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Connolly, J. P.

Publications and source records attributed to Connolly, J. P..

2 recordsLinked to original sources
bioRxiv2018

A highly conserved complete accessory Escherichia coli type III secretion system 2 is widespread in bloodstream isolates of the ST69 lineage

Bacterial type III secretion systems (T3SS) play an important role in pathogenesis of Gram-negative infections. Enteropathogenic and enterohemorrhagic Escherichia coli contain a well-defined T3SS but in addition a second T3SS termed E. coli T3SS 2 (ETT2) has been described in a number of strains of E. coli. The majority of E. coli contain elements of a genetic locus encoding ETT2, but which has undergone significant mutational attrition rendering it without predicted function. Only a very few strains have been reported to contain an intact ETT2 locus. To investigate the occurrence of the ETT2 locus in strains of human pathogenic E. coli, we carried out genomic sequencing of 162 isolates obtained from patient blood cultures in Scotland. We found that all 26 ST69 isolates from this collection contained an intact ETT2 together with an associated eip locus which encodes putative secreted ETT2 effectors as well as eilA, a gene encoding a putative transcriptional regulator of ETT2 associated genes. Using a reporter gene for eilA activation, we defined conditions under which this gene was differentially activated. However, comparison of secreted proteins from ST69 strains under high and low eilA activation failed to identify any ETT2 secreted substrates. The conservation of the genes encoding ETT2 in human pathogenic ST69 strains strongly suggests it has functional importance in infection, although its exact functional role remains obscure.\n\nImportanceOne of the commonest bacteria causing bloodstream infections in humans is Escherichia coli, which has a significant morbidity and mortality. Better understating of the mechanisms by which this microbe can invade blood could lead to more effective prevention and treatment. One mechanism by which some strains cause disease is by elaboration of a specialized secretion system, the type III secretion system (T3SS), encoded by the locus of enterocyte effacement (LEE). In addition to this well-defined T3SS, a second T3SS has been found in some E. coli strains termed E. coli type III secretion system 2 (ETT2). Most strains carry elements of the ETT2 locus, but with significant mutational attrition rendering it functionless. The significance of our work is that we have discovered that human bloodstream isolates of E. coli of sequence type 69 contain a fully intact ETT2 and associated genes, strongly suggesting its functional importance in human infection.

microbiology↗
bioRxiv2018

Propionic acid enhances the virulence of Crohn’s disease-associated adherent-invasive Escherichia coli

The short chain fatty acid propionic acid (PA) is a bacteria-derived human intestinal antimicrobial and immune modulator used widely in Western food production and agriculture. Here we examine the effect of PA on the pathogenicity of the Crohns disease-associated microbe, adherent-invasive Escherichia coli (AIEC). Passage of AIEC through a murine model, where the low intestinal PA levels were increased to replicate those of the human intestine, led to the recovery of AIEC post-infection that had significantly increased virulence. These phenotypic changes, including increased adhesion to intestinal epithelial cells and biofilm formation, could be replicated in AIEC in vitro through exposure to PA alone. This in vitro exposure of AIEC to PA fundamentally changed AIEC virulence, with strains exposed to PA in vitro subsequently persisting at 20-fold higher levels in a murine model compared to non-exposed strains. RNA-sequencing identified the transcriptional changes in AIEC in response to PA with upregulation of genes involved in biofilm formation, stress responses, metabolism, membrane integrity and alternative carbon source utilisation. These PA induced changes in virulence could be replicated in a number of E. coli isolates from Crohns disease patients. Finally, removal of the PA selective pressure was sufficient to reverse these phenotypic changes. Our data indicate that exposure of AIEC to PA evolves bacteria that are both resistant to this natural human intestinal antimicrobial and increasingly virulent in its presence.\n\nImportanceExposure to propionic acid, an intestinal short chain fatty acid and commonly used antimicrobial in Western food production, induces significant virulence associated phenotypic changes in adherent-invasive Escherichia coli (AIEC).

microbiology↗