Coordinated modulation of multiple processes through phase variation of a c-di-GMP phosphodiesterase in Clostridioides difficile.

The opportunistic nosocomial pathogen Clostridioides difficile exhibits phenotypic heterogeneity through phase variation, a stochastic, reversible process that modulates expression. In C. difficile, multiple sequences in the genome undergo inversion through site-specific recombination. Two such loci lie upstream of pdcB and pdcC, which encode phosphodiesterases (PDEs) that degrade the signaling molecule c-di-GMP. Numerous phenotypes are influenced by c-di-GMP in C. difficile including cell and colony morphology, motility, colonization, and virulence. In this study, we aimed to assess whether PdcB phase varies, identify the mechanism of regulation, and determine the effects on intracellular c-di-GMP levels and regulated phenotypes. We found that expression of pdcB is heterogeneous and the orientation of the invertible sequence, or 'pdcB switch', determines expression. The pdcB switch contains a promoter that when properly oriented promotes pdcB expression. Expression is augmented by an additional promoter upstream of the pdcB switch. Mutation of nucleotides at the site of recombination resulted in phase-locked strains with significant differences in pdcB expression. Characterization of these mutants showed that the pdcB locked-ON mutant has reduced intracellular c-di-GMP compared to the locked-OFF mutant, consistent with increased and decreased PdcB activity, respectively. These alterations in c-di-GMP had concomitant effects on multiple known c-di-GMP regulated processes, indicating that phase variation of PdcB allows C. difficile to coordinately diversify multiple phenotypes in the population to enhance survival.

Impact of alcohol-based hand-rub disinfection on bacterial bioburden on stethoscopes in a real-world clinical setting.

In this randomized study, use of alcohol-based hand-rub disinfection significantly reduced bacterial bioburden of stethoscopes in routine clinical use. Prior cleaning of stethoscopes on the study day did not affect baseline contamination rates, which suggests that the efficacy of alcohol disinfection is short-lived and may need to be repeated between patients.

Efficacy of UV-C disinfection in hyperbaric chambers.

Ultraviolet C (UV-C) light reduces contamination on high-touch clinical surfaces. We assessed the efficacy of 2 UV-C devices at eradicating important clinical pathogens in hyperbaric chambers. Both devices were similarly efficacious against MRSA but differed significantly against C. difficile. Additionally, direct UV-C exposure was more efficacious against both species than indirect exposure.