Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 3/31/2006
Publication Date: 7/4/2006
Citation: Diaz-Cinco, M.E., Luchansky, J.B., Moreno-Enriquez, R.I., Garcia-Galaz, A., Acedo-Felix, E., Gonzalez, H., Call, J.E. 2006. Characterization of listeria monocytogenes from a survey of fresh retail cheese and associated farms in sonora,mexico. [Abstract] 2nd Annual Federation of European Microbiological Societies. P.215. Interpretive Summary:
Technical Abstract: The largest food borne listeriosis outbreak to date in North America was caused by consumption of a soft, Hispanic-style cheese contaminated with L. monocytogenes (Lm). In this study, to determine contamination sources and isolate clonality, sampling collection for this type of cheese in Sonora was designed to address geographical (north, central, and south regions) and seasonal (summer and winter) effects, as well as harborage points (dairy farms, cheese processing plants, and retail markets). The microbiology-based Mexican Official Technique (MOT) was used to recover Lm, and pulsed field gel electrophoresis (PFGE) of genomic DNA digested with the enzyme SmaI was used to establish the relatedness of the multiple isolates retained from each positive sample. Of 381 total samples analyzed, Lm was not recovered from samples tested from dairy farms or cheese processing plants. However, 7 cheese samples (17 isolates)from among 201 retail cheese samples analyzed tested positive for Lm. The distribution among the 201 cheese samples by strata was: i)4 of 122 samples (11 isolates) tested positive in summer and 3 of 79 samples (6 isolates) tested positive in winter; and ii)3 of 41 samples (9 isolates) in the northern, 2 of 134 samples (4 isolates) in the central, and 2 of 26 samples (4 isolates) in the southern regions tested positive for Lm. Each of the 17 isolates displayed a unique SmaI pulsotype, which highlights their heterogeneity and suggests that multiple harborage points exist. Recovery of Lm from retail cheese using MOT argues strongly for additional studies employing more highly sensitive detection methods to better determine the sources, prevalence, and types of LM and to establish strategies to manage the potential threat of listeriosis associated with this type of cheese.