Molecular Epidemiology of Ampicillin Resistance in Salmonella spp. and Escherichia coli from Wastewater and Clinical Specimens

Abstract Molecular epidemiology at local scale in Sicily (Italy) of ampicillin resistance in Salmonella spp. isolates from municipal wastewater (n = 64) and clinical specimens (n = 274) is described in comparison with previously examined Escherichia coli isolates (n = 273) from wastewater. High prevalence of antibiotic resistance (28.9%) with highest resistance rates against ampicillin (22.7%) was observed in E. coli isolates. Different resistance rates were observed in Salmonella according to the serovars, with prevalences of the same order in both wastewater and clinical isolates belonging to the same serovar (e.g., 91.7% ampicillin resistance in wastewater isolates vs. 70.8% in clinical isolates of the Salmonella serovar Typhimurium and 0% ampicillin resistance in both wastewater and clinical isolates of the Salmonella serovar Enteritidis). The β-lactam resistance gene blaTEM was present in both wastewater and clinical Salmonella spp. isolates, with the exception of Salmonella enterica serovar Typhimur...