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Minimum Inhibitory Concentration Increase in Clostridioides difficile Isolates from Patients with Recurrence: Results
Pietro Valsecchi1, Erika Asperges1, Marta Corbella2
1Infectious Diseases I Unit, IRCCS Policlinico San Matteo Foundation, 27100 Pavia, Italy.
Abstract:
Antimicrobial susceptibility testing (AST) is not routinely performed for C. difficile infection (CDI); however, reports of antimicrobial resistance to various antibiotics have increased. This study aimed to assess the rate of antimicrobial resistance to four antimicrobials (vancomycin, metronidazole, tigecycline, and ciprofloxacin) to assess risk factors for antimicrobial resistance and evaluate MIC variation in patients with recurrence. Data from consecutive patients with CDI admitted to our institution between 1 January 2022 and 30 April 2023 were collected. We performed AST with gradient diffusion and NAAT to evaluate the presumptive presence of R027/NAP1 and toxin production genes. Antimicrobial susceptibility testing was performed on 108 available isolates. We did not find any resistance to vancomycin (median MIC 0.5 μg/mL), metronidazole (median MIC 1 μg/mL), and tigecycline (median MIC 0.016 μg/mL), while resistance to ciprofloxacin was detected in all the samples. Among the recurrent isolates, 37.5% displayed a 2-fold MIC increase for vancomycin, 75% for metronidazole, and 37.5% for tigecycline. After stratifying clinical outcomes according to vancomycin MIC, patients with higher MIC experienced increased 28-day mortality (p value 0.009). Our results were concordant with European surveillance data. MIC increase in all tested antibiotics in patients with CDI warrants further research since decreased susceptibility has been associated with clinical failure.
Insights
Antimicrobial resistance testing for Clostridioides difficile infection (CDI) revealed no resistance to vancomycin, metronidazole, or tigecycline. However, all isolates showed ciprofloxacin resistance, and increased MICs in recurrent cases warrant further investigation.
Area of Science:
- Infectious Diseases
- Microbiology
- Clinical Pharmacy
Background:
- Antimicrobial susceptibility testing (AST) is crucial for Clostridioides difficile infection (CDI) management.
- Increasing reports of antimicrobial resistance necessitate ongoing surveillance.
- Routine AST for CDI is not standard practice, limiting understanding of resistance patterns.
Purpose of the Study:
- To determine antimicrobial resistance rates to vancomycin, metronidazole, tigecycline, and ciprofloxacin in CDI.
- To identify risk factors associated with antimicrobial resistance in CDI.
- To evaluate Minimum Inhibitory Concentration (MIC) variations in recurrent CDI cases.
Main Methods:
- Collected data from consecutive patients with CDI between January 2022 and April 2023.
- Performed AST using gradient diffusion and NAAT for R027/NAP1 and toxin genes.
- Analyzed 108 available isolates for antimicrobial susceptibility.
Main Results:
- No resistance observed for vancomycin (median MIC 0.5 μg/mL), metronidazole (median MIC 1 μg/mL), or tigecycline (median MIC 0.016 μg/mL).
- All tested isolates exhibited resistance to ciprofloxacin.
- Recurrent isolates showed increased MICs: 37.5% for vancomycin, 75% for metronidazole, and 37.5% for tigecycline.
- Higher vancomycin MICs correlated with increased 28-day mortality (p=0.009).
Conclusions:
- Current CDI isolates show susceptibility to vancomycin, metronidazole, and tigecycline, but universal ciprofloxacin resistance.
- Increased MICs for tested antibiotics in recurrent CDI suggest emerging resistance.
- Higher vancomycin MICs are linked to poorer clinical outcomes, emphasizing the need for further research into decreased susceptibility and clinical failure.
