AUTHOR=Scott Euan , Holden-Dye Lindy , O’Connor Vincent , Wand Matthew E. 

TITLE=Intra Strain Variation of the Effects of Gram-Negative ESKAPE Pathogens on Intestinal Colonization, Host Viability, and Host Response in the Model Organism Caenorhabditis elegans

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.03113

DOI=10.3389/fmicb.2019.03113

ISSN=1664-302X

ABSTRACT=<p>In its native environment of rotting vegetation, the soil nematode <italic>Caenorhabditis elegans</italic> encounters a range of bacteria. This includes species from the ESKAPE group of pathogens that pose a clinical problem in acquired hospital infections. Here, we investigated three Gram-negative members of the ESKAPE group, <italic>Pseudomonas aeruginosa</italic>, <italic>Klebsiella pneumoniae</italic>, and <italic>Acinetobacter baumannii</italic>. Pathogenicity profiles as measured by time to kill adult <italic>C. elegans</italic> showed that <italic>P. aeruginosa</italic> was the most pathogenic, followed by <italic>K. pneumoniae</italic>, while <italic>C. elegans</italic> cultured on <italic>A. baumannii</italic> exhibited the same survival as those on the standard laboratory food source for <italic>C. elegans</italic>, <italic>Escherichia coli</italic> OP50. The pathogenicity was paralleled by a reduction in time that <italic>C. elegans</italic> resided on the bacterial lawn with the most pathogenic strains triggering an increase in the frequency of food-leaving. Previous reports indicate that gut colonization is a feature of pathogenicity, but we found that the most pathogenic strains were not associated with the highest level of colonization. Indeed, clearance of <italic>P. aeruginosa</italic> strains from the <italic>C. elegans</italic> gut was independent of bacterial pathogenicity. We show that this clearance is regulated by neuromodulation as <italic>C. elegans</italic> mutants in <italic>unc-31</italic> and <italic>egl-3</italic> have enhanced clearance of <italic>P. aeruginosa</italic>. Intriguingly this is also not linked to their pathogenicity. It is likely that there is a dynamic balance occurring in the <italic>C. elegans</italic> intestinal environment between maintaining a healthy, beneficial microbiota and removal of pathogenic bacteria.</p>