Comparison of resazurin microtiter assay performance and BACTEC MGIT 960 in the susceptibility testing of Brazilian clinical isolates of Mycobacterium tuberculosis to four first-line drugs.

We assessed the performance of REMA in comparison with BACTEC MGIT 960 in the susceptibility testing of 80 Mycobacterium tuberculosis clinical isolates from Clemente Ferreira Institute against four drugs. REMA proved to be a rapid and accurate method, providing excellent correlation with BACTEC MGIT 960, with the exception of results for the ethambutol drug.

Drug resistance in Mycobacterium tuberculosis clinical isolates from Brazil: phenotypic and genotypic methods.

We determined the susceptibility profile of 80 Mycobacterium tuberculosis (MTB) clinical isolates from Brazil against isoniazid (INH) and rifampicin (RIF) drugs by two phenotypic methods (Resazurin Microtiter Assay - REMA and BACTEC™ MGIT™ Mycobacterial Detection System). DNA polymorphisms were also determined by PCR-SSCP in isolates resistant to INH and RIF. BACTEC™ MGIT™ 960 detected 22 susceptible isolates to INH and RIF, 48 MDR isolates (resistant at least to INH and RIF) and nine mono-resistant isolates (eight to INH and one to RIF). REMA performance was determined by Receiver Operating Characteristic curve, whose assay was validated utilizing as reference the BACTEC™ MGIT™ 960 system. ROC curve showed cut-off values of 0.0625µg/mL and 0.125µg/mL, for INH and RIF, respectively. REMA-INH demonstrated sensitivity and specificity of 100% while REMA-RIF showed sensitivity of 97.2% and specificity of 100%. PCR-SSCP detected DNA polymorphisms in 87.5% and 75.5% of isolates classified as INH-resistant and RIF-resistant, respectively. One discordant sample found to RIF (resistant by BACTEC™ MGIT™ 960 and susceptible by REMA) showed no mutation by PCR-SSCP. In conclusion, our studies demonstrated that the combination of phenotypic method REMA, which allowed rapid detection of MDR-MTB with higher levels of sensitivity and specificity, with the genotypic method PCR-SSCP, which demonstrated high accuracy in the search of polymorphisms in the resistance genes, proved to be a useful strategy to study MDR-MTB clinical isolates from national reference center located in São Paulo city.

Assessment of the quality of dna extracted by two techniques from Mycobacterium tuberculosis for fast molecular identification and genotyping.

We report a comparative study of two DNA extraction techniques, thermolysis and chemical lysis (CTAB), for molecular identification and genotyping of M. tuberculosis. Forty DNA samples were subjected to PCR and the results demonstrated that with thermolysis it is possible to obtain useful data that enables fast identification and genotyping.

Brazilian experience in the management of multidrug-resistance. / A experiência brasileira de controlo da multidroga-resistência.

In this article the author reviews the evolution of the approach to multidrug-resistant tuberculosis (MDR-TB) in Brazil following the introduction of rifampicin associated to isoniazid and pyrazinamide (RHZ). It shows Brazil was one of the world's first countries to use the RHZ regimen within a treatment system, with a first line regimen, another one specific for meningo-encephalic forms, for re-treatment of recurrences or of patients who returned with active tuberculosis after abandoning treatment, and a reserve regimen. The system was applied nationwide with guaranteed cost-free provision of medication, and self-administered. The author evaluates the growth of drug resistance, the emergence of multidrug-resistance and how management of this form of the disease has been organised.

[Epidemiological features of multidrug-resistant tuberculosis in a reference service in São Paulo city]. / Aspectos epidemiológicos da tuberculose multirresistente em serviço de referência na cidade de São Paulo.

In order to study certain epidemiological features of multidrug-resistant tuberculosis (MDR-TB) carriers and their influence on the control and treatment, a group of patients was evaluated over a four-year period, selected by: Mycobacterium tuberculosis isolation from sputum; resistance to Rifampin, Isoniazid and one more drug, or, failure of reserve regimen, all cases were from a tuberculosis reference unit in the City of S o Paulo. A total of 182 patients were reviewed, with a mean age of 35.7 +/- 6.8 years and 112 (61.5%) were male. These patients was classified according to therapeutic history, as: primary MDR-TB (with initial sensitivity test) 11 (6%); post primary MDR-TB (after irregular use previous treatment) 134 (74%), and indeterminate MDR-TB (failure after regular use of initial and reserve regimens) 37 (20%). Contagion was identified in 41/170 patients, acquired through domiciliary rather than institutional transmission. There were four familial outbreaks and none were institutional. The most frequent condition associated with these cases was abandonment of therapy (45%) followed by alcoholism (27%), sequential failure in the treatment regimens (23%), MDR contagion (15%), drug reaction (6%), HIV positive (4%) and diabetes (3%). There was resistance to Rifampin+Isoniazid in 100%, Streptomycin in 83% and Ethambutol in 47%. Conventional X-ray revealed cavities in all, though only 35 (19%) were unilateral. These cases are discussed and some suggestions presented.