Micro2 Flashcards
The ixodes tick is implicated in the transmission of which bacteria?
Anaplasma phagocytophila
Borrelia burgdorferi
Babesia microti
Patient presents with fever, chills, fatigue \+ outdoor hiking trip \+ small rings in RBCs on PBS
What is the diagnosis?
Babesia microti
What are the clinical manifestations of infectious mononucleosis?
- -fever
- -malaise
- -tender lymphadenopathy
- -splenomegaly
also:
- -headache
- -sorethroat
- -pharyngitis
- -tonsillitis
How is a diagnosis of infectious mononucleosis made?
with the heterophile antibody test (monospot)
What is the cause of heterophile-positive mononucleosis?
Epstein-Barr Virus (EBV)
An 18 yo man comes to the physician because of a 2-week history of fever, chills, and sore throat. Physical examination show marked pharyngeal hyperemia, tonsillar exudates, tender cervical lymphadenopathy, and splenomegaly. Treatment with amoxicillin is begun. Two weeks later, he returns to the physician because of a generalized maculopapular rash. What is the most likely diagnosis?
Infectious mononucleosis
An 18 yo man comes to the physician because of a 2-week history of fever, chills, and sore throat. Physical examination show marked pharyngeal hyperemia, tonsillar exudates, tender cervical lymphadenopathy, and splenomegaly. Treatment with amoxicillin is begun. Two weeks later, he returns to the physician because of a generalized maculopapular rash. What is the cause of the rash?
Amoxicillin can lead to a maculopapular rash.
An 18 yo man comes to the physician because of a 2-week history of fever, chills, and sore throat. Physical examination show marked pharyngeal hyperemia, tonsillar exudates, tender cervical lymphadenopathy, and splenomegaly. Treatment with amoxicillin is begun. Two weeks later, he returns to the physician because of a generalized maculopapular rash. Why would a physician advise this patient to restrict physical activity for a year?
This patient’s splenomegaly puts him at increased risk for splenic rupture with physical contact.
Even the abdominal exam should be done with care.
An 18 yo man comes to the physician because of a 2-week history of fever, chills, and sore throat. Physical examination show marked pharyngeal hyperemia, tonsillar exudates, tender cervical lymphadenopathy, and splenomegaly. Treatment with amoxicillin is begun. Two weeks later, he returns to the physician because of a generalized maculopapular rash. Which of these symptoms is consistent with streptococcal pharyngitis?
- -fever
- -sore throat
- -tonsillar exudates
- -tender cervical lymphadenopathy
- -pharyngeal hyperemia (pharyngitis)
An 18 yo man comes to the physician because of a 2-week history of fever, chills, and sore throat. Physical examination show marked pharyngeal hyperemia, tonsillar exudates, tender cervical lymphadenopathy, and splenomegaly. Treatment with amoxicillin is begun. Two weeks later, he returns to the physician because of a generalized maculopapular rash. How can we tell that this is infectious mononucleosis, and not a streptococcal pharyngitis?
Splenomegaly is observed in infectious mononucleosis, but not in streptococcal pharyngitis.
What test is used to diagnose streptococcal pharyngitis?
A rapid antigen test.
What are important points (symptoms) that point to a bacterial cause for pharyngitis?
- -patient under 15 years of age
- -history of fever
- -tonsillar exudates
- -tender anterior cervical lymphadenopathy
- -absence of cough
What is auramine-rhodamine stain used for?
To visualize acid-fast bacilli (using fluorescence microscopy)
What do acid-fast organisms display with auramine-rhodamine stain?
Acid-fast organism display a reddish-yellow fluorescence
What makes mycobacterium tuberculosis resistant to gram-stain agents?
The high lipid content of its cellular envelope, which contains long-chain fatty acids called mycolic acids
What makes mycobacterium tuberculosis resistant to changes in temperature and pH?
The high lipid content of its cellular envelope, which contains the long-chain fatty acids called mycolic acid
What does a polymer of N-acetyl glucosamine and N-acetyl muramic acid refer to/describe?
This describes the peptidoglycan cell wall
What gives bacteria their gram-staining characteristics?
The peptidoglycan cell wall.
What is the clinical significance of the tuberculin protein?
This is the surface protein of mycobacterium TB, which is used to elicit a type IV hypersensitivity skin test to diagnose exposure to the disease
Why/how can mycobacterium TB survive inside macrophages?
The bacteria inhibit the fusion of the phagosome and the lysosome.
What is the infecting agent in TB, and how is it spread?
mycobacterium tuberculosis
due to inhalation of aerosolized bacteria
What are the symptoms of primary TB?
Primary TB is generally asymptomatic, but it does lead to a positive PPD test
What are the gross/histological manifestations of primary TB?
Focal, caseating necrosis (granulomas) in the lower lobe of the lung and hilar lymph nodes; formation of a Ghon complex
With what disease is a Ghon complex associated?
TB
Where are Ghon complexes classically located?
They are classically sub-pleural
What is the Ziehl-Neelsen stain?
This is the acid-fast stain used to identify acid-fast organisms, in particular mycobacterium tuberculosis
How do acid-fast organism appear after Ziehl-Neelsen staining?
Bright red
What is the most common opportunistic infection among HIV-positive individuals?
TB
What is the most common cause of death among HIV-positive individuals?
TB
What is the classic clinical presentation + labs of a TB infection?
(1) cough with bloody sputum
(2) night sweats
(3) fever
(4) weight loss
(5) acid-fast bacilli seen on Ziehl-Neelsen stain
(6) caseating granulomas
Why are AIDS patients at increased risk for TB infection/progression?
The response to TB is cell-mediated. However, HIV+ patients have a decreased CD4+ cell count, leading to defective cell-mediated immunity
Why might HIV-positive patients have impaired ability to form granulomas in response to a TB infection?
Because HIV positive patients have a depressed CD4+ count, and therefore impaired cell-mediated immunity. It is the T helper cell (CD4+) that mediates granuloma formation by inducing macrophages to become epitheliois histiocytes via INF-gamma signalling.
What is the most common cause of typical pneumonia in the US?
streptococcus pneumoniae
What is the number one cause of neonatal meningitis and septicemia in the US?
Streptococcus agalactiae
