Antibacterial Susceptibility Pattern of Pathogenic Bacteria Isolates from Vegetable Salad Sold in Restaurants in Zaria, Nigeria

Abstract

Microbiological analysis of 25 vegetable salad samples collected from five locations in Zaria, Nigeria was analysed using standard microbiological methods. Antibiotic susceptibility pattern of the isolates was determined using Kirby-Bauer CLSI modified disc agar diffusion technique (DAD). Antibacterial susceptibility of the isolates to aqueous and ethanol extracts of dry ginger; ethanol extract of fresh ginger (Zingiber officinale) was also investigated using agar diffusion and broth dilution methods. The bacterial load of the salad samples ranged between 6.0 x 10 4 to 2.0 x 10 6 cfu/ml. The pre- dominant bacteria isolated from the samples were Staphylococcus aureus, Salmonella spp, Escherichia coli and Pseudo- monas aeruginosa. All the bacteria isolates were found to be sensitive to Ofloxacin while Amoxycilin was found to be the least effective as all the bacteria isolates were resistant to it except a strain of Escherichia coli. Some of the strains of these isolates showed multiple antibiotic resistance to the antibiotics used. The aqueous and ethanol extracts of ginger showed moderate antibacterial activity against the isolates with diameter of zones of inhibition ranging from 13.0 to 28.5 mm. The Minimum Inhibitory Concentration (M.I.C.) and Minimum Bactericidal Concentration (M.B.C) values observed from the extracts against the organisms were moderately high. This study has shown that some vegetable salads are heavily con- taminated with potential pathogenic and antibiotic resistant bacteria species; ginger can be an alternative remedy to inhibit pathogenic bacteria isolates from vegetable salad.