Isolation, identification and antimicrobial activity of lactic acid bacteria from the Bahía Blanca Estuary

This study analyzed the biodiversity of lactic acid bacteria present in the Bahía Blanca Estuary and their antimicrobial activity against pathogens associated with the cultivation of salmonid. A total of 21 lactic acid bacteria (LAB) strains were isolated from superficial sediments and fish of the estuary. The fish species were selected from those that spend most of their life cycle in the estuary. According to 16S rDNA analysis, isolates were affiliated with the genera Lactobacillus, Pediococcus, Leuconostoc, Enterococcus and Weissella. The predominant LAB isolates from the fish species belonged to Weissellaviridescens, which was isolated from three of the four species analyzed. None of the LAB species isolated from fish was found in sediments. The agar diffusion method was used for detection of antagonistic activity against Listeriamonocytogenes, Yersinia ruckeri, Aeromonas salmonicida subsp. salmonicida and two strains of Lactococcus garvieae. All the isolates exhibited some degree of antagonistic activity against L. monocytogenes, Y. ruckeri and both strains ofLc. garvieae. Twelve strains were found to be inhibitory for A. salmonicida. This study is the first report on the diversity of lactic acid bacteria in a coastal marine environment and fish from Argentina. The sediments and fish analyzed showed microbial strains with the ability to suppress pathogen growth under in vitro conditions, suggesting their potential as biological control agents for aquaculture and fish processing.