Abstract:
Bacterial pathogens which affect aquatic animals and humans become
resistant to antibiotics due to long term exposure. This study focused on the
antibacterial efficacy of six species of mangroves (Avicennia marina,
Lumnitzera racemosa, Bruguiera sexangula, Acanthus ilicifolius,
Rhizophora mucronata, Excoecaria agallocha) against four pathogenic
bacteria, Pseudomonas fluorescens, P. aeruginosa, Shigella flexneri and
Listeria monocytogenes. Mangrove leaf extracts were obtained using 95%
methanol as a solvent and the final compound was methanol free due to
evaporation. All the extracts concentrations were made in to 350 mg/ml.
Nutrient agar plates were used to culture bacteria and the diameter of
inhibition zones were measured by well diffusion method after 24 hours
incubation at 25°C. The results were compared with Tetracycline as the
positive control and solvent without extract as a negative control. The
highest inhibition zone (18.8 ± 1.04 mm) was observed in R. mucronata leaf
extract against L. Monocytogenes while Tetracycline showed 22 mm of
inhibition. All the other mangrove extracts were effective against all
bacterial pathogens tested at a diameter of 17.4–12.5 mm while Tetracycline
exhibited approximately 22 mm of inhibitions for all bacterial pathogens
except for S. flexneri. S. flexneri was resistant against Tetracycline and
moderately susceptible for all typed of mangrove extracts (7.4–12.3 mm).
The tested mangrove leaf extracts were effective against aquatic bacterial
pathogens used (p<0.5) in vitro and has a potential to develop as an
environmentally friendly antibiotic.
