Macrodilution Method for Determination of Minimum Inhibitory Conecentration of Conventional Antibiotics Against Clinically Isolated Pathogenic Bacteria

Abstract

The macrodilution method has employed to observe Minimum Inhibitory Concentration (MIC) of antibiotic standard powder against different clinically isolated pathogenic bacteria. The study was performed to evaluate antimicrobial resistance pattern of antibiotic standard powder named Levofloxacin, Ciprofloxacin, Cephradine, Cefuroxime, Ceftriaxone, Cefixime, Vancomycin, Azithromycin against four clinical isolate of different strains of

E.coli, Klebsiella, Acinetobacter, Staphylococcus aureus. Serial dilution of antibiotic standard powders has done in different concentration ( from 0.015625-128 mcg/mL). Then 10 µl of bacterial suspension added in test tubes. After that, the test tubes were incubated for 18-20 hours at 37.5ºC.The result was observed by measuring MIC (Minimum Inhibitory Concentration) of antibiotic standard powders. Here, 11 strains of E.coli showed resistant activity against antibiotic standard powder but some strains gives sensitivity MIC values that are Levofloxacin (0.5 mcg/mL, 0.0625 mcg/mL, 0.015625 mcg/mL) for sample 1, sample 7, sample 8, Ciprofloxacin (0.03125 mcg/mL) for sample 10, Cephradine (1 mcg/mL) for sample 7, Azithromycin (0.5 mcg/mL), For two Staphylococcus aureus spp., the sensitivity MIC values are Cephradine (0.125 mcg/mL) for sample 13, Ceftriaxone (4 mcg/mL) for sample 13, Azithromycin (0.5 mcg/mL) for sample 13. In addition, the sensitivity MIC values for five Klebsiella spp. : Levofloxacin ( 0.0625 mcg/mL, 0.125 mcg/mL) for sample 15 and sample 17, Ciprofloxacin (0.5 mcg/mL, 1 mcg/mL) for sample 15 and sample 17, Cefuroxime (1 mcg/mL) for sample 15, Ceftriaxone ( 0.5 mcg/mL, 0.0625 mcg/mL) for sample 15 and sample 17, Cefixime (1 mcg/mL) for sample 15, Azithromycin (0.25 mcg/mL) for both sample 15 and sample 17. On the other hand, Klebsiella spp. Sample 16 showed resistance against all antibiotics. These values compelled to the standard value of CLSI, EUCAST and DIN to know if they are sensitive , intermediate or resistance.