Behaviour of Aeromonas spp. after animal passage.

Abstract

The Aeromonas genus have been consideredas important infectious agents in humans and ani-mals (JM Janda 1991 Clin Microbiol Reviews 4:397-410). The biological characteristics such as,toxins production (e. g. hemolysins, cytotoxins andenterotoxins) and also cell-associated features, thatappear to play important role in infectious pro-cesses in humans and animals, have been studiedin the attempt of elucidate patogenicity of the dif-ferent Aeromonas species (Janda loc. cit.). Evi-dences indicate that the animal passage may influ-ence in the expression of biological characteris-tics in many organisms such as, Plesiomonasshigelloides (SC Sanyal et al. 1980 J Med Microbiol13: 401-409) and Vibrio cholera O1 biotype ElTor (A Tikoo et al. 1994 J Med Microbiol 40: 246-251). DV Singh and SC Sanyal (1992 J MedMicrobiol 37: 262-267) reported that passagethrough rabbit instestines may control the expres-sion of the genes responsible for toxins produc-tion in Aeromonas spp.In this communication we report on the alter-ation of the hemolytic and enterotoxigenic charac-ter and also surface characteristics in one strain ofAeromonas isolated from environment, after ani-mal passage by endovenous route.Four samples of Aeromonas were used in thisstudy, three from polluted estuary water ( A. caviae- 030, Aeromonas sp. - 057, A. trota - 058) and onefrom drain treatment station supplyed by FundacaoOswaldo Cruz, Rio de Janeiro (A. hydrophila -T336). Those strains were maintend in nutrient agar(NA) with 1% of NaCl (FW Hickman-Brenner etal. 1987 J Clin Microbiol 25: 900- 906) at roomtemperature.All samples were tested with regar to hemol-ysin production, through β hemolysis zones aroundthe colonies in rabbit blood agar with 5% (v/v) oferitrocytes and the haemolitic activity was analyzedwith the metodology described by M Cumberbatchet al. (1979 Infect Immun 23: 829-837). The suck-ling mouse test (WA Dean et al. 1972 Infect Dis125: 407), was used for enterotoxin detection, theautoagglutination capacity for self pelleting (SP)and for preciptation after boiling (PAB) as de-scribed by JM Janda et al. (1987 Infect Immun 55:3070-77). The hidrofobic profile by phase parti-tioning with hydrocarbon solvents described by MRosenburg et al. (1980 Fems Microbiol Lett 9: 29-33).Strains for animal experiments were cultivatedin 5ml of BHI (OXOID) at 28