Impact of tebipenem pivoxil on the intestinal microbiota and on establishment of colonization with carbapenem-resistant <i>Klebsiella pneumoniae</i> in mice

Tebipenem pivoxil has potent <i>in vitro</i> activity against <i>Enterobacterales</i> 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 <i>Klebsiella pneumoniae bla</i> _NDM-1, 6 h after the second dose. The concentrations of the MDR <i>K. pneumoniae</i> in stool were measured on days 1, 3, and 6 after challenge. In comparison to saline controls, clindamycin (<i>P</i> = 0.001) and tebipenem pivoxil plus CS319-piv-SAc (<i>P</i> = 0.02) treatment resulted in significant changes in the alpha diversity patterns, whereas tebipenem pivoxil and CS319-piv-SAc individual treatments did not (<i>P</i> > 0.05). Moreover, clindamycin treatment resulted in substantial overgrowth of MDR <i>K. pneumoniae</i> (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 <i>K. pneumoniae</i>.IMPORTANCEIn 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 <i>Klebsiella pneumoniae</i>. 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 <i>K. pneumoniae</i>. Although additional studies are needed to examine the impact of tebipenem pivoxil treatment on other multidrug-resistant Gram-negative bacilli, <i>Clostridioides difficile</i>, and <i>Candida</i> 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.