Antagonistic activity of Aeromonas media strain A199 against Saprolegnia sp., an opportunistic pathogen of the eel, Anguilla australis Richardson

Abstract

A bacteriocin-like inhibitory substance (BLIS) produced by Aeromonas media strain A199 inhibited the growth of Saprolegnia sp. in vitro, an opportunistic pathogen isolated from affected eels, Anguilla australis (Richardson). The presence of BLIS in solid media inhibited the growth of the vegetative state of the aquatic mould as well as the germination of cysts. Uninhibited growth was, however, observed in the presence of inactive BLIS, suggesting that the in vitro antagonism derived from the BLIS of A199. In four independent in vivo tank observations of fish affected with saprolegniosis, the daily addition of A199 to tank water contributed to the subsequent swift recovery of affected hosts from invasion by this opportunistic pathogen.

Bacterial skin flora variation and in vitro inhibitory activity against Saprolegnia parasitica in brown and rainbow trout

“…The inhibition of cyst germination has already been studied by other investigators with contradictory results (Bly et al 1997, Lategan & Gibson 2003, Zhang et al 2008. In the present study Saprolegnia parasitica mycelium growth from cysts was inhibited at lower concentrations of the bacteria than were hyphae from colonized hemp seed.…”

“…In vitro tests, which are used as primary screening, usually comprise several independent tests, which means that they are focused on the demonstration of different bacterial properties. In the case of bacteria for control of Saprolegnia spp., inhibition of myce lium growth and cyst germination (Hatai & Willoug hby 1988, Bly et al 1997, Hussein & Hatai 2001, Lategan & Gibson 2003, Zhang et al 2008, the ability to kill the organism and the capacity to attach to the mucus of fish are theoretically advantageous features. Studying production of extracellular substances by inhibitory bacteria would add information about their mechanism of action and might make it possible to isolate the inhibitory substance for management of fish health (Lategan et al 2006).…”

“…Studying production of extracellular substances by inhibitory bacteria would add information about their mechanism of action and might make it possible to isolate the inhibitory substance for management of fish health (Lategan et al 2006). In vivo tests, used as secondary screening, are crucial in determining whether the bacteria are effective in the biocontrol of saprolegniosis (Lategan & Gibson 2003, Lategan et al 2004.The aim of the present work was to determine the in vitro inhibitory activity of bacteria found on the skin of brown and rainbow trout against Saprolegnia parasitica, in order to isolate one or more bacteria potentially useful for the biocontrol of saprolegniosis. We also present information on the inhibitory effects of bacterial supernatants and on variations in the bacterial populations found on the skin of healthy trout and of those infected with S. parasitica.…”

“…The strongest inhibitory activity was shown by the supernatants of bacteria belonging to the genus Aeromonas, whereas those produced by Enterobacteriaceae did not show this inhibitory effect -although, because these bacteria are fungicidal, other mecha-133 Dis Aquat Org 96: 125-135, 2011 nisms might be implicated for this property. Lategan & Gibson (2003) found a bacteriocin-like substance secreted by a strain of Aeromonas media, which had inhibitory activity against Saprolegnia sp. and other pathogens; its main component was identified to be indole (Lategan et al 2006).…”

Antimicrobial Resistance and Potential Probiotic Application of Enterococcus spp. in Sea Bass and Sea Bream Aquaculture

“…This in vitro screening method has identified very good probiotics in aquaculture (Irianto & Austin, 2002b;Lategan and Gibson, 2003;Vaseeharan et al, 2004;Lategan et al, 2004a,b), with two major limitations for this approach. The first is that other modes of probiotic activity (e.g.…”