Incidence of Salmonella, Listeria monocytogenes, Escherichia coli O157:H7, and Staphylococcal Enterotoxin in Two Types of Mexican Fresh Cheeses

Abstract

Handcrafted fresh cheeses are popular among consumers in Mexico. However, unsafe raw materials and inadequate food safety practices during cheese manufacture and preservation make them a potential public health risk. The incidence of Salmonella, Listeria, Escherichia coli O157:H7, and staphylococcal enterotoxin was analyzed in two types of fresh cheese (panela and adobera) commonly marketed in Mexico. A total of 200 samples, 100 panela and 100 adobera, were acquired from 100 wholesale milk product distributors who supply small retailers in the Guadalajara metropolitan area, Jalisco State, Mexico. Pathogens were identified using culture and immunoassay (miniVidas) methods. The presence of staphylococcal enterotoxin was determined by an immunoassay method. Of the 200 analyzed samples, 92 were positive for at least one of the pathogens. The incidence in the panela samples was 56%: 34% Salmonella, 16% E. coli O157:H7, and 6% L. monocytogenes. In the adobera samples, incidence was 36%: 20% Salmonella, 4% E. coli O157:H7, and 12% L. monocytogenes. Staphylococcal enterotoxin was not detected in any of the 200 samples. Choice of technique had no effect on detection of pathogen incidence, although the immunoassay method identified more Salmonella serotypes than the culture method. Handcrafted panela and adobera fresh cheeses in Mexico frequently contain pathogenic bacteria and therefore pose a public health risk.

Outbreaks Attributed to Cheese: Differences Between Outbreaks Caused by Unpasteurized and Pasteurized Dairy Products, United States, 1998–2011

“…This practice has repeatedly resulted in outbreaks associated with queso fresco and other Mexican-style cheeses made from unpasteurized milk (Linnan et al , 1988; Altekruse et al , 1998; Cody et al , 1999; Villar et al , 1999; MacDonald et al , 2005; Centers for Disease Control and Prevention, 2008). One study found that 46% of cheese samples imported from Mexico were contaminated with Salmonella, E. coli O157:H7, or Listeria, in addition to frequent contamination by debris and insects (Torres-Vitela et al , 2012). Surveys of imported cheeses have found higher levels of pathogens in cheeses imported from Mexico and Central America than other regions (D’Amico and Donnelly, 2011).…”

Pathogen inactivation and quality changes in sliced cheddar cheese treated using flexible thin-layer dielectric barrier discharge plasma

“…In 2010, 41 people across five southwestern states of the United Stateswere afflicted by food poisoning due to Escherichia coli O157:H7 and majority of them reported the consumption of Gouda cheese (McCollum et al, 2012). Moreover, Torres-Vitela et al (2012) observed that high incidence of E. coli O157:H7, Salmonella, Listeria, and staphylococci occurrence in cheeses that are commonly marketed in Mexico. Food safety is undoubtedly the important priority for the food industry as well as consumers.…”

Knowledge, Attitudes, and Practices among Border Crossers during Temporary Enforcement of a Formal Entry Requirement for Mexican-Style Soft Cheeses, 2009

“…For several years before 2009, surveys and enhanced surveillance operations conducted by the FDA, the CBP, and state health agencies at noncommercial ports of entry (POE) along the United States–Mexico border have revealed high violation rates for raw milk cheeses and evidence of pathogens in imported QF, including Salmonella , Escherichia coli O157:H7, Listeria spp., and Mycobacterium bovis ( 14, 16, 18, 21, 29 ) . QF-associated disease is more common in Hispanic populations, among whom pregnant women and the elderly appear to be at increased risk ( 24, 27 ) .…”

“…QF-associated disease is more common in Hispanic populations, among whom pregnant women and the elderly appear to be at increased risk ( 24, 27 ) . Outbreaks and sporadic cases of salmonellosis, listeriosis, brucellosis, and M. bovis infections have been frequently associated with consumption of QF in Hispanic communities in California and throughout the United States ( 4–9, 11, 19, 25, 29 ) .…”