High level isoniazid resistance correlates with multiple mutation in the katG encoding catalase proxidase of pulmonary tuberculosis isolates from the frontier localities of Iran
Abstract:ÖZETİran sınır bölgesindeki pulmoner tüberküloz izolatlarında yüksek düzeyde izoniazid direnci katalaz-peroksidazı kodlayan katG'deki multipl mutasyonla koreledir Bu çalışmanın amacı, katG
“…However, our finding of 315ACC mutations among INH s specimens (2.8%) was unexpected. The katG 315ACC mutation has been associated with an INH MIC of 3 to Ͼ16 g/ml by DST using liquid medium (25)(26)(27)(28) and was shown to confer INH resistance at 5 g/ml in an allelic exchange study (29). Therefore, it is highly unlikely that any M. tuberculosis specimens with the katG 315ACC mutation would have an INH MIC below the critical concentration used in this study (0.1 g/ml).…”
f Molecular diagnostic assays, with their ability to rapidly detect resistance-associated mutations in bacterial genes, are promising technologies to control the spread of drug-resistant tuberculosis (DR-TB). Sequencing assays provide detailed information for specific gene regions and can help diagnostic assay developers prioritize mutations for inclusion in their assays. We performed pyrosequencing of seven Mycobacterium tuberculosis gene regions (katG, inhA, ahpC, rpoB, gyrA, rrs, and eis) for 1,128 clinical specimens from India, Moldova, and South Africa. We determined the frequencies of each mutation among drug-resistant and -susceptible specimens based on phenotypic drug susceptibility testing results and examined mutation distributions by country. The most common mutation among isoniazid-resistant (INH r ) specimens was the katG 315ACC mutation (87%). However, in the Eastern Cape, INH r specimens had a lower frequency of katG mutations (44%) and higher frequencies of inhA (47%) and ahpC (10%) promoter mutations. The most common mutation among rifampin-resistant (RIF r ) specimens was the rpoB 531TTG mutation (80%). The mutation was common in RIF r specimens in Mumbai (83%) and Moldova (84%) but not the Eastern Cape (17%), where the 516GTC mutation appeared more frequently (57%). The most common mutation among fluoroquinolone-resistant specimens was the gyrA 94GGC mutation (44%). The rrs 1401G mutation was found in 84%, 84%, and 50% of amikacin-resistant, capreomycin-resistant, and kanamycin (KAN)-resistant (KAN r ) specimens, respectively. The eis promoter mutation ؊12T was found in 26% of KAN r and 4% of KAN-susceptible (KAN s ) specimens. Inclusion of the ahpC and eis promoter gene regions was critical for optimal test sensitivity for the detection of INH resistance in the Eastern Cape and KAN resistance in Moldova. (This study has been registered at ClinicalTrials.gov under registration number NCT02170441.) I n 2014, an estimated 9.6 million people developed tuberculosis (TB), and 1.5 million people died of their infection (1). Although global TB incidence rates have fallen an average of 1.5% per year since 2000, the rise of drug-resistant TB (DR-TB) globally has complicated TB control efforts (1). The World Health Organization (WHO) estimates that as many as 1 in every 20 new, active TB infections is now drug resistant (1). One of the major roadblocks in combating this growing problem has been the lack of diagnostic technology for DR-TB. Current growth-based culture and drug susceptibility testing (DST) methods can take several weeks to months to yield results (2). While waiting on culture results, physicians are forced to treat their patients empirically, adjusting treatment regimens only once DST results become available. As a result, many undiagnosed DR-TB patients are being given medications that are ineffective, which amplifies resistance, increases the risk of mortality, and increases the risk of transmitting DR-TB infections in the community.Rapid molecular diagnostic assays for DR-TB have the p...
