Drug-resistant Tuberculosis: First Line Drug Resistance Pattern among Mycobacterium Tuberculosis Strains Isolated from a Reference Laboratory in Kerala State, India

Neetha S Murthy,Shibu Balakrishnan,Pk Ramya,M Sunil Kumar,Ps Rakesh,Sairu Philip,B Ravikrishnan,Renu Susan George,Sanjeev Nair

doi:10.22207/jpam.15.4.09

Abstract

Resistance to antimycobacterial agents consistently remains a major obstacle to end TB in India. Geographical prevalence data regarding drug-resistant evolutionary genetics of M. tuberculosis (MTB) remains sparse in India. Our objective was to determine the genotypic drug resistance mutation pattern for Rifampicin and Isoniazid of MTB isolates to gain an understanding of the prevailing molecular epidemiology of drug-resistant tuberculosis. In this study 2528 M. tuberculosis DNA isolates from presumptive DRTB suspects received at the nodal TB reference laboratory in Kerala were tested for Rifampicin and Isoniazid resistance by sequence-based diagnostic Line Probe assay (LPA). Geographical prevalence and associations of rpoB, katG, inhA resistance codons was analyzed from January 2019 to March 2020. Among the 2528 DNA samples subjected for Rifampicin and Isoniazid resistance determination by LPA, 146 (5.8%) isolates were resistant to both drugs. Isoniazid mono-resistance was found in 164 (6.5%) and Rifampicin mono-resistance in 38 (1.5%) isolates. The most frequent rpoB mutation was S531L (60.32%) followed by S531W/L533P mutations seen in 8.15% of the isolates. S315T1 KatG mutation was seen in 97.33% of Isoniazid resistant isolates. 84.68% isolates with rpoB S531L mutation were found to be multidrug-resistant. 82.9% of isolates with rpoB S531L mutation showed katG S315T1 mutation. Mono isoniazid-resistant isolates were significantly higher compared to mono rifampicin-resistant isolates among the DNA isolates studied in our region. The molecular epidemiological pattern most frequently associated with multidrug resistance was rpoB S531L which was significantly associated with the co-presence of S315T1 mutation.

Highlights

Every year tuberculosis (TB) affects approximately 10 million individuals worldwide.[1]
Multiple converging factors have ushered the explosive emergence of Multi Drug Resistant tuberculosis (MDR-TB) in India, paralyzing the regimen applicability of Isoniazid and Rifampicin, the potent first-line anti-TB drugs
5413 diagnostic samples acknowledged at the Intermediate Reference Laboratory from January 2019 to March 2020 were retrospectively analyzed. 2528 DNA isolates were subjected to Line Probe assay by GenoType MTBDRplus kit version 2

Summary

Introduction

Every year tuberculosis (TB) affects approximately 10 million individuals worldwide.[1]. Chromosomal mutations entrapping antimycobacterial drug targets or the mycobacterial enzymes that activate pro-drugs exclusively mediate drug resistance in tuberculosis Rifampicin targets mycobacterial RNA polymerase and inhibits transcription. Rifampicin resistance determining mutations are predominantly (>96%) found in a 27 codon central region (81-bp RIF resistancedetermining region), of the RNA polymerase subunit β (rpoB) encoding gene.[3] Isoniazid (H) is activated by catalase peroxidase enzyme. It acts by formation of reactive radicals capable of damaging mycobacterial cell wall. H resistant isolates delineate mutations in the catalase peroxidase coding gene (katG) or the enoyl acyl reductase encoding promoter region (inh A) required for fatty acid biosynthesis and survival of mycobacterium species.[4,5]

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