Evaluating Neem (Azadirachta indica) Extracts as Alternative Bactericidal Agents Against Antibiotic-Resistant Pathogens

Kehinde O.  Amisu; Solayide A.  Adesida; Fadilat O.  Oyekan; Rebecca F.  Peters; Tosin R.  Solomon; Christopher O.  Fakorede; Oladipupo A.  Lawal

Kehinde O. Amisu Department of Microbiology, Faculty of Science, Lagos State University (LASU), Ojo, Badagry-Expressway, Lagos, Nigeria
Solayide A. Adesida Department of Microbiology, Faculty of Life Sciences, University of Lagos, Akoka, Lagos, Nigeriadagry-Expressway, Lagos, Nigeria
Fadilat O. Oyekan Department of Microbiology, Faculty of Life Sciences, University of Lagos, Akoka, Lagos, Nigeria
Rebecca F. Peters Microboiology and Parasitology Laboratory, Lagos University Teaching Hospital, Idi-Araba, Lagos, Nigeria
Tosin R. Solomon Department of Microbiology, Faculty of Life Sciences, University of Lagos, Akoka, Lagos, Nigeria
Christopher O. Fakorede Department of Biological Science, Lagos State University of Science and Technology, Ikorodu, Lagos, Nigeria
Oladipupo A. Lawal Department of Chemistry, Faculty of Science, Lagos State University (LASU), Ojo, Badagry-Expressway, Lagos, Nigeria

Keywords: Antibiotic resistance, Neem (Azadirachta indica), Bactericidal activity, Time-kill Assay

Abstract

The rise of multidrug-resistant (MDR) pathogens threatens global health, prompting the search for alternative antimicrobials. This study evaluated the bactericidal activity of Azadirachta indica (neem) leaf extracts against clinical strains of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. The leaves were authenticated, air-dried, and extracted using ethanol and water via cold maceration and Soxhlet extraction methods. Bacterial identity was confirmed with standard microbiological tests and subjected to antibiotic susceptibility testing using the disk diffusion method. The neem extract was analysed using a Shimadzu GC-MS-QP 2010 Plus system, and its antimicrobial activity was evaluated using the agar diffusion and broth microdilution methods. Antibiotic susceptibility showed high resistance to amoxicillin and ciprofloxacin, while meropenem was most effective. Hot ethanol extracts exhibited the strongest antibacterial activity, with inhibition zones up to 22.0 ± 1.4 mm for E. coli, and MIC/MBC assays confirmed bactericidal effects. Time–kill studies demonstrated complete elimination within 12–24 hours. GC-MS profiling revealed dominant compounds including n-hexadecanoic acid (19.8%), phytol (9.2%), and 9,12,15-octadecatriene-1-ol (8.1%). These results underscore the effectiveness of neem as a natural antibacterial agent and highlight its potential as a complementary or alternative therapy against antibiotic resistant pathogens.