Evaluation of Antibacterial Activity of Ocimum gratissimum and Zingiber officianale on Bacteria Isolated from the Environment

Background: Antibiotic resistance continues to be an important public health issue and the environment constitutes a major source of antibiotics and antibiotic-resistant bacteria. This is because large amounts of antibiotics are deposited into the environment as a result of several human activities.

Aim: In this study, the antibacterial properties of Ocimum gratissimum and Zingiber officianale were evaluated against bacteria present in effluents from a University sewage treatment plant, health center and horticultural garden.

Methods: Enteric bacterial species and Staphylococcus aureus were isolated and assessed for resistance to different antibiotics. In addition, the ethanolic extracts of two plants Ocimum gratissimum and Zingiber officianale were tested for their antimicrobial activity against some selected antibiotic-resistant bacteria from the environment.

Results: A total of 215 organisms including 76 Escherichia coli, 56 S. aureus, 40 Klebsiella spp, 28 Salmonella spp and 15 Shigella spp, were isolated with more than half possessing resistance to at least one of the antibiotics tested. 57% of S. aureus isolates were resistant to at least one of the antibiotics tested with the most resistance recorded against penicillin (82.22%) and Erythromycin (91.28%). 53.22% of all enterobacterial isolates possessed resistance to at least one antibiotic with Salmonella (91.28%) and E. coli (61.15%) as the most resistant. High levels of antibiotic resistance (65%) were found among isolates from the University horticultural garden. Phytochemical analysis showed the presence of tannins, saponins and cardiac glycosides in both plant fractions. Both plants showed antimicrobial activity against most of the isolates tested with Ocimum gratissimum showing better activity than Zingiber officianale at concentrations lower than 25 mg/ml.

Conclusion: This study adds credence to the local application of both plants as herbal remedies.