Departamento de Investigación y Posgrado en Alimentos, Facultad de Química, Universidad Autónoma de Querétaro, Cerro de las Campanas s/n, Col. Las Campanas, Querétaro, Querétaro, México, C.P. 76010.
Food Safety and Innovation Centre, Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Australia 7005.
J Food Prot. 2022 Aug 1;85(9):1265-1272. doi: 10.4315/JFP-21-432.
In Mexico, the prevalence of Salmonella enterica in low-water-activity foods and its link to outbreaks are unknown. The aim of this study was to determine the microbiological profile and the prevalence of S. enterica in several low-water-activity foods, including peanuts, pecans, raisins, sun-dried tomatoes, and chocolate sprinkles, purchased in retail establishments in Querétaro, Mexico. Seventy samples of each food item sold in bulk were purchased. Aerobic plate count, molds, yeasts, total coliforms, Escherichia coli, and Staphylococcus aureus were quantified in 10-g samples. The prevalence of S. enterica in 25-g samples was determined. From positive samples, S. enterica isolates (60) were characterized based on their antimicrobial susceptibility to 14 antibiotics, the presence-absence of 13 virulence genes, and serotype. The concentration of aerobic plate count, molds, yeasts, total coliforms, and E. coli ranged from 3.1 to 5.2 log CFU g-1, from 2.0 to 2.4 log CFU g-1, from 2.0 to 3.0 log CFU g-1, from 0.6 to 1.1 log most probable number (MPN) g-1, and from 0.5 to 0.9 log MPN g-1, respectively. S. aureus was not detected in any sample (<10 CFU g-1). The prevalence of S. enterica in chocolate sprinkles, raisins, peanuts, pecans, and sun-dried tomatoes was 26, 29, 31, 40, and 52%, respectively. Most isolates (68.3%) were resistant to at least one antibiotic. Chromosome-associated virulence genes were found in all isolates, and only one strain had sopE, and 98.3% of the isolates were grouped in the same virulotype. Among the isolates, the most frequent serotype was Tennessee (51 of 60). According to the characteristics evaluated, we grouped the isolates into 24 clusters. The elevated prevalence of S. enterica highlights the role of low-water-activity food items sold in bulk at markets as potential vehicles for pathogen transmission. Regardless of the low variability among S. enterica isolates, their characterization could be helpful to elucidate which strains are circulating in these foods for improving epidemiological surveillance.
在墨西哥，低水分活度食品中肠炎沙门氏菌的流行情况及其与疫情的关联尚不清楚。本研究的目的是确定几种低水分活度食品（包括花生、山核桃、葡萄干、晒干的西红柿和巧克力糖屑）中的微生物谱和肠炎沙门氏菌的流行情况，这些食品均购自墨西哥克雷塔罗州的零售商店。购买了每种散装食品的 70 份样品。对 10g 样品进行需氧平板计数、霉菌、酵母、总大肠菌群、大肠杆菌和金黄色葡萄球菌的定量检测。用 25g 样品检测肠炎沙门氏菌的检出率。从阳性样品中分离出 60 株肠炎沙门氏菌，根据其对 14 种抗生素的药敏性、13 种毒力基因的有无以及血清型进行特征描述。需氧平板计数、霉菌、酵母、总大肠菌群和大肠杆菌的浓度范围分别为 3.1-5.2log CFU/g、2.0-2.4log CFU/g、2.0-3.0log CFU/g、0.6-1.1log 最可能数（MPN）/g 和 0.5-0.9log MPN/g。任何样本中均未检出金黄色葡萄球菌（<10CFU/g）。巧克力糖屑、葡萄干、花生、山核桃和晒干的西红柿中肠炎沙门氏菌的检出率分别为 26%、29%、31%、40%和 52%。大多数分离株（68.3%）至少对一种抗生素有耐药性。所有分离株均存在染色体相关的毒力基因，只有一株含有 sopE，98.3%的分离株属于同一毒力型。在分离株中，最常见的血清型是田纳西州（60 株中的 51 株）。根据评估的特征，我们将分离株分为 24 个聚类。肠炎沙门氏菌的高检出率强调了市场上销售的低水分活度散装食品作为病原体传播潜在载体的作用。尽管肠炎沙门氏菌分离株的变异性较低，但对其进行特征描述有助于阐明哪些菌株在这些食品中循环，从而改善流行病学监测。
