Resistência à linezolida em estafilococos coagulase negativos resistentes à meticilina provenientes de hospitais da cidade de Natal-RN

Abstract

Coagulase Negative Staphylococci (CoNS) belong to the normal microbiota of the skin and mucous membranes of humans and animals. The most of the infections caused by CoNS are a serious problem, since an elevated number of multi-drug resistant strains. The objective of this study was to investigate resistance to linezolid in methicillin-resistant coagulase negative staphylococci isolates from hospitals in the city of Natal. Bacterial samples were collected from spontaneous demand from Public and Private Hospitals of the city of Natal-RN. The identification staphylococci of the species were conducted by conventional biochemical. Some Samples had the identification to the species level confirmed by automated methodologies VITEK 2® and VITEK MS®. The resistance profile was evaluated with use of the disk diffusion technique (CLSI, 2013). The MIC to vancomycin and linezolid were determined by using E-test method. The antimicrobial resistance profile was evaluated by disk diffusion technique (CLSI 2013). The Minimum Inhibitory Concentration linezolid and vancomycin were determined by using E-test and the presence of the mecA gene and cfr was confirmed by the technique of Polymerase Chain Reaction. Some samples had the V region of the subunit 23S rRNA gene sequenced and subjected to PFGE technique for determining its pulsotype. Of the 43 coagulase negative staphylococci resistant to methicillin included in this study, 33 (77%) were identified as S. epidermidis, 6 (14%) as S. haemolyticus, 3 (7%) as S. homins and 1 (2%) as S. capitis. The catheter tip isolates accounted for 14% (6) and the blood culture 86% (37). Samples showed an alarming resistance profile, since 98% of the isolates were resistant to four or more class drugs. All were positive for mecA gene. No samples were resistant to vancomycin. Three S. hominis and two S. epidermidis exhibited linezolid resistance with MIC ranging from 6 to 64 μL/mL. None of the samples had the cfr gene. When investigated, they showed two point mutations each (C2190T and G2603T) in the V region of the 23s rRNA gene. None of them was the cfr gene. The S.hominis of PFGE showed the presence of a single pulsotype in three hospitals, suggesting a clonal spread, while it was not found genetic similarity among S. epidermidis. These findings highlight the importance of continued vigilance of linezolid resistance in the genus Staphylococcus.