Advances in Foodborne Pathogen Analysis

As the world population has grown, new demands on the production of foods have been met by increased efficiencies in production, from planting and harvesting to processing, packaging and distribution to retail locations. These efficiencies enable rapid intranational and global dissemination of foods, providing longer “face time” for products on retail shelves and allowing consumers to make healthy dietary choices year-round. However, our food production capabilities have outpaced the capacity of traditional detection methods to ensure our foods are safe. Traditional methods for culture-based detection and characterization of microorganisms are time-, labor- and, in some instances, space- and infrastructure-intensive, and are therefore not compatible with current (or future) production and processing realities. New and versatile detection methods requiring fewer overall resources (time, labor, space, equipment, cost, etc.) are needed to transform the throughput and safety dimensions of the food industry. Access to new, user-friendly, and point-of-care testing technologies may help expand the use and ease of testing, allowing stakeholders to leverage the data obtained to reduce their operating risk and health risks to the public. The papers in this Special Issue on “Advances in Foodborne Pathogen Analysis” address critical issues in rapid pathogen analysis, including preanalytical sample preparation, portable and field-capable test methods, the prevalence of antibiotic resistance in zoonotic pathogens and non-bacterial pathogens, such as viruses and protozoa

Sample Preparation: The Forgotten Beginning

Advances in molecular technologies and automated instrumentation have provided many opportunities for improved detection and identification of microorganisms; however, the upstream sample preparation steps needed to apply these advances to foods have not been adequately researched or developed. Thus, the extent to which these advances have improved food microbiology has been limited. The purpose of this review is to present the current state of sample preparation, to identify knowledge gaps and opportunities for improvement, and to recognize the need to support greater research and development efforts on preparative methods in food microbiology. The discussion focuses on the need to push technological developments toward methods that do not rely on enrichment culture. Among the four functional components of microbiological analysis (i.e., sampling, separation, concentration, detection), the separation and concentration components need to be researched more extensively to achieve rapid, direct, and quantitative methods. The usefulness of borrowing concepts of separation and concentration from other disciplines and the need to regard the microorganism as a physicochemical analyte that may be directly extracted from the food matrix are discussed. The development of next-generation systems that holistically integrate sample preparation with rapid, automated detection will require interdisciplinary collaboration and substantially increased funding

Flow cytometry for rapid detection of Salmonella spp. in seed sprouts

Seed sprouts (alfalfa, mung bean, radish, etc.) have been implicated in several recent national and international outbreaks of salmonellosis. Conditions used for sprouting are also conducive to the growth of Salmonella. As a result, this pathogen can quickly grow to very high cell densities during sprouting without any detectable organoleptic impact. Seed sprouts typically also support heavy growth (~108 CFU g−1) of a heterogeneous microbiota consisting of various bacterial, yeast, and mold species, often dominated by non-pathogenic members of the family Enterobacteriaceae. This heavy background may present challenges to the detection of Salmonella, especially if this pathogen is present in relatively low numbers. We combined DNA-based fluorescence in situ hybridization (FISH) with flow cytometry (FCM) for the rapid molecular detection of Salmonella enterica ser. Typhimurium in artificially contaminated alfalfa and other seed sprouts. Components of the assay included a set of cooperatively binding probes, a chemical blocking treatment intended to reduce non-specific background, and sample concentration via tangential flow filtration (TFF). We were able to detect S. Typhimurium in sprout wash at levels as low as 103 CFU ml−1 sprout wash (104 CFU g−1 sprouts) against high microbial backgrounds (~108 CFU g−1 sprouts). Hybridization times were typically 30 min, with additional washing, but we ultimately found that S. Typhimurium could be readily detected using hybridization times as short as 2 min, without a wash step. These results clearly demonstrate the potential of combined DNA-FISH and FCM for rapid detection of Salmonella in this challenging food matrix and provide industry with a useful tool for compliance with sprout production standards proposed in the Food Safety Modernization Act (FSMA)

Probiotic Potential and Antimicrobial Activity of Enterococcus faecium Isolated from Chicken Caecal and Fecal Samples

Enterococci are important inhabitants of the animal intestine and are widely used in probiotic products. A probiotic strain is expected to possess several desirable properties in order to exert beneficial effects. Therefore, the objective of this study was to isolate, characterize and identify Enterococcus sp. from chicken cecal and fecal samples to determine potential probiotic properties. Enterococci were isolated from chicken ceca and feces of thirty three clinically healthy chickens from a local farm. In vitro studies were performed to assess antibacterial activity of the isolated LAB (using agar well diffusion and cell free supernatant broth technique against Salmonella enterica serotype Enteritidis), survival in acidic conditions, resistance to bile salts, and their survival during simulated gastric juice conditions at pH 2.5. Isolates were identified by biochemical carbohydrate fermentation patterns using an API 50 CHL kit and API ZYM kits and by sequenced 16S rDNA. An isolate belonging to E. faecium species exhibited inhibitory effect against S. enteritidis. This isolate producing a clear zone as large as 10.30 mm or greater and was able to grow in the coculture medium and at the same time, inhibited the growth S. enteritidis. In addition, E. faecium exhibited significant resistance under highly acidic conditions at pH 2.5 for 8 h and survived well in bile salt at 0.2% for 24 h and showing ability to survive in the presence of simulated gastric juice at pH 2.5. Based on these results, E. faecium isolate fulfills some of the criteria to be considered as a probiotic strain and therefore, could be used as a feed additive with good potential for controlling S. Enteritidis in chickens. However, in vivo studies are needed to determine the safety of the strain

A Comprehensive Assessment of Aviary Laying-Hen Housing System for Egg Production in the Midwest

Aviary hen housing system is one of the alternative egg production systems that are being used by some U.S. egg producers. The motivation for adopting such a housing system is to improve bird welfare by allowing the hens to exercise natural behaviors, such as foraging, dust-bathing, and perching. However, research-based information on the overall performance and thus sustainability of the system is meager under U.S. production conditions. The goal of this field study is to comprehensively evaluate the performance of the housing system under Midwest production conditions with regards to animal welfare, environmental impact (both indoor environment and air emissions to the atmosphere), bioenergetics (for design and operation of heating, cooling and ventilation system), energy use, production economic efficiency, and microbiological quality