Microbiological quality of high-demand foods from three major cities in Ecuador

Bacterial foodborne diseases are one of the most important public health issues worldwide but in Ecuador reports on the microbiological quality of foods are scarce. In this study, a total of 450 traditional food samples including bolon, encebollado, sauces, ceviche, fruit juices, fruit salads, cheese, raw chicken and ground beef were collected from popular markets in the cities of Guayaquil, Quito and Cuenca. Samples were assessed for microbiological quality using both culture dependent and culture independent techniques. Populations of total aerobic bacteria, total coliforms, fecal coliforms and E. coli were examined by plate count. Representative colonies from each culture were further identified using biochemical tests and sequencing of the 16S rRNA gene. For the culture independent analysis, bacterial DNA was extracted from food samples and submitted to next generation sequencing (NGS) of the v3-v4 region of 16S rDNA. By using culture dependent techniques, high prevalence of opportunistic and true pathogens including E. coli, Klebsiella pneumoneae, Salmonella spp., Listeria monocytogenes, Staphylococcus aureus, and Shigella flexneri was observed.Other potential pathogens were identified by NGS, including Clostridium spp.., Vibrio spp.., Helicobacter spp.., Campylobacter spp.., among others but no E. coli, Salmonella spp.. or Listeria spp. were detected. This is the first report on the microbiological quality of food from Ecuador.细菌性食源性疾病是全球范围内最重要的公共卫生问题之一，但在厄瓜多尔，有关食品微生物质量的研究报告却十分匮乏。本研究从瓜亚基尔、基多和昆卡三座城市的热门市场中，共采集了450份传统食品样本，涵盖bolon、encebollado、调味酱、ceviche、果汁、水果沙拉、奶酪、生鸡肉与绞碎牛肉。研究人员采用依赖培养法与非依赖培养法两种技术，对样本的微生物质量进行评估。通过平板计数法，检测了总需氧菌、总大肠菌群、粪便大肠菌群以及大肠杆菌（E. coli）的菌落数量。从各培养体系中挑取的代表性菌落，进一步通过生化试验与16S rRNA基因（16S rRNA gene）测序完成菌种鉴定。在非依赖培养的分析环节中，研究人员从食品样本中提取细菌DNA，并对16S rDNA的v3-v4可变区进行下一代测序（next generation sequencing, NGS）。依托依赖培养法，研究人员检出了高比例的机会致病菌与真性致病菌，包括大肠杆菌（E. coli）、肺炎克雷伯菌（Klebsiella pneumoniae）、沙门氏菌属（Salmonella spp.）、单核细胞增生李斯特菌（Listeria monocytogenes）、金黄色葡萄球菌（Staphylococcus aureus）以及弗氏志贺菌（Shigella flexneri）。通过NGS还鉴定出其他潜在致病菌，包括梭菌属（Clostridium spp.）、弧菌属（Vibrio spp.）、螺杆菌属（Helicobacter spp.）、弯曲菌属（Campylobacter spp.）等，但未检测到大肠杆菌（E. coli）、沙门氏菌属（Salmonella spp.）或李斯特菌属（Listeria spp.）。本研究为厄瓜多尔境内首份针对食品微生物质量的正式研究报告。