Virulence characteristics of Aeromonas spp. in relation to source and biotype

Abstract

The significance of Aeromonas spp. as potential water-borne enteric pathogens in Tasmania, Australia, an area with a mild climate and comparatively low year-round water temperatures, was investigated in view of the reported marked peak of Aeromonas-associated gastroenteritis in the summer and the apparent influence of temperature on levels of potentially pathogenic species in water supplies. Biochemical characteristics and virulence-associated properties-exotoxin production (hemolysin, enterotoxin), ability to grow at 43°C, and possession of pili-were determined for 105 Tasmanian isolates of Aeromonas spp.; 43 isolates were from clinical specimens (>75% diarrhea associated) and 62 were from water. Current classification schemes were evaluated for these isolates. A. sobria comprised 35% of the clinical isolates and 16% of the water isolates, A. hydrophila comprised 56 and 79%, and A. caviae comprised 9 and 5%. A total of 42% of the clinical isolates and 15% of the environmental isolates were enterotoxigenic (by the suckling mouse assay); these levels were significantly lower than those found in warmer environments. The majority (74%) of enterotoxigenic isolates were A. sobria. Enterotoxin-producing isolates possessed three or more of the following properties. They were Voges-Proskauer positive, did not hydrolyze arabinose, were positive for lysine decarboxylase, were able to grow at 43°C, and produced large amounts of hemolysin (titer, >128). Thus, the biochemical scheme proposed by Burke et al. (V.

Variable expression of O-antigen and the role of lipopolysaccharide as an adhesin inAeromonas sobria

“…The cloning and mutagenesis of the LPS genes of A. sobria will be required to resolve the question of the role of LPS in A. sobria adhesion to HEp-2 cells. Environmental factors such as temperature, nutrient deprivation and growth phase are known to play a role in regulating the virulence of bacterial pathogens including A. hydrophila [3,18,19]. The stable rough and smooth variants of .4. sobria 3767 may have been selected in vivo in response to environmental conditions we were unable to reproduce in vitro.…”

Rattus norvegicus: not a model for Aeromonas-associated gastroenteritis in man

“…All of the culture collection strains had the characteristic phenotypes of their respective species [6,13]. Except for strain A6, speciation had also been con¢rmed by genetic typing (ribotyping) [25].…”

“…Short-term storage of strains was in minimal maintenance medium at room temperature [13]. Long-term storage was in glycerol^peptone (1:4 glycerol:bacteriological peptone 1% Oxoid L37, Oxoid, Basingstoke, UK).…”

“…Although overall virulence, as measured by LD 50 [7^9], intestinal colonisation [10,11], enterotoxigenic [12,13], or invasive [9,14] capabilities, can be assayed in animals, no model has been convincingly shown to reproduce the human diarrhoeal disease syndrome. To our knowledge, a pilot study (one strain of`A.…”

Differences in production of several extracellular virulence factors in clinical and food Aeromonas spp. strains

“…However, the conclusive criteria of pathogenicity of Aeromonas in human and animals is still not clear (Krovacek et al 1992). Many studies have been developed in order to know the relation between endotoxin production and the biochemical characteristics and pathogenicity of these bacteria (Palumbo et al 1985;Kirov et al 1986;Janda et al 1987;Santos et al 1988). Several biochemical properties (production of proteases, haemolysins, enterotoxins, cytotoxins, etc.)…”