Rx_01.20 (Microbio)

Question 1

Enfurtivide: MOA & use

Answer 1

• antiretroviral therapy
• MOA = entry inhibitor
  
  • blocking interaction between gp120 & host CD4 or by interfering w/viral gp41-mediated fusion

Question 2

Rocky mountain spotted fever presentation

Answer 2

• vacation/travel to South Atlantic states (NC, TN, etc)
• classic triad = H/A, fever, rash
  
  • rash = palms/soles/wrists ==> trunk

Question 3

Rocky Mountain spotted fever cause/spread/tx

Answer 3

• cause = Rickettsia rickettsii
• spread via ticks =
  
  • Dermacentor andersoni
  • D. variabilis
• tx = immediate antibiotic therapy
  
  • tetracycline (e.g. doxycycline)
  • chloramphenicol

Question 4

Causes of osteomyelitis in sickle cell patient

Answer 4

• S. aureus
• Salmonella

Question 5

Cholera toxin: MOA

Answer 5

• A1 subunit ==> active adenylate cyclase ==> increased cAMP ==> increased chloride ion secretion ==> secretory diarrhea

Question 6

Hepatitis E presentation + pathology

Answer 6

• Hepatitis E
  
  • fecal-oral
  • high infection rates @ sub-saharan Africa
  • high mortality in pregnant women
• Path ==> focal hepatocyte damage ==> patchy necrosis on biopsy

Question 7

Characteristics of C. albicans

Answer 7

• germ tube-positive fungus
• ==> white plaques (thrush) @ immunocompromised individuals (common in HIV)

Question 8

branching rods on culture from pt w/oral infection ==> ? + tx

Answer 8

• Actinomyces israelii
  
  • gram-positive
  • branching rods
  • anaerobic
  • part of normal oral flora
• Tx =
  
  • IV penicillin for 2-6 wks
  • oral penicillin or amoxicillin 6-12 months

Question 9

Bartonella henseleae causes….?

Answer 9

• cat-scratch fever
  
  • local, chronic lymphadenitis
  • commonly @ children
• bacillary angiomatosis
  
  • usually @ AIDS patients
  • ==> proliferation of blood and lymphatic vessels ==> “mulberry” lesion in skin

Question 10

Characteristics of Bartonella henselae

Answer 10

• small gram-negative
  
  • “proteobacterium”
• visualized w/Warthrin-Starry stain

Question 11

Rotavirus mechanism of infection

Answer 11

• enters host cell by endocytosis
• transcribes viral mRNA w/ a viral RNA polymerase present in virion

Question 12

Presentation of reactive arthritis/”Reiter’s syndrome” + cause

Answer 12

• urethritis, conjuctivitis, arthritis
  
  • “can’t pee, can’t see, can’t climb a tree”
• derm sx
  
  • most plaques on glans penis
  • crusting papules
• usually male, w/HLA-B27
• autoimmune rxn post-infection:
  
  • Chlamydia trachomatis, N. gonorrhoeae
  • Salmonella, Shigella, Yersinia, Campylobacter

Question 13

Characteristics of Legionella pneumophila pneumonia

Answer 13

• occurs @ older pts w/hx of alcoholism, smoking, DM, chronic illness, immunosuppression
• legionella =
  
  • gram-negative rod (coccobaciliary)
  • stains w/silver stain
  • cultures on charcoal yeast extract

Question 14

Protective factor for HIV infection

Answer 14

• homozygous for CCR5 mutation
  
  • CCR5 = chemokine receptor on macrophages that facilitates viral entry
• CCR5 mutation ==> immunity to certain strains of HIV
• present in primarily caucasian individuals

Question 15

Common cause of croup + virus type

Answer 15

• cause = paramyxoviridae family (parainfluenza virus)
• viral characteristics
  
  • envelope + helical capsid
  • RNA virus
    
    • single-stranded
    • negative-sense
    • linear, nonsegment

Question 16

filamentous, gram-positive organism that is weakly acid-fast =

Answer 16

Nocardia asteroides

Question 17

Characteristics/tx of Nocardia asteroides

Answer 17

• filamentous, gram-positive
• weakly acid-fast
• ==> lung abscesses @ immunocompromised patients
• Tx =
  
  • sulfonamides (MOA: inhibition of dihyropteroate synthetase)

Question 18

Yellow fever characteristics

Answer 18

• flavivurs
  
  • SS, RNA virus
  • mosquito vector
• sx = H/A, photophobia, MSK pain, jaundice
• labs/biopsy
  
  • AST > ALT
  • councilman bodies = eosinophilic degeneration + condensed nuclear chromatin

Question 19

Mechanism of staph scalded skin syndrome

Answer 19

• staph releases (epidermolytic) exotoxins A and B
• exotoxins bind desmoglein 1 @ desmosome ==> epidermal separation @ stratum granulosum
• ==> blistering