Genetic Polymorphism at Codon 463 in the <i>katG</i> Gene in Isoniazid-Sensitive and -Resistant Isolates of <i>Mycobacterium tuberculosis</i> from the Middle East

Abstract

Objective: To determine whether substitution R463L within the katG gene is associated with resistance to isoniazid in clinical isolates of Mycobacterium tuberculosis recovered from tuberculosis (TB) patients from the Middle East. Methods: A total of 113 clinical isolates of M. tuberculosis obtained from TB patients residing in Kuwait, UAE and Lebanon were used. The isolates were characterized as isoniazid-susceptible (n = 25) or -resistant (n = 88) based on drug susceptibility testing by BACTEC 460 TB system. The presence of R463L mutation within the katG gene of each isolate was detected by amplification of the DNA region around codon 463 by polymerase chain reaction (PCR) followed by digestion with restriction endonuclease NciI to generate PCR-restriction fragment length polymorphism. The results with selected isolates were further confirmed by DNA sequencing. Results: The mutation R463L was detected in 46 of 59 isoniazid-resistant clinical M. tuberculosis isolates from Kuwait, 9 of 12 from UAE and 3 of 17 from Lebanon. The prevalence of this substitution was much higher in isolates recovered from patients of South Asian/Southeast Asian origin (41/49, 84%) than from patients of Middle Eastern origin (17/39, 44%). Although all the 7 isoniazid-susceptible isolates of M. tuberculosis from Lebanon (recovered exclusively from Middle Eastern patients) contained arginine at codon 463, 3/7 and 10/11 isoniazid-susceptible strains from Kuwait, recovered from Middle Eastern and South Asian patients, respectively, contained leucine at codon 463. Conclusion: The results show that genetic polymorphism exists at codon 463 in the katG gene of M. tuberculosis recovered from patients of different ethnic backgrounds. The data also show that substitution R463L within the katG gene does not contribute to isoniazid resistance.

Molecular Fingerprinting of Isoniazid‐Resistant Mycobacterium tuberculosis Isolates from Chest Diseases Hospital in Kuwait

“…The presence of R463 or L463 at codon 463 and the presence of S315T substitution in the katG gene was determined by amplification of the corresponding katG gene DNA region by PCR followed by restriction endonuclease digestion of the PCR amplified fragments to generate restriction fragment length polymorphism as described previously (1,5).…”

Role of fluoroquinolones in the treatment of tuberculosis

“…The presence of S95 or T95 at gyrA codon 95 is a naturally occurring polymorphism that is not associated with resistance of M. tuberculosis isolates to FQs. However, this polymorphism together with katG codon 463 polymorphism (R463 or L463), is used to define the three principal genetic groups of worldwide collection of M. tuberculosis strains [98][99][100]. The FQ-resistant clinical M. tuberculosis isolates more frequently contain mutations in gyrA gene, particularly at codon 90 (A90) or codon 94 (D94) but also occasionally at codon 74 (A74), codon 88 (G88) and codon 91 (S91) while mutations in few codons of the gyrB gene occur in a small minority of clinical strains [83,[89][90][91].…”

Genotypic Diversity among Isoniazid-Resistant Isolates of <i>Mycobacterium tuberculosis</i> from Rashid Hospital in Dubai, United Arab Emirates

“…The presence of arginine or leucine at codon 463 (R463 or L463) within the katG gene in isoniazid-resistant M. tuberculosis isolates was determined by amplification of the katG gene DNA region around codon 463 by PCR followed by restriction endonuclease digestion of the PCR-amplified fragment with NciI to generate restriction fragment length polymorphism (RFLP), as described previously [8].…”

“…The resistance of M. tuberculosis to isoniazid is caused by mutations in several genes, although, clinically relevant resistance is usually due to mutations within the katG gene, particularly involving codon 315 [7]. However, polymorphism at codon 463 (R463 or L463) in the katG gene is found in both isoniazid-susceptible and -resistant M. tuberculosis strains [7,8].…”

“…Dubai, like many urban centers in the United Arab Emirates (UAE) and other Arabian countries in the Persian Gulf region, has a large expatriate population originating from countries where TB is endemic [8,9]. All expatriates entering UAE are screened for TB (chest radiogram) and visa is granted only to individuals with no active disease.…”