TY - JOUR

T1 - Subinhibitory concentrations of antibiotics affect stress and virulence gene expression in Listeria monocytogenes and cause enhanced stress sensitivity but do not affect Caco‐2 cell invasion

A1 - Knudsen,Gitte Maegaard

A1 - Holch,Anne

A1 - Gram,Lone

AU - Knudsen,Gitte Maegaard

AU - Holch,Anne

AU - Gram,Lone

PB - Wiley-Blackwell Publishing Ltd.

PY - 2012

Y1 - 2012

N2 - Antibiotics can act as signal molecules and affect bacterial gene expression, physiology and virulence. The purpose of this study was to determine whether subinhibitory antibiotic concentrations alter gene expression and physiology of Listeria monocytogenes. Using an agar‐based screening assay with promoter fusions, 14 of 16 antibiotics induced or repressed expression of one or more stress and/or virulence genes. Despite ampicillin‐induced up‐regulation of PinlA‐lacZ expression, Caco‐2 cell invasion was not affected. Subinhibitory concentrations of ampicillin and tetracycline caused up‐ and down‐regulation of stress response genes, respectively, but both antibiotics caused increased sensitivity to acid stress. Six combinations of gene‐antibiotic were quantified in broth cultures and five of the six resulted in the same expression pattern as the agar‐based assay. Antibiotics affect virulence and/or stress gene expression; however, altered expression could not predict changes in phenotypic behaviour. Subinhibitory concentrations of antibiotics led to increased acid sensitivity, and we speculate that this is attributed to changes in cell envelope or reduced σB‐dependent gene expression. Although subinhibitory concentrations of antibiotics affect gene expression in L. monocytogenes, the changes did not increase virulence but did enhance the acid sensitivity.

AB - Antibiotics can act as signal molecules and affect bacterial gene expression, physiology and virulence. The purpose of this study was to determine whether subinhibitory antibiotic concentrations alter gene expression and physiology of Listeria monocytogenes. Using an agar‐based screening assay with promoter fusions, 14 of 16 antibiotics induced or repressed expression of one or more stress and/or virulence genes. Despite ampicillin‐induced up‐regulation of PinlA‐lacZ expression, Caco‐2 cell invasion was not affected. Subinhibitory concentrations of ampicillin and tetracycline caused up‐ and down‐regulation of stress response genes, respectively, but both antibiotics caused increased sensitivity to acid stress. Six combinations of gene‐antibiotic were quantified in broth cultures and five of the six resulted in the same expression pattern as the agar‐based assay. Antibiotics affect virulence and/or stress gene expression; however, altered expression could not predict changes in phenotypic behaviour. Subinhibitory concentrations of antibiotics led to increased acid sensitivity, and we speculate that this is attributed to changes in cell envelope or reduced σB‐dependent gene expression. Although subinhibitory concentrations of antibiotics affect gene expression in L. monocytogenes, the changes did not increase virulence but did enhance the acid sensitivity.

U2 - 10.1111/j.1365-2672.2012.05435.x

DO - 10.1111/j.1365-2672.2012.05435.x

JO - Journal of Applied Microbiology

JF - Journal of Applied Microbiology

SN - 1364-5072

IS - 5

VL - 113

SP - 1273

EP - 1286

ER -