Bacte lec Strep pyogenes Flashcards
Streptococcus and Enterococcus spp. are usually ___________________ and __________________ cocci
Catalase-negative, and gram-positive cocci
The streptococcal cells are more likely to appear in chains when grown in __________________
broth cultures.
Classifications of Streptococci (3)
Bergey’s Academic Classification
Brown and Smith Classification
Lancefield Classification
Most members of the genera Streptococcus and
Enterococcus behave like ________________________
facultative anaerobes.
Classification based on physiologic divisions of Streptococcus
Bergey’s Academic Classification
Bergey’s Academic Classification
Grows neither 45 deg C nor 10 degC but
grows at 11-44 deg C; ave. 37deg C
PYOGENIC
Examples of PYOGENIC Streptococci
Streptococcus pyogenes
Examples of LACTIC
S. cremoris; S. lactis (agent of souring of milk/rancid) (2)
Bergey’s Academic Classification
Grows at 45 deg C but not at 10 deg C
VIRIDIANS Streptococci
Examples of VIRIDIANS (4)
S. salivarius, S. mutans,S.
sanguis; S. anginosus, S.mutans
Bergey’s Academic Classification
Grows at both 45deg C and 10deg C
ENTEROCOCCI
Grows at 10deg C but not at 45deg C
LACTIC
Examples of ENTEROCOCCI
Streptococcus faecalis
Classification based on the presence of serologically active C- CHO polysaccharide
Lancefield’s Classification
Carbohydrate cell wall antigen composition of Group A and C in Lancefield Classification
rhamnose-N-acetylglucosamine
Carbohydrate cell wall antigen composition of Group B in Lancefield Classification
rhamnose-glucosamine polysaccharide
Carbohydrate cell wall antigen composition of Group D in Lancefield Classification
Glycerol teichoic acid containing alanine & glucose
Carbohydrate cell wall antigen composition of Group F in Lancefield Classification
glucopyrasonyl -N-acetylgalactosamine
Classification Based on hemolytic reaction of Streptococci on Blood Agar Plate
Smith and Brown Classification
Smith and Brown Classification
Partial hemolysis of RBC; accompanied by a greenish discoloration
ALPHA
Example for ALPHA hemolysis classification (2)
S. pneumoniae;
S. viridans
Smith and Brown Classification
Complete hemolysis of RBCs indicated by
a clear colorless zone of hemolysis
surrounding the colonies
BETA
Smith and Brown Classification
Non-hemolytic or indifferent
Streptococci. No hemolysis on RBCs
GAMMA
Example for GAMMA classification
S. faecalis
Example for BETA hemolysis classification (2)
S. Pyogenes
S. agalactiae
What Streptococcus spp. has a cell wall structure similar to that of other streptococci and gram-positive
bacteria.
S. pyogenes
Resist phagocytosis (resistance to infection) and plays a role in adherence of the bacterial cell to mucosal cells
M protein
VIRULENCE FACTORS OF Streptococcus pyogenes (7)
o M protein
o Lipoteichoic acid
o Fibronectin binding protein
o Hyaluronic acid capsule
o Streptolysin O
o Streptolysin S
o Streptococcal pyrogenic exotoxins
Most common
serotype seen in pharyngitis.
M1 serotype
More than ___ different serotypes of M protein
exist
80
Mediate attachment
to host epithelial cells.
Adhesion molecules
Affixed to proteins on
the bacterial surface, in concert with M proteins
Lipoteichoic acid
secures the attachment of streptococci to the oral mucosal cells.
Fibronectin binding protein
o Prevents opsonized phagocytosis by neutrophils or macrophages
o Allows the bacterium to mask
its antigens and remain unrecognized by its host.
Hyaluronic Acid Capsule
Responsible for hemolysis on SBA
plates incubated anaerobically
Streptolysin O
The O in Streptolysin O refers to this hemolysin being __________________
oxygen labile
___________________ is highly immunogenic and infected individuals readily form antibodies to the hemolysin
Streptolysin O
o Streptolysin O antibodies can be measured in the
_____________________
o Test to determine whether
an individual has had a recent infection with S. pyogenes.
antistreptolysin O (ASO) test
Is oxygen stable, lyses
leukocytes, and is nonimmunogenic.
Streptolysin S
The hemolysis seen around colonies that have
been incubated aerobically is due to _____________________
streptolysin S.
Some strains of S. pyogenes cause a red spreading
rash, referred to as _______________________
scarlet fever
The most common clinical
manifestations of GAS infection
Bacterial Pharyngitis
Most cases of bacterial
pharyngitis are due to _____________________
S. pyogenes.
is most often seen in children between 5 and 15 years of age
“Strep throat”
“Strep throat” incubation
1-4 days
o Most common cause of acute
pharyngitis
o Classic Strep throat with red swollen tonsils and pharynx
o A purulent exudate on the tonsils, high temperature, and swollen
lymph nodes
Streptococcus pyogenes
an invasive infection characterized by
rapidly progressing inflammation and necrosis of the skin,
subcutaneous fat, and fascia
Necrotizing Fasciitis
is a condition in which the entire organ system collapses, leading to
death.
Streptococcal Toxic Shock Syndrome
GAS associated with streptococcal TSS produce a streptococcal
pyrogenic exotoxin, notably _____________
SpeA.
Typically follows S. pyogenes pharyngitis. It is characterized by fever and inflammation of the heart, joints, blood vessels, and subcutaneous
tissues.
Rheumatic fever
Two serious
complications, or sequelae, of GAS disease are _____________________
(1) rheumatic fever and
(2) acute glomerulonephritis.
SPECIMEN COLLECTION – SITE CONSIDERATIONS of Streptococcus pyogenes
OROPHARYNGEAL SWAB
OROPHARYNGEAL SWAB remains moist, no further
precautions need to be taken for specimen that
are cultured within ___________of collection
4 hours
Cultural Characteristics:
colonies are transparent to translucent, convex or domed entire,
circular, shiny and surrounded by a wide zone of β-hemolysis.
Streptococcus pyogenes
Streptococcus pyogenes is highly resistant to desiccation and remains viable on a dry
swab for _________________
48 to 72 hours.
A presumptive test which differentiates
group A from other β-hemolytic Streptococci
Bacitracin (Taxo A)
Any zone of inhibition regardless of the diameter is a ______________ reaction for Streptococcus pyogenes
(+) Positive
Principle of Bacitracin (Taxo A)
based on the selective inhibition of the growth of
Group A streptococci by a paper disc containing 0.02 – 0.04 units of Bacitracin
Detect the organisms
ability to hydrolyze the substrate
L- pyrrolidonyl-beta-napthylamide
PYR test
PYR test BRIGHT RED END PRODUCT
(+) Positive for Streptococcus pyogenes
Test for susceptibility for scarlet fever
Dicks Test
Dicks test will be tested for reaction after ___
24 hours
Test to Diagnose Scarlet Fever
Schultz-Charlton Reaction (Blanching Phenomenon)
o Based on the neutralization of erythrogenic toxins when an antitoxin is injected into the skin of a patient with scarlet fever skin rashes fade or blanch (+)
o Schultz-Charlton Reaction (Blanching Phenomenon)
Schultz-Charlton Reaction (Blanching Phenomenon)
TREATMENT for Streptococcus pyogenes (3)
o Intramuscular benzathine penicillin as single dose
o Oral penicillin V for 10 days
o For penicillin-allergic patients – erythromycin, clindamycin and cephalexin
