Prevalence of environmental Aeromonas in South East Queensland, Australia: a study of their interactions with human monolayer Caco-2 cells

Abstract

Aims: To investigate the prevalence of Aeromonas in a major waterway in South East Queensland, Australia, and their interactions with a gut epithelial model using Caco-2 cells. Methods and Results: A total of 81 Aeromonas isolates, collected from a major waterway in South East Queensland, Australia, were typed using a metabolic fingerprinting method, and tested for their adhesion to HEp-2 and Caco-2 cells and for cytotoxin production on Vero cells and Caco-2 cells. Aeromonas hydrophila had the highest (43%) and Aeromonas veronii biovar sobria had the lowest (25%) prevalence. Four patterns of adhesion were observed on both HEp-2 and Caco-2 cell lines. Representative isolates having different phenopathotypes (nine strains) together with two clinical isolates were tested for their translocation ability and for the presence of virulence genes associated with pathogenic Escherichia coli. The rate and degree of translocation across Caco-2 monolayers varied among strains and was more pronounced with LogA pattern. Translocation was associated with the adherence of strains to Caco-2 cells microvilli, followed by internalization into Caco-2 cells. Two Aer. veronii biovar sobria strains were positive for the presence of heat-labile toxin genes, with one strain also positive for Shiga-like toxin gene. Conclusions: Pathogenic strains of Aeromonas carrying one or more virulence characteristics are highly prevalent in the waterways studied and are capable of translocating across a human enterocyte cell model. Significance and Impact of the Study: This study indicates that Aeromonas strains carrying one or more virulence properties are prevalent in local waterways and are capable of translocating in a human enterocyte cell culture model. However, their importance in human gastrointestinal disease has yet to be verified under competitive conditions of the gut.

Interaction of Aeromonas Strains with Lactic Acid Bacteria via Caco-2 Cells

“…A number of toxin genes have been found in Aeromonas strains (10). Using a multiplex PCR to detect three enterotoxin genes (act, alt, and ast) of Aeromonas, Bin Kingombe and colleagues (12) showed that the act and alt genes were the most prevalent genes in different species of Aeromonas isolated from foods.…”

“…Clinical isolates of Aeromonas included three type culture strains (A. schubertii ATCC 43700, A. jandaei ATCC 49568, and A. veronii biovar veronii ATCC 35624) and two isolates obtained from a local metropolitan hospital (A. hydrophila RBH1 and A. hydrophila RBH2). The environmental strains were part of a bigger collection of Aeromonas strains isolated from a local river system, of which we included four strains previously shown to belong to different common groups and that were adherent to Caco-2 cells (10 Hemolysin production. Hemolysin production was determined visually after streaking Aeromonas strains on 5% horse blood agar plates (17), with Columbia agar base (Oxoid, Australia), following overnight incubation at 37°C.…”

“…Competitive translocation was carried out by in- oculating 10 8 CFU per well of each of the LAB and the Aeromonas strain concurrently. All translocation assays were performed in duplicate (10).…”

“…Virulence of Aeromonas can be attributed to a few factors, including adhesion to epithelial cells, mediated through flagella or outer membrane protein structures (6)(7)(8), host cytoskeletal rearrangement (9), and translocation in a cell culture model (10). Aeromonas strains are also capable of producing toxins.…”

Prevalence of Hemolytic and Enterotoxigenic Aeromonas Spp. in Healthy and Diseased Freshwater Food Fishes as Assessed by Multiplex PCR

“…A number of virulence factors such as extracellular enzymes, siderophores, cytotoxic and cytotonic enterotoxins, haemolysins, endotoxins and cell associated factors such as S-layers, pili, polar and lateral flagella, outer membrane proteins and plasmids were associated with pathogenicity of Aeromonas spp. (Snowden et al, 2006;Pablos et al, 2009). Exotoxins are major virulence factors of Aeromonas spp.…”