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Phenotypic and Molecular Characterisation of Staphylococcus Aureus with Reduced Vancomycin Susceptibility Derivated

Jia Xu1,2, Long Pang1, Xiao Xue Ma3

  • 1Department of Medical Microbiology and Parasitology, College of Basic Medical Sciences, China Medical University, Shenyang, PR China.

Open Medicine (Warsaw, Poland)
|November 15, 2018
PubMed

Insights

Vancomycin resistance in Staphylococcus aureus is increasing. In vitro studies show that while vancomycin-intermediate strains can develop higher resistance, they rarely become fully resistant (VRSA).

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance

Background:

  • Vancomycin is a critical antibiotic for treating Methicillin-resistant Staphylococcus aureus (MRSA) infections.
  • Increasing MRSA rates and vancomycin use have led to reduced susceptibility, including vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA).
  • Understanding the mechanisms and limitations of vancomycin resistance development is crucial for effective treatment strategies.

Purpose of the Study:

  • To investigate the phenotypic and molecular characteristics of Staphylococcus aureus strains derived for vancomycin resistance in vitro.
  • To compare vancomycin-resistant strains with their parental strains regarding various biological and genetic factors.
  • To determine the potential for vancomycin-susceptible strains to evolve into high-level vancomycin resistance.

Main Methods:

  • Stepwise in vitro selection of vancomycin-resistant Staphylococcus aureus strains.
  • Antimicrobial susceptibility testing, including population analysis profile-area under the curve (PAP-AUC).
  • Molecular typing (PFGE, spa typing), gene expression analysis (qPCR), and phenotypic assays (hemolysin, autolysis, biofilm).

Main Results:

  • Derived vancomycin-resistant strains exhibited reduced hemolysin, autolysis, and biofilm formation.
  • Changes in phenotype and gene expression were inversely proportional to vancomycin minimum inhibitory concentration (MICvan).
  • Most hVISA/VISA strains belonged to spa type t570 and agr group II; derivation to high-level VISA was possible, but not to VRSA.

Conclusions:

  • In vitro derivation of vancomycin resistance in Staphylococcus aureus leads to significant phenotypic alterations.
  • While intermediate resistance can increase, the development of high-level vancomycin resistance (VRSA) is challenging to achieve in vitro.
  • VISA and hVISA strains demonstrate adaptability to increasing vancomycin concentrations, highlighting the dynamic nature of antimicrobial resistance.
Keywords:
Staphylococcus aureusmolecular characterisationphenotype

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