SEPARATION AND CHARACTERIZATION OF ENTEROTOXIN AND TWO HAEMOLYSINS FROM AEROMONAS HYDROPHILA

Abstract

Separation and characterization of enterotoxin and two haemolysins from Aeromonas hydrophila. Acta path. microbiol. a n d . Sect. B, 89: 387-397. I98 1.Aeromonas hydrophila produces two haemolysins, now designated a-and @-haemolysin (formerly aerolysin or cytotoxic protein), and one enterotoxin. These toxins were separated and purified by isoelectric focusing and gel chromatography. Alpha-and @-haemolysin differ with regard to prerequisites for their elaboration, such as selection of A. hydrophila strains and temperature and time for cultivation. The nature of their lytic effects on erythrocytes and toxic effects on tissue culture cells differs significantly. Alpha-but not (bhaemolysin was inactivated by reducing agents and activated by oxygen, while 6-haemolysin was more resistant than a-haemolysin to proteolytic enzymes but was inactivated by crude gangliosides. When separated from the two haemolysins. the enterotoxin gave positive reactions in the rabbit intestinal loop test, the rabbit skin and the adrenal Y I cell test, though the sensitivity of the YI cell was low as -ampared with cholera toxin and E. coli LT toxin. No cytotoxic effects were obtained in HeLa cells. Species of the related genera Aeromonas andVibrio produce several extracellular proteins during growth (5, 17, 22, 24, 35. 37). In addition to chlolera toxin, some biotypes of Vibrio choler@ produce a hsmolysin (15). Culture fluid from Vibrio puruhcemolyticus has been attributed cytotoxic, cardiotoxic and lethal properties, and two different haemolysins have been characterized (22, 37). Whether or not V . parahcemolyticus produces an enterotoxin remains to be clarified ( I 4. 22).Multiple biological activities have been detected also in Aeromonus hydroph/h culture fluids. The reported products of strains include one or two hs!molysins, a necrotizing toxin, fibrinolysin, leucocidin and a lethal toxin ( 5 ) as well as two proteases Accepted 15.vi.8 I (8). One hsmolosyn, here referred to as uhaemolysin, was further characterized by Wretlind et al. (34, 35). Another was designated aerolysin by Bernheimer el a/. (2, 3). Aerolysin shares several properties with the toxin which we earlier called ncytotoxic protein (( ( I 9, 331, and the two toxins are probably indentical. In this paper the toxin will be referred to as p-hsmolysin.Strains of A. hydrophila isolated in different parts of the world were shown to induce fluid accumulation in the rabbit intestinal loop test, indicating the production of an extracellular enterotoxin ( I , 18, 33). The characterization of this enterotoxin has been hampered by the circumstance that many enterotoxigenic strains produce cytolytic factors. The nature of the toxin has therefore been disputed.Some authors have recognized only cytotoxic activity in tissue culture cell (1 0). Others have found both cytotoxic and rabbit loop activity and have claimed that these properties are possessed by the Same toxin, i.e. a cytotoxic enterotoxin (7).The aim of the present study was to separate the activities of the enterotoxin and ...

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