Phytochemical Screening and Antibacterial Evaluation of Conventional Antibiotics, Garlic and Ginger on Isolates from Fish Pond Water Samples in Awka, Anambra State, Nigeria

Abstract

Medicinal plants are used by almost 80% of the world’s population for their basic health care because of their low cost and ease in availability. In the last few decades, many bacteria have continued to show increasing resistance against current antibiotics. Aim: In this study, phytochemical screening and antibacterial effects of conventional antibiotics, garlic and ginger on test isolates from fish pond water samples were evaluated between May-November, 2019. Methods: Standard methods for phytochemical screening and antibacterial analysis were employed. Results: The results showed that amongst the antibiotics used for susceptibility test, Amoxicilin (30 µg) was mostly resisted by all the bacterial isolates except Staphylococcus aureus, Vibrio cholerae, Vibrio parahaemolyticus and Salmonella typhi while erythromycin (10 µg) was unable to inhibit Bacillus subtilis. Ciprofloxacin (10 µg) and pefloxacin (10 µg) inhibited the growth of all the isolates except Pseudomonas aeruginosa. The test isolates showed variable susceptibility to the garlic and ginger extracts (ethanol, methanol and hot water). The extracts inhibited the isolates in descending order; ginger ethanol > ginger methanol > garlic methanol > ginger hot water > garlic ethanol > garlic hot water. Vibrio parahaemolyticus, Vibrio cholerae and Staphylococcus aureus showed little resistant to the extracts while these extracts showed better activity on Klebsiella pneumoniae and Proteus mirabilis. Synergistic effect of garlic and ginger (500mg/ml) inhibited the growth of all the isolates with ethanol extracts having the highest zone diameter (29 mm) on Klebsiella pneumoniae and Proteus mirabilis while hot water extracts had the least zone of inhibition (18 mm) on Acinetobacter calcoaceticus and Vibrio parahaemolyticus. The minimum inhibitory and bactericidal concentration for ethanol, methanol and hot water extracts ranged from 31.25mg/ml to 62.5mg/ml and 62.5mg/ml to 125mg/ml respectively. Conclusion: The outcomes of susceptibility experiment depicted that ethanol and methanol extracts of garlic and ginger (each alone and in combination) showed more inhibitory effect than aqueous extracts and also the combination of ethanol, methanol and aqueous extracts resulted in inhibitory effect greater than each of the extracts when used singly. The use of ginger and garlic for control of fish pathogens appears to be justified.