Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Prolongación Carpio y Plan de Ayala S/N, Col. Casco de Santo Tomas, Mexico City CP 11340, Mexico.
Department of Molecular Biomedicine, CINVESTAV-IPN, Av. IPN 2508, Zacatenco, Mexico City CP 07360, Mexico.
J Food Prot. 2022 Dec 1;85(12):1848-1854. doi: 10.4315/JFP-22-168.
Fresh cheeses and cream are important garnishes of traditional Mexican food, often purchased at street or itinerant open markets or tianguis. However, there is scarce information regarding the microbiological quality of cheeses and cream sold in tianguis. For 2 years, three dairy stalls from three tianguis in Mexico City were visited once each season, trading practices were registered, and 96 dairy products were purchased. In total 72 fresh pasteurized cheeses that were hand-cut to order (24 Panela, 24 Canasto, and 24 Doble Crema) and 24 unpasteurized Crema de Rancho samples were collected. All dairy products remained without refrigeration for 8 h. Based on the National Guidelines limits, 87.5% of cheeses and 8% of Crema de Rancho samples were of low microbiological quality, and 1 sample of each type of cheese and 3 samples of Crema de Rancho exceeded the guidelines limits for Staphylococcus aureus. All dairy products were negative for Salmonella, Listeria monocytogenes, and all diarrheagenic Escherichia coli pathotypes, including Shiga toxin-producing E. coli. Among the 96 dairy samples, the prevalence of uropathogenic E. coli (UPEC) and of mycobacteria strains were determined because food items contaminated with these strains have been associated with urinary tract infections and mycobacteriosis, respectively. UPEC strains were isolated from 43% of cut-to-order cheeses and 29% of Crema de Rancho samples. Nontuberculous mycobacteria (NTM) strains were identified in 12.5% of Doble Crema cheese samples and 21% of Crema de Rancho samples. From the eight NTM-positive samples, 10 strains were identified (3 strains of Mycolicibacterium fortuitum, 2 of Mycobacteroides abscessus, 2 of Mycobacteroides chelonae, 2 of Mycolicibacterium porcinum, and 1 of Mycolicibacterium rhodesiae). All produced biofilms, and 70% had sliding motility (both virulence traits). Trading practices of cut-to-order pasteurized cheeses and unpasteurized Crema de Rancho in tianguis increase the risk of microbiological contamination of these products, including with human pathogens, and their consumption may cause human illness.
新鲜奶酪和奶油是传统墨西哥食品的重要配菜，通常在街头或流动露天市场或集市购买。然而，关于集市上销售的奶酪和奶油的微生物质量的信息却很少。在两年时间里，我们每年都会访问墨西哥城的三个集市的三个乳制品摊位，记录交易情况，并购买了 96 种乳制品。总共收集了 72 种新鲜巴氏杀菌奶酪，这些奶酪是根据订单手工切割的（24 种 Panela、24 种 Canasto 和 24 种 Doble Crema）和 24 种未经巴氏杀菌的 Ranch Crema 样品。所有乳制品在没有冷藏的情况下保存了 8 小时。根据国家指南的限制，87.5%的奶酪和 8%的 Ranch Crema 样品的微生物质量较低，每种奶酪类型各有 1 个样本和 Ranch Crema 的 3 个样本超过金黄色葡萄球菌的指南限制。所有乳制品均未检出沙门氏菌、单核细胞增生李斯特菌和所有致腹泻性大肠杆菌血清型，包括产志贺毒素的大肠杆菌。在 96 个乳制品样本中，我们还确定了尿路致病性大肠杆菌（UPEC）和分枝杆菌菌株的流行情况，因为这些菌株污染的食品与尿路感染和分枝杆菌病有关。UPEC 菌株从 43%的现切奶酪和 29%的 Ranch Crema 样本中分离出来。非结核分枝杆菌（NTM）菌株在 12.5%的多倍体奶酪和 21%的 Ranch Crema 样本中被鉴定出来。在 8 个 NTM 阳性样本中，鉴定出了 10 个菌株（3 株偶发分枝杆菌、2 株脓肿分枝杆菌、2 株龟分枝杆菌、2 株猪分枝杆菌和 1 株罗得西亚分枝杆菌）。所有菌株都能产生生物膜，且 70%具有滑动运动性（均为毒力特征）。集市上的现切巴氏杀菌奶酪和未经巴氏杀菌的 Ranch Crema 的交易做法增加了这些产品的微生物污染风险，包括人类病原体污染，食用这些产品可能会导致人类患病。
