|Year : 2022 | Volume
| Issue : 2 | Page : 134-137
Prevalence of genetic pattern in isoniazid-resistant PTB cases and its association with other TB-resistance drugs
S Lakshmi Kumari1, Srikanti Raghu1, Karri Maruthi Devi2, Aswina Tripura Sundari1, D Sudheer1, P Hima Sanjana3
1 Department of Pulmonary Medicine, Guntur Medical College, Guntur, Andhra Pradesh, India
2 Department of Pathology, Guntur Medical College, Guntur, Andhra Pradesh, India
3 Department House Surgeon, Guntur Medical College, Guntur, Andhra Pradesh, India
|Date of Submission||01-Dec-2020|
|Date of Acceptance||16-Jun-2021|
|Date of Web Publication||3-Aug-2022|
Dr. Karri Maruthi Devi
Associate Professor, Department of Pathology, Guntur Medical College, Kanna Vari Thota, Guntur 522004, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Introduction: Isoniazid (H) is one of the most important first-line antituberculosis drugs used for the treatment of active tuberculosis (TB) and latent TB infection (LTBI) with high bactericidal activity and a good safety profile. The emergence of TB strains resistant to isoniazid threatens to reduce the effectiveness of TB treatment. Specific INH resistance allele is more frequently associated with resistance to other drugs.
Aim and Objectives: To analyze the prevalence of mutations in genes associated with isoniazid resistance and to explore the association of specific mutations conferring other drugs resistance.
Material and Methods: This is a prospective study done from October 2018 to July 2020 in the Department of Pulmonary Medicine, Guntur Medical College, Govt. Fever Hospital, Guntur. A total of 369 sputum-positive isoniazid-resistant pulmonary TB cases were included in the study and subjected to line probe assay (LPA).
Results: The prevalence of InhA and KatG gene mutation is 63.14% and 36.85%, respectively. InhA gene is associated with fifampicin mutation in 7.72%, fluoroquinolone (FQ) in 6%, and second-line injectables (SLI) in 1.71% cases. KatG gene is associated with rifampicin mutation in 13.23%, FQ in 7.35%, and SLI in 1.47% cases.
Conclusion: InhA gene is the most common gene pattern observed in isoniazid-resistant cases and associated equivalently with other drug resistance patterns such as KatG indicating the recent change in the level of resistance of InhA-resistant strains.
Keywords: Active tuberculosis (TB), isoniazid (H), latent TB infection
|How to cite this article:|
Kumari S L, Raghu S, Devi KM, Sundari AT, Sudheer D, Sanjana P H. Prevalence of genetic pattern in isoniazid-resistant PTB cases and its association with other TB-resistance drugs. J NTR Univ Health Sci 2022;11:134-7
|How to cite this URL:|
Kumari S L, Raghu S, Devi KM, Sundari AT, Sudheer D, Sanjana P H. Prevalence of genetic pattern in isoniazid-resistant PTB cases and its association with other TB-resistance drugs. J NTR Univ Health Sci [serial online] 2022 [cited 2022 Dec 10];11:134-7. Available from: https://www.jdrntruhs.org/text.asp?2022/11/2/134/353216
| Introduction|| |
Drug-resistant Mycobacterium tuberculosis is a threat to global tuberculosis (TB) control. Failure to identify and appropriately treat drug-resistant TB patients can lead to increased mortality and the expansion of drug resistance. Isoniazid (H) is one of the most important first-line antituberculosis drugs used for the treatment of active TB and latent TB infection (LTBI) with high bactericidal activity and a good safety profile. The emergence of TB strains resistant to isoniazid threatens to reduce the effectiveness of TB treatment.
Globally in 2019, 11% (range: 6.5%–15%) of all incident cases of TB had isoniazid-resistant and rifampicin-susceptible TB, among which 13.1% are new cases and 17.4% are previously treated cases. Specific INH resistance allele is more frequently associated with resistance to other drugs. Most recent surveys from India also have reported FQ resistance rates close to 21% in non-multi drug resistant (MDR) patients.
