Bacte lec Strep pyogenes Flashcards by ANTOINE GABRIELE Z. JUMAGBAS

Streptococcus and Enterococcus spp. are usually ___________________ and __________________ cocci

Catalase-negative, and gram-positive cocci

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The streptococcal cells are more likely to appear in chains when grown in __________________

broth cultures.

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Classifications of Streptococci (3)

Bergey’s Academic Classification

Brown and Smith Classification

Lancefield Classification

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Most members of the genera Streptococcus and
Enterococcus behave like ________________________

facultative anaerobes.

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Classification based on physiologic divisions of Streptococcus

Bergey’s Academic Classification

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Bergey’s Academic Classification

Grows neither 45 deg C nor 10 degC but
grows at 11-44 deg C; ave. 37deg C

PYOGENIC

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Examples of PYOGENIC Streptococci

Streptococcus pyogenes

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Examples of LACTIC

S. cremoris; S. lactis (agent of souring of milk/rancid) (2)

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Bergey’s Academic Classification

Grows at 45 deg C but not at 10 deg C

VIRIDIANS Streptococci

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Examples of VIRIDIANS (4)

S. salivarius, S. mutans,S.
sanguis; S. anginosus, S.mutans

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Bergey’s Academic Classification

Grows at both 45deg C and 10deg C

ENTEROCOCCI

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Grows at 10deg C but not at 45deg C

LACTIC

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Examples of ENTEROCOCCI

Streptococcus faecalis

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Classification based on the presence of serologically active C- CHO polysaccharide

Lancefield’s Classification

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Carbohydrate cell wall antigen composition of Group A and C in Lancefield Classification

rhamnose-N-acetylglucosamine

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Carbohydrate cell wall antigen composition of Group B in Lancefield Classification

rhamnose-glucosamine polysaccharide

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Carbohydrate cell wall antigen composition of Group D in Lancefield Classification

Glycerol teichoic acid containing alanine & glucose

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Carbohydrate cell wall antigen composition of Group F in Lancefield Classification

glucopyrasonyl -N-acetylgalactosamine

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Classification Based on hemolytic reaction of Streptococci on Blood Agar Plate

Smith and Brown Classification

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Smith and Brown Classification

Partial hemolysis of RBC; accompanied by a greenish discoloration

ALPHA

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Example for ALPHA hemolysis classification (2)

S. pneumoniae;
S. viridans

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Smith and Brown Classification

Complete hemolysis of RBCs indicated by
a clear colorless zone of hemolysis
surrounding the colonies

BETA

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Smith and Brown Classification

Non-hemolytic or indifferent
Streptococci. No hemolysis on RBCs

GAMMA

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Example for GAMMA classification

S. faecalis

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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

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