Strep Manual Flashcards
Certain streptococci will destroy the red blood cells in the medium completely and form a clear zone around the colonies.
These are beta-hernolytic streptococci, as typified by pathogenic_______
S. pyogenes.
Other streptococci cause incomplete destruction of the blood cells, and their colonies are surrounded by an olive green or brown discoloration of the medium. These are alpha-hernolytic streptococci. They include____ and _____, the agent of bacterial lobar pneumonia.
S. mitis and S. pneumoniae
A final group, the non-hemolytic streptococci, cause no hemolysis of red blood cells.______, the organism in yogurt, is a member of the group.
S. lactis
In addition to hemolysis, S. pyogenes can be distinguished from viridians streptococci by means of the______ sensitivity test.
In this test, a filter paper disk impregnated with______ is applied to the surface of a blood agar plate that has been previously streaked with the bacteria to be identified.
The appearance of a zone of inhibition surrounding the disk is a positive test for______. An absence of a zone of inhibition suggests non-Group A bacteria.
bacitracin
0.04 units of bacitracin
Group A streptococci
______is also resistant to SXT disks, which contain a mixture of 1.25 urn____ and 27.75 ug of______.
______are inhibited by these agents.
S. pyogenes
trimethoprim
sulfamethoxazole
Viridians streptococci
Group B streptococci can be distinguished from other beta-hemolytic streptococci by their production of a substance called the_______
CAMP factor.
CAMP is an acronym for the names of the investigators (________) who first described the factor.
This factor is a peptide that acts together with the beta-hemolysin produced by some strains of S. aureus, enhancing the effect of the latter on a sheep blood agar plate.
Christie, Atkins, and Munch-Petersen
Group D streptococci and enterococci can be differentiated from other streptococci by using________.
bile esculin agar slants
Group D streptococci grow readily on the bile esculin agar and hydrolyze the esculin imparting a_______ to the medium.
This reaction denotes their bile tolerance, ability to hydrolyze esculin, and constitutes a positive reaction.
Gram-positive bacteria (other than group D streptococci anc enterococci) are inhibited by the bile salts.
dark brown color
If a beta-hemolytic species of Streptococcus has been isolated, evidence for its grouping may be obtained by performing a_______.
______test for alpha-hemolytic colonies.
For gamma-hemolytic streptococci, perform______.
bacitracin disk sensitivity test
Perform Optochin
esculin hydrolysis test
Aseptically apply a disk containing 0.04 units of bacitracin to a heavily streaked area, and incubate the plate as above.
The presence of a clear ring around the disk indicates that the streptococci have been killed by the antibiotic and that they are probably______ known as_____. The absence of a ring provides evidence that they belong to another group
Group A beta-hemolytic streptococci
Streptococcus pyogenes
is performed to presumptively identify group B streptococci. Lancefield serological typing test is performed to confirm identification.
CAMP test
Optochin (Taxo P) Test
Positive: Zone of inhibition is______ in diameter, with 6-mm disk.
Negative:_____
Equivocal: Any zone of inhibition_____ is questionable for pneumococci; the strain is identified as a pneumococcus only if it is bile-soluble.
14 mm or greater
No zone of inhibition
less than 14 mm
Bile Esculin Agar
Inoculate one to two colonies from an 18-24-hour culture onto the surface of the slant.
Incubate at 35C in ambient air for 48 hours.
Positive:______
Negative:_____
Perform Lancefield serological typing test to confirm identification.
blackening of the agar slant
no blackening of medium
