Objective: Asymptomatic patients colonized with toxigenic Clostridioides difficile are at risk of progressing to C. difficile infection (CDI), but risk factors associated with progression are poorly understood. The objectives of this study were to estimate the incidence and identify risk factors to progression of hospital-onset CDI (HO-CDI) among colonized patients. Methods: This was a nested case-control study at an academic medical center including adult patients colonized with toxigenic C. difficile , detected via polymerase chain reaction (PCR) on a rectal swab collected on admission from 2017 to 2020. Patients with prior CDI or symptoms on admission, neutropenia, prior rectal surgery, or hospitalization less than 24 hours were excluded. Colonized patients that developed HO-CDI were matched 1:3 to colonized patients who did not based on PCR test date. Bivariate and multivariable-adjusted Cox regression analyses were used to identify risk factors. Results: Of 2,150 colonized patients, 109 developed HO-CDI, with an incidence of 5.1%. After exclusions, 321 patients (69 with HO-CDI) were included, with an estimated incidence of 4.2%. Risk factors included cirrhosis (aHR 1.94), ICU admission (aHR 1.76), malignancy (aHR 1.88), and hospitalization within six months (aHR 1.6). Prior antibiotic exposure in the past three months (aHR 2.14) and receipt of at-risk antibiotics were also identified as potential risk factors (aHR 2.17). Conclusions: Progression to HO-CDI among colonized patients was not uncommon. This study highlights key risk factors associated with progression, underscoring the importance of enhanced monitoring and prevention efforts tailored to high-risk populations to mitigate HO-CDI.

Extrapulmonary tuberculosis is an infection by Mycobacterium tuberculosis (MTB) involving any organ besides the lungs. Rarely, tuberculosis (TB) can infect the bones and joints, which accounts for only 1%-5% of total TB cases in Europe and the United States. In this case report, we present a 29-year-old man with history of gout who presented with chronic left wrist pain. Imaging demonstrated synovitis and erosive arthritis of the distal radius, ulna, and carpal bones. An initial synovial biopsy showed granulomatous inflammation but mycobacteria were not detected by microscopic examination or broad-spectrum polymerase chain reaction (PCR). Seven months later, a repeat bone biopsy showed TB osteomyelitis. The patient was then treated with anti-tuberculous therapy. Notably, imaging findings included the “penumbra sign,” a highly specific feature seen on magnetic resonance imaging for subacute osteomyelitis. This case illustrates the challenges in diagnosing extrapulmonary TB osteomyelitis.