Impact of subinhibitory concentrations of metronidazole on proteome of Clostridioides difficile strains with different levels of susceptibility.

Tri-Hanh-Dung Doan,Stéphanie Yen-Nicolaÿ,Isabelle Martin-Verstraete,Séverine Péchiné,Marie-Françoise Bernet-Camard

doi:10.1371/journal.pone.0241903

Abstract

Clostridioides difficile is responsible for various intestinal symptoms from mild diarrhea to severe pseudomembranous colitis and is the primary cause of antibiotic-associated diarrhea in adults. Metronidazole was the first-line treatment for mild to moderate C. difficile infections for 30 years. However, clinical failure and recurrence rates of metronidazole is superior to oral vancomycin and metronidazole is now recommended only as an alternative to vancomycin or fidaxomicin, for an initial non-severe infection. The mechanisms of treatment failure and infection recurrence remain unclear. Given the poor fecal concentrations of metronidazole, the bacteria may be exposed to subinhibitory concentrations of metronidazole and develop adaptation strategy, which is likely to be the origin of an increase in treatment failures. In this study, a proteomic approach was used to analyze changes in the proteome of two strains with different levels of susceptibility to metronidazole in the presence of subinhibitory concentrations of this antibiotic. The two strains were grown to stationary phase: CD17-146, a clinical C. difficile isolate with reduced susceptibility to metronidazole, and VPI 10463, a metronidazole susceptible strain. Our study revealed that, whatever the strain, subinhibitory concentrations of metronidazole modified the amount of proteins involved in protein biosynthesis, glycolysis, and protection against stress induced by metronidazole, as well as in DNA repair. Several proteins involved in stress response are known to be synthesized under the control of Sigma factor B, which suggests a close link between Sigma factor B and metronidazole. Interestingly, impact of metronidazole on protein production for VPI 10463 strain differed from CD17-146 strain, for which the amount of two proteins involved in biofilm formation of CD17-146 were modified by metronidazole.

Highlights

Clostridioides difficile is a Gram-positive, spore forming and obligate anaerobic bacterium responsible for post-antibiotic diarrhea with a spectrum of clinical signs, ranging from selflimiting diarrhea to life-threatening pseudomembranous colitis
In order to elucidate the effect of MTZ on the proteome of C. difficile strains, we described proteomic adaptation of a C. difficile isolate, CD17-146, with reduced susceptibility to MTZ and VPI 10463, a MTZ susceptible strain in response to subinhibitory concentrations of the antibiotic
In accordance with studies of response of other anaerobes to MTZ, our results confirm that the protection of C. difficile from stress induced by MTZ is multifactorial

Summary

Introduction

Clostridioides difficile is a Gram-positive, spore forming and obligate anaerobic bacterium responsible for post-antibiotic diarrhea with a spectrum of clinical signs, ranging from selflimiting diarrhea to life-threatening pseudomembranous colitis. MTZ, which has selective activity against anaerobic or microaerophilic bacteria [3] was widely used as first-line therapy because of its lower cost. Vancomycin therapy is superior to MTZ for clinical cure [4] but its recurrence rate is still high, approximately 25% [5,6]. Fidaxomicin, with a narrow spectrum, appears similar to vancomycin for the clinical response at the end of CDI therapy but has a reduced risk of recurrences and a lower impact on the intestinal microbiota [7]. Since 2018, several studies reported the emergence and spread of C. difficile clinical isolates resistant to MTZ [8], as well as treatment failure and high recurrent rate (20–25%) post MTZ therapy [4].

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Conclusion