Pages: (83-89 )
Abstract
Fish are susceptible to contamination with microorganisms. This investigation was to isolate Gram negative bacteria from tilapia fish
and determine their antibacterial responses to phytochemical agents and antibiotics. Intestines and gills of tilapia fish from University of
Lagos lagoon were homogenized separately in brain-heart infusion broth and incubated at 37 OC for 24 hours for pre-enrichment before
inoculating on Deoxycholate citrate agar, Salmonella Shigella agar and MacConkey agar and incubated at 37 OC for 24 to 48 hours. The
microorganisms isolated were Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris and Escherichia coli. Antibiotics were tested against the isolates. They showed 100% susceptibility to ciprofloxacin, gentamycin, streptomycin, and vancomycin. Escherichia coli had multidrug resistance to perfloxacin, ofloxacin and sparfloxacin; Klebsiella pneumonia and Proteus vulgaris to amoxicillin-clavulanate, trimethoprinsulfamethazole, chloramphenicol and sparfloxacin while Pseudomonas aeruginosa to trimethoprin-sulfamethazo and
chloramphenicol. Ethanoic extracts of spices (Allium cepa, A. sativum, Zingiber officinale and Myristica frangans) were tested against isolates. Zones of inhibition, 12-18 mm were produced. Minimum Inhibitory Concentration (MIC) of extracts was lowest when A. sativum and M. frangans were used against K. pneumoniae and highest when Z. officinale was used against K. pneumoniae and P. aeruginosa. The most resistant organism to spices was P. aeruginosa and with highest MIC. The Minimum Bacteriocidal Concentration (MBC) was lowest when A. sativum was used against K. pneumoniae and highest when Z. officinale was used against K. pneumoniae and P. aeruginosa. Bacterial isolates from Tilapia zilli were susceptible to the plant extracts which concludes that their antimicrobial constituents can be exploited in the fish industry as natural preservatives.
Keywords: Gram negative bacteria, antibiotics, spice extract, susceptibility,