The Small Colony Variant Of Listeria Monocytogenes Is More Tolerant To Antibiotics And Grows Better Within Caco-2 Epithelial Cells Than The Wild Type

Thomas Curtis, Lone Gram, Gitte Maegaard Knudsen

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    Abstract

    Introduction: Small Colony Variants (SCV) of bacteria are a slow growing phenotype with a pinpoint colony morphology and several specific characteristics. In several pathogens they have been linked to recurrent and chronic infections. SCV of Listeria monocytogenes can be generated when exposed to sublethal concentration of triclosan, and in this study, we characterized their tolerance to antibiotics and ability to invade and survive in host cells. Results: Complementation assays showed that SCV E18 phenotype is caused by a mutation in the heme biosynthesis pathway. Although no difference in MIC, the SCV E18 survived significantly better than the wild type N53-1 (one and three log10 higher CFU/ml) when exposed to super-MIC concentrations of most tested antibiotics, indicating a persister-like phenotype of the SCV. While SCV E18 displayed sensitivity towards oxygen, it was significantly more tolerant of 20mM H2O2 as compared to the wild type, with 6.3 log10 CFU/ml and 3.7 log10 CFU/ml, respectively. The SCV E18 had lower survival rate in unactivated macrophages, however, it was able to survive and multiply to almost 100-fold higher CFU/ml than the wild type in CaCo-2 epithelial cells. Conclusions: This study is the first to demonstrate that the persister-like SCV phenotype of L. monocytogenes potentially could complicate treatment by causing an increase in tolerance towards most of the clinically relevant antibiotics, while also enabling the bacteria to persist in the protected intracellular environment.
    Original languageEnglish
    Title of host publicationThe Danish Microbiological Society Annual Congress 2015 : Programme & Abstracts
    Place of PublicationCopenhagen
    Publication date2015
    Pages55-55
    Publication statusPublished - 2015
    EventThe Danish Microbiological Society Annual Congress 2015 - Eigtved's Pakhus, Copenhagen, Denmark
    Duration: 9 Nov 20159 Nov 2015

    Conference

    ConferenceThe Danish Microbiological Society Annual Congress 2015
    LocationEigtved's Pakhus
    CountryDenmark
    CityCopenhagen
    Period09/11/201509/11/2015

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