MECHANISMS INVOLVED IN THE RESISTANCE OF MYCOBACTERIUM TUBERCULOSIS TO PARA-AMINOSALICYLIC ACID, 12

ABSTRACT The emergence of Mycobacterium tuberculosis resistant to first-line antibiotics has renewed interest in second-line antitubercular agents. Here, we aimed to extend our understanding of the mechanisms underlying para-aminosalicylic acid (PAS) resistance by analysis of six genes of the folate metabolic pathway and biosynthesis of thymine nucleotides (thyA, dfrA, folC, folP1, folP2, and thyX) and three N-acetyltransferase genes [nhoA, aac(1), and aac(2)] among PAS-resistant clinical isolates and spontaneous mutants. Mutations in thyA were identified in only 37% of the clinical isolates and spontaneous mutants. Overall, 24 distinct mutations were identified in the thyA gene and 3 in the dfrA coding region. Based on structural bioinformatics techniques, the altered ThyA proteins were predicted to generate an unfolded or dysfunctional polypeptide. The MIC was determined by Bactec/Alert and dilution assay. Sixty-three percent of the PAS-resistant isolates had no mutations in the nine genes considered in this study, revealing that PAS resistance in M. tuberculosis involves mechanisms or targets other than those pertaining to the biosynthesis of thymine nucleotides. The alternative mechanism(s) or pathway(s) associated with PAS resistance appears to be PAS concentration dependent, in marked contrast to thyA-mutated PAS-resistant isolates.

Download Full-text

Para-aminosalicylic acid increases the susceptibility to isoniazid in clinical isolates of Mycobacterium tuberculosis

Infection and Drug Resistance ◽

10.2147/idr.s200697 ◽

2019 ◽

Vol Volume 12 ◽

pp. 825-829 ◽

Cited By ~ 2

Author(s):

Tingting Zhang ◽

Guanglu Jiang ◽

Shu’an Wen ◽

Fengmin Huo ◽

Fen Wang ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Clinical Isolates ◽

Aminosalicylic Acid

Download Full-text

Binding Pocket Alterations in Dihydrofolate Synthase Confer Resistance topara-Aminosalicylic Acid in Clinical Isolates of Mycobacterium tuberculosis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01775-13 ◽

2013 ◽

Vol 58 (3) ◽

pp. 1479-1487 ◽

Cited By ~ 47

Author(s):

Fei Zhao ◽

Xu-De Wang ◽

Luke N. Erber ◽

Ming Luo ◽

Ai-zhen Guo ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Resistance Mechanism ◽

Binding Pocket ◽

Multidrug Resistant ◽

Clinical Isolates ◽

Missense Mutations ◽

Aminosalicylic Acid ◽

Content Type ◽

Resistant Tuberculosis ◽

Mechanistic Basis

ABSTRACTThe mechanistic basis for the resistance ofMycobacterium tuberculosistopara-aminosalicylic acid (PAS), an important agent in the treatment of multidrug-resistant tuberculosis, has yet to be fully defined. As a substrate analog of the folate precursorpara-aminobenzoic acid, PAS is ultimately bioactivated to hydroxy dihydrofolate, which inhibits dihydrofolate reductase and disrupts the operation of folate-dependent metabolic pathways. As a result, the mutation of dihydrofolate synthase, an enzyme needed for the bioactivation of PAS, causes PAS resistance inM. tuberculosisstrain H37Rv. Here, we demonstrate that various missense mutations within the coding sequence of the dihydropteroate (H2Pte) binding pocket of dihydrofolate synthase (FolC) confer PAS resistance in laboratory isolates ofM. tuberculosisandMycobacterium bovis. From a panel of 85 multidrug-resistantM. tuberculosisclinical isolates, 5 were found to harbor mutations in thefolCgene within the H2Pte binding pocket, resulting in PAS resistance. While these alterations in the H2Pte binding pocket resulted in reduced dihydrofolate synthase activity, they also abolished the bioactivation of hydroxy dihydropteroate to hydroxy dihydrofolate. Consistent with this model for abolished bioactivation, the introduction of a wild-type copy offolCfully restored PAS susceptibility infolCmutant strains. Confirmation of this novel PAS resistance mechanism will be beneficial for the development of molecular method-based diagnostics forM. tuberculosisclinical isolates and for further defining the mode of action of this important tuberculosis drug.

Download Full-text

Thr202Ala in thyA Is a Marker for the Latin American Mediterranean Lineage of the Mycobacterium tuberculosis Complex Rather than Para-Aminosalicylic Acid Resistance

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00738-10 ◽

2010 ◽

Vol 54 (11) ◽

pp. 4794-4798 ◽

Cited By ~ 16

Author(s):

Silke Feuerriegel ◽

Claudio Köser ◽

Leona Trübe ◽

John Archer ◽

Sabine Rüsch Gerdes ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Latin American ◽

Acid Resistance ◽

Multidrug Resistant ◽

Nucleotide Polymorphisms ◽

Aminosalicylic Acid ◽

Phenotypic Resistance ◽

Clear Cut ◽

Development Of Resistance ◽

Phylogenetic Lineages

ABSTRACT Single nucleotide polymorphisms (SNPs) involved in the development of resistance represent powerful markers for the rapid detection of first- and second-line resistance in clinical Mycobacterium tuberculosis complex (MTBC) isolates. However, the association between particular mutations and phenotypic resistance is not always clear-cut, and phylogenetic SNPs have been misclassified as resistance markers in the past. In the present study, we investigated the utility of a specific polymorphism in thyA (Thr202Ala) as a marker for resistance to para-aminosalicyclic acid (PAS). Sixty-three PAS-susceptible MTBC strains comprising all major phylogenetic lineages, reference strain H37Rv, and 135 multidrug-resistant (MDR) strains from Germany (comprising 8 PAS-resistant isolates) were investigated for the presence of Thr202Ala. In both strain collections, the Thr202Ala SNP was found exclusively in strains of the Latin American Mediterranean (LAM) lineage irrespective of PAS resistance. Furthermore, PAS MICs (0.5 mg/liter) for selected LAM strains (all containing the SNP) and non-LAM strains (not containing the SNP), as well as the results of growth curve analyses performed in liquid 7H9 medium in the presence of increasing PAS concentrations (0 to 2.0 mg/liter), were identical. In conclusion, our data demonstrate that the Thr202Ala polymorphism in thyA is not a valid marker for PAS resistance but, instead, represents a phylogenetic marker for the LAM lineage of the M. tuberculosis complex. These findings challenge some of the previous understanding of PAS resistance and, as a consequence, warrant further in-depth investigations of the genetic variation in PAS-resistant clinical isolates and spontaneous mutants.

Download Full-text