Antibacterial and antifungal activities of benzimidazole and benzoxazole derivatives.

The in vitro antibacterial and antifungal activities of six benzimidazole and benzoxazole derivatives were tested against standard strains and 59 clinical isolates. Of the six compounds, only compounds II and III (both benzoxazoles) were active, whereas the rest were devoid of any activity. Considerable growth inhibition of all of the standard strains, including fungi and gram-positive and gram-negative bacteria, resulted when they were treated with these compounds. Fifty-nine clinical isolates of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were tested for susceptibility to the two compounds. The most susceptible were the S. aureus isolates. The two compounds were of comparable activity against all of the isolates, with compound III showing a slightly higher activity than compound II. Their respective minimal inhibitory concentrations for 90% inhibition of S. aureus were 25 and 50 microgram/ml. The gram-negative bacteria were resistant to the two compounds and required minimal inhibitory concentrations of 200 microgram/ml for a similar degree of inhibition.