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Adaptation of L isteria monocytogenes in a simulated cheese medium: effects on virulence using the G alleria mellonella infection model
Author(s) -
Schrama D.,
Helliwell N.,
Neto L.,
Faleiro M.L.
Publication year - 2013
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/lam.12064
Subject(s) - galleria mellonella , virulence , listeria monocytogenes , microbiology and biotechnology , biology , food science , bacteria , gene , biochemistry , genetics
The aim of this study was to evaluate the effect of the acid and salt adaptation in a cheese‐based medium on the virulence potential of L isteria monocytogenes strains isolated from cheese and dairy processing environment using the G alleria mellonella model. Four L . monocytogenes strains were exposed to a cheese‐based medium in conditions of induction of an acid tolerance response and osmotolerance response ( pH 5·5 and 3·5% w/v NaCl ) and injected in G . mellonella insects. The survival of insects and the L . monocytogenes growth kinetics in insects were evaluated. The gene expression of hly , actA and inlA genes was determined by real‐time PCR . The adapted cells of two dairy strains showed reduced insect mortality ( P < 0·05) in comparison with nonadapted cells. L isteria monocytogenes Scott A was the least virulent, whereas the cheese isolate C882 caused the highest insect mortality, and no differences ( P > 0·05) was found between adapted and nonadapted cells. The gene expression results evidenced an overexpression of virulence genes in cheese‐based medium, but not in simulated insect‐induced conditions. Our results suggest that adaptation to low pH and salt in a cheese‐based medium can affect the virulence of L . monocytogenes, but this effect is strain dependent. Significance and Impact of the Study In this study, the impact of adaptation to low pH and salt in a cheese‐based medium on L . monocytogenes virulence was tested using the W ax M oth G . mellonella model. This model allowed the differentiation of the virulence potential between the L . monocytogenes strains. The effect of adaptation on virulence is strain dependent. The G . mellonella model revealed to be a prompt method to test food‐related factors on L . monocytogenes virulence.