Prevalence of antiseptic-resistance genes in Staphylococcus aureus and coagulase-negative staphylococci colonising nurses and the general population in Hong Kong
Introduction
Staphylococcus aureus is a major human pathogen, and resistant strains, especially meticillin-resistant S. aureus (MRSA), are important causes of nosocomial infection. There are increasing numbers of reports of coagulase-negative staphylococci (CoNS) as causative organisms of disease in immunocompromised patients and increased prevalence of multidrug-resistant strains.1
To prevent the spread of pathogens in the hospital and community, disinfectants/antiseptics such as those containing chlorhexidine and benzalkonium chloride (BC) are widely used for decontamination of surfaces, hand disinfection, and decolonisation of patients. Guidelines also recommend their use for decolonisation of high risk groups and routine bathing of patients when basic interventions have failed to reduce rates of MRSA infection.2 Though rigid implementation of infection control practices has led to reductions in infection rates, the ability of MRSA strains to persist in hospital environments has been demonstrated.3, 4
Evidence suggests that widespread use of biocides may impose selective pressure and could contribute to the emergence of bacteria with decreased antiseptic susceptibility. Extensive use may also contribute to emergence of cross-resistance between widely used biocides and antibiotics.5 Quaternary ammonium compound (QAC) resistance determinants, including qacA/B and smr (qac genes), have been shown to be located adjacent to antibiotic resistance genes on transferrable genetic elements, which can allow rapid spread of resistance.6 These genes encode for proton-dependent export proteins and their efflux mechanisms appear to be the major mechanism of tolerance in staphylococci.7
Staphylococcal strains harbouring plasmid-encoded genes, conferring increased minimum bactericidal concentrations (MBCs) to antiseptics, have been demonstrated in clinical isolates of MRSA from Japan (32.6%), Europe (63%), and China (62%).8, 9, 10 Prevalence of these genes may be increasing in MRSA strains, as a longitudinal study reported absence of antiseptic resistance genes in 1990 but 26.7% of isolates were qacA/B positive by 1995, rising to 33.3% by 2005.11
The distribution of qac genes in S. aureus and CoNS has been investigated in clinical isolates, with most focus on MRSA, but little is known about the frequency of these genes in flora of the general public.8, 9, 10, 11, 12 This study determined the prevalence of qac genes in colonising strains of S. aureus and CoNS from nurses and the general public and investigated risk factors for their carriage. The association between the presence of qac genes and antibiotic resistance in isolates was investigated.
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Study design
A cross-sectional study of nasal colonisation rates with S. aureus and CoNS harbouring qac genes in nurses and the general public was performed. A minimum sample size of 202 was estimated based on an S. aureus carriage rate of 20% and an assumed 5% carriage rate of qac genes in S. aureus and CoNS with 3% error and 95% confidence intervals (CIs).8, 13, 14 Nurses were recruited from 15 local hospitals and designated as ‘fresh’ (<2 years of nursing experience in the hospital) or ‘experienced’ (≥2
Results
Samples were obtained from 249 nurses, of whom 157 (63.1%) were experienced and 92 (36.9%) fresh. There was no significant difference between S. aureus carriage rates of nurses (51/249; 20.5%) and the general population (186/775; 24%). Eight nurses (3.2%), seven experienced, were colonised with MRSA compared with only 4/775 (0.5%) of the general population (OR: 6.4; 95% CI: 1.9–21.4; P = 0.002). There was a significantly lower rate of meticillin resistance in CoNS isolated from the general public
Discussion
To our knowledge, this is the first report of qac genes in colonising staphylococci from the general public, though these genes have previously been reported in clinical isolates.8, 9, 10, 11, 12, 20 Carriage rates of S. aureus in nurses and the general population were similar to those of previous studies.13, 14 MRSA carriage was lower in the general population and in young nurses. The comparatively shorter exposure time or limited exposure to critically ill patients may explain the lower MRSA
Acknowledgements
The authors wish to thank F. Wong and M. Tsang for their technical assistance.
References (28)
MRSA and MRSE: is there an answer?
Clin Microbiol Infect
(2000)- et al.
Decline in the rates of meticillin-resistant Staphylococcus aureus acquisition and bacteraemia in a general intensive care unit between 1996 and 2008
J Hosp Infect
(2009) - et al.
Distribution of antiseptic-resistance genes qacA/B in clinical isolates of meticillin-resistant Staphylococcus aureus in China
J Hosp Infect
(2008) - et al.
Development of bacterial resistance to several biocides and effects on antibiotic susceptibility
J Hosp Infect
(2003) - et al.
Health-care workers: source, vector, or victim of MRSA?
Lancet Infect Dis
(2008) - et al.
Nasal colonization by methicillin-resistant coagulase-negative staphylococcus in community skilled nursing facility patients
Am J Infect Control
(2000) Guidelines for the control and prevention of meticillin-resistant Staphylococcus aureus (MRSA) in healthcare facilities
J Hosp Infect
(2008)- et al.
Chlorhexidine resistance in antibiotic-resistant bacteria isolated from the surfaces of dispensers of soap containing chlorhexidine
Infect Control Hosp Epidemiol
(2002) - et al.
Analysis on distribution and genomic diversity of high-level antiseptic resistance genes qacA and qacB in human clinical isolates of Staphylococcus aureus
Microbial Drug Resist
(2003) - et al.
Distribution of the antiseptic resistance genes qacA, qacB and qacC in 497 meticillin-resistant and -susceptible European isolates of Staphylococcus aureus
J Antimicrob Chemother
(2001)
Bacterial resistance to disinfectants: present knowledge and future problems
J Hosp Infect
Longitudinal analysis of chlorhexidine susceptibilities of nosocomial methicillin-resistant Staphylococcus aureus isolates at a teaching hospital in Taiwan
J Antimicrob Chemother
Frequency of disinfectant resistance genes and genetic linkage with beta-lactamase transposon Tn552 among clinical staphylococci
Antimicrob Agents Chemother
Susceptibilities to antiseptic agents and distribution of antiseptic-resistance genes qacA/B and smr of methicillin-resistant Staphylococcus aureus isolated in Asia during 1998 and 1999
J Med Microbiol
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