Efficacy of crude extracts of garlic (Allium sativum Linn.) against nosocomial Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniea and Pseudomonas aeruginosa

Abstract

The presence of pathogenic microorganisms causing infections to hospitalized populations in the 750 bed Specialist Hospital, Yola, Nigeria was investigated for a period of two and a half years. Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniea and Pseudomonas aeruginosa were selected through the use of questionnaires as the commonest bacteria causing nosocomial infections, and were isolated from clinical specimens obtained from patients who were admitted to the hospital for reasons other than the infections caused by these bacteria. The effects of water, ethanol and chloroform extracts of garlic against the nosocomial S. aureus, E. coli, S. pneumoniea and P. aeruginosa were investigated under various use conditions, such as variations in temperatures and pH. At a concentration of 100 mg/ml, all the crude extracts inhibited the growth of the pathogenic bacteria, though with varying degrees of susceptibility. However, laboratory based bacteria which were used as controls were more susceptible than their corresponding nosocomial bacteria. Activities were stronger under elevated temperatures and slightly acidic pH values. The MBC values of the aqueous extract for S. aureus was 75 mg/ml; S. pneumoneae, 100 mg/ml; E. coli,125 mg/ml and P. aeruginosa, 150 mg/ml. The water extract was more potent than the organic extracts, and all were inferior in activity, when compared to the standard antibiotic, metronidazole. The gram positive S. aureus was more susceptible to the toxic effects of garlic than its gram negative counterparts. The results obtained in this study indicate that water extracts of garlic can be used alongside conventional antibiotics to fight agents of nosocomial infections that are so prevalent in our hospitals. Key words: Pathogenic, antibacterial, garlic, susceptibility, nosocomial, prevalent.