Inhibition of frog antimicrobial peptides by extracellular products of the bacterial pathogenAeromonas hydrophila

Abstract

Aims: To determine whether the extracellular products (ECPs) from Aeromonas hydrophila, a frog bacterial pathogen that is resistant to skin antimicrobial peptides of three different frog species Xenopus laevis, Litoria aurea and Litoria raniformis, can modulate the activity of these peptides. Methods and Results: ECPs were collected from cultures of Klebsiella pneumoniae, a pathogen susceptible to skin antimicrobial peptides of all three tested frog species, and from cultures of Aer. hydrophila. They were tested for protease activity and for inhibition of the antimicrobial activity of natural peptide mixtures and single peptides of all three frog species against Escherichia coli ATCC 25922. ECPs from cultures of Aer. hydrophila grown for 16, 24 and 36 h showed protease activity and inhibited the antibacterial activity of all peptides against E. coli ATCC 25922. In contrast, the ECPs from cultures of Kl. pneumoniae neither had protease activity nor inhibited the activity of any peptides. Conclusion: The proteolytic ECPs of Aer. hydrophila have the ability to inhibit the skin antimicrobial peptides of frogs. Significance and Impact of the Study: The results of this study provide new information on the association of ECPs with the resistance of Aer. hydrophila to frog antimicrobial peptides.

Interacting Symbionts and Immunity in the Amphibian Skin Mucosome Predict Disease Risk and Probiotic Effectiveness

“…This organism shows antifungal characteristics including activity against Bd growth [33]. The ability of extracellular products of A. hydrophila to inhibit amphibian antimicrobial peptides indicates a co-evolutionary relationship between host and symbionts [59]. In addition, Pseudomonas mirabilis and Serratia liquefaciens were found to be resistant to antimicrobial peptides from several host frog species [60].…”

Life history linked to immune investment in developing amphibians

“…and Ribeiroia ondatrae . Although the Gram-negative bacterium A. hydrophila is not inhibited by amphibian skin peptides tested to date (Rollins-Smith et al ., 2002; Schadich and Cole, 2009; Tennessen et al ., 2009), both ranaviruses and Bd can be inhibited (Rollins-Smith et al ., 2002; Chinchar et al ., 2004). The ability of tadpole peptides to inhibit other bacterial pathogens, protozoa or fungal infections, such as S. ferax (Romansic et al ., 2006), remains to be tested.…”

Hybrid advantage in skin peptide immune defenses of water frogs (Pelophylax esculentus) at risk from emerging pathogens

“…Host endopeptidases are produced by some amphibians to degrade peptides, or to cleave propeptides in order to activate their antimicrobial potential (Resnick et al, 1991 Mignogna et al, 1996;Steinborner et al, 1997). In addition, some pathogens can deactivate AMPs as part of an immune evasion strategy (Kraus and Peschel, 2008;Schadich and Cole, 2009). Indeed, recent studies with Rana pipiens have shown that 60 min after secretion onto the skin some AMPs are cleaved and their ability to inhibit Bd growth is diminished (Pask et al, 2012).…”