An immunocompromised patient develops a disseminated fungal infection. Blood cultures are consistently negative. However, a serum beta-D-glucan assay is markedly elevated. Tissue biopsy reveals the presence of hyaline, septate hyphae with dichotomous branching. The MOST likely causative organism is:

A research laboratory is developing a novel diagnostic assay for early detection of sepsis. They are investigating the use of host biomarkers that are rapidly upregulated in response to bacterial infection. Which of the following biomarkers has shown promise for differentiating between systemic inflammatory response syndrome (SIRS) and sepsis?

A microbiology laboratory is investigating a possible outbreak of Salmonella infection. Serological testing of patient isolates reveals they all possess the same O antigen but different H antigens. This suggests:

A patient with a history of heart valve replacement develops subacute bacterial endocarditis. Blood cultures grow a Gram-positive coccus that is alpha-hemolytic on blood agar, catalase-negative, and optochin-resistant.
The MOST likely organism is:

A patient develops a severe skin infection after a puncture wound sustained while gardening. Culture of the wound exudate grows a Gram-positive, spore-forming bacillus that is anaerobic and produces a potent neurotoxin causing sustained muscle contraction. The MOST likely organism is: