RESUMO
The spectrum of gram-negative rods occurring in surface waters is wide and depending on the season, i.e. the water temperature. The concentration of bacteria is higher in summer than in winter. However, the seasonal difference of the concentration of Enterobacteriaceae is less than that of the Aeromonas spec. and of the non-fermenters. The comparison of yields of total and faecal coliforms determined in samples of surface water by using the brilliant green bile lactose 4-methylumbelliferyl-beta-D-glucuronide (BRI-LA-MUG) broth and the lauryl sulfate-MUG broth, respectively, shows that the BRILA-MUG broth is more sensitive and gives higher yields than the lauryl sulfate-MUG broth. On the other hand, the lauryl sulfate-MUG broth inhibits more the growth of gram-negative rods, especially that of Aeromonas spec. and non-fermenters, whereas the Enterobacteriaceae are less inhibited.