ARS | Publication request: PREVALENCE AND TYPES OF LISTERIA MONOCYTOGENES IN QUESO FRESCO PROCESSED IN SONORA, MEXICO

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 22, 2006
Publication Date: August 13, 2006
Citation: Diaz-Cinco, M., Iniguez-Palomares, C., Acedo-Felix, E., Gonzales-Rios, H., Call, J.E., Luchansky, J.B. 2006. Prevalence and types of listeria monocytogenes in queso fresco processed in sonora, mexico. [Abstract] International Association for Food Protection's Annual Meeting. P2-08. pg. 117

Technical Abstract: Queso fresco (QF) is arguably the most popular Hispanic-style cheese consumed in Mexico. However, because it is often produced by small processors using raw milk, QF provides a favorable environment for the presence/growth of listeriae and serves as a common vehicle for listeriosis. The objective of this study was to determine the prevalence and types of L. monocytogenes in QF manufactured in Sonora, Mexico. We examined 101 QF samples that were obtained from 24 processors located in the northern, central, and southern regions of Sonora. For each cheese sample, a PCR-based and an enrichment/culture-based method were used to detect/recover L. monocytogenes. Isolates were characterized by serotyping, PFGE, and ribotyping. The pathogen was detected in 19 cheese samples using PCR and in eight samples using the enrichment/culture method. A total of 14 isolates were obtained from the eight cheese samples from which the pathogen was recovered by the enrichment/culture method. Ten of the isolates were recovered from six processors in northern Sonora and four of the isolates were recovered from two processors in southern Sonora. All of the isolates were serotype 4b and ribotyping revealed that ten isolates were ribotype DUP1038 and four isolates were ribotype DUP1042. Additionally, PFGE analysis showed that the same 14 isolates associated into eight distinct, but similar, XbaI pulsotypes. This study established the prevalence of L. monocytogenes in QF processed in northern Mexico at between 8 to 19%. Additionally, each isolate was serotype 4b, the serotype that causes most food borne outbreaks, and displayed two ribotypes that have been implicated in a number of food borne outbreaks. These results emphasize the need to conduct additional studies to examine the impact that processing has on the prevalence of L. monocytogenes in this variety of cheese and to develop interventions that will reduce and/or eliminate the pathogen.