Open AccessAssessment of Listeria monocytogenes virulence in the Galleria mellonella insect larvae model
Author(s) -
Mira Rakic Martinez,
Martin Wiedmann,
Martine Ferguson,
Atin R. Datta
Publication year - 2017
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0184557
Subject(s) - virulence , galleria mellonella , listeria monocytogenes , biology , microbiology and biotechnology , listeria , pathogen , bacteria , gene , genetics
Several animal models have been used to understand the molecular basis of the pathogenicity, infectious dose and strain to strain variation of Listeria monocytogenes . The greater wax worm Galleria mellonella , as an alternative model, provides some useful advantages not available with other models and has already been described as suitable for the virulence assessment of various pathogens including L . monocytogenes . The objectives of this study are: 1) confirming the usefulness of this model with a wide panel of Listeria spp. including non-pathogenic L . innocua , L . seeligeri , L . welshimeri and animal pathogen L . ivanovii ; 2) assessment of virulence of several isogenic in-frame deletion mutants in virulence and stress related genes of L . monocytogenes and 3) virulence assessment of paired food and clinical isolates of L . monocytogenes from 14 major listeriosis outbreaks occurred worldwide between 1980 and 2015. Larvae injected with different concentrations of Listeria were incubated at 37°C and monitored over seven days for time needed to kill 50% of larvae (LT 50 ) and to determine change of bacterial population in G . mellonella , 2 and 24 hours post-inoculation. Non-pathogenic members of Listeria and L . ivanovii showed significantly (P < 0.05) higher LT 50 (lower virulence) than the wild type L . monocytogenes strains. Isogenic mutants of L . monocytogenes with the deletions in prfA , plcA , hly , actA and virR genes, also showed significantly (P < 0.05) higher LT 50 than the wild type strain at the inoculum of 10 6 CFU/larva. Food isolates had significantly (P < 0.05) lower virulence than the paired clinical isolates, at all three inoculum concentrations. L . monocytogenes strains related to non-invasive (gastroenteritis) outbreaks of listeriosis showed significantly (P < 0.05) lower virulence than isolates of the same serotype obtained from outbreaks with invasive symptoms. The difference, however, was dose and strain- dependent. No significant differences in virulence were observed among the serotype tested in this study.