Antibacterial and Cytotoxic Activities of Acacia nilotica Lam (Mimosaceae) Methanol Extracts Against Extended Spectrum Beta-Lactamase Producing Escherichia coli and Klebsiella Species

Purpose: To investigate lysates from Acacia nilotica pods for their antimicrobial and cytotoxic activities against a variety of extended spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae as well as methicillin resistant Staphylococci aureus (MRSA). Methods: ESBLs-producing E. coli and Klebsiella spp were isolated from clinical and environmental specimens and incubated with Acacia nilotica pod lysates. The bactericidal activity and cytotoxic effects of the lysates were evaluated while fast protein liquid chromatography (size exclusion FPLC) was used to identify the various compounds showing bactericidal activity. Results: The lysates showed remarkable bactericidal properties, killing almost 100 % of the bacteria they were tested against, including neuropathogenic Escherichia coli, MRSA, and Klebsiella spp. The bactericidal activity was heat-resistant and showed minimal cytotoxic effects on human brain microvascular endothelial cells. FPLC revealed eight peaks, with three of them representing compounds that had maximum bactericidal activity against all the tested isolates, but showed < 30 % host cell cytotoxicity. Conclusion: The lysate of Acacia nilotica pods is a potentially good candidate for the therapy of antibacterial-resistant bacteria, and would therefore require further studies.