Molecular Identification of Mutations Associated with Pyrazinamide-Resistance in Multidrug-Resistant Tuberculosis in Eight Provinces of Iran DC09-DC12
Dr. Parviz Mohajeri,
Associate Professor, Department of Microbiology, School of Medicine,
Kermanshah University of Medical Sciences, Kermanshah, Iran.
Introduction: Multidrug-Resistant Tuberculosis (MDR-TB) is a growing concern which has always played a role in controlling infectious diseases. Pyrazinamide (PZA) is one of the four front line cures of tuberculosis during the first two months of the treatment course. Diagnosis of PZA resistance is imperative in order to optimize the efficacy of new treatment regimens and minimize the risk of developing resistance to new drugs. In addition, high prevalence of PZA resistance, especially among those afflicted with MDR-TB, points to the need for developing those medicinal regimens that can be used in patients with PZA resistant MDR-TB.
Aim: The aim of this study was to determine anti-tuberculosis drug resistance rate and identify the correlation between MDR-TB and of mutations in pncA gene among Mycobacterium tuberculosis isolates and frequency of mutations associated with PZA resistance in all the isolates.
Materials and Methods: This is a cross-sectional descriptive study conducted from April 2014 to June 2015. A total of 118 Mycobacterium tuberculosis (M. tuberculosis) clinical strains were isolates from patients referred to TB reference laboratory of Kermanshah from 8 provinces including: Kermanshah, Lorestan, Hamadan, Ilam, Kurdistan, Ardabil, Uromia and Tabriz. Antimicrobial susceptibility testing was performed using the proportional method and Minimum Inhibitory Concentration (MIC) and mutations in pncA for the PZA resistant isolates were studied using monoplex- Polymerase Chain Reaction (PCR) and then PCR products were sent for sequencing.
Results: Among the 118 clinical samples of M. tuberculosis investigated in various parts of Iran, 10 isolates (8.5%) were resistant to Isoniazid, 10 isolates (8.5%) were resistant to Rifampin, 7 isolates (6%) were MDR, and 23 isolates (19.5%) were resistant to PZA. Only did one MDR-TB isolate resistant (14.3%) to PZA show inactive mutation at Glu-122 codon that was found in pncA gene. According to our results, a significant correlation was found between MDR strains and of mutations in pncA gene (pv=0.049). pncA gene was not isolated from any of the PZA resistant isolates.
Conclusion: Our findings indicated that only one MDR-TB isolate resistant to PZA showed a mutation in the pncA gene (14.3%) and mutations were not observed in the other PZA-resistance isolates. The reason for resistance to PZA in the other PZA-resistance strains might be related to mutations in other genes or to some other factors. Thus, these reasons need to be further investigated in our study population.