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Umamaheshwari et al.: Diagnosis of mycobacterial drug resistance in HIV reactive patients by phenotypic and genotypic assay-a comparative study. BMC Infectious Diseases 2014 14(Suppl 3):P58.

Background:Emergence of drug resistance has complicated the treatment of tuberculosis (TB). WHO reports India to be one among 27 “high burden” multidrug-resistant (MDR) TB countries.Objective:To diagnose TB and detect drug resistance of mycobacterial isolates in acid-fast bacilli (AFB) smear negative HIV reactive patients (Group A) and compare them with HIV seropositive AFB smear positive (Group B) and HIV-seronegative AFB positive cases (Group C).Materials and Methods:Clinical specimens collected in all groups were processed as per the standard protocol except blood, which was processed by lysis centrifugation technique. They were then inoculated with Lowenstein-Jensen media and the isolates obtained were subjected to drug susceptibility test (DST) by proportion method and genotype MTBDR plus assay.Results:In Group A, 162 patients were included. Of the 443 clinical samples collected, 76 mycobacterial strains were obtained from 67 (41%) patients. Of these, 50 (65.8%) were sensitive to all drugs and 26 (34.2%) resistant to one or more anti-tubercular drugs. Antibiogram of Group A when compared with Group B and C showed that the MDR rate 6.6%, 6.7% and 8% respectively) did not differ much; but resistance to at least single drug was (26 [34.2%], 3 [10%], and 8 [16%]), respectively.Conclusion:Our study suggests that HIV has no influence on the anti-tubercular resistance pattern, but increased MDR rate along with HIV in high TB burden setting stresses the need for early diagnosis and DST in providing proper regimens and improve prognosis.

: A molecular method for diagnosis of drug-resistant Tuberculosis is Multiplex allele-specific PCR (MAS-PCR), which is more time-efficient. Also, understanding the role of mutations when translated to protein, in causing resistance helps better drug designing. Aims: To study MAS-PCR in the detection of drug resistance in comparison to DNA sequencing, and understand the mechanism of interaction of drugs with mutant proteins in Mycobacterium tuberculosis. Methods: Detection of drug-resistant mutations using MAS-PCR and validation through DNA sequencing. MAS-PCR targeted four genes, iniA for the drug Ethambutol, rpsL and rrs for Streptomycin, and gyrA for Fluoroquinolone resistance, respectively. Further, the sequence data was analysed and modelled to study the effect on interaction of the anti-TB drug molecule with the target protein using in silico docking. Results: We identified drug-resistant mutations in four out of 95 isolates with one of them carrying a mutation at codon iniA501, two at gyrA94, and one for both iniA501 and gyrA94 using MAS-PCR. DNA sequencing confirmed drug-resistant mutations in only two isolates, whereas two others had mutation adjacent to the target allele. Molecular docking showed Estimated Free Energy of Binding (ΔG) being higher for Fluoroquinolone binding with GyrA D94V mutant. Both, wild and mutant IniA interact with EMB but had no significant effect on binding energy. Conclusions: DNA sequencing-based drug resistance detection of TB is more accurate than MAS-PCR. Understanding the role of mutations in influencing the drug-protein interaction will help in designing effective drug alternatives.