Sensitivity of staphylococcus epidermidis to chlorhexidine and associated resistance properties

  • Manijeh Ghods

Student thesis: Doctoral ThesisDoctor of Philosophy


Staphylococcus epidermidis are common Gram-positive bacteria and are responsible for a number of life-threatening nosocomial infections. Treatment of S. epidermidis infection is problematic because the organism is usually resistant to many antibiotics. The high degree of resistance of this organism to a range of antibiotics and disinfectants is widely known.
The aims of this thesis were to investigate and evaluate the susceptibility of isolates of S. epidermidis from various infections to chlorhexidine (CHX) and to other disinfectants such as benzalkonium chloride (BKC), triclosan (TLN) and povidone-iodine (PI). In addition, the mechanisms of resistance of S. epidermidis to chlorhexidine (the original isolates and strains adapted to chlorhexidine by serial passage) were examined and co-resistance to clinically relevant antibiotics
In 3 of the 11 S. epidermidis strains passaged in increasing concentrations of
chlorhexidine, resistance to the disinfectant arose (16-fold). These strains were
examined further, each showing stable chlorhexidine resistance. Co-resistance to
other disinfectants such as BKC, TLN and PI and changes in cell surface
hydrophobicity were observed. Increases in resistance were accompanied by an
increase in the proportion of neutral lipids and phospholipids in the cell membrane. This increase was most marked in diphosphatidylglycerol. These observations suggest that some strains of S. epidermidis can become resistant to chlorhexidine and related disinfectants/antiseptics by continual exposure. The mechanisms of resistance appear to be related to changes in membrane lipid compositions.
Date of AwardOct 2003
Original languageEnglish
SupervisorPeter Lambert (Supervisor)


  • staphylococcus epidermidis
  • disinfectant/chlorhexidine resistance
  • serial passage

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