ABSTRACT
Objectives: Reduced biocide susceptibility in Staphylococci is associated with various antiseptic resistance genes encoding efflux systems. Our aim was to determine the susceptibility to three disinfectant agents, including benzalkonium chloride [BAC], benzethonium chloride [BZT], and chlorhexidine digluconate [CHDG] among clinical isolates of Staphylococcus aureus and coagulase-negative Staphylococci [CoNS]
Methods: The minimum inhibitory concentration [MIC] of 60 methicillin-resistant S. aureus [MRSA], 54 methicillin-sensitive S. aureus [MSSA] and 51 CoNS isolates from a single hospital to three biocidal agents [BAC, BZT, and CHDG] was determined. Biocide resistance genes [qacA/B, smr, qacG, qacH, qacJ, and norA] were analyzed by the polymerase chain reaction assay
Results: All isolates had MICs for BAC and BZT from 0.25 to 8 microg/mL, and for CHDG from 0.5 to 64 microg/mL. qacA/B was the most common biocide resistance gene among all 165 Staphylococcus isolates [76; 46%], which comprised 38 [63.3%] MRSA, 14 [25.9%] MSSA, and 24 [47%] CoNS. Eleven [6.7%] and 24 [14.5%] isolates among the 165 Staphylococci carried smr and norA genes, respectively. In contrast, other resistance genes such as qacG, qacH, and qacJ were absent in all Staphylococci studied. The qacA/B and smr genes were detected concomitantly in 3% of isolates, and 23.6% strains of the total 165 Staphylococcus isolates were negative for each studied gene
Conclusions: The carriage of several biocide resistance genes, including qacA/B, smr, and norA, alone or concurrently, is associated with reduced susceptibility. Use of antiseptics may select for antibiotic-resistant strains and assist their survival in the healthcare environment