Lab 30: Throat Culture/Respiratory Tract Flashcards
(33 cards)
what are two examples of respiratory tract pathogens?
- Streptococcus pneumoniae
- Streptococcus pyogenes
what is the presence of Streptococcus pneumoniae bacteria?
Gram-positive cocci in chains
what is the rate of asymptomatic carriers of Streptococcus pneumoniae?
high rate
what can Streptococcus pneumoniae cause?
It can cause infections of the middle ear and sinuses in children.
It can cause pneumonia, meningitis, and bacteremia.
what is the presence of Streptococcus pyogenes bacteria?
Gram-positive cocci in chains
what is the amount of asymptomatic carriers of Streptococcus pyogenes?
asymptomatic carriers are 1 in 10 people
what can Streptococcus pyogenes cause?
It can cause:
-Strep throat (if untreated, can cause rheumatic fever)
-Skin infections: impetigo, cellulitis
-Necrotizing fasciitis: infection of connective tissue covering muscles
what is the growth of respiratory pathogens bacteria?
Fastidious bacteria: it requires special nutrients to grow. it is hard to grow, and doesn’t ‘t grow on nutrient agar or TSA
what agar do respiratory pathogens need to grow on?
The medium is Sheep’s Blood Agar (which is an agar with sheep’s blood in it)
what does the blood from the agar provide and allow for respiratory pathogens?
-The blood provides extra nutrients
-It also allows identification: some microbes can destroy RBCs using a process called hemolysis to give specific patterns that can be used to ID unknowns
what is hemolysis?
when microbes destroy RBCs to give specific patterns that can be used to ID unknowns
what are three types of hemolysis?
Alpha hemolysis
Beta hemolysis
Gamma hemoylsis
what is Alpha hemolysis? what is it caused by and what does it cause?
It is a partial hemolysis of RBCs.
It is caused by the production of H2O2.
It causes leakage of hemoglobin from cells and its oxidation to methemoglobin, which is green in color.
what do the leakage of hemoglobin from cells and its oxidation to methemoglobin in alpha hemolysis cause?
green color
what is beta hemolysis? what is it caused by and what does it create?
It is complete hemolysis of RBCs.
It is caused by exotoxins called hemolysins.
It creates a complete clearing (a halo) of RBCs around the colonies.
what is Gamma hemolysis?
no hemolysis of RBCs
what type of hemolysis does Streptococcus pyogenes perform?
Beta hemolysis
what type of hemolysis does Streptococcus pneumoniae perform?
Alpha (usually) or
non-hemolytic (rarely)
is Streptococcus pyogenes sensitive or resistant to Bacitracin?
It is sensitive (any size zone of inhibition)
is Streptococcus pneumoniae sensitive or resistant to Bacitracin?
Resistant (no zone of inhibition)
is Streptococcus pyogenes sensitive or resistant to Optochin?
It is resistant (less than or equal to 14 mm zone of inhibition)
is Streptococcus pneomoniae sensitive or resistant to Optochin?
Sensitive (greater than 14 mm zone of inhibition)
what group is Streptococcus pyogenes caused by?
GAS (Group A streptococci)
who classified Streptococcus spp. based of the presence of different ______.
Rebecca Lancefield classified Streptococcus spp. based on the presence of different cell wall carbohydrate antigens (20 serotypes)
