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. 2025 Mar 31;25(1):209.
doi: 10.1186/s12876-025-03800-7.

In vitro susceptibility of clinical Clostridioides difficile isolates in Israel to metronidazole, vancomycin, fidaxomicin, ridinilazole and ibezapolstat

Orna Schwartz  1   2 , Maya Azrad  3 , Avi Peretz  4   5
Affiliations

In vitro susceptibility of clinical Clostridioides difficile isolates in Israel to metronidazole, vancomycin, fidaxomicin, ridinilazole and ibezapolstat

Orna Schwartz et al. BMC Gastroenterol. .

Abstract

Background: Antibiotics are currently the primary treatment of Clostridioides difficile (C. difficile) infection. Yet, due to rapid development of resistance and high recurrences rates, there is an unmet need for new antimicrobials for C. difficile infections. This study assessed the in vitro susceptibility of clinical isolates from Israel to two recently developed antibiotics, ridinilazole (RDZ) and ibezapolstat (IBZ), and to standard-of-care antibiotics.

Methods: C. difficile isolates (n = 313) recovered from patients at both community and hospital medical centers across Israel, were typed to different sequence types (ST) by multi-locus sequencing typing (MLST). Susceptibility to metronidazole (MTZ) and vancomycin (VAN) was determined using the gradient strip test (Etest). Susceptibility to fidaxomicin (FDX), RDZ and IBZ was determined by agar dilution.

Results: ST42 (39; 12.5%) and ST2 (36; 11.5%) were the most prevalent STs. Resistance to MTZ and VAN was low (2.2%, 1.6%, respectively), while 23 (7.35%) isolates were FDX-resistant. RDZ MIC ranged between 0.06 and 0.5 mg/L, and MIC50/90 was 0.25/0.5 mg/L. IBZ had an MIC50/90 of 4 mg/L. No significant differences were noted in IBZ MIC of different strains.

Conclusions: RDZ and IBZ demonstrated potent in vitro activity against 313 C. difficile isolates belonging to different STs. These two antimicrobials may serve as effective agents for C. difficile infection.

Keywords: C. difficile; Antibiotic susceptibility; Fidaxomicin; Ibezapolstat; MLST; Ridinilazole; Strains.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: The study adhered to the Declaration of Helsinki. Tzafon Medical Center, Poriya and W. Hirsch Regional Microbiology Laboratory Clalit Health Services, Haifa, Center - Edith Wolfson Medical Center, Holon, and South - Soroka University Medical Center, Be’er Sheva. The local Ethics (Helsinki) Committee of Tzafon Medical Center, W. Hirsch Regional Microbiology Laboratory Clalit Health Services and Soroka University Medical Center approved the study (approval numbers-POR-0085-15, WOMC-0115-20, SOR-0307-20, respectively). The need for informed consent was waived by all three mentioned committees. All experiments were performed in accordance with relevant guidelines and regulations. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests. Clinical trial number: not applicable.

Figures

Fig. 1
Fig. 1
Distribution of C. difficile sequence types (STs) among study isolates
Fig. 2
Fig. 2
Distribution of MIC of different antibiotics in C. difficile isolates
See this image and copyright information in PMC

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