State’s Listeria Tests ‘Not Good Enough’

California’s efforts to test dairy herds for a dangerous strain of bacteria that caused a deadly epidemic earlier this year are deficient and need to be upgraded, according to a federal scientist who reported that the government has been unable to pinpoint the source of the contamination.

Dr. Michael Linnan, an epidemiologist with the Atlanta-based Centers for Disease Control, said in an interview that the state program “is not good enough” because it commingles milk from too many cows--hundreds or more at a time--which makes it difficult to isolate infected herds. He said smaller samples, such as from 50 cows, would be more effective.

Linnan was chief of a special team summoned to Los Angeles earlier this year to investigate the epidemic linked to listeria bacteria found in the Mexican-style soft cheese products produced by Jalisco Mexican Products Inc. of Artesia. The company was shut down in mid-June, and the Los Angeles County district attorney began a criminal investigation which has not yet been completed.

Linnan said potentially toxic listeria bacteria was found by the Atlanta center in one of 26 California control herds that did not supply Jalisco. This fact, he said, provides “a very important lesson” in that there is evidence of “pathogenic listeria” in some California cows. Knowing this, he said, the state should tighten its testing procedures.

Also, Linnan said, the state should devise a more sensitive test for detecting the bacteria, Listeria monocytogenes, noting that current state methods missed the bacteria in the one control herd owned by a Southern California dairy.

Linnan, in a three-page report to Food and Agriculture Director Clare Berryhill dated Oct. 7 and released Tuesday, said that, after 11 weeks of testing, federal investigators could find no evidence of the bacteria in any of the 27 dairy herds that supplied Jalisco.

‘No Closer to Answer’

The results, he said, “have brought us no closer to the answer” of what caused the contamination of the cheese which led to about 100 illnesses statewide and 39 deaths.

“All that can be inferred from the results thus far,” Linnan said, “is that at a point in time a week after the closing of the (Jalisco) plant there were no demonstrable listeria in the milk supplying the plant. . . .

“We are not able to state whether or not the milk supplied to the Jalisco plant was contaminated with listeria during the time that the contaminated cheese was being produced.”

A federal Food and Drug Administration source in Washington said it has no firm evidence pointing to a contamination source either. The county prosecutor will not comment on its investigation.

Asked to respond to Linnan’s remarks, Hans Van Nes, the state Food and Agriculture deputy director, said the state’s listeria-testing program “is something we need to be concerned with.”

In this context, he said, the state has scheduled a meeting for Nov. 19 in Sacramento at which Jalisco investigators from several agencies will analyze the outbreak and “what might have to be done in the future” to prevent a recurrence.