“…However, our finding of 315ACC mutations among INH s specimens (2.8%) was unexpected. The katG 315ACC mutation has been associated with an INH MIC of 3 to Ͼ16 g/ml by DST using liquid medium (25)(26)(27)(28) and was shown to confer INH resistance at 5 g/ml in an allelic exchange study (29). Therefore, it is highly unlikely that any M. tuberculosis specimens with the katG 315ACC mutation would have an INH MIC below the critical concentration used in this study (0.1 g/ml).…”
f Molecular diagnostic assays, with their ability to rapidly detect resistance-associated mutations in bacterial genes, are promising technologies to control the spread of drug-resistant tuberculosis (DR-TB). Sequencing assays provide detailed information for specific gene regions and can help diagnostic assay developers prioritize mutations for inclusion in their assays. We performed pyrosequencing of seven Mycobacterium tuberculosis gene regions (katG, inhA, ahpC, rpoB, gyrA, rrs, and eis) for 1,128 clinical specimens from India, Moldova, and South Africa. We determined the frequencies of each mutation among drug-resistant and -susceptible specimens based on phenotypic drug susceptibility testing results and examined mutation distributions by country. The most common mutation among isoniazid-resistant (INH r ) specimens was the katG 315ACC mutation (87%). However, in the Eastern Cape, INH r specimens had a lower frequency of katG mutations (44%) and higher frequencies of inhA (47%) and ahpC (10%) promoter mutations. The most common mutation among rifampin-resistant (RIF r ) specimens was the rpoB 531TTG mutation (80%). The mutation was common in RIF r specimens in Mumbai (83%) and Moldova (84%) but not the Eastern Cape (17%), where the 516GTC mutation appeared more frequently (57%). The most common mutation among fluoroquinolone-resistant specimens was the gyrA 94GGC mutation (44%). The rrs 1401G mutation was found in 84%, 84%, and 50% of amikacin-resistant, capreomycin-resistant, and kanamycin (KAN)-resistant (KAN r ) specimens, respectively. The eis promoter mutation ؊12T was found in 26% of KAN r and 4% of KAN-susceptible (KAN s ) specimens. Inclusion of the ahpC and eis promoter gene regions was critical for optimal test sensitivity for the detection of INH resistance in the Eastern Cape and KAN resistance in Moldova. (This study has been registered at ClinicalTrials.gov under registration number NCT02170441.) I n 2014, an estimated 9.6 million people developed tuberculosis (TB), and 1.5 million people died of their infection (1). Although global TB incidence rates have fallen an average of 1.5% per year since 2000, the rise of drug-resistant TB (DR-TB) globally has complicated TB control efforts (1). The World Health Organization (WHO) estimates that as many as 1 in every 20 new, active TB infections is now drug resistant (1). One of the major roadblocks in combating this growing problem has been the lack of diagnostic technology for DR-TB. Current growth-based culture and drug susceptibility testing (DST) methods can take several weeks to months to yield results (2). While waiting on culture results, physicians are forced to treat their patients empirically, adjusting treatment regimens only once DST results become available. As a result, many undiagnosed DR-TB patients are being given medications that are ineffective, which amplifies resistance, increases the risk of mortality, and increases the risk of transmitting DR-TB infections in the community.Rapid molecular diagnostic assays for DR-TB have the p...
“…One INH-resistant isolate possessed both S315T katG and C-15T fabG1 mutations. Resistant isolates have been reported previously to acquire multiple mutations in the same resistance-causing gene 39 . Five of the INH-resistant isolates had two mutations while one isolate had three mutations in katG .Figure 2Frequency of resistance mutations identified in 98 isolates.…”
Drug-resistant tuberculosis (TB), one of the leading causes of death worldwide, arises mainly from spontaneous mutations in the genome of
Mycobacterium tuberculosis
. There is an urgent need to understand the mechanisms by which the mutations confer resistance in order to identify new drug targets and to design new drugs. Previous studies have reported numerous mutations that confer resistance to anti-TB drugs, but there has been little systematic analysis to understand their genetic background and the potential impacts on the drug target stability and/or interactions. Here, we report the analysis of whole-genome sequence data for 98 clinical
M. tuberculosis
isolates from a city in southern India. The collection was screened for phenotypic resistance and sequenced to mine the genetic mutations conferring resistance to isoniazid and rifampicin. The most frequent mutation among isoniazid and rifampicin isolates was S315T in
katG
and S450L in
rpoB
respectively. The impacts of mutations on protein stability, protein-protein interactions and protein-ligand interactions were analysed using both statistical and machine-learning approaches. Drug-resistant mutations were predicted not only to target active sites in an orthosteric manner, but also to act through allosteric mechanisms arising from distant sites, sometimes at the protein-protein interface.
“…The genes involved primarily include katG , inhA , KasA , ndh and ahpC (15,16). Among these, katG encodes catalase-peroxidase, which is involved in the transition of INH into its active form.…”
The objective of the present study was to evaluate the potential development of DNA microarray chips to detect rifampicin (RFP) and isoniazid (INH) resistance in Mycobacterium tuberculosis (MTB), using samples from clinical tuberculosis (TB) patients in Soochow City, China. The sputum samples of 42 patients with TB in the Affiliated Hospital of Infectious Diseases of Soochow University (Soochow, China) were collected. The conventional Lowenstein-Jensen culture medium (Gold Standard) was used to assess drug sensitivity using the absolute concentration method. GeeDom MTB drug detection kits were also used to create a DNA microarray chip and examine the RFP-resistance associated gene mutation points rpoB-RRDR 511, 513, 516, 526, 531 and 533, and the INH-resistance associated gene mutation points katG315 and inhA-15 of the sputum samples. Compared with the results from the absolute concentration method, the susceptibility and specificity of RFP sensitivity detected by the DNA microarray chip were 92.8 and 93.8%, respectively. The susceptibility and specificity of INH sensitivity detected were 66.7 and 81%, respectively. The rpoB-RRDR 526, 531 mutations were the primary causes of MTB RFP resistance and the katG315 mutation was the primary cause of INH resistance. The detection of rpoB and katG gene mutation points by a DNA microarray chip may be used as a rapid, accurate and bulk clinical detection method for RFP and INH resistance in MTB. This is very valuable for the control of TB epidemics.
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