2358. Understanding the Clinical Implications of Clostridium difficile Detection in the Molecular Age: Colonization vs. Infection in Children Less Than 3 Years of Age

BACKGROUND: Infants have a high rate of asymptomatic Clostridium difficile (CD) colonization (up to 37%) but can rarely develop true CD infection (CDI). However, currently available polymerase chain reaction (PCR) and enzyme immunoassays (EIA) have suboptimal sensitivity/specificity to distinguish CDI from colonization. Recent data from adults showed that lower cycle threshold (Ct) values of a semi-quantitative CD toxin B gene (tcdB) PCR assay in stool correlated with detection of free CD toxin in stool and poor clinical outcomes. We hypothesized that a tcdB PCR assay may be utilized to distinguish CDI from colonization in patients < 3 years old. METHODS: Symptomatic patients < 3 years old with CD detected by the BioFire FilmArray Gastrointestinal Panel (FGP) were enrolled 2/2018–3/2019. We performed CD tcdB PCR and toxin A/B/GDH EIA on frozen aliquots of stool in Cary Blair. CDI was defined among those that were tcdB PCR positive as (1) a consistent clinical syndrome (diarrhea + no current laxative use), (2) CD EIA toxin+, (3) symptomatic improvement with CDI-directed treatment, and (4) no alternative etiology of diarrhea identified. Patients who did not meet criteria for CDI were considered colonized. We compared median tcdB PCR Ct values between the CDI and colonized groups using the Mann–Whitney test. RESULTS: Of 193 FGP CD+ patient samples with charts available for review, 37 (19%) samples were EIA GDH+/toxin+, 121 (63%) were GDH+/toxin− and 35 (18%) were EIA−. 150 (78%) samples had detectable tcdB by PCR. Six (4%) patients met criteria for CDI and 144 (96%) for colonization. Median (interquartile range) tcdB PCR Ct values were 23.8 (22.0–29.5) and 30.5 (26.3–35.8) in patients with CDI and colonization, respectively (P = 0.03). CONCLUSION: Using a strict clinical and laboratory definition, 4% of evaluable patients < 3 years old met criteria for CDI and had significantly lower tcdB PCR Ct values than colonized patients. A combination of clinical and laboratory criteria, including semi-quantitative tcdB PCR, may help differentiate colonization from CDI in this patient population. DISCLOSURES: All authors: No reported disclosures.