HEMOLYSIN PRODUCED BY VIBRIO-CHOLERAE NON-O1 IS NOT ENTEROTOXIC

Of 28 isolates of Vibrio cholerae non-O1 (10 from diarrhoeal patients and 18 from environmental sources) examined for haemolytic activity an d its correlation, if any, with enterotoxic activity, 24 showed haemol ysis. The four non-haemolytic isolates showed haemolysis after consecu tive passages through rabbit ileal loops (RILs), The titres of haemoly tic activity were 4-64 HU/ml irrespective of their source. Eight (28.5 %) of the non-Ol isolates caused fluid accumulation; six (25%) were ha emolytic and two (50%) non-haemolytic. The remaining isolates showed e nterotoxic activity after one-to-three consecutive passages through RI Ls irrespective of their haemolytic character and source. Environmenta l isolates caused significantly more fluid accumulation than the diarr hoeal isolates. All these isolates reverted to their original non-toxi genic character on repeated subculture or on storage in the laboratory , but continued to show haemolytic activity. The results of the presen t study indicate that V. cholerae non-O1 strains are potentially enter otoxigenic independent of their haemolytic character and source, and e nterotoxin, not haemolysin, is the factor most likely to be responsibl e for their enterotoxic activity.