Adherence and intracellular survival within human macrophages of Enterococcus faecalis isolates from coastal marine sediment

Raffaella Sabatino, Andrea Di Cesare, Sonia Pasquaroli, Carla Vignaroli, Barbara Citterio, Mehdi Amiri, Luigia Rossi, Mauro Magnani, Alessandro Mauro, Francesca Biavasco

Research output: Contribution to journalArticlepeer-review

Abstract

Enterococcus faecalis is part of the human intestinal microbiota and an important nosocomial pathogen. It can be found in the marine environment, where it is also employed as a fecal indicator. To assess the pathogenic potential of marine E. faecalis, four strains isolated from marine sediment were analyzed for their ability to survive in human macrophages. Escherichia coli DH5α was used as a negative control. The number of adherent and intracellular bacteria was determined 2.5 h after the infection (T0) and after further 24h (T24) by CFU and qPCR counts. At T24 adherent and intracellular enterococcal CFU counts were increased for all strains, the increment in intracellular bacteria being particularly marked. No CFU of E. coli DH5α were detected. In contrast, qPCR counts of intracellular enterococcal and E. coli bacteria were similar at both time points. These findings suggest that whereas E. coli was killed within macrophages (no CFU, positive qPCR), the E. faecalis isolates not only escaped killing, but actually multiplied, as demonstrated by the increase in the viable cell population. These findings support earlier data by our group, further documenting that marine sediment can be a reservoir of pathogenic enterococci.

Original languageEnglish
Pages (from-to)660-664
Number of pages5
JournalMicrobes and Infection
Volume17
Issue number9
DOIs
Publication statusPublished - Sep 1 2015

Keywords

  • Adhesion
  • Enterococcus faecalis
  • Internalization
  • Macrophages

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Infectious Diseases

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