Multistate Outbreak of Listeria monocytogenes Associated with Mexican-Style Cheese Made from Pasteurized Milk among Pregnant, Hispanic Women

Enteric Diseases Epidemiology Branch, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
Journal of food protection (Impact Factor: 1.85). 06/2011; 74(6):949-53. DOI: 10.4315/0362-028X.JFP-10-536
Source: PubMed


Listeriosis is a severe infection caused by Listeria monocytogenes. Since 2004, the Centers for Disease Control and Prevention has requested that listeriosis patients be interviewed using a standardized Listeria Initiative (LI) questionnaire. In January 2009, states and the Centers for Disease Control and Prevention began investigating a multistate outbreak of listeriosis among pregnant, Hispanic women. We defined a case as an illness occurring between October 2008 and March 2009 with an L. monocytogenes isolate indistinguishable from the outbreak strain by pulsed-field gel electrophoresis. We conducted a multistate case-control study using controls that were selected from L. monocytogenes illnesses in non-outbreak-related pregnant, Hispanic women that were reported to the LI during 2004 to 2008. Eight cases in five states were identified. Seven of these were pregnant, Hispanic females aged 21 to 43 years, and one was a 3-year-old Hispanic girl, who was excluded from the study. Seven (100%) cases but only 26 (60%) of 43 controls had consumed Mexican-style cheese in the month before illness (odds ratio, 5.89; 95% confidence interval, 1.07 to ∞; P = 0.04). Cultures of asadero cheese made from pasteurized milk collected at a manufacturing facility during routine sampling by the Michigan Department of Agriculture on 23 February 2009 yielded the outbreak strain, leading to a recall of cheeses produced in the plant. Recalled product was traced to stores where at least three of the women had purchased cheese. This investigation highlights the usefulness of routine product sampling for identifying contaminated foods, of pulsed-field gel electrophoresis analysis to detect multistate outbreaks, and of the LI for providing timely exposure information for case-control analyses. Recalls of contaminated cheeses likely prevented additional illnesses.

