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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Food Safety and Intervention Technologies Research » Research » Publications at this Location » Publication #207938

Title: Sources of contamination and control of Listeria monocytogenes in milk, cheese, and the environment wherein they are produced

item Brito, Jose Renaldi
item Arcuri, Edna
item Dos Santos, Emilia
item Luchansky, John
item Lange, Carla
item Nunes De Souza, Guilherme
item Brito, Maria Aparecida

Submitted to: Revista Leite & Derivados
Publication Type: Trade Journal
Publication Acceptance Date: 2/28/2007
Publication Date: 3/1/2007
Citation: Brito, J., Arcuri, E.F., Dos Santos, E.M., Luchansky, J.B., Lange, C.C., Nunes De Souza, G., Brito, M. Sources of contamination and control of Listeria monocytogenes in milk, cheese, and the environment wherein they are produced. Revista Leite & Derivados. v.16(96):p.89-93.

Interpretive Summary:

Technical Abstract: Listeriosis is an animal and foodborne human disease caused by bacteria of the genus Listeria, especially Listeria monocytogenes. Listeriosis is a very serious and often fatal infection primarily affecting the elderly and perinates. Immunocompromised adults are also highly susceptible to virulent Listeria. Outbreaks caused by L. monocytogenes have been associated with various foods, including dairy products. As a result of its widespread distribution in the environment, its ability to survive for long periods of time under adverse conditions, and its ability to grow at low temperatures, this bacterium is often difficult to control. A collaborative project on foodborne pathogens in cheese and other animal products is being conducted by a network of research centers of Embrapa (Brazilian Agricultural Research Corporation, of the Brazilian Department of Agriculture / MAPA). This project, initiated in 2005, is conducted in cooperation with the USDA-ARS-ERRC. An initial survey was performed to identify L. monocytogenes in pasteurized milk and Minas frescal cheese (MF) sold in Juiz de Fora, State of Minas Gerais, Brazil. MF is a traditional and widely-consumed Brazilian fresh cheese. This pathogen was only recovered from 1 of 10 brands (Brand F) of MF; however, 4 of 5 cheese samples of Brand F were contaminated. These data identified the dairy establishment as the origin of contamination, thus a survey was conducted to localize the source of L. monocytogenes contamination. Samples from 22 environmental sites (9 positives) and 5 cheese (all positives) were subjected to microbiological examination. All L. monocytogenes isolates from cheese obtained at retail, cheese obtained directly from the dairy plant, and the dairy plant environment belonged to the same serotype (1/2a) and the same pulsotype (PFGE type 9). These results identified cold storage equipment as the source of contamination. Based on this knowledge, measures were taken to improve the design and physical condition of the plant, as well as its cleaning and sanitization procedures. The dairy establishment and the cheese produced were surveyed on 4 subsequent visits and all samples examined were negative for Listeria. These findings confirm: (a) the environment of the processing plant plays an important role in preventing Listeria contamination and should be a matter of primary concern for the dairy sector and health authorities; (b) post-processing contamination is probably a common event in dairy establishments; (c) the benefit of proper sanitization and design of small dairy plants, thus reducing the risk of contamination with L. monocytogenes and probably other pathogens; (d) PFGE is a useful tool for identification of the genetic similarity among isolates, and for identifying the source of contamination.