Wayne’s Assay: A Screening Method for Indirect Detection of Pyrazinamide Resistance in Mycobacterium Tuberculosis Clinical Isolates

Tuberculosis (TB) caused by members of Mycobacterium tuberculosis (MTB) complex is one of the common lung diseases, causing 3,000,000 deaths per year worldwide [1]. This global epidemic has become more dangerous due to the presence of HIV/AIDS especially in developing countries, the emergence of multidrug-resistant (MDR)TB and recently described extensively drug-resistant TB [1]. Timely detection of drug resistance in patients with TB is a priority and reliable methods for rapid drug susceptibility testing (DST) are needed for better control of the disease [2]. The increasing number of drug-resistant MTB strains has made the rapid identification of susceptibility clinically important because patients suffering from infections due to these strains require specialized antibiotic treatment [1]. Antimycobacterial drug susceptibility testing (DST) is necessary for the proper treatment of patients with TB. Pyrazinamide (PZA) is an important first-line anti-TB drug used in combination with rifampicin, isoniazid and ethambutol forms the cornerstone of modern TB therapy. MDR-TB has recently become a serious public health problem [3,4]. It is recommended by the World Health Organization (WHO) for treatment of every TB patient. It is also used to treat MDR-TB patients [2]. The PZA is an analogue of nicotinamide, which is a vitamin B3 (nicotinic acid; also called niacin) precursor. The discovery of PZA in the late 1940s as a powerful drug against TB was based on the serendipitous observation that nicotinamide, curiously, had activity against tubercle bacilli in animal models. Subsequent synthesis of analogues of nicotinamide led to the identification of PZA as the most active derivative against MTB strains [3,5]. Although PZA was synthesized before 1940s its anti-TB activity was not recognized until the early 1950’s [4]. Despite many studies since its discovery 50 years ago, the mechanism of action of PZA is the least understood of all TB drugs, because of its unusual properties [6].