The lower respiratory system is usually sterile because of the efficient functioning of the _____ ________.
The upper respiratory tract is in contact with ___________ - air _________________.
The ______ is moist, warm environment allowing many ________ to establish residence.
Species of many different genera can be found residing in the throat: name them
Despite the presence of potentially pathogenic bacteria in the URS the rate of infection is minimized by ______________.
What is microbial antagonism?
_________ are predominant organisms in the throat cultures and some species are the major cause of bacterial sore throat (acute pharyngitis).
Streptococcal species are identified by _______
characteristics including ________, and __________
Hemolytic reactions are based on ___________ that are produced by streptococci while growing on blood- enriched agar.
Blood agar is usually made from ________.
1. Alphahemolysis- Green, cloudy zone around the colony. Partial destruction of the RBCs is due to bacteria-produced by hydrogen peroxide.
2. Beta-hemolysis: complete hemolysis, giving a clear zone with a clean edge around the colony
3. Gamma-hemolysis: No hemolysis and no change in the blood agar around the colony.
_____ and _____ streptococci are usually _________.
S. pneumoniae is a causative agent of pneumonia and cannot be differentiated from other alpha-hemolytic streptococci on blood agar. How do they identify it?
With optochin inhibition a zone of inhibition = to or > than ______ or larger indicated optochin sensitivity.
Bile solubility is also used to distinguish S. pneumoniae from other hemolytic streptococci. The addition of bile salts activates an enzyme that destroys _________ and the cells ______- colonies will disappear after the addition of bile salts. The other alpha-hemolytic streptococci do not have this enzyme.
The streptococci can be antigenically classified into Lancefield's groups A through O by ________ in their cell walls.
Over 90% of streptococcal infections are caused by _________ group ______ ______.
S. pyogenes is sensitive to the antibiotic _______; other streptococci are resistant to _______.
Procedure for throat culture:
Procedure for streptococcus:
-inoculate each 1/2 of blood red agar plate one side with S. pyogenes and other with S. pneumoniae
-dip forceps in alcohol and burn off the alcohol
-using the forceps place and press a bacitracin disk and an optochin disk on each 1/2
-space the disks so that the zones of inhibition may be observed
-incubate plates at 35*C for 24 hours
Second phases are gram stains of each
suspension of each into nutrient broth
add a few drops of bile salts
observe the tubes after 15 mins for lysis of the cells.
Is blood agar selective or differential?
Blood agar is considered differential because it is used to distinguish pathogenic bacteria based on the effect of bacterial enzymes known as hemolysins which lyse red blood cells. Blood agar is mainly used clinically to detect the presence of Streptococcus pyogenes, the human pathogen which causes "strep throat".
Is the Gram stain of significant importance in identifying the organisms studied in this exercise?