Viral Villains
This virus with icosahedral symmetry causes "slapped cheek" rash in children but can cause severe complications in pregnant women.
What is Parvovirus B19?
This dimorphic fungus exists as a yeast at 37°C and as a mold at 25°C, a characteristic that aids in its laboratory identification.
What is Blastomyces, Histoplasma, Coccidiodes, or Sporothrix?
The eggs of this helminth have a characteristic terminal spine and the adult worms reside in the venous plexus surrounding the bladder, causing hematuria.
What is Schistosoma haematobium?
This "atypical" bacterial pathogen lacks a cell wall and causes walking pneumonia with a characteristic bullseye pattern on colony growth.
What is Mycoplasma pneumoniae?
This immune evasion strategy used by Trypanosoma brucei involves sequential expression of different variant surface glycoproteins encoded by approximately 1000 VSG genes, allowing escape from antibody recognition.
What is antigenic variation?
Characterized by painful vesicles in a dermatomal distribution, this viral reactivation is treated with acyclovir, valacyclovir, or famciclovir.
What is Herpes zoster (shingles)?
This antifungal medication works by binding to ergosterol and forming pores in the fungal cell membrane, but has significant nephrotoxicity.
What is Amphotericin B?
This intestinal protozoan causes right upper quadrant pain and flask-shaped ulcers in the colon.
What is Entamoeba histolytica?
This Gram-negative coccobacillus is a common cause of exacerbations in COPD patients and requires factors V (NAD) and X (hemin) for growth on chocolate agar.
What is Haemophilus influenzae?
These immune cells are critical for defense against intracellular bacteria like Mycobacterium tuberculosis through activation of macrophages via IFN-gamma production.
What are CD4+ Th1 cells?
A 25-year-old man presents with pharyngitis, fatigue, and cervical lymphadenopathy. Laboratory findings show atypical lymphocytosis and positive heterophile antibody test. The virus responsible inhibits apoptosis through its EBER RNA and LMP-1 protein.
What is Epstein-Barr virus (EBV)?
A 65-year-old diabetic patient presents with facial pain, proptosis, and black eschar on the palate. Biopsy shows non-septate hyphae with right-angle branching.
What is Mucor or Rhizopus?
Schistosoma mansoni causes hepatosplenomegaly and portal hypertension due to granulomatous reaction to its eggs, which have this distinctive morphological feature.
What is a lateral spine?
Pneumonia caused by this organism presents with rust-colored sputum and lobar consolidation. Its virulence factors include a polysaccharide capsule and pneumolysin.
What is Streptococcus pneumoniae?
A virulence mechanism used by Staphylococcus aureus involves production of this factor that cross-links MHC II and TCR Vβ regions, leading to massive cytokine release.
What is superantigen?
A 30-year-old woman presents with painful genital ulcers. Tzanck smear shows multinucleated giant cells. The virus establishes latency in dorsal root ganglia by expressing LAT (latency-associated transcript).
What is Herpes simplex virus type 2 (HSV-2)?
Pneumocystis pneumonia prophylaxis is indicated when CD4 counts drop below this threshold in HIV patients.
What is 200 cells/mm³?
A traveler returns from sub-Saharan Africa with cyclical fevers, chills, and hemolysis. The causative parasite evades immunity through antigenic variation of its PfEMP1 surface protein.
What is Plasmodium falciparum?
A dairy farmer develops pneumonia with rounded opacities on chest X-ray. The causative organism is acquired through inhalation of aerosolized spores and forms spherules in tissue.
What is Coccidioides immitis/posadasii?
This pattern recognition receptor recognizes viral dsRNA in endosomes and induces type I interferon production.
What is TLR3 (Toll-like receptor 3)?
A liver transplant recipient develops cholestatic hepatitis with inclusion bodies in biliary epithelium. The causative virus uses glycoprotein B (gB) to enter cells and produces pp65 antigen that can be detected in blood leukocytes.
What is Cytomegalovirus (CMV)?
A patient on chronic steroids develops a brain abscess with ring enhancement on MRI. CSF analysis reveals capsular yeast cells with a wide gelatinous capsule on India ink stain. The virulence factor that allows this organism to evade phagocytosis is its polysaccharide capsule composed of glucuronoxylomannan.
What is Cryptococcus neoformans?
This vector-borne protozoan causes Chagas disease and evades the immune system by expressing different variants of surface glycoproteins (VSGs). Its amastigote form replicates intracellularly and forms characteristic pseudocysts in cardiac muscle.
What is Trypanosoma cruzi?
A cystic fibrosis patient colonized with a mucoid strain of this bacterium develops pneumonia. The alginate production by this organism is regulated by the mucA gene and contributes to biofilm formation and antibiotic resistance.
What is Pseudomonas aeruginosa?
A patient with recurrent viral infections shows impaired interferon production. Genetic analysis reveals a mutation affecting this signaling pathway that normally activates transcription of interferon-stimulated genes through phosphorylation of STAT1 and STAT2.
What is JAK-STAT pathway?