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Updated: Jul 2, 2025
A Protocol to Characterize the Morphological Changes of Clostridium difficile in Response to Antibiotic Treatment
Published on: May 25, 2017
Antibacterial activity of ibezapolstat against antimicrobial-resistant clinical strains of Clostridioides difficile
Eugénie Bassères1, Taryn A Eubank1, Khurshida Begum1
1Department of Pharmacy Practice and Translational Research, University of Houston College of Pharmacy, Houston, Texas, USA.
Abstract:
Antimicrobial resistance is emerging in clinical strains of Clostridioides difficile. Ibezapolstat (IBZ) is a DNA polymerase IIIC inhibitor that has completed phase II clinical trials. IBZ has potent in vitro activity against wild-type, susceptible strains but its effect on C. difficile strains with reduced susceptibility to metronidazole (MTZ), vancomycin (VAN), or fidaxomicin (FDX) has not been tested. The primary objective of this study was to test the antibacterial properties of IBZ against multidrug-resistant C. difficile strains. The in vitro activity, bactericidal, and time-kill activity of IBZ versus comparators were evaluated against 100 clinical strains of which 59 had reduced susceptibility to other C. difficile antibiotics. Morphologic changes against a multidrug resistance strain were visualized by light and scanning electron microscopy. The overall IBZ MIC50/90 values (µg/mL) for evaluated C. difficile strains were 4/8, compared with 2/4 for VAN, 0.5/1 for FDX, and 0.25/4 for MTZ. IBZ MIC50/90 values did not differ based on non-susceptibility to antibiotic class or number of classes to which strains were non-susceptible. IBZ bactericidal activity was similar to the minimum inhibitory concentration (MIC) and maintained in wild-type and non-susceptible strains. Time-kill assays against two laboratory wild-type and two clinical non-susceptible strains demonstrated sustained IBZ activity despite reduced killing by comparator antibiotics for IBZ and VAN non-susceptible strains. Microscopy visualized increased cell lengthening and cellular damage in multidrug-resistant strains exposed to IBZ sub-MIC concentrations. This study demonstrated the potent antibacterial activity of IBZ against a large collection of C. difficile strains including multidrug-resistant strains. This study highlights the therapeutic potential of IBZ against multidrug-resistant strains of C. difficile.
Insights
Ibezapolstat (IBZ) shows potent activity against multidrug-resistant Clostridioides difficile strains, including those resistant to other antibiotics. This DNA polymerase IIIC inhibitor demonstrates therapeutic potential for treating difficult C. difficile infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Emerging antimicrobial resistance in clinical Clostridioides difficile strains poses a significant threat.
- Ibezapolstat (IBZ), a DNA polymerase IIIC inhibitor, has completed Phase II trials with known activity against susceptible strains.
- The efficacy of IBZ against C. difficile strains with reduced susceptibility to metronidazole (MTZ), vancomycin (VAN), or fidaxomicin (FDX) remains largely untested.
Purpose of the Study:
- To evaluate the antibacterial properties of Ibezapolstat (IBZ) against multidrug-resistant Clostridioides difficile clinical isolates.
- To assess the in vitro activity, bactericidal effects, and time-kill kinetics of IBZ compared to standard antibiotics.
Main Methods:
- Evaluated in vitro activity, bactericidal activity, and time-kill kinetics of IBZ against 100 clinical C. difficile strains, including 59 with reduced susceptibility to other antibiotics.
- Determined minimum inhibitory concentration (MIC) values for IBZ, VAN, FDX, and MTZ.
- Utilized light and scanning electron microscopy to visualize morphologic changes in multidrug-resistant strains exposed to sub-MIC concentrations of IBZ.
Main Results:
- IBZ exhibited potent in vitro activity with MIC50/90 values of 4/8 µg/mL against all tested C. difficile strains, irrespective of prior antibiotic resistance.
- IBZ demonstrated sustained bactericidal activity comparable to its MIC, maintaining efficacy against both wild-type and non-susceptible strains.
- Microscopy revealed cell lengthening and damage in multidrug-resistant strains upon exposure to sub-inhibitory concentrations of IBZ, indicating a novel mechanism of action.
Conclusions:
- Ibezapolstat displays significant antibacterial potency against a diverse collection of Clostridioides difficile strains, including multidrug-resistant isolates.
- IBZ maintains its activity even when strains exhibit reduced susceptibility to vancomycin, metronidazole, or fidaxomicin.
- These findings underscore the therapeutic potential of Ibezapolstat as a novel treatment option for challenging Clostridioides difficile infections.
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