2025-06-172025-06-172025-03-14https://hdl.handle.net/2133/29668Tebipenem pivoxil has potent in vitro activity against Enterobacterales pathogens, but requires combination with β-lactamase inhibitor to achieve activity against carbapenemase producers, including metallo-β-lactamases (MBLs). Herein, we evaluate the potential of tebipenem pivoxil, alone and in combination with the prodrug of the experimental MBL inhibitor CS319 (CS319-piv-SAc), to disrupt the indigenous mice microbiota of the colon and promote colonization by pathogens. The effect of antibiotic treatment (daily for 3 days with subcutaneous saline [control], subcutaneous clindamycin, oral tebipenem pivoxil alone and in combination with CS319-piv-Sac, or oral CS319-piv-Sac) on the intestinal microbiota was assessed by culture for enterococci and facultative Gram-negative bacilli and by 16S rRNA amplicon sequencing. Mice were also challenged with 10,000 colony-forming units (CFU) of multidrug-resistant (MDR) strain Klebsiella pneumoniae blaNDM-1, 6 h after the second dose. The concentrations of the MDR K. pneumoniae in stool were measured on days 1, 3, and 6 after challenge. In comparison to saline controls, clindamycin (P = 0.001) and tebipenem pivoxil plus CS319-piv-SAc (P = 0.02) treatment resulted in significant changes in the alpha diversity patterns, whereas tebipenem pivoxil and CS319-piv-SAc individual treatments did not (P > 0.05). Moreover, clindamycin treatment resulted in substantial overgrowth of MDR K. pneumoniae (mean concentration after 6 days of infection, 6.1 vs 2.9 log10 CFU/g stool), whereas the other treatments did not (≤3.6 log10 CFU/g). Although tebipenem pivoxil alone or in combination with an MBL inhibitor, CS319, caused alteration of the mice intestinal microbiota, neither treatment promoted overgrowth of carbapenem-resistant K. pneumoniae. IMPORTANCE: in this work, we used a mouse model to determine the impact of tebipenem pivoxil alone and in combination with a prodrug of an experimental metallo-β-lactamase inhibitor, CS319, on the intestinal microbiota and on the establishment of colonization with carbapenem-resistant Klebsiella pneumoniae. We found that while treatment with tebipenem pivoxil plus the prodrug of CS319 caused alteration of the intestinal microbiota, it did not promote the overgrowth of carbapenem-resistant K. pneumoniae. Although additional studies are needed to examine the impact of tebipenem pivoxil treatment on other multidrug-resistant Gram-negative bacilli, Clostridioides difficile, and Candida spp., our study is a step forward in the understanding of the potential effect of this oral carbapenem on the indigenous microbiota of the colon and on the promotion of colonization by pathogens.1-12enopenAccessTebipenemMetallo-β-lactamase inhibitorGut microbiomeIntestinal colonizationCarbapenem-resistant EnterobacteralesGastrointestinal MicrobiomeKlebsiella pneumoniaeTebipenem pivoxilarticuloMojica, María F.Hausman, Bryan S.Pearlmutter, Basya S.Zink, Elizabeth G.Wilson, Brigid M.Villamil, ValentinaSaiz, CeciliaMahler, Graciela S.Vila, Alejandro J.Sangwan, NaseerDonskey, Curtis J.Bonomo, Robert A.Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y FarmacéuticasAttribution 4.0 International2165-0497