Epidemic Listeriosis Associated with Mexican-Style Cheese

Abstract

In Los Angeles County, California, 142 cases of human listeriosis were reported from January 1 through August 15, 1985. Ninety-three cases (65.5 percent) occurred in pregnant women or their offspring, and 49 (34.5 percent) in nonpregnant adults. There were 48 deaths: 20 fetuses, 10 neonates, and 18 nonpregnant adults. Of the nonpregnant adults, 98 percent (48 of 49) had a known predisposing condition. Eighty-seven percent (81 of 93) of the maternal/neonatal cases were Hispanic. Of the Listeria monocytogenes isolates available for study, 82 percent (86 of 105) were serotype 4b, of which 63 of 86 (73 percent) were the same phage type. A case-control study implicated Mexican-style soft cheese (odds ratio, 5.5; 95 percent confidence interval, 1.2 to 24.8) as the vehicle of infection; a second case-control study showed an association with one brand (Brand A) of Mexican-style soft cheese (odds ratio, 8.5; 95 percent confidence interval, 2.4 to 26.2). Laboratory study confirmed the presence of L. monocytogenes serogroup 4b of the epidemic phage type in Brand A Mexican-style cheese. In mid-June, all Brand A cheese was recalled and the factory was closed. An investigation of the cheese plant suggested that the cheese was commonly contaminated with unpasteurized milk. We conclude that the epidemic of listeriosis was caused by ingestion of Brand A cheese contaminated by one phage type of L. monocytogenes serotype 4b.

An Epidemic of Food-Borne Listeriosis in Western Switzerland: Description of 57 Cases Involving Adults

“…First, the overall mortality observed in this outbreak (32%) was similar to mortality rates reported in regard to other outbreaks (29%-37%) [11,12]. The higher meningoencephalitis-associated case-fatality rate in this outbreak (36%) was counterbalanced by a lower bacteremia-associated case-fatality rate (25% vs. 44%-68% in previous descriptions) [7,28].…”

“…Third, underlying conditions were present in only 42% of the patients, a proportion close to the 50% observed in a cluster of 20 cases in Boston [20] but much lower than that reported in association with two previous outbreaks (98% and 100%) [11,12]. However, in another outbreak [13], none of seven nonpregnant adults had an underlying condition.…”

“…In previous outbreaks [11][12][13], CNS listeriosis accounted for 28%, 31%, and 86% of the cases, respectively, and there was a majority of meningitis cases. Variation in case definition may explain the higher proportion of cases of meningoencephalitis but cannot explain the lower number of bacteremia cases.…”

The use of the bacteriocin, nisin, as a preservative in ricotta‐type cheeses to control the food‐borne pathogen Listeria monocytogenes

“…In 1985 consumption of contaminated Jalisco brand Platt 1987), could effectively control contamination with the Mexican-style cheese (queso blanco) manufactured in Calpathogen L. monocytogenes and extend the shelf-life of the ifornia was directly linked to more than 142 cases of listeriosis, product. Cheeses developed with the use of starter culture including 48 deaths (Linnan et al 1988).…”

What Do We Do aboutListeria monocytogenes?

“…The ecological niche of the organism as well as anecdotal case reports of infection with L monocytogenes had pointed to the possibility of foodborne transmission, but this outbreak provided the first solid evidence that epidemic and probably sporadic disease due to L monocytogenes was of food borne origin. Since that time a number of even larger outbreaks of foodborne listeriosis have been described (2)(3)(4).…”