Influence of temperature on the growth, protease production, and heat resistance of Aeromonas hydrophila [HG-1], A. bestiarum [HG-2], and A. salmonicida [HG-3]

The aim of the study was to evaluate the effect of different temperatures on caseinase and elastase production and growth of Aeromonas hydrophila K-101, A. bestiarum 15s, and A. salmonicida A-11 strains, isolated from diseased carp. In order to study the influence of the temperature on proteolytic yield and growth of the strains, standard spectrophotometric methods were used. For the determination of caseinase and elastase activity, the azocasein and elastin- Congo red as substrates were used. It was shown that K-101, 15s, and A-ll strains isolated from motile Aeromonas septicaemia (MAS) affected carp grew better at 28°C than at 18°C and 38°C. The highest proteolytic activity of all studied strains was obtained when the bacteria were grown at 28°C. At 60°C the D-value for K-101, 15s, and A-11 were 7, 4, and 3, respectively. In summary, the temperature influenced the growth of the strains isolated from MAS affected carp. The adaptation of these strains to environmental factors imply their possible long survival in the water, which is a potential threat to public and animal health. From these results, it can be concluded that the potential virulent ability of the ECP might vary due to culturing at different incubation temperatures.