Rapid detection of resistant tuberculosis by nitrate reductase assay performed in three settings in Brazil.
OBJECTIVE
To evaluate nitrate reductase assay (NRA) efficacy for streptomycin, isoniazid, rifampicin and ethambutol susceptibility testing of Mycobacterium tuberculosis strains.


METHODS
Results were generated by three laboratories: the Instituto Adolfo Lutz (IAL) Mycobacteria Reference Laboratory and two IAL Regional Laboratories in Santo André and Sorocaba, São Paulo State, Brazil. One hundred and twenty M. tuberculosis strains were simultaneously tested using NRA and the proportion method (PM), while 117 strains were tested using both NRA and BACTEC MGIT 960 (M960).


RESULTS
Repeatability analysis of NRA results showed rates of 100% for isoniazid and ethambutol and 97% for streptomycin and rifampicin susceptibility detection, representing substantial agreement. McNemar testing of the data also indicates that NRA and PM, as well as NRA and M960, do not differ significantly. On average, NRA results were available after 10 days.


CONCLUSIONS
The data demonstrate that NRA is reliable for susceptibility testing of isoniazid and rifampicin, the two most important drugs for the treatment of tuberculosis. In addition, the reduction in the time necessary to obtain susceptibility results is of fundamental importance.
Shikama
Maria de Lourdes
Mde L
Regional Laboratory Sorocaba, Brazil.
Silva
Regina Ruivo Ferro E
RR
Martins
Maria Conceição
MC
Giampaglia
Carmen Maria Saraiva
CM
Oliveira
Rosângela Siqueira
RS
Silva
Rosmari F A M
RF
Silva
Paula Ferro E
PF
Telles
Maria Alice da Silva
MA
Martin
Anandi
A
Palomino
Juan Carlos
JC
D000995:Antitubercular Agents / Q000494:pharmacology*; D001938:Brazil; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000201:enzymology*; D050901:Nitrate Reductase / Q000378:metabolism*; D015203:Reproducibility of Results; D013997:Time Factors; D018088:Tuberculosis, Multidrug-Resistant / Q000175:diagnosis / Q000382:microbiology*
D000995:Antitubercular Agents; D050901:Nitrate Reductase