The recognition of different INH-resistance mutation patterns and their frequency in various geographical areas may help to guide decision-making about standardization of treatment regimens or individualized treatment, as in the case of INH mono resistance or the case of MDR-TB or extensively drug-resistant (XDR)-TB.
The present study aims to analyze the prevalence of mutations in genes associated with isoniazid resistance and to explore the association of specific mutations conferring other drugs resistance.
| Materials and Methods|| |
This is a prospective study conducted in the Department of Pulmonary Medicine, Guntur Medical College, Govt. Fever Hospital, Guntur from October 2018 to July 2020, which included both new and previously treated isoniazid-resistant PTB patients of more than 18 years of age. Patients with mono-drug resistance other than isoniazid resistance are excluded from the study. A total of 369 sputum-positive isoniazid-resistant pulmonary TB cases are included in the study.
All sputum smear-positive samples are subjected to line probe assay (LPA; Genotype MTBDR plus assay version 2.0 Hain Life Sciences, Nehran, Germany) and also drug susceptibility testing (DST). The detection of the patterns of genetic mutation is done by LPA based on DNA strip technology. Permission from ethical committee with IEC(Institutional Ethics Committee) with application no GMC/IEC/348/2020 was approved.
| Results|| |
Of the total 369 isoniazid-resistant PTB cases included in the study, InhA gene patterns were seen in 233 (63.14%) and KatG patterns were seen in 136 (36.85%) cases [Figure 1].
Out of 369 total study population, 73 (19.78%) patients are in the age group between 15–30 years, 115 (31.16%) patients are between 31–45 years, 124 (33.60%) are between 45–60 years, and 57 (15.44%) patients are above 60 years of age. There are 299 (81.02%) males, which included 191 InhA (63.87%) and 108 KatG (36.12%) cases, and 70 (18.97%) females which included 42 InhA (60%) and 28 KatG (40%) cases in the study population.
Diabetics are 32 (8.67%), which included 12 InhA (37.5%), 20 KatG (62.5%), and people living with HIV (PLHIV) are 19 (5.14%), which included 11 InhA (57.89%) and eight KatG (42.10%) cases in the study. Newly diagnosed PTB cases are 165 (44.71%) and previously treated PTB cases are 204 (55.28%). Among the new cases, InhA gene pattern was seen in 91 (55.15%), KatG was seen in 74 (44.84%) cases and in previously treated cases InhA pattern was seen in 142 (69.60%) and KatG was seen in 62 (30.39%) cases [Table 1].
InhA gene was associated with rifampicin drug resistance in 18 (7.72%), fluoroquinolone (FQ) in 14 (6%), SLI (second-line injectable) in four (1.71%), both rifampicin and SLI drug resistance in one (0.42%), and all three drugs resistance (rifampicin and FQ and SLI) in one (0.42%) cases. KatG gene was associated with rifampicin drug resistance in 18 (13.23%), fluoroquinolone in 10 (7.35%) SLI (second-line injectable) in two (1.47%), and both FQ and SLI in one (0.73%) case in the study [Table 2] [Figure 2].
|Table 2: INH-Resistance mutation patterns associated with other drugs resistance|
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InhA association with other drug resistance was seen in seven new and 16 previously treated PTB cases in the study. KatG association with other drug resistance was seen in nine new and 21 previously treated cases in the study. Diabetics associated with other drug resistance were seen in rifampicin one case, both FQ and SLI in one case, and PLHIV associated with rifampicin drug resistance was seen in two cases.
| Discussion|| |
Isoniazid is a prodrug that must first be activated by KatG (encoded by katG), the catalase-peroxidase to form an adduct with NAD33, which then inhibits InhA (encoded by InhA), an NADH-dependent enoyl-acyl carrier protein reductase and ultimately, inhibits mycolic acid biosynthesis. Mutations in several genes, including KatG, InhA, AhpC, and KasA, have all been associated with INH resistance among which KatG and InhA are the major contributors.
