A rapid viability and drug-susceptibility assay utilizing mycobacteriophage as an indicator of drug susceptibilities of Anti-TB drugs against Mycobacterium smegmatis mc 2 155.

Background: A rapid in-house TM4 mycobacteriophage-based assay, to identify multidrug resistance against various anti-tuberculosis drugs, using the fast-growing Mycobacterium smegmatis mc ² 155 in a microtiter plate format was evaluated, based on phage viability assays.
Methods: A variety of parameters were optimized before the study including the minimum incubation time for the drugs, phage and M. smegmatis mc ² 155 to be in contact. An increase in phage numbers over 2 h was indicative that M. smegmatis mc ² 155 is resistant to the drugs under investigation, however when phage numbers remained static, M. smegmatis mc ² 155 found to be sensitive to the drug.
Results: The study confirmed that the data are statistically significant and that M. smegmatis mc ² 155 is, in fact, sensitive to isonazid, iifampicin, pyranzaimide, and ethambutol as phage numbers doubled over 2 h (P = 0.015, 0.018, 0.014, and 0.020). The study also confirmed that M. smegmatis mc ² 155 is resistant to the drugs ampicillin, erythromycin, amoxicillin streptomycin as phage numbers remain static over the same 2 h period (P = 0.028, 0.052, 0.049, and 0.04). This drug-susceptibility profiling of eight different drugs against M. smegmatis mc ² 155 was detected in as little as 1½ days with a cost of ~ one euro and fifteen cent to test four drugs.
Conclusion: This test is rapid to perform and will have widespread applications in drug-susceptibility testing of other members of the mycobacterial genus. In addition, the platform could also be used as a tool for high-throughput screening of novel antimycobacterial drugs. The main assets of this assay include its relatively cheap cost, versatility, and quick turnaround time.
Competing Interests: None