The pncA gene mutations of Mycobacterium tuberculosis in multidrug‐resistant tuberculosis

Abstract

The pncA gene encodes pyrazinamidase enzyme which converts drug pyrazinamide to active form pyrazinoic acid, but mutations in this gene can prevent enzyme activity which leads to pyrazinamide resistance. The cross‐sectional study was carried out during 2016–2017 for 12 months. The purpose of the study was to detect mutation at codon 12 and codon 85 in the pncA gene in local multidrug‐resistant tuberculosis (MDR‐TB) patients by developing a simple molecular test so that disease could be detected timely in the local population. DNA extracted from sputum‐cultured samples from MDR‐TB patients and subjected to semi‐multiplex allele‐specific PCR by using self‐designed primers against the pncA gene. Among 75 samples, 53 samples were subjected to molecular analysis based on purified DNA quantity and quality. The primers produced 250 and 480 bp fragments, indicating the mutations at codon 12 (aspartate to alanine) and codon 85 (leucine to proline) respectively. MDR‐TB was more common in the age group 21–40 years. Fifty‐seven percent of samples (n = 30) were found positive for pncA mutations, whereas 43% of samples (n = 23) showed negative results. Thirteen percent of samples (n = 4) had mutations at codon 12 in which aspartate was converted to alanine, and they produced an amplified product of 480 bp. Eighty‐seven percent of samples (n = 26) had mutations at codon 85 in which leucine was converted to proline and amplified product size was 250 bp. The mutations were simple nucleotide substitutions. The prevalence of mutations in which leucine was substituted by proline was higher than the mutations in which aspartate was substituted by alanine. A high prevalence of substitution mutation (CTG → CCG; leucine to proline) was detected in MDR‐TB cases. Earlier detection of MDR‐TB via an effective molecular diagnostic method can control the MDR tuberculosis spread in the population.

HigA2 (Rv2021c) Is a Transcriptional Regulator with Multiple Regulatory Targets in Mycobacterium tuberculosis

“…pncA ( Rv2043c ) is co-transcribed into a polycistron along with Rv2044c , which is located 40 bp upstream of pncA . pncA encodes the pyrazinamidase enzyme, which is responsible for the conversion of an important first-line anti-TB drug, pyrazinamide (PZA), into its active form, and resistance to PZA is primarily due to mutations in pncA [ 36 , 37 ]. The detection of novel pyrazinamide-resistant mutations in clinical isolates of multidrug-resistant Mtb revealed novel non-synonymous mutations (Tyr70His, Ile71Asn) with effects on PZase activity in Rv2044c , all in the HigA2 binding site [ 38 ].…”

Screening of Microbial Fermentation Products for Anti-M. tuberculosis Activity

“…CmaA2 is a mycolic acid synthase, and mycolic acids make the cell wall less permeable, contribute to antibiotic resistance and host immunomodulation, and protect from injury [ 35 ]. PncA also involves fatty acid biosynthesis and encodes pyrazinamidase, an enzyme which converts the drug pyrazinamide to the active form pyrazinoic acid [ 36 ]. The above genes are all involved in the important life process of M.tb .…”