Background: A rapid in-house TM4 mycobacteriophage-based assay, to identify multidrug resistance against various anti-tuberculosis drugs, using the fast-growing Mycobacterium smegmatis mc2 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 mc2 155 to be in contact. An increase in phage numbers over 2 h was indicative that M. smegmatis mc2 155 is resistant to the drugs under investigation, however when phage numbers remained static, M. smegmatis mc2 155 found to be sensitive to the drug.
Results: The study confirmed that the data are statistically significant and that M. smegmatis mc2 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 mc2 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 mc2 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.
Keywords: Drug susceptibility; Mycobacterium smegmatis; mycobacteriophages; optimization study.