GSE65558
Sublethal concentrations of antibiotics cause shift to anaerobic metabolism in Listeria monocytogenes and induce phenotypes linked to antibiotic tolerance
The human pathogenic bacterium Listeria monocytogenes was exposed to antibiotics both during clinical treatment and as a saprophyte. As one of the keys to successful treatment is continued antibiotic sensitivity, the purpose of this study was to determine if exposure to sublethal antibiotic concentrations would affect the bacterial physiology and potentially induce tolerance to antibiotics. Transcriptomic analyses demonstrated that each of four antibiotics caused a compound-specific gene expression pattern related to (the) mode-of-action of the particular antibiotic. All four antibiotics caused the same changes in expression of several metabolic genes indicating a shift from aerobic to anaerobic metabolism driven by the induction of lmo1634 and the repression of alsA and lmo1992. This shift in metabolism could be a survival strategy in response to antibiotics and is further supported by the observation that a ?lmo1634 mutant was more sensitive to bactericidal antibiotics. The monocin locus encoding a cryptic prophage was induced by co-trimoxazole and repressed by ampicillin and gentamicin. This expression pattern correlated with the observed antibiotic-dependent biofilm formation, indicating a role of monocin in antibiotic-induced biofilm formation and a ?lmaDCBA mutant confirmed this correlation. Thus, sublethal concentrations of antibiotics caused metabolic and physiological changes indicating that the organism is preparing to withstand lethal concentrations of antibiotics. Overall design: Investigation of mRNA and sRNA expression profiles of L. monocytogenes EGD cells exposed to sublethal concentrations of four different antibiotics i.e. ampicillin, tetracycline, gentamicin and co-trimoxazole for 3h.