1122. Early Infectious Diseases Consultation and Procalcitonin-Guided Therapy Limits Unnecessary Antibiotic Use in COVID-19

Background

Antibiotic stewardship has been a central challenge of the COVID-19 pandemic. Empiric antibiotic therapy is offered in 56.6%-74.6% of inpatients with COVID-19, with microbiologically confirmed bacterial pneumonia reported in only 3.5%-16% of cases. Procalcitonin (PCT) as a biomarker for bacterial infection is of interest in improving antibiotic use. PCT-guided antibiotic stewardship initiatives have demonstrated reduction in the use of antibiotics in the COVID-19 pandemic.  

 An Infectious Diseases (ID) consultation was obtained on most patients at our institution throughout the COVID-19 pandemic. We report a significant reduction in antibiotic use among COVID-19 patients in the setting of near-universal ID consultation in COVID-19 patients. 

Methods

We evaluated the records of 1346 patients with COVID-19 from March 2020 – May 2021 at four hospitals with ID consultant availability. We assessed the inclusion of an ID consultant, antibiotic indication, initiation and discontinuation, PCT levels, radiologic images, and changes to therapy decisions. A chi-square test of independence and simple logistic regression were conducted to determine whether an association exists between the PCT level and the decision to discontinue antibiotics. 

Results

Of 1346 patients with a confirmed COVID-19 diagnosis, 64.6% (870/1346) received antibiotics on admission. The most common diagnosis associated with initial antibiotic administration was bacterial pneumonia (692/870, 79.5%).  An ID consultation was obtained on 97.8% (677/692) of the patients that received antibiotics for suspected bacterial pneumonia. In 48.1% (326/677) of these patients, antibiotics were discontinued within the first 48 hours of the ID consultation. A statistically significant difference was noted between the PCT level and continuation of antibiotics (Χ2= 67.02, p < .01). The odds of discontinuing antibiotics for the upper (PCT > 0.51) and middle (PCT = 0.26-0.50) groups were 0.22 and 0.37, respectively, when compared to the lower (PCT ≤ 0.25) group.

Conclusion

Early consultation of an ID specialist and evaluation of PCT levels leads to significant reductions in inappropriate antibiotic use. PCT may be a useful adjunct in assisting with the decision to discontinue antibiotics.

Disclosures

All Authors: No reported disclosures.

IFITM3 requires an amphipathic helix for antiviral activity

Interferon-induced transmembrane protein 3 (IFITM3) is a cellular factor that blocks virus fusion with cell membranes. IFITM3 has been suggested to alter membrane curvature and fluidity, though its exact mechanism of action is unclear. Using a bioinformatic approach, we predict IFITM3 secondary structures and identify a highly conserved, short amphipathic helix within a hydrophobic region of IFITM3 previously thought to be a transmembrane domain. Consistent with the known ability of amphipathic helices to alter membrane properties, we show that this helix and its amphipathicity are required for the IFITM3-dependent inhibition of influenza virus, Zika virus, vesicular stomatitis virus, Ebola virus, and human immunodeficiency virus infections. The homologous amphipathic helix within IFITM1 is also required for the inhibition of infection, indicating that IFITM proteins possess a conserved mechanism of antiviral action. We further demonstrate that the amphipathic helix of IFITM3 is required to block influenza virus hemagglutinin-mediated membrane fusion. Overall, our results provide evidence that IFITM proteins utilize an amphipathic helix for inhibiting virus fusion.

Identification of an amphipathic helix within IFITM3 that promotes inhibition of influenza virus

Interferon-induced transmembrane protein 3 (IFITM3) inhibits influenza virus fusion with endosomes by altering cellular membrane properties through mechanisms that are largely uncharacterized. In order to identify regions of secondary structure within IFITM3 that may contribute to its mechanism of action, we performed structural predictions using the I-TASSER and PSSpred algorithms. Insterestingly, we identified a 10-amino acid region of likely helicity that possesses an amphipathic distribution of amino acids. Consistent with the known role of amphipathic helices in altering membrane properties, we observed that cells expressing a helix-deleted mutant of IFITM3 were infected with influenza virus at a 4-fold higher rate than cells expressing WT IFITM3. Confirming that the amphipathicity of this helix contributes to antiviral activity, single, double and triple alanine mutations of the three residues making up the hydrophilic face of the helix progressively decreased antiviral activity of IFITM3, as did single polar mutations in the hydrophobic face of the helix, or single amino acid insertions that disrupted amphipathicity. Amino acid sequence alignments suggest that amphipathicity in this region is highly conserved in IFITMs throughout evolution. Overall, we utilized bioinformatics methods coupled with functional infectivity assays to provide the first evidence that IFITM3 utilizes an amphipathicity-based mechanism for inhibition of viruses.