Arr-cb, a rifampin resistance determinant found active or cryptic in Clostridium bolteae [PublishAheadOfPrint]

Clostridium bolteae, which belongs to the Clostridium clostridioforme complex is a member of the human gut microbiota. Recent analysis of seven genomes of C. bolteae revealed the presence of an arr-like gene. Among these strains only 90A7 was found to be resistant to rifampin in the absence of alteration in RpoB. Cloning of arr-cb from 90A7 in Escherichia coli combined with directed mutagenesis demonstrated that Arr-cb is functional but that a Q127->R variant present in 90A9 and 90B3 was inactive. qRT-PCR analysis indicated that arr-cb was silent in the four remaining strains due to a defective transcription. Thus, two independent mechanisms can lead to the crypticity of the likely intrinsic arr-cb gene of C. bolteae.

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