title: Does the presence of QAC genes in staphylococci affect the efficacy of disinfecting solutions used by orthokeratology lens wearers?
abstract: OBJECTIVE
  There has been increasing evidence of the emergence of antiseptic resistance mediated by quaternary ammonium compound (QAC) resistance genes, which may reduce the efficacy of disinfection. Although the presence of QAC-positive staphylococci has been shown to be elevated in contact lens wearers, the efficacy of multipurpose solutions (MPS) against such isolates has not been determined. This study investigated the efficacy of four MPS for rigid gas permeable (RGP) lenses against staphylococci-harbouring QAC genes.
  
  
  METHODS
  Ability to reduce viability by three or more log reductions of four MPS for RGP lenses was tested against 60 disinfectant-resistant gene-positive staphylococci, comprising 38 coagulase-negative staphylococci (CNS) (17 ITALIC! qacA/B, 7 ITALIC! smr, 5 ITALIC! qacH, 9 habouring two or more genes) and 22 ITALIC! Staphylococcus aureus (16 ITALIC! qacA/B, 4 ITALIC! smr, 2 ITALIC! qacA/B+ ITALIC! smr)). 60 gene-negative isolates of staphylococci (30 CNS and 30 ITALIC! S aureus) were used as controls. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of these four MPS were determined.
  
  
  RESULTS
  Although there was some variation between solutions, all failed to achieve a 3-log reduction in some ITALIC! S aureus and CNS isolates. Strains harbouring disinfectant-resistant genes were significantly less likely to be reduced by 3 logs by three of the solutions. Overall, the MIC and MBC of the four MPS against gene-positive clinical isolates were significantly higher than those of gene-negative isolates.
  
  
  CONCLUSIONS
  The efficacy of MPS solutions for RGP lenses against staphylococci varied. The presence of disinfectant-resistance genes significantly adversely affected disinfecting capacity of RGP solutions.
authors.affiliation: School of Optometry, The Hong Kong Polytechnic University, Hung Hum, Kowloon, Hong Kong.
authors.forename: Guang-sen
authors.initials: GS
authors.lastname: Shi
authors.affiliation: Squina Centre for Infection Control, School of Nursing, The Hong Kong Polytechnic University, Hum Hom, Kowloon, Hong Kong.
authors.forename: Maureen V
authors.initials: MV
authors.lastname: Boost
authors.affiliation: School of Optometry, The Hong Kong Polytechnic University, Hung Hum, Kowloon, Hong Kong Squina Centre for Infection Control, School of Nursing, The Hong Kong Polytechnic University, Hum Hom, Kowloon, Hong Kong.
authors.forename: Pauline
authors.identifier: http://orcid.org/0000-0002-7866-7513
authors.initials: P
authors.lastname: Cho
mesh_terms: D017920:Antiporters / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D015169:Colony Count, Microbial; D003228:Conjunctiva / Q000382:microbiology; D018639:Contact Lens Solutions / Q000494:pharmacology*; D003261:Contact Lenses / Q000382:microbiology*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D019450:Genes, MDR / Q000502:physiology*; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics; D008826:Microbial Sensitivity Tests; D054158:Orthokeratologic Procedures; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012097:Repressor Proteins / Q000235:genetics; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D017920:Antiporters; D001426:Bacterial Proteins; D018639:Contact Lens Solutions; D026901:Membrane Transport Proteins; C099272:QacB protein, Staphylococcus aureus; C442128:QacR protein, Staphylococcus aureus; D000644:Quaternary Ammonium Compounds; D012097:Repressor Proteins; C521590:small multidrug-resistance pump, Staphylococcus aureus; C068498:qacA protein, Staphylococcus aureus
keywords: Contact lens; Infection; Microbiology