Recently introduced qacA/B genes in Staphylococcus epidermidis do not increase chlorhexidine MIC/MBC

Sissel Skovgaard, Marianne Halberg Larsen, Lene Nørby Nielsen, Robert Leo Skov, Christian Wong, Henrik Westh, Hanne Ingmer

Research output: Contribution to journalJournal articleResearchpeer-review


Objectives: Chlorhexidine is used as a disinfectant to prevent surgical infections. Recently, studies have indicated that chlorhexidine usage has selected methicillin-resistant Staphylococcus aureus strains that are tolerant to chlorhexidine and that this may be related to the presence of the qacA/B-encoded efflux pumps. Here, we evaluated if high-level exposure to chlorhexidine selects for tolerant colonizing Staphylococcus epidermidis and we addressed the consequences of long-term exposure to chlorhexidine.Methods: Chlorhexidine susceptibility and carriage of qacA/B was determined for colonizing S. epidermidis isolated from scrub nurses heavily exposed to chlorhexidine and were compared with isolates from non-users of chlorhexidine hand rubs. S. epidermidis blood isolates from the 1960s, before the wider introduction of chlorhexidine to the market, were also tested and compared with recently collected S. epidermidis blood isolates.Results: There was no correlation between the use of chlorhexidine in scrub nurses and the presence of qacA/B genes in S. epidermidis isolates or increased MICs/MBCs of chlorhexidine for S. epidermidis isolates. While 55% of current blood isolates harboured the qacA/B genes, none of the 33 historical S. epidermidis isolates did, although their MICs and MBCs of chlorhexidine were comparable to those for current isolates.Conclusions: Chlorhexidine used as a hand rub does not select for S. epidermidis isolates with increased MICs or MBCs of chlorhexidine. However, the absence of qacA/B genes in S. epidermidis isolates obtained in the 1960s suggests that long-term use of biocides like chlorhexidine or related compounds may select for the presence of qacA/B genes.
Original languageEnglish
JournalJournal of Antimicrobial Chemotherapy
Issue number10
Pages (from-to)2226-2233
Number of pages8
Publication statusPublished - 2013
Externally publishedYes


  • biocide susceptibility
  • antimicrobial resistance
  • hospital disinfection
  • hand rubs
  • infection control
  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases
  • Antimicrobial resistance
  • Biocide susceptibility
  • Hand rubs
  • Hospital disinfection
  • Infection control
  • bacterial protein
  • biocide
  • chlorhexidine
  • chlorhexidine gluconate
  • iduscrub
  • qacA protein
  • qacB protein
  • unclassified drug
  • antibiotic resistance
  • antibiotic sensitivity
  • article
  • bacterial colonization
  • bacterial gene
  • bacterial genetics
  • bacterium identification
  • bacterium isolate
  • controlled study
  • disinfection
  • drug marketing
  • gene
  • genetic analysis
  • hand washing
  • hospitalization
  • human
  • infectious arthritis
  • long term exposure
  • major clinical study
  • methicillin resistant Staphylococcus aureus
  • minimum inhibitory concentration
  • Staphylococcus epidermidis
  • surgical infection
  • Bacterial Proteins
  • Chlorhexidine
  • Disinfectants
  • Drug Tolerance
  • Gene Transfer, Horizontal
  • Hand Disinfection
  • Humans
  • Infection Control
  • Membrane Transport Proteins
  • Microbial Sensitivity Tests
  • Nurses
  • QacB protein, Staphylococcus aureus
  • qacA protein, Staphylococcus aureus
  • Gram-Positive Cocci Eubacteria Bacteria Microorganisms (Bacteria, Eubacteria, Microorganisms) - Micrococcaceae [07702] Staphylococcus epidermidis species pathogen
  • Primates Mammalia Vertebrata Chordata Animalia (Animals, Chordates, Humans, Mammals, Primates, Vertebrates) - Hominidae [86215] human common host Danish
  • Staphylococcus epidermidis qacA/B gene [Micrococcaceae]
  • chlorhexidine 55-56-1 antiinfective-drug, antiseptic/disinfectant-drug dosage
  • 03502, Genetics - General
  • 03508, Genetics - Human
  • 12502, Pathology - General
  • 12512, Pathology - Therapy
  • 15002, Blood - Blood and lymph studies
  • 15004, Blood - Blood cell studies
  • 22002, Pharmacology - General
  • 22005, Pharmacology - Clinical pharmacology
  • 31000, Physiology and biochemistry of bacteria
  • 31500, Genetics of bacteria and viruses
  • 36002, Medical and clinical microbiology - Bacteriology
  • 38502, Chemotherapy - General, methods and metabolism
  • 39500, Disinfection, disinfectants and sterilization
  • Human Medicine
  • Infection
  • Molecular Genetics
  • Staphylococcus epidermidis infection bacterial disease drug therapy, genetics
  • drug resistance
  • drug susceptibility
  • drug tolerance
  • Biochemistry and Molecular Biophysics
  • Medical Sciences
  • blood blood and lymphatics
  • Original research


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