Rapid indication of multidrug-resistant tuberculosis from liquid cultures using FASTPlaqueTB-RIF, a manual phage-based test.
METHODS
A Mycobacteriology Reference Laboratory in Johannesburg, South Africa.


OBJECTIVE
To determine the ability of FASTPlaqueTB-RIF, a rapid bacteriophage-based test, to correctly identify rifampicin susceptibility in clinical strains of Mycobacterium tuberculosis after growth in the Bactec 460 semi-automated liquid culture system.


METHODS
A comparative study of FASTPlaqueTB-RIF and conventional drug susceptibility methods, with selection bias to include sufficient rifampicin-resistant strains.


RESULTS
Rifampicin susceptibility results were available for 133 strains of M. tuberculosis. Using the Bactec 460 method, 42 of these strains were rifampicin-resistant and 91 strains were rifampicin-susceptible. A further one strain was found to have a mutation in the rpoB gene which was strongly indicative of rifampicin resistance. Sensitivity, specificity and overall accuracy for the FASTPlaqueTB-RIF were respectively 100%, 98.8% and 99.2% for detection of rifampicin resistance; 95.3% (41/43) of the rifampicin-resistant strains were also resistant to isoniazid (multidrug-resistant).


CONCLUSIONS
FASTPlaqueTB-RIF offers performance comparable to the Bactec 460 method, with results available within 2 days and without the need for specialised equipment. This makes FASTPlaqueTB-RIF a rapid test for rifampicin resistance suitable for widespread application. A combination of the FAST-PlaqueTB-RIF test with semi-automated liquid culture reduces the time required to report susceptibility results, enabling rapid and appropriate management of patients with MDR-TB. Rifampicin resistance was a good predictor of multidrug resistance in this population.
Albert
H
H
Biotec Laboratories Ltd., Johannesburg, South Africa. tbunit@mail.saimr.wits.ac.za
Trollip
A P
AP
Mole
R J
RJ
Hatch
S J B
SJ
Blumberg
L
L
D000904:Antibiotics, Antitubercular / Q000494:pharmacology*; D000995:Antitubercular Agents / Q000494:pharmacology; D001331:Automation; D001435:Bacteriophages; D018929:Cell Culture Techniques; D018432:Drug Resistance, Multiple; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000472:pathogenicity*; D012016:Reference Values; D015203:Reproducibility of Results; D012293:Rifampin / Q000494:pharmacology*; D012680:Sensitivity and Specificity
D000904:Antibiotics, Antitubercular; D000995:Antitubercular Agents; D007538:Isoniazid; D012293:Rifampin