Heme is crucial for medium-dependent metronidazole resistance in clinical isolates of C. difficile

Boekhoud, I. M.; Sidorov, I.; Nooij, S.; Harmanus, C.; Bos-Sanders, I. M. J. G.; Viprey, V.; Spittal, B.; Clark, E.; Davies, K.; Freeman, J.; Kuijper, E. J.; Smits, W. K.; COMBACTE-CDI Consortium,; European Study Group for Clostridioides difficile,

doi:10.1101/2020.11.18.388959

bioRxiv · 10.1101/2020.11.18.388959

Heme is crucial for medium-dependent metronidazole resistance in clinical isolates of C. difficile

Boekhoud, I. M.·Sidorov, I.·Nooij, S.·Harmanus, C.·Bos-Sanders, I. M. J. G.·Viprey, V.·Spittal, B.·Clark, E.·Davies, K.·Freeman, J.·Kuijper, E. J.·Smits, W. K.·COMBACTE-CDI Consortium,·European Study Group for Clostridioides difficile,

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Abstract

Until recently, metronidazole was the first-line treatment for Clostridioides difficile infection and it is still commonly used. Though resistance has been reported due to the plasmid pCD-METRO, this does not explain all cases. Here, we investigate resistance to metronidazole in a collection of clinical isolates of C. difficile. We find that nearly all isolates demonstrate a heme-dependent increase in the minimal inhibitory concentration for metronidazole, which in some cases leads to isolates being qualified as resistant (MIC > 2 mg/L). Moreover, whole genome sequence analysis reveals a single nucleotide polymorphism in the heme responsive gene hsmA, which defines a metronidazole resistant lineage of PCR ribotype 010 / multilocus sequence type 15 isolates that also includes pCD-METRO containing strains. Together our data demonstrate that heme is crucial for medium-dependent metronidazole resistance in C. difficile.

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Boekhoud, I. M., Sidorov, I., Nooij, S., Harmanus, C., Bos-Sanders, I. M. J. G., Viprey, V., Spittal, B., Clark, E., Davies, K., Freeman, J., Kuijper, E. J., Smits, W. K., COMBACTE-CDI Consortium,, European Study Group for Clostridioides difficile,. 2020-11-18. Heme is crucial for medium-dependent metronidazole resistance in clinical isolates of C. difficile. https://doi.org/10.1101/2020.11.18.388959

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