embB Gene association with Ethambutol drug Resistance in Mycobacterium Tuberculosis Patients

Background: Tuberculosis (TB) is fatal and life threatening infectious disease. The transmission rate of tuberculosis is very high. Various drugs are used as treatment for TB. Recently it has been observed that one of the most important factor for fast TB spread is development of anti-TB drug resistant mycobacterium tuberculosis (MTB). Various combination of drugs like isoniazid (INH), rifampicin (RIF), Streptomycin(SM), pyrazinamide (PZA) or ethambutol (EMB) are in global use for TB treatment. Improper usage of these drugs makes the person prone to develop anti-TB drug resistant tuberculosis. Aim: To evaluate association of embB gene with ethambutol resistance in Mycobacterium Tuberculosis. Methods: 104 Specimens of sputum from suspected tuberculosis patients were processed for inoculation in Lowenstein J Medium after it has been decontaminated properly. Kit method by using QIAamp DNA Mini kit was utilized for extraction of DNA. Then region from base 6953 to 10249 of embB gene was amplified through PCR and then followed by sequencing with the aid of softwares blast2seq and ClustalW2. Three primer sets were utilized to amplify embB gene. Ethambutol (EMB) Resistant MTB specimens were processed to study mutation in embB gene. Results: Out of the total 104 sputum specimens, 14 samples were found to have ethambutol resistance. These 14 samples were then processed for mutational analysis. DNA sequence analysis of these 14 samples confirmed embB gene mutation in 10 samples. Mutational analysis revealed that 08 samples showed mutation at codon 306 and two samples showed mutation at 319 codon. The reported mutation Methionine →Isoleucine was seen in 07 samples with ATG codon replaced by ATA codon at codon position 306. One sample showed mutation as Methionine →Isoleucine with ATG codon replaced by ATC codon at codon position 306. Two samples showed mutation as Tyrosine →Serine with TAT codon replaced by TCT at 319 codon position in embB gene. Conclusion: This study concludes that mutation of certain genes particularly point mutation of embB gene at codon 306 and 319 is associated with drug resistance of ethambutol in ethambutol resistant mycobacterium tuberculosis patients. Keywords: Ethambutol, embB gene, Mycobacterium tuberculosis.

Identification of rpoB, gyrA and embB Gene Mutations in Mycobacterium Tuberculosis Isolates from Retreatment Tuberculosis Patients in Nepal

Introduction: Tuberculosis remains one of the major public health problems in Nepal and increasing trend of multi drug resistant and extensively drug resistant tuberculosis (MDR /XDR TB) is a big challenge. Rapid diagnosis and appropriate treatment of MDR/XDR TB is crucial. Identification and comparison of MDR TB using rapid molecular techniques (for rpob, gyrA, rrs and embB gene mutations) with reference to drug susceptibility test (DST) were the main objectives of this study.Methodology: A cross sectional study was carried out in National TB Centre (NTC). Gene Xpert, proportion method and Line Probe Assay (LPA) were used for first and second line drugs susceptibility testing (FLD-DST and SLD-DST). A total of 29 mucopurulent sputum samples were freshly collected from retreatment TB patients (Female 41.4%, Male 58.6%) with median age of 40 years attending to the four MDR TB treatment centres of eastern and central Nepal (via private courier and directly to National TB Reference Laboratory (NRL) at NTC from April 2013 to October 2017.Results: Among 29 sputum samples (Female 41.4%; all smear+ve, Male 58.6%; 16 smear+ve and 1 smear-ve), Gene Xpert MTB/RIF assay detected 100% M. tuberculosis and rifampicin resistance (rpoB gene resistant) of which, 100% were culture positive by conventional Lowenstein–Jensen (LJ) method. FLDDST was performed on all culture positives of which, 96.6% showed MDR TB and 3.4% showed mono resistance to isonizid only. SLD-DST on 29 MDRTB strains by LPA showed 100%, 58.6%, 44.8% wild type for rrs, gyrA and emb B genes respectively. Mutation for gyrA and emb B genes was 41.4% and 51.2% respectively, rrs genes none. Twelve (Female 6, Male 6) MDR TB strains were identified as pre-XDR-TB. Chi square (χ2) for trend was used to analyze Gene Xpert, smear, FLD-DST and LPA results.Conclusion: From this study, 29(100%) MDRTB were detected from retreatment TB cases by Gene Xpert and FLDDST. Almost 41.4% MDR TB strains were detected as pre-XDR TB by LPA, which were found to be higher in 15-60 years group of females and males. Samples from retreatment TB patients need to be tested by rapid molecular techniques with reference to culture and DST.SAARC Journal of Tuberculosis, Lung Diseases and HIV/AIDS, Vol. 14, No. 2, 2017, Page: 39-50

Frequency of mutational changes in the embB among the ethambutol-resistant strains of Mycobacterium tuberculosis in Iran

Introduction: Early detection of drug resistant tuberculosis is one of the main priorities of TB control program. Ethambutol (EMB) is a first-line anti-TB drug that is effective for preventing treatment failures caused by Mycobacterium tuberculosis strains that are resistant to other drugs. The aim of this study was to sequence the embB gene to characterize the mutations causing resistance to EMB and to analyze the relationship between bacterial genotype and EMB resistance among M. tuberculosis isolates in Iran. Methodology: A total of 20 M. tuberculosis isolates comprising 10 multidrug-resistant (MDR) and 10 non-MDR isolates, recovered from TB patients in four regions: Tehran, Isfahan, Zahedan, Khorasan, were analyzed. Mutational profiling was performed by amplifying and sequencing the embB gene. Spoligotyping was carried out to characterize the bacterial genotype. Results: Phenotypic EMB resistance was found in 13 strains. Mutations affecting ethambutol resistance-determining region (ERDR) of the embB were identified in 6 of 13 EMB-resistant isolates. The majority of these mutations resulted in amino acid substitution at position 306 (M306V). A novel mutation at codon 366 was identified (S366L) in one isolate. Ural was the most predominant genotype in the studied population. Beijing genotype was associated with both MDR and EMB resistance in which all mutations occurred at codon 306 of the embB gene. Conclusion: A significant association between Beijing genotype and EMB resistance was found, mainly due to mutations at embB306. Results of this study can be used as a basis to develop or improve rapid molecular tests to monitor drug-resistant strains in this country.