Redução da susceptibilidade à clorexidina e distribuição dos genes qacA/B em isolados de estafilococos coagulase-negativa

Abstract

Health Care Associated Infections (HAI) are currently a of major public health problem. The coagulase-negative Staphylococci (CNS) are among the most prevalent species in this type of infection due to their ability to colonize invasive medical devices. Chlorhexidine is extensively used in the hospital setting as a means of prevention and control of HAI. However, the existence of strains with reduced susceptibility caused possibly by the presence of the qacA/B genes has been reported in the literature. The main of this study was to investigate the susceptibility to chlorhexidine and its relation to the presence of the qacA/B genes in 211 isolates of ECN from diferente hospitals in the city of Natal-RN. Samples were identified by standard biochemical tests; the susceptibility to antimicrobials was performed using the disc-diffusion methodology; the susceptibility to chlorhexidine was evaluated by determining the Minimum Inhibitory Concentration (MIC) by the agar dilution technique; the PCR method was used to investigate the qacA/B genes and mecA gene. In total of 211 CNS samples, 69% were isolated from blood cultures. The most frequent species were S. epidermidis, S. hominis hominis, S. auricularis and S. haemolyticus, respectively. The strains had a multidrug resistance profile of 87%, including resistance to oxacillin; 31% demonstrated reduced susceptibility to chlorhexidine. The qacA/B genes were detected in both chlorhexidine resistant (32/32) and susceptible samples (17/32). Most of the strains with reduced susceptibility to chlorhexidine also showed multidrug resistance to the tested antibiotics (94%). Identification of strains with reduced susceptibility to chlorhexidine in this study poses a threat to HAIs control practices. Although all strains resistant to chlorhexidine had the qacA/B genes, their presence was not a determining factor for the expression of the resistance, requiring additional studies. The decrease in susceptibility to antiseptics may allow bacteria to persist in the hospital environment, thus contributing to the survival of multiresistant strains.