Micro

Question 1

Legionella pneumophila

Answer 1

Gram- rod, stains poorly –> use silver stain.
Charcoal yeast extract medium with iron and cysteine.
Detect via antigen in urine.
Hyponatremia.
Aerosol transmission from environmental water source.
No person-to-person transmission.
Treat: macrolide and quinolone.
Legionnaires’ disease: severe pneumonia (unilateral, lobar), fever, GI and CNS symptoms. Common in smokers and in chronic lung disease.
Pontiac fever: mild flu-like syndrome.

Question 2

Pseudomonas aeruginosa

Answer 2

Aerobic, motile, gram- rod.
Non-lactose fermenting.
Oxidase+
Produces pyocyanin (blue-green pigment) and grape-like odor.
Produces endotoxin (fever, shock), exotoxin A (inactivates EF-2), phospholipase C (degrades cell membranes), and pyocyanin (generates reactive oxygen species).
PSEUDOMONAS: Pneumonia and pyocyanin, Sepsis, Ecthyma gangrenosum, UTIs, Diabetes and drug use, Osteomyelitis, Mucoid polysaccharide capsule, Otitis external (swimmer’s ear), Nosocomial infections (catheters, esp), exotoxin A, Skin infections (hot tub folliculitis).
Treat with CAMPFIRE: Carbapenems, Aminoglycosides, Monobactams, Polymyxins, Fluoroquinolones, thIRd and fourth generation cephalosporins, Extended spectrum penicillins (piper- and ticar- cillin)
Mucoid polysaccharide capsule may contribute to chronic pneumonia in CF patients due to biofilm formation.
Wound infection in burn victims.
Frequently in water –> hot tub folliculitis.
Ecthyma gangrenosum: rapidly progressive necrotic cutaneous lesion typically in immunocompromised.

Question 3

Mycoses

Answer 3

Histoplasmosis, blastomycosis, coccidioidomycosis, paracoccidioidomycosis
Can cause pneumonia and can disseminate.
Caused by dimorphic fungi: cold (20C)= mold, heat (37C) = yeast (except coccidioidomycosis - spherule in tissue, not yeast).
Treat: fluconazole or itraconazole for local infection, amphotericin B for systemic infection.
Can form granulomas (like TB), but can’t be transmitted person-to-person (unlike TB).

Question 4

Histoplasmosis

Answer 4

Mississippi and Ohio River Valleys
Macrophage filled with Histoplasma (smaller than RBCs)
(Histo Hides in macrophages).
Bird or bat droppings

Question 5

Blastomycosis

Answer 5

Eastern US and Central America
Causes inflammatory lung disease and can disseminate to skin and bone.
Forms granulomatous nodules.
Broad-based budding (same size as RBCs).

Question 6

Coccidioidomycosis

Answer 6

SW US, CA
Causes pneumonia and meningitis.
Can disseminate to skin and bone.
Case rate ^ after earthquakes (spores in dust thrown into air and inhaled --> spherules in lung).
Spherule (much larger than RBC) filled with endospores.
San Joaquin Valley Fever
Desert bumps = erythema nodosum
Desert rheumatism = arthralgias

Question 7

Paracoccidioidomycosis

Answer 7

Latin America

Budding yeast with “captain’s wheel” formation (much larger than RBC)

Question 8

Rhinovirus

Answer 8

\+ssRNA
Icosahedral capsid
Non-enveloped
Replication in cytoplasm
Cold
Diagnose based on symptoms

Question 9

RSV (Respiratory Syncytial Virus)

Answer 9

Paramyxovirus
-ssRNA
Helical capsid
Enveloped
Replication in cytoplasm
URT, croup, bronchitis
Diagnose: symptoms, antigen detection by ELISA or IFA, virus culture, RT-PCR

Question 10

Adenovirus

Answer 10

dsDNA
Icosahedral capsid
Non-enveloped
Replication in nucleus
Pharyngitis, conjunctivitis, ARD, pneumonia
Diagnosis: symptoms, antigen detection by ELISA or IFA, CFT, virus culture, PCR

Question 11

Epstein-Barr Virus (EBV)

Answer 11

dsDNA
Icosahedral capsid
Enveloped
Replication in nucleus
Infectious mono, exudative pharyngitis, cervical lymphadenopathy
Diagnosis: symptoms, heterophile antibody, atypical lymphocytes. EBV antibody ELISA, PCR