Newer derivatives of previous antibiotics may have good antibacterial activity. They may also have a much broader-spectrum antibacterial activity than the older antibiotics. Isoniazid (INH) is a well-known antibacterial drug in as a crucial drug in all multiple drug treatment of tuberculosis (TB) as approved by the WHO. Pyridine-2-Carboxaldehyde Isonicotinoyl Hydrazone (2-PINH) is one of the new isoniazid derivatives. The aim of current study was to evaluate the antibacterial activity of Pyridine-2- Carboxaldehyde Isonicotinoyl Hydrazone against Escherichia coli and Staphylococcus aureus. In this study, after preparing the solid form of Pyridine-2-carboxaldehyde Isonicotinoyl Hydrazon, 7.5 mg/ml, was completely dissolved in 50 ml of normal saline solution that containing 1 mg/ml NaOH. The solution was passed through a filter with pores of 0.2 μm under sterile conditions. Antibacterial activity of the filtered solution against E. coli ATCC 8739 and S. aureus ATCC 25923, were determined by minimum inhibitory concentration (MIC) method. First, a constant amount of Mueller Hinton Agar culture medium (50 μl) was added to each well of a microplate. Then serial dilutions of 2-PINH were prepared by micro-titration method and were added to the wells. At last, 50 μl of bacterial suspension (0/5 McFarland turbidity) was added to each well. After the overnight culture, the microplate growth inhibition assay was conducted for monitoring any growth inhibition by 2-PINH. The results showed that the minimum inhibitory concentration against E. coli and S. aureus was 0.5 and 1 mg/ml, respectively. In conclusion, the aqueous solution of Pyridine-2-carboxaldehyde Isonicotinoyl Hydrazone had a good antibacterial effect on E. coli and S. aureus. These results suggest that 2-PINH may have antibacterial effects against other bacteria.
