This Puscast episode, covering August 2013, discusses transmission routes, drug efficacy trials, and diagnostic pitfalls in infectious diseases. MERS-CoV is strongly linked to single-humped camels (100% seropositive in Oman). New interferon-free regimens show promise for Hepatitis C treatment. Concerning diagnostics, the video highlights that empiric therapy for C. difficile significantly impairs PCR results rapidly, emphasizing the need for diagnosis before treatment. A meta-analysis comparing linezolid and daptomycin for VRE bloodstream infections is dismissed as useless, concluding only that the underlying data is inadequate. Finally, the host recommends key readings on cognitive bias to improve clinical reasoning.
The Puscast: Infectious Disease Literature Review (August 2013)
0:03 Introduction & Setting: The host is physically sore from moving furniture, which you don't care about. The podcast is recorded outside; expect background noises (cars, dogs). You must live with it, as the host finds walking stairs painful.
1:10 MERS-CoV Reservoir: Evidence suggests single-humped camels (dromedaries) are exposed to the new Middle East coronavirus. 100% (50/50) of Omani camels tested were seropositive, pointing to camels as a likely intermediate host between bats and humans.
2:26 CMV and Alzheimer's: A study suggests CMV infection is associated with Alzheimer's disease, showing CMV can induce beta-amyloid in vitro. This is noted as an interesting association, but causality is not proven.
3:17 Hepatitis C Treatment: New, non-interferon regimens combining the protease inhibitor faldaprevir and the polymerase inhibitor deleobuvir (plus ribavirin) achieved sustained virologic response (SVR) in 52–69% of patients, offering a less toxic alternative.
Fatal West Nile virus transmission was presumptively acquired via a blood transfusion in a non-Hodgkin's lymphoma patient.
Genital ulcers caused by a diphtheria toxin-producing strain of Corynebacterium diphtheriae were transmitted via oral sex. The patient refused post-cure vaccination, possibly relying on natural immunity.
5:28 European Lyme Disease: CNS involvement in European Lyme (Borrelia garinii) is typically rare, except in patients presenting with pleocytosis in CSF and radiculopathy. This distinction is crucial, as it does not apply to the B. burgdorferi prevalent in the US.
7:02 Syphilis Rates: A Baltimore study tracking syphilis in men who have sex with men (MSM) found high rates of repeat infection (1 in 5, usually 12 months apart), especially among HIV-positive individuals. This highlights a critical need for targeted safer sex education.
8:24 VRE Treatment Meta-analysis: A systematic review comparing linezolid versus daptomycin for VRE bloodstream infections concluded they look similar, but the host dismisses the finding as worthless because the data sources ("crappy studies") are insufficient. Randomized trials are obviously needed.
8:56 VRE Carriage & Isolation: The host strongly dislikes contact isolation. A study suggests VRE carriage may diminish over time; no patients were found to be current carriers if their history of VRE was more than four years prior. Continued antibiotic exposure remains a risk for chronic carriage.
10:19 C. diff Diagnosis Pitfall: Empiric treatment for C. difficile significantly compromises diagnostic accuracy, with 45% of patients converting to negative PCR by day three. It is critical—it "behooves us"—to order the diagnostic assay before initiating therapy. The host loathes empiric treatment.
12:11 Obesity and C. diff: Obesity is confirmed as a risk factor for C. difficile diarrhea, hypothesized to be due to an altered gut microbiota profile (more Firmicutes, fewer Bacteroides).
12:38 Probiotics for Diarrhea: A large Lancet study (1,400+ patients) found no preventative benefit from Lactobacillus and Bifidobacterium against antibiotic-associated diarrhea (AAD) or CDI. The host, however, maintains a "preponderance of data" preference and still slightly favors probiotics, despite being "less enthusiastic" now.
15:49 Mimi Virus: The large Mimi virus, isolated from a pneumonia patient, is suggested to be a cause of human disease. The host notes that only a human challenge study (à la Barry Marshall) remains to fulfill Koch’s postulates.
17:35 Vitamin D Prevention: A study found that regular Vitamin D supplementation did not decrease the risk of community-acquired pneumonia (CAP). This suggests taking the vitamin preventatively is ineffective, though treating an established deficiency might be different.
18:00 Bradyrhizobium Colitis: A unique, antibiotic-responsive colitis in umbilical cord stem cell transplant recipients was linked via DNA sequencing to the organism Bradyrhizobium enteroides.
19:57 Cryptococcus gattii Treatment: Retrospective analysis suggests optimal treatment for C. gattii (pulmonary or meningeal) requires induction with Amphotericin B plus 5-Flucytosine (6 weeks for meningitis, 2 weeks for pneumonia), followed by azoles. The host agrees this induction regimen is best practice, despite the limitations of retrospective data.
21:15 Cognitive Bias: The host strongly recommends reading "Clinical Reasoning for the Infectious Disease Specialist: A Primer to Recognize Cognitive Bias" (and two related articles) to become a "vastly superior thinking physician."