Escherichia coli O157:H7: animal reservoir and sources of human infection

Escherichia coli O157:H7/NM prevalence in raw beef, camel, sheep, goat, and water buffalo meat in Fars and Khuzestan provinces, Iran

Enterohemorrhagic Escherichia coli (EHEC) of the O157:H7 serotype is a worldwide zoonotic pathogen responsible for the majority of severe cases of human EHEC disease. The aim of the present study was to investigate the prevalence of E. coli O157: H7/NM in raw meat samples from two provinces of Iran. During a period from March 2010 to March 2011. Two hundred and ninety five raw meat samples were collected from beef (n= 85), camel, (n= 50), sheep (n= 62), goat (n= 60), and water buffalo (n=38). Fourteen (4.7%) of the 295 samples were positive for E. coli O157. The highest prevalence of E. coli O157 was found in beef samples (8.2%), followed by water buffalo (5.3%), sheep (4.8%), camel (2.0%), and goat (1.7%). Of fourteen E. coli O157 isolates, only one was determined to be serotype O157: H7 while 13 were determined as serotype O157: NM. Of the 14 E. coli O157:H7/NM isolates, one, four, two, and one strains were positive for stx1, stx2, eaeA and ehlyA genes, respectively. The prevalence of this organism varied between seasons with the highest prevalence of E. coli O157 occurring in summer (9.3%). The results of this study showed that beef and water buffalo meat are a significant source for human EHEC E. coli O157:H7/NM infection in Iran. The data reported in this study provides some useful baseline in formation for future research such as molecular or epidemiologic works.

Modern approaches in probiotics research to control foodborne pathogens

Foodborne illness is a serious public health concern. There are over 200 known microbial, chemical, and physical agents that are known to cause foodborne illness. Efforts are made for improved detection, control and prevention of foodborne pathogen in food, and pathogen associated diseases in the host. Several commonly used approaches to control foodborne pathogens include antibiotics, natural antimicrobials, bacteriophages, bacteriocins, ionizing radiations, and heat. In addition, probiotics offer a potential intervention strategy for the prevention and control of foodborne infections. This review focuses on the use of probiotics and bioengineered probiotics to control foodborne pathogens, their antimicrobial actions, and their delivery strategies. Although probiotics have been demonstrated to be effective in antagonizing foodborne pathogens, challenges exist in the characterization and elucidation of underlying molecular mechanisms of action and in the development of potential delivery strategies that could maintain the viability and functionality of the probiotic in the target organ.

Mainstreams of horizontal gene exchange in enterobacteria: consideration of the outbreak of enterohemorrhagic E. coli O104:H4 in Germany in 2011

BACKGROUND

Escherichia coli O104:H4 caused a severe outbreak in Europe in 2011. The strain TY-2482 sequenced from this outbreak allowed the discovery of its closest relatives but failed to resolve ways in which it originated and evolved. On account of the previous statement, may we expect similar upcoming outbreaks to occur recurrently or spontaneously in the future? The inability to answer these questions shows limitations of the current comparative and evolutionary genomics methods.

PRINCIPAL FINDINGS

The study revealed oscillations of gene exchange in enterobacteria, which originated from marine γ-Proteobacteria. These mobile genetic elements have become recombination hotspots and effective 'vehicles' ensuring a wide distribution of successful combinations of fitness and virulence genes among enterobacteria. Two remarkable peculiarities of the strain TY-2482 and its relatives were observed: i) retaining the genetic primitiveness by these strains as they somehow avoided the main fluxes of horizontal gene transfer which effectively penetrated other enetrobacteria; ii) acquisition of antibiotic resistance genes in a plasmid genomic island of β-Proteobacteria origin which ontologically is unrelated to the predominant genomic islands of enterobacteria.

CONCLUSIONS

Oscillations of horizontal gene exchange activity were reported which result from a counterbalance between the acquired resistance of bacteria towards existing mobile vectors and the generation of new vectors in the environmental microflora. We hypothesized that TY-2482 may originate from a genetically primitive lineage of E. coli that has evolved in confined geographical areas and brought by human migration or cattle trade onto an intersection of several independent streams of horizontal gene exchange. Development of a system for monitoring the new and most active gene exchange events was proposed.

Gastrointestinal colonization rates for human clinical isolates of Aeromonas veronii using a mouse model

A variety of environment-associated gastrointestinal infections have been associated with the Aeromonas group of bacteria which contain both non-virulent strains as well as virulent strains within a particular species. This study monitors the colonization rates of colon tissue in a mouse-streptomycin dose/response model involving isolates of Aeromonas veronii biovar sobria obtained from human clinical specimens. The ability to successfully colonize mouse colon tissues by the human clinical isolates was then compared with the rates achieved in a previous study of Aeromonas isolates obtained from environmental drinking water samples. Results suggest that strains of Aeromonas isolated from drinking water environmental samples contain pathogenic and virulence capabilities similar to those seen in Aeromonas veronii clinical isolates from human infections.

Shiga toxin: expression, distribution, and its role in the environment

In this review, we highlight recent work that has increased our understanding of the production and distribution of Shiga toxin in the environment. Specifically, we review studies that offer an expanded view of environmental reservoirs for Shiga toxin producing microbes in terrestrial and aquatic ecosystems. We then relate the abundance of Shiga toxin in the environment to work that demonstrates that the genetic mechanisms underlying the production of Shiga toxin genes are modified and embellished beyond the classical microbial gene regulatory paradigms in a manner that apparently "fine tunes" the trigger to modulate the amount of toxin produced. Last, we highlight several recent studies examining microbe/protist interactions that postulate an answer to the outstanding question of why microbes might harbor and express Shiga toxin genes in the environment.