Occurrence of Nontuberculous Mycobacteria, Salmonella, Listeria monocytogenes, and Staphylococcus aureus in Artisanal Unpasteurized Cheeses in the State of Michoacan, Mexico

Abstract

This study investigated the presence of nontuberculous mycobacteria (NTM) for the first time in two types of unpasteurized fresh cheese produced in the state of Michoacan, Mexico. We tested for this pathogen along with the others to broaden the study of microbiological quality in a total of 60 samples of cheese, 30 fresh and 30 adobera, which were collected from six artisanal cheese factories (ACF). The hygienic conditions of these establishments and the practices of cheese manufacture were generally poor. Although Mycobacterium bovis was not detected, four cheese samples harbored NTM isolates. The four NTM isolates were identified using three molecular markers (hsp65, rrs and rpoB genes) which corresponded to Mycolicibacterium fortuitum (n=3) and Mycolicibacterium mageritense (n=1). All 60 cheese samples analyzed had unsatisfactory microbiological quality according to the Mexican Official Guideline. Regarding fresh cheeses, all 30 samples analyzed were positive for aerobic mesophilic bacteria (AMB), total coliforms (TC), fecal coliforms (FC) and yeasts and moulds. Escherichia coli and Staphylococcus aureus were present in 23 and 21 samples, respectively. Listeria monocytogenes was identified in a sample and was isolated from a bulk milk tank in the same ACF. With regard to adobera cheeses, all samples were positive for AMB, TC, FC, yeasts and moulds and S. aureus. E. coli was isolated from 28 samples. Salmonella was isolated from a sample and also from a wooden shovel used in the manufacture of the cheeses in the same ACF. Thus, the consumption of unpasteurized fresh cheese may represent a public health risk. Because of this, health authorities should enforce the legislation that forbids the processing of cheese with unpasteurized milk and encourage producers to follow good manufacturing practices from original ingredients all the way through the production process of the cheese to its sale, in order to assure a safe product.

Microbiological Characteristics and Behavior of Staphylococcus aureus, Salmonella spp., Listeria monocytogenes and Staphylococcal Toxin during Making and Maturing Cotija Cheese

“…The presence of pathogens in cheese depends on several factors: the type of cheese, the microbiological quality of the milk used, and the storage conditions. Fresh cheeses made with unpasteurized milk represent a greater risk because nothing inhibits the pathogen that may be present in the raw milk, favoring the development and/or survival of pathogens [2,4,20]. The difference with a fermented cheese is that the same fermentation process causes the production of compounds and changes in some parameters that can inhibit the development of the pathogens, like pH, lactic acid and the bacteriocins produced by some of the lactic acid bacteria that participate in the fermentation and cheese ripening [18].…”

“…In Mexico, most fresh cheeses are handmade using rustic methods in micro-industries located in small cities. These industries generally have little or no quality control and high composition and sensory parameters variability, leading to a limited shelf life [2][3][4]. However, artisanal matured cheeses show a different reality due to the fermentative processes during the maturation time, giving rise to the Appl.…”

Utilization of Whey for Eco-Friendly Bio-Preservation of Mexican-Style Fresh Cheeses: Antimicrobial Activity of Lactobacillus casei 21/1 Cell-Free Supernatants (CFS)

“…Raw milk used in cheese production may contain pathogens such as E. coli, Listeria, Salmonella, and S. aureus [6,9,12]. These pathogens can survive and spread during cheese production if the milk is not pasteurized correctly or becomes contaminated during handling [52].…”

“…It is common for this variety of cheese to be a vehicle for pathogenic microorganisms, which can be attributed to unpasteurized milk or handling techniques during its production [4]. Unfortunately, there have been multiple cases of illness linked to the consumption of this cheese, as it may contain harmful microorganisms such as Salmonella [5][6][7], Listeria monocytogenes [8][9][10], Escherichia coli [11,12], and Staphylococcus aureus [6,13,14].…”

Koyun Sütünden Üreti̇lmi̇ş Geleneksel Adiyaman Peyni̇ri̇ni̇n Kali̇te Özelli̇kleri̇ni̇n Beli̇rlenmesi̇

“…In the cheeses examined in our study, the presence of E. coli was determined throughout the entire period, and the highest value was determined in June. Vural et al [50] determined the presence of E. coli in 65.21% of the Örgü cheese samples, Costanzo et al [51] in 8.16% of the cheeses produced from raw milk, and Soria-Herrera et al [52] in 38.33% of the unpasteurized cheese samples. The number of E. coli detected in Adıyaman cheese is quite high compared to other studies and considering that the diseases that may be caused by E. coli pathogenic strains, Adıyaman cheese may pose a risk in terms of public health.…”