Srikar Anagoni, Ramana B V, Sarma P V G K, Mohan Alladi, Chaudhury Abhijit
Department of Microbiology, Father Colombo Institute of Medical Sciences, Warangal, Telangana, 506001, India.
Department of Microbiology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, 517507, India.
Indian J Med Microbiol. 2025 Sep-Oct;57:100939. doi: 10.1016/j.ijmmb.2025.100939. Epub 2025 Jul 18.
The molecular epidemiological methods are important in the study of transmission dynamics and population structure of Mycobacterium tuberculosis strains circulating in a geographical region.
A total of 104 patients were selected who were diagnosed for the first time with pulmonary tuberculosis and were sputum smear positive. Drug sensitivity test, spoligotyping, and MIRU-VNTR typing were done with all strains.
In our series, three isolates were resistant to all the four agents, while 13(12.5 %) were classified as multi-drug resistant. Spoligotyping revealed the predominance of East African-India (EAI) lineage (66.3 %) with EAI 3-Ind (44.2 %) and EAI 5 (18.2 %) making up the majority. Our study found no presence of Beijing strains, while 15 isolates exhibited 9 distinct spoligotyping patterns (orphan or novel) that are not listed in the spoligotyping database. Three strains belonging to CAS1-Delhi, EAI3-Ind, and Manu1 lineages were resistant to all four anti-tuberculosis agents. The discriminatory power of various MIRU-VNTR alleles was found to be lower for EAI family strains compared to Non-EAI family strains. The clustering rates of MIRU-VNTR and Spoligotyping were 0.52 and 0.711 respectively. The neighbor-joining tree, based on 24-loci MIRU-VNTR typing, revealed two main clusters: one group included the CAS1-Delhi, LAM6, Cameroon, and MANU families, while the other group contained the EAI family.
The finding of half of the strains resistant to one or more anti-tuberculosis drugs and 12.5 % MDR strains emphasizes the importance of susceptibility testing before initiation of treatment.EAI lineage is considered to be predominant in Southern part of India which was corroborated in our study. MIRU-VNTR should be used in addition to spoligotyping since it has got finer discriminatory power. Molecular epidemiological studies should be performed periodically to assess the circulating strains in a particular geographic area.
