Flexible Cobamide Metabolism in Clostridioides (Clostridium) difficile 630 Δerm.

Clostridioides (Clostridium) difficile is an opportunistic pathogen known for its ability to colonize the human gut under conditions of dysbiosis. Several aspects of its carbon and amino acid metabolism have been investigated, but its cobamide (vitamin B12 and related cofactors) metabolism remains largely unexplored. C. difficile has seven predicted cobamide-dependent pathways encoded in its genome in addition to a nearly complete cobamide biosynthesis pathway and a cobamide uptake system. To address the importance of cobamides to C. difficile, we studied C. difficile 630 Δerm and mutant derivatives under cobamide-dependent conditions in vitro Our results show that C. difficile can use a surprisingly diverse array of cobamides for methionine and deoxyribonucleotide synthesis and can use alternative metabolites or enzymes, respectively, to bypass these cobamide-dependent processes. C. difficile 630 Δerm produces the cobamide pseudocobalamin when provided the early precursor 5-aminolevulinic acid or the late intermediate cobinamide (Cbi) and produces other cobamides if provided an alternative lower ligand. The ability of C. difficile 630 Δerm to take up cobamides and Cbi at micromolar or lower concentrations requires the transporter BtuFCD. Genomic analysis revealed genetic variations in the btuFCD loci of different C. difficile strains, which may result in differences in the ability to take up cobamides and Cbi. These results together demonstrate that, like other aspects of its physiology, cobamide metabolism in C. difficile is versatile.IMPORTANCE The ability of the opportunistic pathogen Clostridioides difficile to cause disease is closely linked to its propensity to adapt to conditions created by dysbiosis of the human gut microbiota. The cobamide (vitamin B12) metabolism of C. difficile has been underexplored, although it has seven metabolic pathways that are predicted to require cobamide-dependent enzymes. Here, we show that C. difficile cobamide metabolism is versatile, as it can use a surprisingly wide variety of cobamides and has alternative functions that can bypass some of its cobamide requirements. Furthermore, C. difficile does not synthesize cobamides de novo but produces them when given cobamide precursors. A better understanding of C. difficile cobamide metabolism may lead to new strategies to treat and prevent C. difficile-associated disease.

Risk factors for development of anti-adalimumab antibodies in non-infectious uveitis.

Purpose: To evaluate risk factors associated with development of anti-adalimumab antibodies (AAA) in patients with non-infectious uveitis treated with adalimumab. Methods: A retrospective, cross-sectional, case-control study was done evaluating patients with non-infectious uveitis treated with adalimumab for at least 12 months and have undergone testing for AAA levels. Demographics, clinical characteristics, grading of ocular inflammation, and previous and concomitant immunomodulatory therapy were assessed. Univariate and multivariate analysis were done to estimate odds ratio (OR) with 95% confidence intervals for the various risk factors. Results: A total of 31 patients were included in the analysis, in which 12 patients who tested positive (Group 1) were matched with 19 patients who tested negative for AAA (Group 2). The groups differed significantly in terms of sex (female) (91.7% vs 52.6%, p = 0.046), presence of systemic disease (91.7% vs 42.1%, p = 0.008), and presence of anterior chamber inflammation at baseline (100% vs 63.2%, p = 0.026). A history of interruption in anti-TNF therapy prior to starting or restarting adalimumab was found to have an increased odds for development of AAA (OR 16.89 [2.92, 107.11], p = 0.008), as well as flare-ups (reactivation of disease) during adalimumab therapy (OR 6.77 [1.80, 61.80], p = 0.027). Weekly dosing of adalimumab was shown to decrease odds of AAA development (OR 0.34 [0.02, 0.70], p = 0.040), while concomitant anti-metabolite therapy was not shown to be a statistically significant protective factor (OR 2.22 [0.50, 9.96], p = 0.148). Conclusions: History of interruption in anti-TNF therapy and flare during adalimumab were associated with development of AAA, while weekly dosing of adalimumab was protective against AAA. Identification of those with higher risk of developing AAA may guide in clinical decision making to optimize management for these patients.

Importance of Baseline Fluorescein Angiography for Patients Presenting to Tertiary Uveitis Clinic.

PURPOSE: To ascertain whether the use of ultra-wide-field fluorescein angiography (UWFFA) at baseline visit alters the assessment of disease activity and localization, as well as the management of patients presenting to a tertiary uveitis clinic. DESIGN: Retrospective comparison of diagnostic approaches. METHODS: Baseline visits of 158 patients who presented to the Uveitis Clinic at the Byers Eye Institute at Stanford between 2017 and 2022 were evaluated by 3 uveitis-trained ophthalmologists (I.K., A.B., and H.G.). Each eye had undergone clinical examination along with ultra-wide-field fundus photography (UWFFP) (Optos Plc), spectral-domain optical coherence tomography (SD-OCT, Spectralis Heidelberg, Heidelberg Engineering) and UWFFA (Optos Plc) at the baseline visit. Investigators were asked to successively determine disease activity, localization of disease (anterior, posterior or both), and management decisions based on clinical examination and UWFFP and SD-OCT (Set 1) and Set 1 plus UWFFA (Set 2). The primary outcome was the percentage of eyes whose management changed based on the availability of UWFFA compared with Set 1. RESULTS: The mean age of the patients was 46.9 ± 22.4 years (range, 7-96), and 91 (57.6%) were female. With Set 1 alone, 138 eyes (55.2%) were found to have active disease; localization was anterior in 58 eyes (42.0%), posterior in 53 eyes (38.4%), and anterior + posterior in 27 eyes (19.6%). With Set 2, 169 eyes of 107 patients had active anterior, posterior, or panuveitis. In comparison with Set 1, assessment with Set 2 identified additional 31 eyes (18.3%) with active disease (P = .006) and an additional 31 eyes (18.3%) having disease in both anterior + posterior segments (P < .001). Regarding the primary outcome, management was changed in 68 eyes (27.4%) in Set 2 compared with Set 1. CONCLUSIONS: Baseline UWFFA may alter assessment of disease activity, localization, and management decisions compared with clinical examination with only UWFFP and SD-OCT for eyes with uveitis. Thus, UWFFA may be considered as an essential tool in the evaluation of patients with uveitis at the baseline visit.