Pantoprazole promotes sustained intestinal carriage of multidrug-resistant Escherichia coli in amoxicillin-treated mice

Aims: The main objective of this study was to compare extended-spectrum beta-lactamase (ESBL) Escherichia coli fecal titers during 12 days between two groups: mice who received proton pump inhibitors (PPIs) and those that did not.Methods and results: We tested three different in vivo models: model 1, high inoculum (106 CFU ml(-1)); model 2, low inoculum (102 CFU ml(-1)); and model 3, low inoculum and 2-day amoxicillin wash-out. There was no significant difference between the two groups in fecal ESBL E. coli titers in models 1 and 2. The fecal titers of ESBL E. coli were probably too high to show differences in colonization related to PPI treatment. By introducing a 2-day wash-out period after stopping amoxicillin (model 3), the fecal ESBL E. coli titers were higher in the PPI-treated mice during 12 days (3 log versus 11 log day CFU g(-1); P < 0.05). This result highlighted that PPIs promote stable ESBL E. coli digestive carriage in mice. Fecal quantitative PCR showed that mice with low ESBL E. coli fecal titers had a much higher concentration of equol-producing bacteria, Muribaculum sp., and Adlercreutzia caecimuris.Conclusions: Pantoprazole treatment promotes sustained digestive carriage of ESBL E. coli in amoxicillin-treated mice.