Bacteriocin-based Strategies for Food Biopreservation

An overview of foodborne pathogen detection: In the perspective of biosensors

The gram-negative bacterium Campylobacter jejuni has extensive reservoirs in livestock and the environment and is a frequent cause of gastroenteritis in humans. To date, the lack of (i) methods suitable for population genetic analysis and (ii) a universally accepted nomenclature has hindered studies of the epidemiology and population biology of this organism. Here, a multilocus sequence typing (MLST) system for this organism is described, which exploits the genetic variation present in seven housekeeping loci to determine the genetic relationships among isolates. The MLST system was established using 194 C. jejuni isolates of diverse origins, from humans, animals, and the environment. The allelic profiles, or sequence types (STs), of these isolates were deposited on the Internet (http://mlst.zoo.ox.ac.uk), forming a virtual isolate collection which could be continually expanded. These data indicated that C. jejuni is genetically diverse, with a weakly clonal population structure, and that intra- and interspecies horizontal genetic exchange was common. Of the 155 STs observed, 51 (26% of the isolate collection) were unique, with the remainder of the collection being categorized into 11 lineages or clonal complexes of related STs with between 2 and 56 members. In some cases membership in a given lineage or ST correlated with the possession of a particular Penner HS serotype. Application of this approach to further isolate collections will enable an integrated global picture of C. jejuni epidemiology to be established and will permit more detailed studies of the population genetics of this organism.

Multilocus Sequence Typing System for Campylobacter jejuni

Campylobacter jejuni is a foodborne bacterial pathogen that is common in the developed world. However, we know less about its biology and pathogenicity than we do about other less prevalent pathogens. Interest in C. jejuni has increased in recent years as a result of the growing appreciation of its importance as a pathogen and the availability of new model systems and genetic and genomic technologies. C. jejuni establishes persistent, benign infections in chickens and is rapidly cleared by many strains of laboratory mouse, but causes significant inflammation and enteritis in humans. Comparing the different host responses to C. jejuni colonization should increase our understanding of this organism.

Campylobacter jejuni : molecular biology and pathogenesis

Recent advances in chromatographic identification of CLA isomers, combined with interest in their possible properties in promoting human health (e.g., cancer prevention, decreased atherosclerosis, improved immune response) and animal performance (e.g., body composition, regulation of milk fat synthesis, milk production), has renewed interest in biohydrogenation and its regulation in the rumen. Conventional pathways of biohydrogenation traditionally ignored minor fatty acid intermediates, which led to the persistence of oversimplified pathways over the decades. Recent work is now being directed toward accounting for all possible trans-18:1 and CLA products formed, including the discovery of novel bioactive intermediates. Modern microbial genetics and molecular phylogenetic techniques for identifying and classifying microorganisms by their small-subunit rRNA gene sequences have advanced knowledge of the role and contribution of specific microbial species in the process of biohydrogenation. With new insights into the pathways of biohydrogenation now available, several attempts have been made at modeling the pathway to predict ruminal flows of unsaturated fatty acids and biohydrogenation intermediates across a range of ruminal conditions. After a brief historical account of major past accomplishments documenting biohydrogenation, this review summarizes recent advances in 4 major areas of biohydrogenation: the microorganisms involved, identification of intermediates, the biochemistry of key enzymes, and the development and testing of mathematical models to predict biohydrogenation outcomes.

http://webpages.icav.up.pt/PTDC/CVT/122245/2010/02.pdf

Board-invited review: Recent advances in biohydrogenation of unsaturated fatty acids within the rumen microbial ecosystem.

Bacteriophages as biocontrol agents in food

Phage inactivation of foodborne pathogens on cooked and raw meat

Aims: To use a published polymerase chain reaction (PCR) method for the detection and identification of thermotolerant Campylobacter species (Camp. jejuni, Camp. coli and Camp. lari) in tandem with a Most Probable Number (MPN) technique to enumerate these species in water samples.



Methods and Results: An initial study of 42 river water samples compared the use of conventional culture and PCR methods for the detection of Campylobacter in MPN enrichment tubes. It was found that all samples positive by culture were also positive by PCR. Thirty-seven percent more MPN tubes were positive by PCR compared with culture. The MPN/PCR technique was subsequently applied to 96 additional samples collected from rivers, drinking, roof and shallow ground water. Campylobacter was especially prevalent in river water (60% positive) and shallow ground water (75% positive) samples. Drinking water (29·2% positive) and roof water (37·5% positive) also contained Campylobacter, but the numbers detected were very low (maximum 0·3 and 0·56 MPN 100 ml–1, respectively).



Conclusions: River waters contained Campylobacter at higher levels than any other water type and in a high percentage of the samples. Although Campylobacter was present in treated drinking water, the levels detected were low.



Significance and Impact of the Study: These results suggest that water may act as a significant transmission route for human campylobacteriosis.

https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2672.2001.01337.x

Enumeration of Campylobacter in New Zealand recreational and drinking waters

Fermented dairy products provide nutrients in our diet, some of which are produced by the action of microorganisms during fermentation. These products can be populated by a diverse microbiota that impacts the organoleptic and physicochemical characteristics foods as well as human health. Acidification is carried out by starter lactic acid bacteria (LAB) whereas other LAB, moulds, and yeasts become dominant during ripening and contribute to the development of aroma and texture in dairy products. Probiotics are generally part of the nonstarter microbiota, and their use has been extended in recent years. Fermented dairy products can contain beneficial compounds, which are produced by the metabolic activity of their microbiota (vitamins, conjugated linoleic acid, bioactive peptides, and gamma-aminobutyric acid, among others). Some microorganisms can also release toxic compounds, the most notorious being biogenic amines and aflatoxins. Though generally considered safe, fermented dairy products can be contaminated by pathogens. If proliferation occurs during manufacture or storage, they can cause sporadic cases or outbreaks of disease. This paper provides an overview on the current state of different aspects of the research on microorganisms present in dairy products in the light of their positive or negative impact on human health.

https://downloads.hindawi.com/journals/bmri/2015/412714.pdf

Impact on Human Health of Microorganisms Present in Fermented Dairy Products: An Overview

Aim: To identify potential reservoirs and transmission routes of human pathogenic Campylobacter spp



Methods and Results:  An enrichment PCR method for the detection and identification of Campylobacter jejuni and/or Campylobacter coli in faecal, food and river water samples was applied to 1450 samples of 12 matrix types obtained from a defined geographical area PCR-positive samples were cultured to yield isolates for typing, and the data for 616 C jejuni isolates obtained



Serotyping and SmaI macrorestriction profiling using pulsed field gel electrophoresis revealed a high level of diversity within the isolates from each matrix Campylobacter jejuni and C coli subtypes indistinguishable from those obtained from human cases were detected in most of the matrices examined No Campylobacter isolates were isolated from possum faeces



Conclusions:  Ten of the 12 matrices examined may be involved in the transmission of human campylobacteriosis as they contained Campylobacter subtypes also isolated from clinical cases



Significance and Impact of the Study:  Results indicate that, for this rural population, a range of potential transmission routes that could lead to campylobacteriosis exist Their relative importance needs to be assessed from an exposure assessment standpoint

https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2672.2005.02541.x

John Andrew Hudson

Papers

Bacteriophages as biocontrol agents in food

Phage inactivation of foodborne pathogens on cooked and raw meat

Enumeration of Campylobacter in New Zealand recreational and drinking waters

Impact on Human Health of Microorganisms Present in Fermented Dairy Products: An Overview

The occurrence of Campylobacter subtypes in environmental reservoirs and potential transmission routes