Evaluation of rapid alternative methods for drug susceptibility testing in clinical isolates of Mycobacterium tuberculosis

Abstract

A study was carried out to compare the performance of a commercial method (MGIT)

Susceptibility of Mycobacterium tuberculosis to first-line antimycobacterial agents in a Brazilian hospital: assessing the utility of the tetrazolium (MTT) microplate assay

“…The assay results were in agreement with Bactec-MGIT 960™, but few TB resistance isolates were tested. These results are compatible with results reported by others (WHO 1997, Palomino & Portaels 1999, Caviedes et al 2002, Ribeiro et al 2004, Mengatto et al 2006. DST for EM and SM has been reported to have low reproducibility (WHO 1997).…”

Utilidad del ensayo de nitrato reductasa en la detección de Mycobacterium tuberculosis multirresistente en caso de recursos limitados

“…In accordance with previous studies (5,(7)(8)(9)(10)(11)(12)(17)(18)(19), its 100% specificity for rifampicin and isoniazid, avoids in a non-multidrug-resistant patient which is conducting a first-line drug treatment, any change to a treatment with second line drugs to that is more toxic, less effective and very expensive.…”

“…The current findings with these two drugs agreed with previous and recent data for nitrate reductase assay (5,21,22), demonstrating insufficient concordance of the assay with the normally recommended standards to recommend them for routine use. Nonetheless, Rosales et al (23) have recently evaluated the nitrate reductase assay for the rapid detection of resistance to secondline drugs such as ofloxacin and kanamycin.…”

“…It provided support for the findings of earlier studies made on isolates maintained at low temperatures (7)(8)(9)(10)(11)(12), as the evaluation was made under more controlled methodological conditions. These conditions were specified as follows: (1) the study was performed in an appropriately broad group of patients with and without multidrug-resistant tuberculosis and in pertinent patients groups (without selection bias); (2) the nitrate reductase assay and the proportion method were made in all patients simultaneously (preventing verification bias); (3) all nitrate reductase assay results were interpreted by staff members who were unaware of the other test results, using an appropriate reference standard for comparison; and (4) in contrast with previous evaluations, in which bacilli to be tested were obtained from colonies from fresh subcultures in solid medium (5,7,8,11,12), the present study analyzed the isolates, as they arrived, regardless of previous manipulation or culture maintenance conditions.…”

“…In a previous study carried out in our laboratory (5) , this technique was compared with other rapid drug susceptibility testing methods using a panel of 64 strains. The NRA appears as rapid, inexpensive, and easy to perform (5). Nevertheless, the performance characteristics of drug susceptibility tests may change when moving from the research stage to implementation at a population level in actual public health practice (6).…”