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Updated: Jan 28, 2026

Methodology for the Study of Horizontal Gene Transfer in Staphylococcus aureus
Published on: March 10, 2017
Decreased susceptibility to chlorhexidine and distribution of qacA/B genes among coagulase-negative Staphylococcus
Bruna Costa Moura do Vale1, Acácia Gentil Nogueira1, Thiago André Cidral1
1Department of Microbiology and Parasitology, Medical Bacteriology Laboratory, Bioscience Center, Federal University of Rio Grande do Norte - UFRN, Av. Senador Salgado Filho, S/N, Campus Universitário, Lagoa Nova, Natal, RN, 59072-970, Brazil.
Background:
Healthcare-associated infection (HAI) is a major public health problem. As a form of prevention and control, preparations of chlorhexidine are used extensively; however, the reduction of susceptibility to chlorhexidine has been reported. The aim of this study was to investigate the susceptibility to chlorhexidine and the distribution of the qacA/B genes in 211 clinical isolates of coagulase-negative Staphylococci (CoNS).
Methods:
CoNS were identified by conventional biochemical tests. Antimicrobial susceptibility was tested by disk-diffusion. Minimum inhibitory concentration (MIC) of chlorhexidine was determined by agar dilution test; detection of the qacA/B and mecA genes were evaluated by PCR.
Results:
The most frequently isolated species were S. epidermidis, S. hominis hominis, S. auricularis, and S. haemolyticus, respectively. The strains presented a multidrug resistance profile of 87%, including methicillin resistance. Reduced susceptibility to chlorhexidine was observed in 31%. The qacA/B genes were detected in samples resistant (32/32) and susceptible (17/32) to chlorhexidine. The vast majority (94%) of the samples with reduced susceptibility to chlorhexidine were multidrug resistant.
Conclusions:
Our results show that qacA/B genes are not restricted to strains expressing chlorhexidine resistance. Further studies are needed to understand how the expression of these genes occurs.
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