EVALUATION OF THE SYNERGISTIC HEMOLYSIS (CAMP-LIKE) TEST IN THE IDENTIFICATION OF MOTILE, MESOPHILIC AEROMONAS SPECIES

Usefulness of the synergistic haemolysis (CAMP-like) test in the ident ification of Aeromonas hydrophila, Aeromonas sobria, and Aeromonas cav iae was evaluated, using beta-toxin producing Staphylococcus aureus AT CC 25923 and alpha-toxin producing Clostridium perfringens ATCC 13124 as sphingomyelinase producing indicator strains. The tests were done o n Columbia Blood Agar Base supplemented with 5% sheep blood (CBA; Difc o Laboratories, Detroit, MI, USA). When cultured aerobically, 77% of A . hydrophila isolates, 75% of A. sobria isolates, and 23% of A. caviae isolates elicited synergistic haemolysis of sheep erythrocytes with t he beta-toxin producing strain of S. aureus. Anaerobically, using the same indicator strain, synergistic haemolysis was given by 91%, 51% an d 82% of A. hydrophila, A. sobria, and A. caviae, respectively. When a -toxin producing C. perfringens was used in the test instead of beta-t oxin producing S. aureus, 100%, 86%, and 93% of A. hydrophila, A. sobr ia, and A. caviae isolates, respectively, showed synergistic haemolysi s of sheep erythrocytes. Due to the high number of the tested isolates of A. hydrophila, A. sobria, and A. caviae giving a positive synergis tic haemolysis reaction in both atmospheric conditions of culture, thi s test cannot be used to identify any oi the three Aeromonas spp. The use of a-toxin producing C. perfringens did not improve discriminatory power of the test. Because the nature of the product of Aeromonas spp . responsible for the lyric phenomenon is not known, the use of Aeromo nas factor and synergistic haemolysis terms was proposed rather than C AMP (reaction, test) or CAMP (-like) factor.