Avaliação de testes fenotipicos de cepas do mycobacterium tuberculosis frente aos antituberculosos, isoladas de pacientes atendidos emhospital geral, Belo Horizonte, Brasil

Abstract

Tuberculosis (TB) remains as one of the major causes of infectious mortality and morbidity in humans, all over the world. The appearance of multidrug resistant tuberculosis (MDR-TB) strains associated with TB/HIV co-infection has become this one, a preoccupying situation.Within high complexity hospitals, there is an urgent need for actions enabling the fast identification of tuberculosis smear-positive patients, as well as options offering diagnostic tests for susceptibility studies that are quick, accurate, and of easy execution and low cost, to be applied in the determination of the profile of strains present in the patients assisted by the hospital and, in case of MDR-TB d tection, to avoid their dissemination and contribute for the epidemiological surveillance. This study has evaluated the performance of the NRA (itrateReductase Assay), REMA (Resazurin Microplate Assay), and MTT (3-[4.5-dimethylthiazol-2- yl]-2.5-diphenyltetrazolium bromide) tests over strains of M. tuberculosis, facing the antituberculous: Rifampin (R); Isoniazide (H); Streptomycin (S); Ethambutol (E). The Proportions Method (PM) was utilized as a reference method. We evaluated 57 strains of M. tuberculosis isolates from 43 patients and 14 strains ofproficiency for the NRA method. For the MTT and REMA methods were used 14 strains of proficiency compared to R and H, respectively. The results of the NRA were: 100% agreement with the MP for R and H. The positive predictive value (PPV) and negative (NPV) for R and H were 100%, the PPV and NPV of S and E were 88,9 and 100% and 98 and 98,2% respectively and kappa of 0,87 (very good agreement) for S and 0,79 (good agreement) to E.With regard to the methods MTT and REMA some adjustments needed to achievebetter performance.The average time for results collection with the three assessed tests was of 10days. The NRA, REMA, and MTT methods are important laboratory tools thanks to their quickness and low cost; being also useful alternatives for laboratories implementation in countries with resources scarcity.