Of the 9 antibacterials, vancomycin alone at its break-point (optimum blood level) revealed highest (93.3%) efficacy on Gram-positive cocci. The remarkable activity of carbenicillin, chloramphenicol and vancomycin on Gram-positive cocci (95.4 to 96.9%), carbenicillin and chloramphenicol on Gram-positive bacilli (94.8% to 98.2%) and chloramphenicol on Gram-negative bacilli (95.4%) was noted by increasing their concentrations 1.5 to 2.5 times above their break-points. These (and even higher) concentration, however, showed relatively lower efficacy of metronidazole, rifampicin, penicillin, clindamycin and erythromycin on Gram-positive cocci (76 to 84.1%), rifampicin, tetracycline, erythromycin, clindamycin and vancomycin on Gram-positive bacilli (81 to 87.9%) and clindamycin, metronidazole, rifampicin and carbenicillin in Gram-negative bacilli (72.7 to 84%). By and large, rifampicin, chloramphenicol and carbenicillin are also quite effective (72.1 to 75.1%) at lower concentration.