Mainstreams of Horizontal Gene Exchange in Enterobacteria: Consideration of the Outbreak of Enterohemorrhagic E. coli O104:H4 in Germany in 2011

Abstract

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 FindingsThe 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.ConclusionsOscillations 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.

Evolutionary analyses of non-genealogical bonds produced by introgressive descent

“…The bla CTX-M-15 gene was then captured by new plasmids, which were captured in their turn by other E. coli clones. Because some of these clones are particularly suited to be integrated in the intestinal microbiome of different types of animals, the bla CTX-M-15 gene expanded multidimensionally, finally reaching even the hemolytic-uremic E. coli O104 responsible for food poisoning in Germany in 2011 (72)(73)(74). Consideration of M-P3s, the true binding of unlike to unlike at the origin of original evolutionary units, explicitly includes such evolutionary quantum leaps in studies of evolutionary novelties.…”

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“…The European Union is currently searching for ways to overcome the problem of antimicrobial resistance within its member countries against some of the common microbes found in Ghanaian foods, such as Klebsiella pneumoniae, Escherichia coli and Pseudomonas aeruginosa. The recent E. coli outbreak in Germany, a food-borne antimicrobial resistant clone, is an example of the seriousness of the problem [9].…”

“…Diarrhoea is the most common illness experienced by international travellers in developing tropical and semitropical regions [8]. The outbreak of the lethal strain of Escherichia coli in Europe in 2011 highlighted the limits of our present understanding of the evolutionary trends of new pathogens [9].…”

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