The direct fluorescent antibody (DFA) test is commonly used for the rapid detection of which respiratory pathogen directly from nasopharyngeal specimens?

A patient with HIV infection and a CD4+ T-cell count below 100 cells/µL presents with headache, fever, and altered mental status. CSF analysis reveals elevated protein and low glucose. India ink stain is negative.
Cryptococcal antigen test of the CSF is positive. The MOST appropriate initial treatment is:

Besides traditional Giemsa-stained thick and thin blood smears, which diagnostic approach is commonly employed as a rapid diagnostic test (RDT) for malaria detection, particularly in resource-limited settings?

The gut microbiome has been implicated in the pathogenesis of autoimmune diseases. Dysbiosis, a disruption in the composition and function of the gut microbiota, can lead to increased intestinal permeability and the translocation of microbial products that trigger inflammatory responses. Which of the following bacterial components is a potent activator of the innate immune system and has been linked to the development of autoimmunity?

A 6-year-old child presents with a pharyngitis characterized by a grayish-white pseudomembrane covering the tonsils and posterior pharynx. Gram stain of the membrane reveals Gram-positive bacilli. Culture on Loeffler's medium shows growth of metachromatic granules. The MOST significant virulence factor associated with this organism's pathogenicity is: