Week 1
A patient with a confirmed collection of pus in the retrofascial space of the posterior abdominal wall will most likely experience severe pain when the examiner passively performs this specific movement of the thigh, which some regard as an important sign.
What is extension of the hip - psoas sign.
A biopsy of a newly transplanted kidney displaying severe oliguria 2 weeks post-op reveals dense interstitial infiltrates of CD8+ T lymphocytes and tubulitis. This specific type of rejection is heavily initiated when donor dendritic cells migrate to recipient lymph nodes to present antigen via this mechanism.
What is acute cellular rejection
The likely causative organism grown from Trevon's pre-antibiotic blood culture is a Gram-positive coccus that is catalase-negative, beta-hemolytic, and highly sensitive to this specific topical antibiotic, distinguishing it from other organisms in its group.
What is bacitracin
The formation of this patient's Staphylococcal abscess begins when lipoteichoic acid from the Gram-positive bacterial cell wall is recognized by this specific pattern recognition receptor on the surface of host macrophages.
What is Toll-like receptor 2 (TLR2). Classically recognizes components of gram-positive bacterial cell walls such as peptidoglycan and lipoteichoic acid. This triggers NFKB activation and the release of proinflammatory cytokines.
This immunosuppressant, used to prevent acute cellular rejection in a kidney transplant recipient, forms an intracellular complex with FKBP to specifically inhibit a phosphatase that normally dephosphorylates NFAT.
Tacrolimus - complexes with FKBP to inhibit calcineurin - prevents dephosphorylation of NFAT and transcription of IL-2.
Added to Trevon's regimen after the rapid onset of profound hypotensive shock, this lincosamide antibiotic is utilized not for its bactericidal properties, but because it binds the 50S ribosomal subunit to specifically halt the production of the bacterial superantigen.
What is clindamycin -> protein synthesis inhibitors rapidly shut down ribosomal translation of superantigens
The development of small, cavitary pulmonary lesions in a patient with MRSA bacteremia and a history of unsterilized needle use is most commonly due to septic emboli originating from infected vegetations on this specific cardiac valve.
What is the tricuspid valve -> IV drug use predisposes to right-sided infective endocarditis, commonly of the tricuspid valve. The infected vegetation can break off and travel via the pulmonary artery to the lungs causing pulmonary emboli
The urine culture of a hospitalized patient grows a non-lactose fermenting, oxidase-positive Gram-negative rod. The primary tissue-damaging exotoxin secreted by this organism shares its exact intracellular mechanism of action with the exotoxin produced by Corynebacterium diphtheriae.
What is exotoxin A - ADP ribosylates and inactivates EF-2
The massive cytokine storm causing this 6-year-old's shock is triggered by a bacterial exotoxin that bypasses normal intracellular antigen processing, instead directly cross-linking the T-cell receptor beta chain with this specific cell-surface molecule on macrophages.
What is MHC II
In a patient presenting with an epidural abscess and septic shock, this cell-surface glycoprotein is heavily upregulated by TNF-alpha and directly binds Factor VII to initiate widespread microvascular thrombosis.
Tissue Factor (Factor 13) - upregulated by inflammatory cytokines like TNF-a and IL-1 during sepsis. Binds to Factor 7 to activate the extrinsic coagulation cascade leading to DIC
A renal transplant recipient develops systemic CMV infection. Following acute antiviral treatment, the virus enters a latent state, primarily hiding in these specific nucleated cells to evade immune clearance.
What are mononuclear cells (monocytes/macrophages) - CMV establishes lifelong latency in cells of the myeloid lineage.
The causative beta-hemolytic organism in Trevon's necrotizing infection evades host phagocytosis via its M protein. This virulence factor binds serum Factor H, which subsequently accelerates the destruction of this specific complement fragment, effectively stripping the bacteria of its primary opsonin.
What is C3b. Factor H accelerates the cleavage and destruction of C3b on its surface, preventing opsonization
The rapid, necrotic breakdown of leukocytes within a newly formed psoas abscess in a young patient is primarily driven by this specific pore-forming cytotoxin, a hallmark virulence factor of community-associated MRSA strains.
Panton-valentine leukocidin (PVL). Pore forming cytotoxin associated with CA-MRSA. Lyses neutrophils and macrophages leading to sever necrotic skin and soft issue abscesses
A patient with a positive Influenza A swab is prescribed oseltamivir. This medication exerts its antiviral effect by directly binding and inhibiting a viral surface enzyme required to cleave this specific host cell-surface residue, thereby trapping newly formed virions.
What is sialic acid -> influenza virions bind to sialic acid to enter, to leave viral neuroaminidase cleaves sialic acid to release. Oseltamivir inhibits this enzyme
As a fully immunized 6-year-old, Trevon recently received a pre-school booster vaccine containing a toxoid that prevents a disease characterized by a grayish pseudomembrane; this vaccine induces IgG antibodies that prevent the native toxin from ADP-ribosylating this specific cellular target.
What is elongation factor 2 (EF-2) -> Dtap vaccine contains the diphtheria toxin