Prevalence and molecular typing of the antiseptic resistance genes qacA/B among Staphylococcus aureus strains isolated in a teaching hospital

Abstract

The qacA/B genes are found in Staphylococcus aureus and confer resistance to various antiseptics and disinfectants. Herein, the prevalence of the qacA/B genes in methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) was investigated. Molecular typing systems were used to analyse the relatedness of these qacA/B-positive strains. 176 six strains of clinically isolated S. aureus were collected between July, 2008 and June, 2010. The strains carrying the qacA/B genes were characterised by pulse-field gel electrophoresis (PFGE) typing, Staphylococcus protein A (spa) typing, Panton-Valentine leucocidin (pvl) polymerase chain reaction (PCR) detection, staphylococcal chromosomal cassette (SCC) mec typing, and antimicrobial resistance profiles. Strains carrying the qacA/B genes composed 9.1% of the strains isolated, but the incidence of qacA/B genes in MRSA strains was significantly higher than that in MSSA strains (14.6 versus 4.3%, p < 0.05). Additionally, two predominant PFGE (B and A) and spa types (t037 and t042) were identified along with two major antimicrobial resistance profiles. All of these qacA/B-positive strains strains were pvl-negative by PCR. The qacA/B-positive MRSA strains all contained the group III SCCmec element. These strains were obtained mainly from patients in surgical wards; therefore, the neurosurgical ward and ICU may be considered as a source of MRSA strains carrying the qacA/B genes. Finally, the strain identified as spa type t037 is likely to be an epidemiological clone. The presence of the antiseptic resistance genes qacA/B by MRSA could potentially lead to MRSA strain prevalence. Thus, the optimal usage of antiseptics and disinfectants is warranted. A policy of molecular typing needs to be implemented to track the possible dissemination of these resistance genes.

Key words: Staphylococcus aureus, mecA, qacA/B and pvl genes, methicillin-resistant,  Staphylococcus aureus (MRSA), methicillin-sensitive Staphylococcus aureus (MSSA).