Avaliação das metodologias de detecção bacteriana e de resistência dos Staphylococcus coagulase negativa isolados das bolsas de concentrados plaquetários

Abstract

Platelet transfusion therapy has played an important role in the treatment of patients with hematological and oncological diseases. However, platelet transfusion represents a risk for bacterial sepsis. Platelet Concentrates (PCs) are blood components with the highest rate of bacterial contamination, being responsible for the vast majority of septic transfusion reactions. Among contaminants, coagulase-negative Staphylococci (CoNS) are the most frequently isolated. Therefore, this study aimed to assess the methods of bacterial detection and micro-organisms identification, as well as to investigate the susceptibility profile, biofilm formation and the mechanisms of resistance of Staphylococci strains isolated from bags of PCs. The PCs units were obtained from the Blood Bank of the State of Rio Grande do Sul (HEMORGS), in Santa Maria. Qualitative and quantitative culture techniques and daily growth were employed to detect bacterial contamination. The isolated micro-organisms were identified through VITEK® 2, and the susceptibility profile was determined by means of conventional and automated testing. Biofilm and mechanisms of resistance were assessed by phenotypic tests and investigation of the presence of genes. A high rate of bacterial contamination was detected (2.32% - 16/691) and the best method for detection were the combination of quantitative and qualitative methodologies. All contaminants were characterized as CoNS and S. haemolyticus was the predominant specie (31.25%). All isolates were susceptible to vancomycin and resistant to penicillin and benzylpenicillin. Approximately 62.5% were resistant to clindamycin and erythromycin, and 50% were classified as multiple drug resistance (MDR) strains. Furthermore, biofilm formation and the presence of icaACD genes were detected, as well as MRSCoN strains, and presence of the mecA gene, D-Test positive (iMLSB) and ermAC genes. The use of adhesion in borosilicate tube (ABT) test for the detection of biofilm formation, and D-Test to investigate the iMLSB resistance, in CoNS, are recommended. Thus, we concluded that all identified species are inhabitants of the skin flora and the most probable cause of bags contamination is the skin of the donor. The association of culture systems will reduce the risk of transfusion of contaminated PCs and septic transfusion reactions. Moreover, the results show the need for attention to knowing the virulence and resistance shown by micro-organisms isolated from PCs, and it is expected that this study be a stimulus for more research in this area.