Antimicrobial potentials of indigenous Lactobacillus strains on gram-negative indicator bacterial species from Clarias gariepinus (Burchell.) microbial inhibition of fish-borne pathogens

Abstract

This study tries to evaluate the ability of L. fermentum LbFF4 isolated from Nigerian fermented food (fufu)
and L. plantarum LbOG1 from a beverage (ogi), to inhibit some fish bacterial pathogens (Citrobacter,
Enterobacter, Escherichia coli, Klebsiella, Proteus, Pseudomonas and Salmonella species) under in vitro
conditions. Overall phenotypic antibiotic resistance of 124 Gram-negative bacterial isolates obtained from
the gut contents of cat fish, Clarias gariepinus, using agar disc-diffusion method, indicated very high
resistance to amoxicillin (88.8%), augmentin (85.1%), cotrimoxazole (80.6%), tetracycline (72.3%), gentamicin
(61.9%) and nalidixic acid (57.5%). Multiple antibiotic resistance (MAR) of 37.5 - 87.5% were also recorded.
None of the forty four Lactobacillus strains (L. brevis, L. delbruekii, L. fermentum, L. plantarum and L.
reuterii) isolated from the gut contents of C. gariepinus was inhibitory in vitro towards the Gram-negative
bacterial species. However, L. fermentum LbFF4 and L. plantarum LbOG1 exhibited in vitro antibacterial
activities against 41.1 and 47.6% of the Gram- negative bacterial species respectively. The susceptibility
patterns of the indicator pathogens using the probiotic candidates were significant. The potential probiotic
candidates were able to survive relatively low pH (3.5 - 5.5) and the fish bile. This study therefore, signifies
that lactobacilli-based probiotic candidates from Nigerian fermented foods and beverages can serve as
adjunct, inhibitory food-supplements in the control of bacterial fish-borne pathogens of C. gariepinus.