Evaluation of Caenorhabditis elegans as the Host in an Infection Model for Food-borne Pathogens

Abstract

The bacteriophagous nematode Caenorhabditis elegans has been recognized as a surrogate host for human pathogens. The aim of this study was to examine whether food-borne pathogens are pathogenic in nematodes. Young adult worms were allocated onto peptone-free medium covered with a bacterial suspension of each pathogen. The plates were incubated and as the number of live and dead worms scored at least every 24 h. Twelve of the 14 pathogenic strains, namely Aeromonas sobria, the diarrheagenic Escherichia coli strains (enteroaggregative E. coli, enterohemorrhagic E. coli, enteropathogenic E. coli, enterotoxigenic E. coli, enteroaggregative E. coli heat-stable enterotoxin 1 gene-possessing E. coli, and di#usely adherent E. coli), Listeria monocytogenes, Salmonella Enteritidis, Staphylococcus aureus, Vibrio parahaemolyticus, and Yersinia enterocolitica reduced the survival rate of worms to varying degrees. The remaining 2 strains, Bacillus cereus and enteroinvasive E. coli, did not. Thus, food-borne pathogens can infect and proliferate within bacteriophagous nematodes on peptone-free medium to the same extent as reported with conventional peptone-containing medium. However, the non-enteropathogenic E. coli strain HS and deletion mutants of L. monocytogenes, which have lost their virulence in the murine model, were also still nematocidal. Although this nematode could be an alternative host for these pathogens, the nematocidal activity of these pathogens may not necessarily reflect enteropathogenicity in humans. Pathogens and the virulence genes to be analyzed must be carefully selected before using this alternative host.Key words: C. elegans, Enteric pathogen, Virulence, Screening, Infection model Introduction A variety of experimental models have been developed to study microbial virulence or the pathogenicity of protein toxins. However, due to increasing ethical considerations as well as economic reasons, the use of mammalian hosts is decreasing in popularity, and the establishment of e#ective alternative non-mammalian systems is urgently required.There has recently been increasing interest in the soil nematode Caenorhabditis elegans as a possible host of human pathogenic bacteria, since it was reported by Ausubel et al. in 1999 that Pseudomonas aeruginosa caused fatal infection of C. elegans 31) . C. elegans has also been reported as a successful model for the investigation of virulence-associated factors of human pathogens such as Burkholderia pseudomallei 10) , Cryptococcus neoformans 19) , Enterococcus faecalis 27) , enteropathogenic Escherichia coli 2, 16) , Listeria monocytogenes 34) , P. aeruginosa 32) , Serratia marcescens 14) , Shigella flexneri 6) , Staphylococcus aureus 11,28) , and Vibrio vulnificus 9) .We recognized nematodes as a potential new surrogate host, and the degree of similarity between this nematode, C. elegans, and humans is greater than expected 17) . In the above-cited reports, the human pathogens and associated ῍ Ί̮ ῌ558ῌ8585 ̮ῒ ̮ῐῑ̮Ὶ 3ῌ3ῌ138 ῖῚ̮Ῐῗ̮Ῑ῏῎ΐ Jpn.

Caenorhabditis elegans as an Alternative Model Host for Legionella pneumophila , and Protective Effects of Bifidobacterium infantis

“…Numerous authors have reported Caenorhabditis elegans to be a suitable model to investigate virulence-associated factors of human pathogens (2,8,11,14,16,20,23,24,30,31,33). In the present study, we examined whether C. elegans can serve as an alternative host for L. pneumophila.…”

Development of a method for oral administration of hydrophobic substances to Caenorhabditis elegans: pro-longevity effects of oral supplementation with lipid-soluble antioxidants

“…T3s protected the worms from infection with the opportunistic pathogen Legionella, but T3s did not prevent infection with Salmonella unlike the lactic acid bacteria. The discrepancy is probably due to the higher virulence of Salmonella organisms (Hoshino et al 2008;Komura et al 2010). Mechanisms of how T3s protected worms against death from Legionella infection still remain to be elucidated.…”

Prolonged Lifespan, Improved Perception, and Enhanced Host Defense of Caenorhabditis elegans by Lactococcus cremoris subsp.cremoris

“…OP50 was used as the standard feed for nematode cultivation and was grown on tryptone soya agar (Nissui Pharmaceutical, Tokyo, Japan). Cultured bacteria (100 mg wet weight) were suspended in 0.5 mL M9 buffer, and 50 μL of the resulting bacterial suspension was then spread on peptone-free NGM (pfNGM) in 5.0-cm-diameter plates to feed the worms ( 56 ).…”

“… Staphylococcus aureus strain 96-55-17A was used as a Gram-positive pathogen. These pathogenic bacteria were reported as infection models using C. elegans ( 56 ) and were grown on tryptone soya agar at 37°C for 24 h.…”