Comparative antimicrobial activities of the aqueous and ethanol leaf extracts of Alchornea cordifolia and some Cephalosporin antibiotics of different generations available in Uy, LGA of Akwa Ibom state of Nigeria were evaluated using macro dilution assay to determine the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the plant aqueouse and ethanol leaf extracts and of the Cephalosporin antibiotics against some pathogenic Gram positive and Gram negative organisms. Results: The extraction yielded 59.9g for aqueouse leaf extract (ALE) and 74.10 g of the ethanol leaf extract. The MIC of the leaf extracts ranging from (1.953 mg/mL - 15.625 mg/ mL) and MBC ranging from (3.906 mg/mL – 62.50 mg/mL). The cephalosporin antibiotics; Ceftriaxone (Chupet®) MIC ranging from (0.0078-0.25 mg/mL), MBC (0.0312 mg/mL – 0.25 mg/mL), Cephalexin (Sporidex®) MIC ranging from (0.009766 mg/ mL - 0.625 mg/ mL), MBC (0.01953 mg/ mL -2.50 mg/ mL) and Cefuroxime with MIC ranging from (0.0078 mg/mL-0.25 mg/mL) and MBC (1.25 mg/mL - 2.5 mg/mL). Antimicrobial substances are considered as bactericidal agent when the ratio MBC/MIC ≤ 4 and bacteriostatic when the ratio MBC/MIC is > 4. The antimicrobial activities evaluated increased in the following order of potency; A. cordifolia leaf extracts > Ceftriaxone > Cefalexin > Cefuroxime considering the values of MBC/MIC. Keywords: Antimicrobial activities, bacteriostatic, bactericidal, cephalosporin, comparative.

Antimicrobial activities of the leaves and stem bark in aqueouse and ethanol extracts of Alchornea cordifolia were evaluated using tube dilution assay to determine the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) and Minimum Fungicidal Concentration (MFC) of the plant parts and to determine spectrum of activities considering the antimicrobial effect on Gram positive, Gram negative and yeast (Candida albicans), these organisms are known to be pathogenic in nature. Results showed leaves extracts, both aqueouse and ethanol exerted higher activities than the stem bark extracts with MIC values ranging from 1.95 mg/mL – 15.63 mg/mL, although the stem bark extract exhibited good inhibitory activities as well with MIC values ranging from 3.91 mg/mL – 62.50 mg/mL. The antimicrobial spectrum of activities against the organisms was determined by the ratio (R) of MBC/MIC. The leaf extract is bactericidal against the Gram-positive and Gram negative organism with the exception of E. coli that MBC was not determined and, fungicidal against Candida albicans with (R) MBC/MIC ≤ 2. The stem bark extracts were bactericidal against all the Gram positive organisms but bacteriostatic against Salmonella spp and fungistatic against Candida albicans with (R) MBC/MIC ≥ 2. This study revealed that the aqueous and ethanol extracts of leaf and stem bark of A. cordifolia plant exhibited strong antibacterial activities on Staphylococcus aureus, Streptococcus pneumoniae, Bacillus Subtilis, (Gram positive), Escherichia coli, Pseudomonas aeruginosa, Salmonella spp (Gram negative) and also exhibit anti-fungal activity against the Candida albicans. The leaf extract exhibited broad antimicrobial spectrum with bactericidal activities against Gram positive, Gram negative and yeast (Candida albicans).