Concentration-Dependent Inhibitory Effect of Garlic (Allium sativum) Ethanolic Extract against Zoonotic Staphylococcus aureus from Bovine Feces: A Molecular and Immunological Investigation

Abstract

Antimicrobial resistance (AMR) is a major threat to public health for both people and animals due to the widespread use of resistant micro-organisms. New methods for treatment need to be developed as a matter of urgency. This paper investigates the effects of the ethanolic extract of garlic (Allium sativum) (20%-100%) on the zoonotic Staphylococcus aureus from bovine feces and its bactericidal properties. Garlic extract (in agar well diffusion assay) showed a dose response. At 100% concentration of garlic extract, the inhibition zone measured 28.5 mm and at 20% concentration, it measured 10.2 mm. The minimum inhibitory concentration (MIC) was evaluated at 31.25 mg/mL and the minimum bactericidal concentration (MBC) was measured at 62.5 mg/mL (2 MBC/MIC ratio). Thus, garlic extract demonstrates bactericidal properties. Isolated strains underwent a molecular study and PCR results showed the presence of virulence genes and the mecA gene (conferring methicillin resistance) in 65% of the strains. Nuc was detected in all strains. An ELISA showed a decrease in staphylococcal enterotoxin A and B of 75.0% and 77.9% respectively (p < 0.001) when the strains were treated with garlic extract at ½ MIC. The study shows that garlic extract has the ability to inhibit the two enterotoxins and is a natural antimicrobial agent that has the possibility of controlling S. aureus in livestock. This study also confirmed the antimicrobial action of garlic via molecular and immunological methods. Utilizing both PCR and ELISA assists in detailing the mechanisms of antibacterials and reinforces the use of garlic extract in veterinary medicine in place of or in combination with traditional antibiotic therapy.