800. Oral Vancomycin Prophylaxis Against Clostridioides difficile in Patients Admitted to a Tertiary Academic Medical Center

Background

In an effort to more accurately diagnose Clostridioides difficile infection (CDI), many hospitals have switched to two-step testing algorithms that rely on nucleic acid amplification testing with reflex enzyme immunoassay for toxin. Additionally, oral vancomycin prophylaxis (OVP) against CDI is increasingly being used; initial studies focused on preventing recurrence in patients with a prior history of CDI, but OVP is also being studied in primary prevention. We hypothesized that following the implementation of two-step testing, clinicians may use OVP for prevention of a patient’s first episode of CDI based on knowledge of prior PCR+/Toxin- testing.

Methods

We performed a single-center, retrospective cohort study of patients admitted to Beth Israel Deaconess Medical Center. We identified patients who received oral vancomycin once daily or BID for the prevention of CDI following implementation of two-step testing. Patients who received oral vancomycin as part of a taper following acute infection were excluded. We categorized rationale for prophylaxis based on clinical documentation and collected details of patients’ CDI history, antibiotic exposure, and subsequent CDI testing during hospitalization.

Results

In the 12 months following implementation of two-step testing, there were 80 patients who received OVP during hospitalization (2 daily and 78 BID). The vast majority (73, 91.3%) had a history of CDI and received OVP for secondary prevention while receiving systemic antibiotics. There were only 3 patients (3.8%) without known clinical history of CDI whose clinicians documented prophylaxis based on previous PCR+/Toxin- testing. Patients on OVP received a mean of 4.1 systemic antibiotics during hospitalization. When continuing OVP for a finite period after discontinuation of systemic antibiotics, this was most commonly done for 2-7 days (16 of 26, 61.5%). 22 patients underwent stool testing for CDI while receiving OVP in the hospital and all resulted PCR-negative.

OVP Indication

OVP Duration

Conclusion

Following implementation of two-step testing for CDI, use of OVP for primary prevention based solely on knowledge of PCR+/Toxin- testing in patients without a history of CDI was rare. Acute CDI appears unlikely in patients actively receiving OVP.

Disclosures

All Authors: No reported disclosures

Characterization of coding synonymous and non-synonymous variants in ADAMTS13 using ex vivo and in silico approaches

Synonymous variations, which are defined as codon substitutions that do not change the encoded amino acid, were previously thought to have no effect on the properties of the synthesized protein(s). However, mounting evidence shows that these “silent” variations can have a significant impact on protein expression and function and should no longer be considered “silent”. Here, the effects of six synonymous and six non-synonymous variations, previously found in the gene of ADAMTS13, the von Willebrand Factor (VWF) cleaving hemostatic protease, have been investigated using a variety of approaches. The ADAMTS13 mRNA and protein expression levels, as well as the conformation and activity of the variants have been compared to that of wild-type ADAMTS13. Interestingly, not only the non-synonymous variants but also the synonymous variants have been found to change the protein expression levels, conformation and function. Bioinformatic analysis of ADAMTS13 mRNA structure, amino acid conservation and codon usage allowed us to establish correlations between mRNA stability, RSCU, and intracellular protein expression. This study demonstrates that variants and more specifically, synonymous variants can have a substantial and definite effect on ADAMTS13 function and that bioinformatic analysis may allow development of predictive tools to identify variants that will have significant effects on the encoded protein.