The reported frequency of mutations in these genes varies with different geographical regions. As mutations in katG confer high-level INH resistance, even high-dose INH is ineffective for the treatment of those patients. Mutations in InhA, on the other hand, may respond to high doses of INH. Isoniazid-resistance patients have worse outcomes when compared with drug-susceptible TB, i.e., higher treatment failure (11% vs. 1%); relapse (10% vs. 5%); as well as higher rates of acquired drug resistance (8% vs. 0.3%).
In this study, most of the patients are in the age group of 31–60 years indicating that drug-resistant TB affects economically productive age groups with male preponderance (81.02%) and male to female ratio is 4:1, this is in accordance with Charan et al. the study, which also reported 83.9% males.
Out of 369 isoniazid-resistant cases, the InhA gene was detected in 233 (63.14%) cases, which is the most common type of mutation observed and also in both genders when compared with 136 (36.85%) KatG gene mutations. A study by Tudo et al. from Equatorial Guinea similarly observed that out of 41 isoniazid-resistant strains, 33 (80.5%) had mutations in the InhA gene; none had mutations in the katG gene, and eight had mutations in other genes such as kasA, oxy R-ahpC, and furA. A study by Tang et al. from China also reported that among 50 study subjects, katG, InhA, and both gene mutations were seen in 44.0%, 42%, and 14% cases, respectively, but a study by Charan et al. from Rajasthan, India reported that the most common mutation in INH mono resistance is katG 65.1% as compared with InhA 28.1% and both InhA and katG 6.7%. The present study did not observe the same distribution of genetic pattern mutations in comparison with the studies by Ashok et al. and Tang et al., which may be due to geographical variations in the occurrence of isoniazid-resistance mutation patterns and also more sample size in the present study compared with all other studies [Table 3].
The present study observed that both InhA and KatG gene mutations are associated with rifampicin, fluoroquinolone, second-line injectables drug resistance in equal proportion. However, a study by Das et al. reported that the InhA resistance pattern is seen in 11.7% and katG resistance is 90% among the rifampicin-resistant isolates. Therefore, InhA mutation is low-level resistance, it is associated with all other drug resistance in this study. This study also highlights the fact that even though rifampicin resistance is most commonly associated with isoniazid drug resistance, other second-line drugs should also be looked out for resistance, especially FQ as they are the replacement drugs.
In this study, among the new cases, InhA gene pattern was seen in 55.15% more than KatG, which is 44.84% and among previously treated PTB cases, InhA 69.60% is the most common pattern than KatG (30.39%). In previously treated PTB cases, although the KatG pattern is the most common pattern anticipated, this study showed that the InhA pattern is seen exceedingly high. Previously treated cases (50) are associated more with other drug resistance than new cases (16) in this study.
Among diabetics, KatG (62.5%) pattern is seen more than InhA (37.5%), whereas in PLHIV both InhA and KatG are found to have almost equal distribution. Diabetics are found to be associated with two cases of rifampicin resistance and one case of FQ and SLI resistance in this study. PLHIV is associated with two cases of rifampicin resistance in this study.
| Conclusion|| |
InhA gene mutation is the most common pattern observed in this study, which emphasizes the recent trend of increasing InhA gene pattern in drug-resistant cases. Factors associated with more INH resistance observed are previously treated PTB cases, diabetics, and PLHIV. Therefore, drug susceptibility testing for isoniazid should be done along with rifampicin to reduce the morbidity of patients with a single sample.
InhA mutation is associated equivalently with other drug resistance such as KatG indicating the recent change in the level of resistance of InhA resistant strains. Fluoroquinolone and second-line injectables resistance is also observed along with the anticipated rifampicin drug resistance. This highlights the importance of SL-LPA in either INH or RMP resistant cases as per the 2019 DR-TB algorithm guidelines.
Increasing INH resistance cases may suggest the irrational empirical use of the INH drug as prophylaxis. To control TB cases globally, we should focus on universal drug sensitivity testing for all cases if resources permit. Even though RMP resistance is most commonly associated with isoniazid drug resistance, other second-line drugs should also be looked out for resistance, especially FQ as they are the replacement drugs.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]