Expression of multidrug resistance efflux pump genes in clinical and environmental isolates of Staphylococcus aureus

Christos Kosmidis, Bryan D Schindler, Pauline L Jacinto, Diixa Patel, Karanpreet Bains, Susan M Seo, Glenn W Kaatz

Research output: Contribution to journalArticlepeer-review


Increased expression of multidrug resistance efflux pump (MDR-EP) genes in clinical isolates of Staphylococcus aureus occurs frequently, but its temporal and geographic variability is unknown. Such strains may contaminate the hospital environment, posing an infection control problem. Nearly 700 clinical isolates from different geographic locales as well as 91 environmental isolates recovered from two Detroit hospitals were studied. Ethidium bromide (EtBr) minimum inhibitory concentration (MIC), quantitative expression of all characterised chromosomal MDR-EP genes, and the presence of qacA/B and smr were determined for all strains. In addition, for norA- and/or mepA-overexpressing strains, the spa type was established. MDR-EP gene overexpression varied temporally and geographically, and overexpressing strains were present in the hospital environment. Increased expression of norA was associated with meticillin resistance and spa type t002, a rare type among control strains, consistent with widespread dissemination of a norA-overexpressing, meticillin-resistant S. aureus (MRSA) clone. Clonal spread also played a role for spa type t008, mepA-overexpressing, meticillin-susceptible strains. An EtBr MIC of ≤12.5 μg/mL was highly specific (>90%) in identifying strains lacking MDR-EP gene overexpression.

Original languageEnglish
Pages (from-to)204-9
Number of pages6
JournalInternational Journal of Antimicrobial Agents
Issue number3
Publication statusPublished - Sept 2012


  • Anti-Bacterial Agents/pharmacology
  • Bacterial Proteins/biosynthesis
  • Biological Transport, Active
  • Canada
  • Cluster Analysis
  • Drug Resistance, Multiple, Bacterial
  • Environmental Microbiology
  • Gene Expression Regulation, Bacterial
  • Genes, Bacterial
  • Genotype
  • Hospitals
  • Humans
  • Membrane Transport Proteins/biosynthesis
  • Microbial Sensitivity Tests
  • Real-Time Polymerase Chain Reaction
  • Staphylococcal Infections/microbiology
  • Staphylococcus aureus/classification


Dive into the research topics of 'Expression of multidrug resistance efflux pump genes in clinical and environmental isolates of Staphylococcus aureus'. Together they form a unique fingerprint.

Cite this