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    • "Several categories of ready-to-eat (RTE) foods have been associated with listeriosis outbreaks including vegetables (corn, celery, coleslaw, sprouts/taco salad) [6] [7] [8] [9]; fruits (cantaloupe ) [10]; processed deli meats (beef, turkey, hog head cheese, hot-dogs, cooked ham, jellied pork, RTE sandwiches) [11] [12] [13] [14] [15] [16] [17]; seafoods (crab meat, cold-smoked trout, smoked mussels, shrimp) [6, 18–20]; unpasteurized dairy products (Mexican soft cheese, raw milk cheeses, on farm fresh cheese) [21] [22] [23] [24] [25]; pasteurized dairy products (butter, soft cheese, sour milk curd cheese, fluid milk) [26] [27] [28] [29] [30] [31] [32]. "
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    ABSTRACT: Soft ripened cheese (SRC) caused over 130 foodborne illnesses in British Columbia (BC), Canada, during two separate listeriosis outbreaks. Multiple agencies investigated the events that lead to cheese contamination with Listeria monocytogenes (L.m.), an environmentally ubiquitous foodborne pathogen. In both outbreaks pasteurized milk and the pasteurization process were ruled out as sources of contamination. In outbreak A, environmental transmission of L.m. likely occurred from farm animals to personnel to culture solutions used during cheese production. In outbreak B, birds were identified as likely contaminating the dairy plant’s water supply and cheese during the curd-washing step. Issues noted during outbreak A included the risks of operating a dairy plant in a farm environment, potential for transfer of L.m. from the farm environment to the plant via shared toilet facilities, failure to clean and sanitize culture spray bottles, and cross-contamination during cheese aging. L.m. contamination in outbreak B was traced to wild swallows defecating in the plant’s open cistern water reservoir and a multibarrier failure in the water disinfection system. These outbreaks led to enhanced inspection and surveillance of cheese plants, test and release programs for all SRC manufactured in BC, improvements in plant design and prevention programs, and reduced listeriosis incidence.
    BioMed Research International 03/2015; 2015:12 p.. DOI:10.1155/2015/131623 · 2.71 Impact Factor
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    • "Over the last eight years, incidence rates ranging from 0.3 to 1.3 per 100,000 capita have been reported in European countries, the U.S., Canada and Australia (Todd and Notermans, 2011). Cheese-related foodborne outbreaks were often linked to major deficiencies in good hygiene practices, inadequate process monitoring and fluctuation in L. monocytogenes contamination dynamics (Fretz et al., 2010; Koch et al., 2010; Jackson et al., 2011; Schoder et al., 2012; Yde et al., 2012). L. monocytogenes is difficult to eradicate due to surface and niche colonization, resistance conditions of low pH (b 4.4), water activity (b 0.94) and growth at refrigeration temperatures (Ortiz et al., 2010; Tasara and Stephan, 2006). "
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    ABSTRACT: The aim of this study was to analyze the changing patterns of Listeria monocytogenes contamination in a cheese processing facility manufacturing a wide range of ready-to-eat products. Characterization of L. monocytogenes isolates included genotyping by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Disinfectant-susceptibility tests and the assessment of L. monocytogenes survival in fresh cheese were also conducted. During the sampling period between 2010 and 2013, a total of 1284 environmental samples were investigated. Overall occurrence rates of Listeria spp. and L. monocytogenes were 21.9% and 19.5%, respectively. Identical L. monocytogenes genotypes were found in the food processing environment (FPE), raw materials and in products. Interventions after the sampling events changed contamination scenarios substantially. The high diversity of globally, widely distributed L. monocytogenes genotypes was reduced by identifying the major sources of contamination. Although susceptible to a broad range of disinfectants and cleaners, one dominant L. monocytogenes sequence type (ST) 5 could not be eradicated from drains and floors. Significantly, intense humidity and steam could be observed in all rooms and water residues were visible on floors due to increased cleaning strategies. This could explain the high L. monocytogenes contamination of the FPE (drains, shoes and floors) throughout the study (15.8%). The outcome of a challenge experiment in fresh cheese showed that L. monocytogenes could survive after 14days of storage at insufficient cooling temperatures (8 and 16°C). All efforts to reduce L. monocytogenes environmental contamination eventually led to a transition from dynamic to stable contamination scenarios. Consequently, implementation of systematic environmental monitoring via in-house systems should either aim for total avoidance of FPE colonization, or emphasize a first reduction of L. monocytogenes to sites where contamination of the processed product is unlikely. Drying of surfaces after cleaning is highly recommended to facilitate the L. monocytogenes eradication.
    International Journal of Food Microbiology 08/2014; 189C:98-105. DOI:10.1016/j.ijfoodmicro.2014.08.001 · 3.08 Impact Factor
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    • "Over the past 27 years Listeria monocytogenes has become increasingly important as a food-associated pathogen, and dairy products are seen as one of the main vehicles (Gaulin et al., 2012; Jackson et al., 2011; Lomonaco et al., 2009). Recently, an invasive multinational listeriosis outbreak was linked to cheese. "
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    ABSTRACT: It has been possible to determine the genotype diversity of Listeria monocytogenes in the actual cheese lots of acid curd cheese that caused a multinational outbreak between 2009 and 2010. Following product recall in January 2010 all lots were investigated. A total of 422 L. monocytogenes isolates were characterized by genotyping. In a first approach the PCR serogroups were defined by multiplex-PCR assays. Subsequently, the isolates were subtyped by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Sequence types were assigned by submitting the DNA sequences to the Listeria MLST database at the Institute Pasteur. The serogroup PCR resulted in a homogeneous 1/2a – 3a (genetic linage II) cluster. The generated PFGE patterns divided the strains into two clusters (type 1 and 2) diverging at a homogeneity level of 74%. PFGE-type 2 was predominant, accounting for 98.3% (n = 415/422) of the isolates and was isolated during the whole period of acid curd cheese processing (01.12.2009–13.01.2010). 1.7% of all tested L. monocytogenes isolates (n = 7/422) belonged to PFGE-type 1 and were isolated from 28% of all cheese lots (n = 5/18) produced between the time span of 08.12.2009 to 13.01.2010. Furthermore, PFGE-type 1 and 2 showed the same PFGE patterns as the human outbreak strains (clone 1 and clone 2).
    Food Microbiology 05/2014; 39:68–73. DOI:10.1016/ · 3.33 Impact Factor
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