Comparison of prevalence of quaternary ammonium compounds resistant genes G,H,J between general public and nurses in Hong Kong

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Comparison of prevalence of quaternary ammonium compounds resistant genes G,H,J between general public and nurses in Hong Kong


Author: Ye, Huifen
Title: Comparison of prevalence of quaternary ammonium compounds resistant genes G,H,J between general public and nurses in Hong Kong
Degree: M.Sc.
Year: 2010
Subject: Hong Kong Polytechnic University -- Dissertations
Drug resistance in microorganisms -- Genetic aspects.
Staphylococcal infections
Department: Dept. of Health Technology and Informatics
Pages: x, 93 leaves : ill. ; 31 cm.
Abstract: With widespread use of disinfectants in household and hospital environments, it is not surprising that so many microorganisms are becoming increasingly resistant to various kinds of antiseptics. Nurses are in contact with disinfectants regularly in their routine work, and it is worthy to investigate distribution of certain disinfectant resistant genes between nurses and general public. Aim: Several genes increasing tolerance to disinfectants have been described. However, the presence of the recently identified qacG, H and J have not been demonstrated in human isolates. This project aimed to compare prevalence of quaternary ammonium compounds resistant genes qacG, H and J between staphylococci isolated from nurses and general public; to investigate minimum inhibitory concentrations of benzalkonium chloride and chlorhexidine in isolates harboring qacG, H and J genes and to compare antibiotic resistance patterns between qac positive and negative strains. Methods and results: 240 nurses and 775 members of the general public participated in this project, and a total of 865 staphylococci strains were isolated from these subjects. S.aureus were identified by the femention of mannitol, positive plasma-coagulase, production of acetoin, absence of β-galactosidase and resistance to polymyxin B. Conventional PCR was required to detect qac genes in S.aureus and coagulase negative staphylococci. Only nine strains were confirmed to be carrying a qacG,H or J gene. Of the four strains containing the qacG gene, one harbored qacG and qacA/B and another one hosted qacG and smr concomitantly. Only one strain harbored the qacH gene and four strains were positive for qacJ. Eight of these nine strains were S.aureus and one qacJ isolate was identified as S.epidermidis. Minimum inhibitory concentrations (MIC) were determined by broth dilution and the mean MICs of benzalkonium chloride and chlorhexidine in qacG, qacH and qacJ groups were 6 and 2.5 mg/l, 4 and 2 mg/l, 5 and 2 mg/l respectively. All qacG,H and J strains were susceptible to Quinupristin/Dalfopristin, Linezolid, Ciprofloxacin, Imipenem and Vancomycin. Resistance to Fusidic acid(33.3%), Clindamycin(55.6%), Tetracycline(44.4%) and Gentamycin(33.3%) was observed, and there were significant differences between qacG,H,J positive and qac negative strains, which indicate the presence of qacG,H and J genes is probably associated with resistant mechanisms of these antibiotics. Conclusion: The prevalence of qacG, qacH and qacJ genes are low in both general public and nurses. However, attention should be paid for the elevated MICs of disinfectants of these qac positive strains, which indicate improper use of disinfectants can increase numbers of resistance microorganisms. Cross resistance between disinfectants and antibiotics is also a promising aspect for further research.

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