The Most Probable Number (MPN) of thermotolerant coliforms at 45o C was estimated in 60 samples of oyster (Crassostrea rhizophorae), sold at two commercial areas (A and B) of Futuro beach, Fortaleza, Ceara State, Brazil, from January 2002 to February 2003. Each pool was composed of 12 oysters, totaling 720 individuals tested. The MPNs for thermotolerant coliforms at 45oC ranged from 4 g-1 to 930 g-1, and from 4 g-1 to 430 g-1 for the oysters sampled at areas A and B, respectively. Upon isolation of the individuals, chemical characterization of 70 (86,6%) and 45 (64,3%) strains of Escherichia coli, 7 (8,6%) and 20 (28,5%) of Enterobacter spp., and 4 (5%) and 3 (4,2%) of Citrobacter freundii were performed for the areas A and B, respectively. Plus, 5 (3%) strains of Klebsiella spp. were identified. The ant microbial susceptibility of the E. coli strains to different groups of drugs was performed. The results showed that the strains isolated from commercial area A were susceptible to chloramphenicol (CHL) and tetracycline (TCY). Resistance to cephalothin (CEP) and nitrofurantoin (NIT) was observed in 6 strains for commercial areas A and B, respectively. Neither of the isolated strains from both commercial areas belonged to the enteroinvasive (EIEC), enteropathogenic (EPEC), or 0157 serotype. No enterotoxic (ETEC) was observed throughout trails.
