Related Experiment Video

Updated: May 20, 2026

Characterizing Multidrug Efflux Systems in Acinetobacter baumannii Using an Efflux-Deficient Bacterial Strain and a Single-Copy Gene Expression System
05:06

Characterizing Multidrug Efflux Systems in Acinetobacter baumannii Using an Efflux-Deficient Bacterial Strain and a Single-Copy Gene Expression System

Published on: January 5, 2024

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

Christos Kosmidis1, Bryan D Schindler, Pauline L Jacinto

  • 1Department of Medicine, Division of Infectious Diseases, Wayne State University School of Medicine, Detroit, MI 48201, USA.

International Journal of Antimicrobial Agents
|July 7, 2012
PubMed

Insights

Multidrug resistance efflux pump gene overexpression in Staphylococcus aureus varies by time and location, impacting hospital environments. Identifying these strains early is crucial for infection control.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Genetics

Background:

  • Multidrug resistance efflux pump (MDR-EP) genes are frequently overexpressed in clinical Staphylococcus aureus isolates.
  • The temporal and geographic variability of MDR-EP gene expression and its role in hospital contamination remain largely unknown.

Purpose of the Study:

  • To investigate the temporal and geographic variability of MDR-EP gene expression in Staphylococcus aureus.
  • To determine the prevalence of MDR-EP overexpressing strains in clinical and environmental settings.
  • To identify associations between MDR-EP gene overexpression, specific clones, and antimicrobial resistance.

Main Methods:

  • Analysis of nearly 700 clinical and 91 environmental Staphylococcus aureus isolates.
  • Determination of ethidium bromide (EtBr) minimum inhibitory concentration (MIC).
  • Quantitative expression analysis of chromosomal MDR-EP genes, qacA/B, and smr.
  • spa typing for norA- and/or mepA-overexpressing strains.

Main Results:

  • MDR-EP gene overexpression demonstrated significant temporal and geographic variation.
  • Overexpressing strains were detected in the hospital environment.
  • Increased norA expression correlated with methicillin resistance and spa type t002, suggesting clonal spread of a specific MRSA clone.
  • Clonal spread was also implicated in mepA-overexpressing, methicillin-susceptible strains with spa type t008.
  • An EtBr MIC ≤12.5 μg/mL showed high specificity (>90%) for identifying strains lacking MDR-EP gene overexpression.

Conclusions:

  • MDR-EP gene expression in Staphylococcus aureus is dynamic and geographically influenced, posing potential infection control challenges.
  • Specific clones, such as a norA-overexpressing MRSA clone (spa type t002) and a mepA-overexpressing MSSA clone (spa type t008), are associated with MDR-EP overexpression.
  • EtBr MIC serves as a reliable indicator for detecting strains with reduced MDR-EP gene expression.

More Related Videos

A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues07:10

A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues

Published on: February 19, 2019

Related Concept Videos

Mechanism of Antibiotic Resistance in MRSA01:25

Mechanism of Antibiotic Resistance in MRSA

Antibiotic resistance in bacteria arises when microorganisms evolve the ability to withstand drugs designed to kill them or inhibit their growth, rendering once-effective treatments useless. This phenomenon, driven by genetic change and selection under antibiotic exposure, poses a profound threat to modern medicine. Mechanisms include drug-inactivating enzymes (e.g., β-lactamases), efflux pumps that eject antibiotics, mutations altering antibiotic targets, decreased drug uptake, and acquisition...
Clinical Significance of Antibiotic Resistance01:25

Clinical Significance of Antibiotic Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) presents a critical public health threat, arising from its capacity to resist β-lactam antibiotics due to acquisition of the mecA gene within the staphylococcal cassette chromosome mec (SCCmec). This gene encodes penicillin-binding protein 2a (PBP2a), which impairs binding efficacy of methicillin and other β-lactams. MRSA has evolved into distinct clonal lineages impacting humans and animals alike, reinforcing its significance within the One...
Development of Antibiotic Resistance01:30

Development of Antibiotic Resistance

Antibiotic resistance is a major public health concern that arises when bacteria evolve mechanisms to withstand the effects of antibiotic treatments. This resistance can be intrinsic, acquired through genetic mutations, or transferred between bacteria via horizontal gene transfer. The development of antibiotic resistance poses significant challenges in treating bacterial infections and necessitates ongoing research to develop new therapeutic strategies.Intrinsic resistance occurs when bacterial...
Staphylococcal Skin Infections01:29

Staphylococcal Skin Infections

Staphylococcus aureus is a Gram-positive coccus that resides harmlessly on the skin and mucous membranes of healthy individuals. When the skin barrier is breached, it can shift from a commensal to an opportunistic pathogen. This transition is facilitated by surface adhesins, such as clumping factor B and S. aureus surface protein G (SasG), which bind to structural proteins, including loricrin and cytokeratin, in the damaged epidermis. Protein A, another key factor, binds the Fc region of...
Gene Regulation in Microbial Communities: Quorum Sensing01:28

Gene Regulation in Microbial Communities: Quorum Sensing

Quorum sensing is a mechanism of bacterial communication that enables coordinated gene expression in response to changes in population density. This facilitates collective behaviors that enhance survival, resource acquisition, and ecological adaptation. This process relies on small signaling molecules called autoinducers that accumulate as bacterial populations grow. When a critical threshold concentration of autoinducers is reached, bacterial cells collectively modify gene expression,...