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Open Access Highly Accessed Research article

Characterization of multi-drug tolerant persister cells in Streptococcus suis

Jörg Willenborg1*, Daniela Willms1, Ralph Bertram2, Ralph Goethe1 and Peter Valentin-Weigand1

Author Affiliations

1 Institute of Microbiology, University of Veterinary Medicine, Hannover, Germany

2 Department of Microbial Genetics, University of Tübingen, Tübingen, Germany

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BMC Microbiology 2014, 14:120  doi:10.1186/1471-2180-14-120

Published: 12 May 2014

Abstract

Background

Persister cells constitute a subpopulation of dormant cells within a microbial population which are genetically identical but phenotypically different to regular cells. Notably, persister cells show an elevated tolerance to antimicrobial agents. Thus, they are considered to represent a microbial ‘bet-hedging’ strategy and are of particular importance in pathogenic bacteria.

Results

We studied the ability of the zoonotic pathogen Streptococcus (S.) suis to form multi-drug tolerant variants and identified persister cells dependent on the initial bacterial growth phase. We observed lower numbers of persisters in exponential phase cultures than in stationary growth phase populations. S. suis persister cells showed a high tolerance to a variety of antibiotics, and the phenotype was not inherited as tested with four passages of S. suis populations. Furthermore, we provide evidence that the persister phenotype is related to expression of genes involved in general metabolic pathways since we found higher numbers of persister cells in a mutant strain defective in the catabolic arginine deiminase system as compared to its parental wild type strain. Finally, we observed persister cell formation also in other S. suis strains and pathogenic streptococcal species.

Conclusions

Taken together, this is the first study that reports multi-drug tolerant persister cells in the zoonotic pathogen S. suis.

Keywords:
Streptococcus suis; Persister cells; Multidrug tolerance; Antibiotics