Phenotypic Characterization of pncA Mutants of Mycobacterium tuberculosis

• DOI: 10.1128/aac.44.9.2291-2295.2000
• Publication Date: 2002-07-27T09:55:30Z
• Authors: Glenn P. Morlock; Jack T. Crawford; W. Ray Butler; Suzanne E. Brim; David Sikes; Gerald H. Mazurek; Charles L. Woodley; Robert C. Cooksey
• Keywords: Nonsense mutation; Pyrazinamide

ABSTRACT We examined the correlation of mutations in pyrazinamidase (PZase) gene ( pncA ) with pyrazinamide (PZA) resistance phenotype 60 Mycobacterium tuberculosis isolates. PZase activity was determined by method Wayne (L. G. Wayne, Am. Rev. Respir. Dis. 109: 147–151, 1974), and entire nucleotide sequence, including 74 bp upstream start codon, determined. PZA susceptibility testing performed proportions on modified Middlebrook Cohn 7H10 medium. The MICs were ≥100 μg/ml for 37 isolates, 34 which had alterations gene. These included missense substitutions 24 nonsense 3 frameshifts deletion 4 a three-codon insertion 1 isolate, putative regulatory 2 Among 21 isolates <100 μg/ml, same mutation (Thr47→Ala) 18 wild-type sequence. For three Thr47→Ala mutants 12.5 agar; two these resistant to 100 μg per ml third 800 BACTEC method. In all, 30 different found among mutants. No detected 35 strains that or Reduced mutation. This study demonstrates may serve as reliable indicator ml.