Strain-specific adaptations of streptococcus mitis-oralis to serial in vitro passage in daptomycin (DAP): Genotypic and phenotypic characteristics

Nagendra N. Mishra, Truc T. Tran, Cesar A. Arias, Ravin Seepersaud, Paul M. Sullam, Arnold S. Bayer

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Viridans group streptococci (VGS), especially the Streptococcus mitis-oralis subgroup, are pivotal pathogens in a variety of invasive endovascular infections, including “toxic shock” in neutropenic cancer patients and infective endocarditis (IE). Previously, we showed that the serial in vitro passage of S. mitis-oralis strains in sublethal daptomycin (DAP) resulted in rapid, high-level and stable DAP-resistance (DAP-R), which is accompanied by distinct changes in several genotypic and phenotypic signatures: (1) the disappearance of two key membrane phospholipids, phosphatidylglycerol (PG) and cardiolipin (CL); (2) increased membrane fluidity; (3) increased positive surface charge; (4) single nucleotide polymorphisms (SNPs) in two loci involved in CL biosynthesis (pgsA; cdsA); and (5) DAP hyperaccumulation. The current study examined these same metrics following in vitro serial DAP passages of a separate well-characterized S. mitis-oralis bloodstream isolate (SF100). Although some metrics seen in prior DAP post-passage strains were recapitulated with SF100 (e.g., pgsA SNPs, enhanced membrane fluidity), we observed the following major differences (comparing the parental versus post-passage variant): (1) no change in PG content; (2) reduced, but not absent, CL, with enhancement in phosphatidic acid (PA) content; (3) an unusual pattern of CL localization; (4) significantly decreased positive surface charge; (5) no difference in DAP accumulation; and (6) no cdsA SNPs. Thus, S. mitis-oralis strains are not “pre-programmed” phenotypically and/or genotypically to adapt in an identical manner during the evolution of the DAP-R.

Original languageEnglish (US)
Article number520
Pages (from-to)1-10
Number of pages10
Issue number8
StatePublished - Aug 2020


  • Daptomycin resistance
  • Streptococcus mitis-oralis

ASJC Scopus subject areas

  • Microbiology
  • Biochemistry
  • Pharmacology, Toxicology and Pharmaceutics(all)
  • Microbiology (medical)
  • Infectious Diseases
  • Pharmacology (medical)


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