Standard antibiotic discs (diameter 6 mm) used in this study were: methicillin 5 μg, tetracycline 30 μg, carbenicillin 100 μg and streptomycin 10 μg. In our preliminary studies, these antibiotics were found to be active against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Mycobacterium smegmatis respectively. All standard antibiotic discs were purchased from Oxoid (UK). Disc containing chlorhexidine which was active against Candida albicans, were prepared by loading dry sterile filter paper discs (Whatman No. 54, diameter 5.5 mm) with chlorhexidine solution to give a total weight of approximately 100 μg of chlorhexidine per disc. The impregnated discs were dried overnight at 40°C and stored (less than five days) in a desiccator until use.