ADEYEMI O. ABELLO M. AALABA A. E.MOHAMMED M2026-06-182026-06-182023https://repository.acu.edu.ng/handle/123456789/1867This enquiry was conducted to appraise the synergistic antimicrobial effect of Allium cepa and Allium sativum, which are food spices of the family Alliaceae. Eight test isolates were screened out from over forty organisms, sourced from environmental samples, using standard microbiological methods. The test isolates were subjected to antibacterial analyses using commercially available antibiotics and ethanoic crude extracts from Allium sativum and Allium cepa leaves, to ascertain their individual and synergistic effects. Biochemical tests revealed the test isolates as: Staphylococcusaureus (15.8%); Escherichia coli (5.3%); Shigella sonnei (15.8%); Aeromonas species (10.5%); Clostridium species(15.8%); Corynebacterium xerosis (21.1%); Bacillus species (10.5%);and Streptococcus species (5.3%).All tested extracts showed varying sensitivities against the test organisms. With individual extracts tested, the red garlic extract (16 mm) revealed the highest zone of inhibition against Aeromonas species, while the least zone of inhibition (4mm) was observed with white onion extract against Bacillus species. Similarly the highest inhibition zone (30 mm) was produced by the pooled extracts of both red onion and red garlic against Streptococcus species. Of all test isolates, Bacillus species showed overall susceptibility to the various combinations of extracts used. The study concluded that the synergistic effects of Allium cepa and Allium sativum has greater antimicrobial effect than individual extracts, and this effect is not general to all organisms but specific ones. The crude extracts also proved more potent than conventional antibiotics. Further research work was recommended on the antimicrobial effects of other members of the Allium family.Allium cepaAllium sativumAntimicrobialCrude ExtractEnvironmental isolates.