Detection and characterization of mutations in genes related to isoniazid resistance in Mycobacterium tuberculosis clinical isolates from Iran

Abstract

Background The global rise in drug-resistant Mycobacterium tuberculosis ( M.tb ), and especially the significant prevalence of isoniazid (INH)-resistance constitute a significant challenge to global health. Therefore, the present study aimed to investigate mutations in prevalent gene loci—involved in INH-resistance phenotype—among M.tb clinical isolates from southwestern Iran. Methods Drug susceptibility testing (DST) was performed using the conventional proportional method on confirmed 6620 M.tb clinical isolates, and in total, 15 INH-resistant and 18 INH-susceptible isolates were included in the study. Fragments of six genetic loci most related to INH-resistance ( katG , inhA promoter, furA , kasA , ndh , oxyR-ahpC intergenic region) were PCR-amplified and sequenced. Mutations were explored by pairwise alignment with the M.tb H37Rv genome. Results The analysis of gene loci revealed 13 distinct mutations in INH-resistant isolates. 60% (n = 9) of the INH-resistant isolates had mutations in katG , with codon 315 predominately (53.3%, n = 8). Mutation at InhA − 15 was found in 20% (n = 3) of resistant isolates. 26.7% (n = 4) of the INH-resistant isolates had kasA mutations, of which G269S substitution was the most common (20%, n = 3). The percentage of mutations in furA , oxyR-ahpC and ndh was 6.7% (n = 1), 46.7% (n = 7), and 20% (n = 3), respectively. Of the mutations detected in ndh and oxyR-ahpC , 5 were also observed in INH-susceptible isolates. This study revealed seven novel mutations, four of which were exclusively in resistant isolates. Conclusions This study supports the usefulness of katG and inhA mutations as a predictive molecular marker for INH resistance. Co-detection of katG S315 and inhA -15 mutations identified 73.3% (11 out of 15 isolates) of INH-resistant isolates.

Comparative genomics of drug-resistant strains of Mycobacterium tuberculosis in Ecuador

“…Our results showed that annotations of protein-encoding genes are mainly associated with metabolisms being Amino acids and their derivatives, Energy production and conversion, and lipid metabolism, the most representative. Similar studies in other M. tuberculosis populations also showed a high presence of genes related to energy production and conversion (C), amino acid transport and metabolism (E), and lipid transport and metabolism (I) [72][73][74]. This suggests that these genes are widely conserved to ensure the interactions of M. tuberculosis with its human host, especially in mycobacterial persistence, host pathogens struggle for nutrients and immune recognition.…”

“…In the case of the first-line drug in Mtb treatment, mutations in the 81-bp rifampicin resistance determining region (RRDR) of the rpoB gene, also known as a hotspot region, have been accurate predictors of rifampicin resistance in many studies [69][70][71]. On the other hand, it has been established that INH resistance, predominantly mediated through loss of catalase-peroxidase activity via mutations in katG, produces high-level resistant strains [18,72,73]. Finally, in ethambutol, most resistance-related genes are located on the embB, embC, and upstream of the embA [74,75].…”

A precision overview of genomic resistance screening in isolates ofMycobacterium tuberculosisusing web-based bioinformatics tools

“…Mutations in katG, kasA, inhA, fabG1 genes and the oxyR-ahpC intergenic region are associated with conferring resistance to isoniazid (44,62,63), thus ethA/R mutations are associated with ethionamide resistance (48,64,65). Our results were in concordance with previous studies (44,63,66) due to the higher prevalence of mutations in katG (88.8%). Furthermore, it has been shown that mutations in the ahpC promoter conferred resistance by compensatory mechanism (67,68) like L427P in the katG gene (69,70).…”

A precision overview of genomic resistance screening in Ecuadorian isolates of Mycobacterium tuberculosis using web-based bioinformatics tools

“…These mutations may contribute to the faster emergence of MDR strains and highlight the importance of monitoring these genetic changes to prevent the spread of drug resistance. Likewise, mutations in various genes have been associated with conferring resistance to isoniazid [ 55 , 72 , 73 ] and ethionamide [ 59 , 74 , 75 ]. Our study found a higher prevalence of mutations in the katG gene (88.8%), which is consistent with prior research [ 55 , 73 , 76 ].…”