STREPTOCOCCUS Flashcards
Inhabit various sites, notably the upper respiratory
tract, and live harmlessly as commensals.
Streptococcus and Enterococcus
More pronounced growth on media enriched with
blood or serum
Streptococcus
This classification scheme was developed in
the 1930s
Rebecca Lancefield.
Produces a zone of partial hemolysis with a greenish
discoloration around the colonies on blood agar
● Streptococci producing α-hemolysis are also known as
Alpha-hemolytic (α) Streptococci
Produces a complete hemolysis
- Sharply defined, clear, colorless zone of
hemolysis around the colony induced by
bacterial hemolysins
- No red blood cell is visible on microscopic
examination in the clear zone of complete
hemolysis.
ß-hemolysis
constitutes the principal marker for
potentially pathogenic streptococci in cultures of throat
swabs or other clinical samples.
ß-hemolysis
● Produce no hemolysis on blood agar
Gamma (γ) or Non-hemolytic Streptococci
is an important organism of Gamma (γ) or Non-hemolytic Streptococci
Enterococcus faecalis
beta h members
S. equisimilis
S. pyogenes
S. agalactiae
E. faealis
based on the serological
properties of the streptococci
A, B, C, D, and G Lancefield Grouping
Organisms in possess the same
antigenic C-carbohydrate organisms.
Group A
group a
pyogenes
group b
agalactiae
group c
s.equisimilis, ewqui, dysogalactiae, zoopidimidus
group d
enteroccoci, non entero
group does not grow
under 10°C but grows best at 37°C.
Pyogenic and viridans
group grows at all temperatures
Entero
group grows best at 10°C and 37°C,
but does not grow at 45°C
Lactic
All of the grows best at optimum
temperature of 37°C
streptococci
part of cell wall ps strep; antiphagocytic
m protein
(oxygen labile)
- highly immunogenic; measured using ASO
(antistreptolysin O) test
Streptolysin O
(oxygen stable)
- nonimmunogenic
Streptolysin S
M-protein is genes of what strep specie
s.pyogenes
formerly
called erythrogenic toxin; causes Scarlet Fever
Streptococcal pyrogenic exotoxin
Streptococcal pyrogenic exotoxin
Nephrogenic toxin
camp factor produced by; heat stable protein;
enhances the beta-hemolysis of staph. aureus
S. agalactiae
small, transparent and smooth;
beta-hemolytic; when grows in sheep’s blood agar
S. pyogenes
grayish white mucoid colonies;
beta-hemolytic (small zone)
S. agalactiae
The __test is a particularly important test used
to determine whether the gram positive cocci is a
staphylococci or a streptococci.
catalase
Differentiates Group A Streptococci from other
Streptococci
Bacitracin Susceptibility Test (Taxo A)
Positive: arrowhead hemolysis [Group B Strep] or
bowtie appearance [S. agalactiae]
camp test
Positive: Cherry Red/Pink
● Test for Group A and Group D Streptococci
test is useful in the identification of
group A, beta hemolytic streptococci and the
streptococcus pyogenes.
PYR hydrolysis
● Test for Group B Streptococci
● Medium: Broth with hippurate
● Positive: Purple (S. agalactiae)
Hippurate Test
indicator of hippurate
glycine is oxidated by this which turns the broth purple
ninhydrin
● Positive: blackening of medium [Group D]
● Differentiate Group D from Beta-hemolytic
is widely used for the
differentiation of enterococci and group B streptococci
which are bile tolerant and can hydrolyze esculin to
esculetin with the help of the enzymes esculinase from
non-group D viridans groups streptococci which grow
poorly on bile
Bile Esculin Tes
● Further test from Bile Esculin Test
● To identify Enterococci
● Positive: Turbid [Enterococci]
● Negative: Clear/Transparent [Non-enterococci]
Salt Tolerance Test (6.5% NaCl)
● Reagent: paradimethylaminocinnamaldehyde reagent
● Positive color: Red color
this test identify which group
● Positive: Viridans Streptococci
based from the previous question, which test is conducted
Leucine Aminopeptidase Test
SXT or sulfamethoxazole this susceptibility test in
conjunction with bacitracin is used for the presumptive
identification of beta hemolytic streptococci on blood
agar. The resistance of sulfamethoxazole is used for the
primary recovery of group ________streptococci from
specimens with mixed culture
A and B
BACTERIAL PHARYNGITIS
● “Strep throat” The most common clinical manifestations of
streptococcus _ are pharyngitis and
tonsillitis.
pyogenes
a localized skin disease, begins as small
vesicles that progress to weeping lesions;
inoculation of organisms through minor
abrasions or insect bites
impetigo
- followed by deeper invasion of streptococci;
life-threatening; with bacteremia or sepsis
Patients with peripheral vascular disease or
diabetes – leads to gangrene
cellulitis
s a rare infection of the skin and
subcutaneous tissues observed frequently in
elderly patients
Erysipelas
- cause by streptococcal pyrogenic exotoxin
- Diffuse red rash on upper chest and spreads
to the trunk and extremities - Infection with strains of streptococcus
pyogenes that produce streptococcal
pyrogenic exotoxins can result in
scarlet fever
“Flesh-eating disease or syndrome”, “Suppurative
fasciitis”, “Hospital gangrene”, “Necrotizing erysipelas”
● An invasive infection characterized by rapidly
progressing inflammation and necrosis of the skin,
subcutaneous fat, and fascia
NECROTIZING FASCIITIS
A condition in which the entire organ system
collapses, leading to death
Caused by a type of streptococcal pyrogenic
exotoxin – SpeA
STREPTOCOCCAL TOXIC SHOCK SYNDROME
● GAS are susceptible to (drug of choice for
treatment)
penicillin
If allergic to penicillin -
erythromycin will do
● Todd-Hewith Broth
● Significant cause of invasive disease in newborn
● Todd-Hewith Broth
● Significant cause of invasive disease in newborn
Ends of the cells are slightly pointed (oval or
lancet shape)
BHIA, TSA with 5% sheep RBCs or Chocolate
Agar are necessary for good growth
- SBA – large zone of alpha-hemolysis
S. pneumoniae
