:Prototheca species are achlorophyllic algae that are a rare cause of infection in humans. It most commonly causes localized cutaneous disease and rarely disseminated infection. Immunocompromised patients have the highest risk of disseminated protothecosis, with a higher mortality rate than localized cutaneous infections. At the species level, infections caused by Prototheca zopfii are reported less frequently than those caused by Prototheca wickerhamii. The diagnosis can be made using histopathology, culture, and molecular testing. There is no definitive evidence for an effective treatment, which currently consists of antifungals (primarily amphotericin B). With only a handful of cases of disseminated protothecosis reported worldwide that are caused by P. zopfii, we herein present an additional case of a postbone marrow transplant patient in the Midwest of the United States.

Background Many clinical laboratories rely on polymerase chain reaction (PCR) as the sole test for diagnosis of C. difficile infection (CDI). The objective of this study was to determine if the C. difficile (CD) PCR cycle threshold could be used to predict a positive CD toxin test. Methods We reviewed the characteristics and outcomes of 149 consecutive patients who tested positive for by PCR (Xpert CD, Cepheid) between October 2019 and December 2021 at one VA Hospital where reflex toxin testing (Cdiff quick check complete, Alere/TechLab) was performed after a positive PCR result. Baseline characteristics, symptoms, initial laboratory data, and treatments were compared as well as clinical outcomes. Determination of CDI or CD colonization was made for each patient after review of symptoms: including chronicity of symptoms, laboratory values, stool frequency, use of laxatives, and response to treatment. The cycle threshold for the CD-PCR results were recorded and positive stools were cultured for CD. Results Toxin testing was positive in 38% (57/149) of cases. The mean PCR cycle threshold value for all specimens tested was 27.89 (95% CI [27.14, 28.66]). Toxin-positive stools had lower mean PCR cycle thresholds when compared to toxin-negative stools (24.56 and 29.97, respectively p < 0.0001). Among the 149 cases reviewed, 109 were determined to be CDI (73%), 36 were colonized (24%), and 4 cases were undetermined. Among those with toxin-positive stools, 96% (54/56) patients were determined to have CDI. 98% (56/57) of all toxin-positive stools had a cycle threshold of ≤ 32.2 compared to 63% (58/92) of toxin-negative stools, resulting in a negative predictive value of 97.2% (p < 0.0001). The mean cycle threshold was lower in patients who were determined to have a CDI when compared to colonized patients (27.02 vs 30.44, p = 0.0001). [Figure] Of the patients that had CDI, 83% (91/109) had a cycle threshold of ≤ 32.2 and 58% (21/36) of colonized patients had a cycle threshold of ≤ 32.2. Conclusion Conclusions: In a setting where a CD toxin assay is not readily available, a CD stool PCR cycle threshold could be used to predict toxin status. In our study, a cycle threshold of ≤ 32.2 predicted both toxin-positivity and CDI. Disclosures Stuart Johnson, M.D., Ferring Pharmaceuticals: Membership on Ferring Publication Steering Committee|Ferring Pharmaceuticals: Employee|Summit Plc: Advisor/Consultant.

Background There is a lack of consensus on the most appropriate testing for C. difficile infection (CDI). The objective of this study was to determine the clinical and microbiological characteristics of CDI following a switch from stool PCR testing only to PCR reflexed to toxin testing. Figure 1. PCR Cycle Threshold Values Methods We reviewed the characteristics and outcomes of 50 consecutive patients who tested positive for CD by PCR (Xpert CD, Cepheid) between October 2019 and January 2020 at the Hines VA Hospital. Cases were defined by results of reflex toxin testing (Cdiff quick check complete, Alere/TechLab) after a positive PCR result. Baseline characteristics, symptoms, initial laboratory data, and treatments were compared as well as patient outcomes, including hospital readmission due to CDI at 30 days, and recurrent CDI (rCDI) at 30 and 90 days. The cycle threshold for the stool PCR result was recorded. Stools were cultured anaerobically for CD, and restriction endonuclease analysis (REA) strain typing was performed on the recovered CD isolates. Results Toxin testing was positive in 19/50 (38%) cases. Compared to stool toxin-negative cases, toxin-positive cases were older (95% vs. 71% were age ≥ 65, p = 0.06), more likely to have a history of CDI (37% vs. 23%, p = 0.34), and have ≥ 1 CDI episodes within 6 months (37% vs. 19%, p = 0.26). Treatment for CDI was more common in patients who had a positive toxin text. (95% vs 61%, p= 0.009). Among the 38 patients that received treatment, 33 received vancomycin (87%) and 8 patients (21%) had rCDI at 30 days. Of the 8 patients with rCDI, 2 were re-admitted to the hospital for CDI. The average PCR cycle threshold was lower in the toxin-positive stools compared to toxin-negative stools (24.46 and 29.96, p< 0.001; Fig. 1) The endemic REA group Y was the most common CD strain recovered (30%) and the previously epidemic and virulent REA group BI strain was recovered in 11% of the cases. Conclusion CDI cases diagnosed by positive stool PCR and positive toxin tests had more typical risk factors for CDI, a lower PCR cycle threshold and were more likely to have been treated for CDI. Outcomes were similar in this setting where infection with the virulent BI strain was uncommon. Disclosures Stuart Johnson, MD, Acurx Pharmaceuticals (Advisor or Review Panel member)Bio-K+ (Advisor or Review Panel member)Ferring Pharmaceutical (Advisor or Review Panel member)

Background: Polymerase chain reaction (PCR) testing for the detection of C. difficile is a highly sensitive test. Some clinical laboratories have included a 2-step testing algorithm utilizing PCR plus toxin enzyme immunoassays (EIAs) to increase specificity. Objective: To determine the risk factors and outcomes of C. difficile PCR-positive/toxin-positive encounters compared to PCR-positive/toxin-negative encounters. Design: Retrospective study. Setting: A Veterans’ Affairs hospital. Methods: A retrospective case–control study of patient encounters with a positive C. difficile test by PCR and either a toxin EIA–positive assay (ie, cases) or toxin EIA–negative assay (ie, controls). Clinically relevant exposures and risk factors were determined to assess CDI recurrence at 30 days. Available encounter stool specimens were cultured for C. difficile and were subjected to restriction endonuclease analysis (REA) strain typing. Results: Among 130 C. difficile PCR-positive patient encounters, 80 (61.5%) were toxin EIA negative and 50 (38.5%) were toxin EIA positive. Encounters that were toxin positive were more frequently treated (96.0%) compared to toxin-negative encounters (71.3%; P < .01). A multivariable logistic regression model revealed that toxin-negative encounters were less likely to suffer a recurrent CDI episode within 30 days (odds ratio [OR], 0.20, 95% confidence interval [CI], 0.05–0.83). Additionally, a higher C. difficile PCR cycle threshold predicted a lower risk of CDI recurrence at 30 days. (OR, 0.82; 95% CI, 0.68–0.98). During the study period, the REA group Y strain accounted for most toxin-negative encounters (32.5%; P = .05), whereas REA group BI strain accounted for most toxin-positive encounters (24.3%; P = .02). Conclusions: A testing strategy of PCR plus toxin EIA helped predict recurrent CDI.