Pyrazinoic acid is a pyrazinamide metabolite.

Mycobacterium tuberculosis converts pyrazinamid into pyrazinoic acid.

[1] The use of pyrazinoic acid has been investigated as a possible treatment for pyrazinamid resistant strains of Mycobacterium tuberculosis.

[1] It has been shown that the MICs of esters of pyrazinoic acid are lower, therefore they are more potent antibiotics.

Moreover, they cross the bacterial membrane more easily, due to their higher lipophilicity.