Antimicrobial activity, antibiotic susceptibility and virulence factors of Lactic Acid Bacteria of aquatic origin intended for use as probiotics in aquaculture

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.

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“…Probiotics immune-stimulatory effect, resistance to pathogenic organisms and disease is well documented (Merrifield et al, 2010;Muñoz-Atienza et al, 2013). The results of the present study also indicated that administration of probiotic in water during early life stages of L. rohita increased resistance to S. aureus and significantly lower the mortality rate (P= 0.003) as compared to control group (Figure.…”

“…They could improve growth performance and feed conversion efficiency of fish by producing short chain fatty acids, digestive enzymes and vitamins (Martínez et al, 2012), enhance immune response by effecting T-cell differentiation ( Merrifield et al, 2010), provide resistance to pathogenic organisms ( Muñoz-Atienza et al, 2013) and increase tolerance under stressful condition (Varela et al, 2010). Moreover, also assure the digestion of anti-nutritional factors (Suzer et al, 2008), enhance fish appetite, improve carcass and flesh quality (van Nuenen et al, 2005).…”

Evaluation of probiotic potential of lactic acid bacteria isolated from traditional Malaysian fermentedBambangan(Mangifera pajang)

“…Nevertheless, none of the selected probiotic candidates showed undesired β-glucuronidase activity, which is often associated with the conversion of precarcinogens to carcinogens (Collado & Sanz, 2007). A similar finding was reported by Muñoz-Atienza et al (2013) showing the absence of β-glucuronidase activity in 99 strains of LAB tested.…”

Antimicrobial antagonists against food pathogens: a bacteriocin perspective

“…Finally, a study of LAB associated with fish for human consumption showed that bacteriocin activity against fish pathogens is a widespread probiotic property. Indeed LAB active against lactococcosis were common among LAB isolated from edible fish, further supporting the theory that the best place to find antimicrobials against a specific pathogen is in the niche the pathogen proliferates [58].…”