Antibiotic pressure can induce the viable but non-culturable state in Staphylococcus aureus growing in biofilms

S. Pasquaroli, G. Zandri, C. Vignaroli, C. Vuotto, G. Donelli, F. Biavasco

Research output: Contribution to journalArticlepeer-review


Objectives: Staphylococcal biofilms are among the main causes of chronic implant-associated infections. We have recently suggested that their transformation into viable but non-culturable (VBNC) forms (i.e. forms capable of resuscitation) could be responsible for the recurrent symptoms. This work aims to establish whether Staphylococcus aureus biofilms can give rise to VBNC forms capable of being resuscitated in suitable environmental conditions, the role of different stressors in inducing the VBNC state and the conditions favouring resuscitation. Methods: S. aureus 10850 biofilms were exposed to different concentrations of antibiotic (vancomycin or quin-upristin/dalfopristin) and/or to nutrient depletion until loss of culturability. The presence of viable cells and their number were examined by epifluorescence microscopy and flow cytometry. Gene expression was measured by real-time PCR. Resuscitation ability was tested by growth in rich medium containing antioxidant factors. Results: Viable subpopulations were detected in all non-culturable biofilms. However, viable cell numbers and gene expression remained constant for 150 days from loss of culturability in cells from antibiotic-exposed bio-films, but not in those that had only been starved. Resuscitation was obtained in rich medium supplemented with 0.3% sodium pyruvate or with 50% filtrate of a late-log culture. Conclusions: Our findings demonstrate that S. aureus can enter the VBNC state in infectious biofilms. The presence of vancomycin or quinupristin/dalfopristin can inadvertently induce a true VBNC state or its persistence in S. aureus cells embedded in biofilms, supporting previous findings on the role of staphylococcal biofilms in recurrent infections.

Original languageEnglish
Article numberdkt086
Pages (from-to)1812-1817
Number of pages6
JournalJournal of Antimicrobial Chemotherapy
Issue number8
Publication statusPublished - Aug 2013


  • Quinupristin/dalfopristin
  • Recurrent infections
  • Vancomycin

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases


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