Biofilm formation by Aeromonas hydrophila and Staphylococcus aureus on stainless steel using milk and different conditions of cultivation

The aim of this research was to verify the capability of biofilm formation on stainless steel by Aeromonas hydrophila and Staphylococcus aureus I using milk and different conditions of cultivation. The variables consisted in mono and multi-species cultivation of these microorganisms and in the temperatures of 4, 7 and 18 degrees C. Containers containing 1000 mL of milk, population density of 10(5) CFU.mL(-1) of each microorganism, and ten suspended chips of stainless steel AISI 304 (10 x 20 mm) were used to seal up and storage, under 60 rpm of agitation for 10 days. The analyses were conducted every 48 hours. Sessile cells of A. hydrophila and S. aureus and were enumerated by plating in m-Aeromonas selective agar and Baird-Parker agar. Complementary studies included the generation time calculation, enumeration of planktonic cells and visualization of chips by scanning electron microscopy. S. aureus, in mono-cultivation, formed biofilm at 18 degrees C and at 7 degrees C. At 4 degrees C was observed attachment. The presence of A. hydrophila reduced the performance of S. aureus. In this condition, S. aureus formed biofilm at 18 degrees C. A. hydrophila formed biofilm under all conditions.