McMahon Tanis C, Kingombe Cesar Bin, Mathews Amit, Seyer Karine, Wong Alex, Blais Burton W, Carrillo Catherine D
Research and Development, Ottawa Laboratory (Carling), Ontario Laboratory Network, Canadian Food Inspection Agency, Ottawa, ON, Canada.
Department of Biology, Carleton University, Ottawa, ON, Canada.
Front Microbiol. 2022 Jun 23;13:880043. doi: 10.3389/fmicb.2022.880043. eCollection 2022.
Bacterial pathogens, such as Shiga toxin-producing (STEC) and spp., are important causes of foodborne illness internationally. Recovery of these organisms from foods is critical for food safety investigations to support attribution of illnesses to specific food commodities; however, isolation of bacterial cultures can be challenging. Methods for the isolation of STEC and spp. from foods typically require enrichment to amplify target organisms to detectable levels. Yet, during enrichment, target organisms can be outcompeted by other bacteria in food matrices due to faster growth rates, or through production of antimicrobial agents such as bacteriocins or bacteriophages. The purpose of this study was to evaluate the occurrence of and STEC inhibitors produced by food microbiota. The production of antimicrobial compounds in cell-free extracts from 200 bacterial strains and 332 food-enrichment broths was assessed. Cell-free extracts produced by 23 (11.5%) of the strains tested inhibited growth of at least one of the five and seven STEC indicator strains used in this study. Of the 332 enrichment broths tested, cell-free extracts from 25 (7.5%) samples inhibited growth of at least one of the indicator strains tested. Inhibition was most commonly associated with recovered from meat products. Most of the inhibiting compounds were determined to be proteinaceous (34 of the 48 positive samples, 71%; including 17 strains, 17 foods) based on inactivation by proteolytic enzymes, indicating presence of bacteriocins. The cell-free extracts from 13 samples (27%, eight strains, five foods) were determined to contain bacteriophages based on the observation of plaques in diluted extracts and/or resistance to proteolytic enzymes. These results indicate that the production of inhibitors by food microbiota may be an important challenge for the recovery of foodborne pathogens, particularly for . The performance of enrichment media for recovery of and STEC could be improved by mitigating the impact of inhibitors produced by food microbiota during the enrichment process.
产志贺毒素大肠杆菌（STEC）等细菌性病原体是全球食源性疾病的重要病因。从食品中分离出这些病原体对于食品安全调查至关重要，有助于将疾病归因于特定食品；然而，细菌培养物的分离可能具有挑战性。从食品中分离STEC等病原体的方法通常需要进行增菌，以便将目标微生物扩增到可检测水平。然而，在增菌过程中，由于其他细菌生长速度更快，或者通过产生诸如细菌素或噬菌体等抗菌剂，目标微生物可能会在食品基质中被其他细菌竞争淘汰。本研究的目的是评估食品微生物群产生的[某种细菌名称]和STEC抑制剂的存在情况。评估了200株细菌菌株和332份食品增菌肉汤的无细胞提取物中抗菌化合物的产生情况。在所测试的菌株中，23株（11.5%）产生的无细胞提取物抑制了本研究中使用的五种[某种细菌名称]和七种STEC指示菌株中至少一种的生长。在所测试的332份增菌肉汤中，25份（7.5%）样品的无细胞提取物抑制了所测试的至少一种指示菌株的生长。抑制作用最常与从肉制品中分离出的[某种细菌名称]有关。基于蛋白酶对其的灭活作用，确定大多数抑制化合物为蛋白质类（48个阳性样品中的34个，71%；包括17株菌株、17份食品），表明存在细菌素。基于稀释提取物中噬菌斑的观察和/或对蛋白酶抗性的观察，确定13份样品（27%，8株菌株、5份食品）的无细胞提取物含有噬菌体。这些结果表明，食品微生物群产生抑制剂可能是食源性病原体分离的一个重要挑战，尤其是对于[某种细菌名称]而言。通过减轻食品微生物群在增菌过程中产生的抑制剂的影响，可以提高用于分离[某种细菌名称]和STEC的增菌培养基的性能。
