Morphological Diversity and Cytological Studies in Some Accessions of Vigna vexillata (L.) A. Richard

Aim: To assess and compare the antimicrobial efficacy of methanol and aqueous extracts derived from Acacia nilotica ssp. nilotica against standard strains of microorganisms and clinical isolates.

Study Design: An experimental study which was carried out at the microbiology laboratory, Medicinal and Aromatic Plants Research Institute (MAPRI), Khartoum, Sudan, during the period from September 2012 to March 2013.

Methodology: Leaves and barks methanol extracts of A. n. ssp. nilotica at concentration of 100 mg/ml were subjected to antimicrobial screening against six standard strains and 133 clinical isolates including bacterial and fungal species. Screening for antimicrobial activity of extracts, standard antibiotics and antifungal drug were detected by the agar well diffusion method. The Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and Minimum Fungicidal Concentration (MFC) of tested extracts were determined using the broth dilution method. The MDIZs of clinical isolates were analyzed statistically using One- Way analysis of variance.

Results: The highest antibacterial activity of leaves and barks methanol extracts of A. n. ssp. nilotica on standard microorganisms was noted against Pseudomonas aeruginosa with zone of inhibition of 40 mm and the minimum activity was showed against Escherichia coli with zone of inhibition of 27 mm. The antifungal activity of leaves and barks methanol extracts was ranged from 23 mm to 24 mm. The MIC showed by the methanol leaves and barks extracts on standard bacterial strains was ranged from 3.125 mg/ml to 12.50 mg/ml and the MBC was ranged from 6.25 mg/ml to 50 mg/ml. On the other hand, the MIC of methanol leaves and barks extracts toward standard fungi was 6.25 mg/ml, while MFC was 12.50 mg/ml. Statistical analysis showed that, there are significant differences between effects of methanol and aqueous extracts of A. n. ssp. nilotica on the standard microorganisms (P=.000). The highest MDIZ produced by leaves methanol extract was against clinical isolates of Escherichia coli which was 25.03 ±3.59 mm, while the lowest MDIZ was obtained by Klebsiella pnuemoniae which was 22.67±7.83 mm. Clinical isolates of Staphylococcus saprophyticus showed higher MDIZ toward barks methanol extract which was 25.71±1.98 mm, while the lowest MDIZ for the same extract was revealed by Enterococcus spp. which was 22.82±7.85 mm. There is highly statistical significant differences between the effect of leaves and barks methanol extracts and Gentamicin 20 µg/ml on the clinical isolates (P = .000). The MIC exhibited by methanol leaves and barks extracts on the bacterial isolates was ranged from 3.125 mg/ml to 12.50 mg/ml, the MBC was ranged from 6.25 mg/ml to 25 mg/ml. The MIC of methanol leaves and barks extracts toward Candida albicans was 6.25 mg/ml, whereas the MFC was 12.50 mg/ml.

Conclusion: Methanol extracts of leaves and barks of A. n. ssp. nilotica were found to be effective against both standard microorganisms and clinical isolates.