Genotypic Characterization of katG, inhA, and ahpC in Isoniazid-Resistant Mycobacterium tuberculosis Clinical Isolates in Shanghai, China

Abstract

Background: Mycobacterium tuberculosis is a pathogen that causes Tuberculosis and can invade various organs in infected patients. Its high morbidity and high mortality seriously threaten human health. In recent years, the continuous emergence of drug-resistant Tuberculosis bacteria has brought severe challenges to the prevention and control of Tuberculosis. Objectives: This study aimed to characterize the most frequent mutations of the katG, inhA, and ahpC genes in isoniazid (INH)resistant M. tuberculosis clinical isolates in Shanghai Pulmonary Hospital, China, and investigate the relationship between gene mutations and the minimum inhibitory concentrations (MICs) of INH against M. tuberculosis. Methods: We collected 92 INH-resistant and 30 INH-susceptible clinical isolates of M. tuberculosis. The drug resistance profiles of M. tuberculosis clinical isolates against common anti-tuberculosis drugs were determined and sequencing analysis was performed. Results: Of 92 INH-resistant strains, mutations in the katG and inhA genes were observed in 64 (69.6%) isolates and five (5.4%) isolates, respectively, and only had one (1.1%) strain both katG and inhA mutations. Among them, 62 (67.4%) strains carried a single mutation at codon 315 of the katG gene and a new mutation site was found in the katG gene of two strains. We detected a single mutation site at codon 271 and three simultaneous mutation sites at codons 315, 431, and 439. Only one (3.3%) of the 30 isoniazid-sensitive strains had the katG mutation. The AhpC mutation was detected in no experimental strains. The KatG Ser 315 Thr (AGC315ACC) mutation occurred in 53 (68.8%) out of 77 strains with high MICs (≥ 1 g/mL) of isoniazid-resistant M. tuberculosis while five (33.3%) out of 15 strains with low MICs (less than 1 g/mL) had katG Ser 315 Thr (AGC315ACC) mutation. Conclusions: Isoniazid-resistant strains were dominated by Ser315 → Thr (AGC → ACC) substitution, which seems to be associated with multidrug resistance and high-level resistance to INH. Multisite mutations are related to multidrug-resistant M. tuberculosis and the discovery of new mutation sites provides a new basis for the detection of drug-resistant M. tuberculosis.

Prediction of Mycobacterium tuberculosis drug resistance by nucleotide MALDI-TOF-MS

“…In our study, there were four cases of these mutations, which led to the phenotypic resistance being misjudged as susceptibility by nucleotide MALDI-TOF-MS. Similar to other studies, katG315 (86.8%, 70/91) was the most common isoniazid-resistance mutation site in this study, followed by inhA-15 (15.4%, 14/91) ( Cao et al, 2020 ;Smaoui et al, 2016 ;Vilchèze and Jacobs, 2014 ). Among the streptomycin-resistant isolates, mutations at codon 43 in rpsL were the most prevalent, but this mutation was also found in streptomycin-susceptible strains, and has been reported in other studies ( Sreevatsan et al, 1996 ;Wang et al, 2019 ;Wu et al, 2020 ).…”

WITHDRAWN: Prevalence ofkatGandinhAmutations in genes associated with isoniazid resistance inMycobacterium tuberculosisclinical isolates in Cameroon

“…Several other studies worldwide have demonstrated a similar trend of the prevalence of katG S315T mutations but with considerable geographical variations. The frequency of katG S315T mutation was reported in 65.4% of INH-R isolates in Australia [18], 71% in India [26], 63% in China [11], and 53.3% in Iran [8]. Furthermore, several systematic reviews reported a variation in the frequency of katG S315T mutations (64.2%) [27], 73.6% [28], and 95.8% [29].…”

“…[30]. The uneven occurrence of katG gene mutations may be primarily caused by variations in clinical pharmaceutical practices throughout nations and the limits of particular experimental strains [11].…”

“…In addition, it is a crucial step in the development of MDR-TB [10]. Resistance to INH involves a complex set of genes [11] with mutations at codon 315 of the katG gene and the regulatory region of the mabA- inhA operon being the main contributors, accounting for 40% – 95% and 20% - 42% of phenotypic resistance in clinical TB isolates respectively [12]. Mutation at these two gene loci results in a decrease or complete loss of catalase-peroxidase activity and structural change of the INH target [13].…”