Retail Survey of Brazilian Milk and Minas Frescal Cheese and a Contaminated Dairy Plant To Establish Prevalence, Relatedness, and Sources of Listeria monocytogenes Isolates

Abstract

A study was designed to recover Listeria monocytogenes from pasteurized milk and Minas frescal cheese (MFC) sampled at retail establishments (REs) and to identify the contamination source(s) of these products in the corresponding dairy processing plant. Fifty milk samples (9 brands) and 55 MFC samples (10 brands) were tested from REs located in Juiz de Fora, Minas Gerais, Brazil. All milk samples and 45 samples from 9 of 10 MFC brands tested negative for L. monocytogenes; however, "brand F" of MFC obtained from REs 119 and 159 tested positive. Thus, the farm/plant that produced brand F MFC was sampled; all samples from the milking parlor tested negative for L. monocytogenes, whereas several sites within the processing plant and the MFC samples tested positive. All 344 isolates recovered from retail MFC, plant F MFC, and plant F environmental samples were serotype 1/2a and displayed the same AscI or ApaI fingerprints. Since these results established that the storage coolers served as the contamination source of the MFC, plant F was closed so that corrective renovations could be made. Following renovation, samples from sites that previously tested positive for the pathogen were collected from the processing environment and from MFC on multiple visits; all tested negative for L. monocytogenes. In addition, on subsequent visits to REs 159 and 119, all MFC samples tested negative for the pathogen. Studies are ongoing to quantify the prevalence, levels, and types of L. monocytogenes in MFC and associated processing plants to lessen the likelihood of listeriosis in Brazil.

Occurrence of Escherichia coli and Coliforms in Minas Cheese Plants from S?o Paulo, Brazil

“…Minas cheeses usually have pH values of 5.0 -6.3, salt concentration between 1.4 and 1.6%, high water activity and moisture content above 55% [3,4]. These characteristics provide ideal conditions for the multiplication of pathogenic and spoilage microorganisms [5][6][7].…”

Detection of the contamination sources of Listeria monocytogenes in pickled white cheese production process line and genotyping with the pulsed-field gel electrophoresis method

“…High contamination levels of L. monocytogenes in raw milk in cheese production lines have been observed by many researchers (16,17). In this study, the isolation of L. monocytogenes from 3 different points of the production process, and especially from raw milk, illustrates the contamination risk during pickled white cheese production.…”

Formación de biopelículas por Listeria monocytogenes aisladas de queso fresco de mercados del Cercado de Lima

“…En México, Soto (21) investigó la incidencia de dicha bacteria en 75 quesos frescos, obteniendo un valor de 9,3%. En Brasil, Brito (22) aisló L. monocytogenes en leche, queso fresco y ambientes industriales, obteniendo una incidencia de 11% (6/55) en quesos frescos. Por otro lado, la proporción de L. monocytogenes en nuestro estudio es mayor a lo hallado por investigadores peruanos en Trujillo, como Díaz (23) quien detectó su presencia en 3,34% de muestras de quesos frescos.…”