Abstract
BackgroundThe microorganisms intended for use as probiotics in aquaculture should exert antimicrobial activity and be regarded as safe not only for the aquatic hosts but also for their surrounding environments and humans. The objective of this work was to investigate the antimicrobial/bacteriocin activity against fish pathogens, the antibiotic susceptibility, and the prevalence of virulence factors and detrimental enzymatic activities in 99 Lactic Acid Bacteria (LAB) (59 enterococci and 40 non-enterococci) isolated from aquatic animals regarded as human food.ResultsThese LAB displayed a broad antimicrobial/bacteriocin activity against the main Gram-positive and Gram-negative fish pathogens. However, particular safety concerns based on antibiotic resistance and virulence factors were identified in the genus Enterococcus (86%) (Enterococcus faecalis, 100%; E. faecium, 79%). Antibiotic resistance was also found in the genera Weissella (60%), Pediococcus (44%), Lactobacillus (33%), but not in leuconostocs and lactococci. Antibiotic resistance genes were found in 7.5% of the non-enterococci, including the genera Pediococcus (12.5%) and Weissella (6.7%). One strain of both Pediococcus pentosaceus and Weissella cibaria carried the erythromycin resistance gene mef(A/E), and another two P. pentosaceus strains harboured lnu(A) conferring resistance to lincosamides. Gelatinase activity was found in E. faecalis and E. faecium (71 and 11%, respectively), while a low number of E. faecalis (5%) and none E. faecium exerted hemolytic activity. None enterococci and non-enterococci showed bile deconjugation and mucin degradation abilities, or other detrimental enzymatic activities.ConclusionsTo our knowledge, this is the first description of mef(A/E) in the genera Pediococcus and Weissella, and lnu(A) in the genus Pediococcus. The in vitro subtractive screening presented in this work constitutes a valuable strategy for the large-scale preliminary selection of putatively safe LAB intended for use as probiotics in aquaculture.
Highlights
The microorganisms intended for use as probiotics in aquaculture should exert antimicrobial activity and be regarded as safe for the aquatic hosts and for their surrounding environments and humans
We present the antimicrobial activity against fish pathogens and the in vitro safety assessment beyond the Qualified Presumption of Safety (QPS) approach of a collection of 99 Lactic Acid Bacteria (LAB) belonging to the genera Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Pediococcus and Weissella, previously isolated from aquatic animals regarded as human food [14] and intended for use as probiotics in aquaculture
This work shows that antimicrobial/bacteriocin activity against fish pathogens is a widespread probiotic property amongst LAB isolated from aquatic animals regarded as human food
Summary
The microorganisms intended for use as probiotics in aquaculture should exert antimicrobial activity and be regarded as safe for the aquatic hosts and for their surrounding environments and humans. The objective of this work was to investigate the antimicrobial/bacteriocin activity against fish pathogens, the antibiotic susceptibility, and the prevalence of virulence factors and detrimental enzymatic activities in 99 Lactic Acid Bacteria (LAB) (59 enterococci and 40 non-enterococci) isolated from aquatic animals regarded as human food. We present the antimicrobial activity against fish pathogens and the in vitro safety assessment beyond the QPS approach of a collection of 99 LAB belonging to the genera Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Pediococcus and Weissella, previously isolated from aquatic animals regarded as human food [14] and intended for use as probiotics in aquaculture
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