food product and the amount of human illness caused by consumption of unpasteurized milk,” they wrote.

Occurs in Summer

Listeriosis is caused by a germ called Listeria monocytogenes. It occurs most frequently during the summer and can result in spontaneous abortion, meningitis and blood infection called septicemia.

All the milk implicated in the outbreak was pasteurized at a single plant. Inspectors found that the dairy was clean, modern and well-run, and it seemed to have processed the milk correctly.