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Effect of Selective Antibiotic Pressure on the MLS-B Phenotype in Methicillin-Resistant Staphylococcus aureus Strains

K Szymanek-Majchrzak1, A Mlynarczyk2, M Bilinska3

  • 1Department of Medical Microbiology, Medical University of Warsaw, Warsaw, Poland; Department of Medical Microbiology, The Infant Jesus Teaching Hospital, Warsaw, Poland.

Transplantation Proceedings
|May 27, 2018
PubMed
Abstract

Insights

Antibiotic resistance in health care-associated-methicillin resistant Staphylococcus aureus (HA-MRSA) is linked to clindamycin use. Reducing antibiotic selection pressure can decrease resistance, potentially restoring inductive resistance mechanisms.

Area of Science:

  • Medical Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance

Background:

  • Health care-associated-methicillin resistant Staphylococcus aureus (HA-MRSA) poses a significant threat to transplant patients.
  • Combined resistance to macrolides, lincosamides, and streptogramin-B (MLS-B) antibiotics limits therapeutic options.

Purpose of the Study:

  • To investigate the mechanisms of MLS-B resistance in HA-MRSA strains from surgical-transplantation wards over 24 years.
  • To assess the correlation between clindamycin usage and the prevalence of specific resistance phenotypes.

Main Methods:

  • Analysis of 112 HA-MRSA strains collected between 1991 and 2014.
  • Phenotypic and genetic detection of methicillin resistance (mecA gene).
  • E-test and D-test methods to determine erythromycin/clindamycin resistance and MLS-B phenotypes (iMLS-B, cMLS-B).
  • Calculation of defined daily doses (DDD) per 1000 person-days for clindamycin.

Main Results:

  • Erythromycin/clindamycin resistance in MRSA increased significantly from 1991 to 2004-2007.
  • The constitutive MLS-B (cMLS-B) phenotype frequency rose from 5.9% in 1991 to 76.9% in 2010-2011, correlating with increased clindamycin use.
  • In 2012, a decrease in cMLS-B (to 69.7%) and an increase in MLS-B-sensitive isolates (to 21.7%) coincided with reduced clindamycin usage.

Conclusions:

  • The prevalence of cMLS-B versus iMLS-B phenotypes in HA-MRSA is directly influenced by clindamycin consumption in hospital settings.
  • Decreasing antibiotic selection pressure can lead to the loss of resistance or a shift back to inducible resistance mechanisms.

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