B2.2 GROUP A STREPTOCOCCI Flashcards by 횐호 강

GROUP A STREPTOCOCCI SPP

Streptococcus pyogenes

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How is Group A Streptococcus acquired?

Through contaminated droplets from coughing and sneezing

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Where does Streptococcus pyogenes colonize in humans?

Throat and skin

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S. pyogenes is resistant to drying that is why this method is used for acquiring specimen

can be recovered from swabs several hours after the collection

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VIRULENCE FACTORS of S. pyogenes

1.M PROTEIN
2. PROTEIN F
3. LIPOTEICHOIC ACID
4. HYALURONIC ACID CAPSULE
5. STREPTOKINASE
6. HEMOLYSINS
7. DEOXYRIBONUCLEASE (DNASE)
8. HYALURONIDASE
9. C5a PEPTIDASE
10. Streptococcal Pyrogenic Exotoxins (SPEs)

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What major virulence factor of Streptococcus pyogenes resists phagocytosis and adherence of the bacterial cell to mucosal cells

M protein

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M protein is found in what part of S. pyogens

attached to peptidoglycan of cell wall and extends to cell surface

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What are the post-streptococcal diseases and what M protein mediates them

Rheumatic fever - class 1 M
Acute glomerulonephritis - class I or II

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regulatory protein involved in the degradation of C3b

beta globulin factor H

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M protein binds to what proteins in S. pyogenes

beta globulin factor H
fibrinogen

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What serotype of M protein is most common in pharyngitis?

M1 serotype

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Which post-streptococcal diseases are mediated by M protein?

Rheumatic fever (Class I M) and Acute glomerulonephritis (Class I or II)

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What is the function of Protein F in Streptococcus pyogenes?

Mediates epithelial cell attachment

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PROTEIN F is also known as

FIBRONECTIN-BINDING PROTEIN

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What molecule in Streptococcus pyogenes is responsible for adherence to respiratory epithelial cells?

Lipoteichoic acid

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Prevents opsonized phagocytosis and masks bacterial antigens

weakly immunogenic

hyaluronic acid capsule in Streptococcus pyogenes

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Lysis of fibrin clots to spread infection

binds plasminogen and activates the production of plasmin

allows bacteria to move from clotted area (spread infecion)

streptokinase

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What is the clinical application of streptokinase?

Treatment of pulmonary emboli, coronary artery, and venous thromboses

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HEMOLYSINS types

STREPTOLYSIN O (SLO)
STREPTOLYSIN S (SLS)

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Which hemolysin of Streptococcus pyogenes is oxygen labile?

Streptolysin O (SLO)

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Which hemolysin of Streptococcus pyogenes is oxygen stable?

Streptolysin S (SLS)

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Hemolysin

responsible for subsurface hemolysis on BAP incubated anaerobically
causes lysis of RBC, WBC, platelets, tissue cells

STREPTOLYSIN O (SLO)

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STREPTOLYSIN O (SLO) is inhibited by

cholesterol in skin lipids

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What test detects antibodies against Streptolysin O?

Anti-Streptolysin O (ASO) test

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surface hemolysis seen around colonies that have been incubated aerobically causes lysis of RBC, WBC and platelets in the presence of room air nonimmunogenic

STREPTOLYSIN S (SLS)

STREPTOLYSIN S (SLS) inhibited by

nonspecific inhibitor that is frequently present in sera of humans and animals

What is another name for streptococcal deoxyribonuclease (DNase)

Streptodornase

lowers viscosity of exudates, giving pathogens more mobility

DEOXYRIBONUCLEASE (DNASE)

How many types of DNase are there, and which is most common?

Four types; DNase B is the most common

solubilizes the ground substance of mammalian connective tissues antigenic and specific for each bacterial or tissue source

hyaluronidase

HYALURONIDASE aka

SPREADING FACTOR

serine protease capable of inactivating the chemotactic factor for neutrophils and monocytes (C5a)

C5a PEPTIDASE

What does C5a peptidase inactivate?

The chemotactic factor C5a

What are streptococcal pyrogenic exotoxins (SPEs) formerly called?

Erythrogenic toxins

Cause scarlet fever rash and act as superantigens inducing immune mediator release

streptococcal pyrogenic exotoxins

Streptococcal Pyrogenic Exotoxins (SPEs) heat reaction and rarely found in what groups

heat labile and rarely found in group C and G

act as SUPERANTIGENS activating macrophages and T helper cells

Streptococcal Pyrogenic Exotoxins (SPEs)

SPEs induce release of powerful immune mediators such as and causes what

IL-1, IL-2, IL-6, TNF-alpha, TNF-beta, interferons, and cytokines shock and organ failure

What are the four types of streptococcal pyrogenic exotoxins?

SpeA, SpeB, SpeC, and SpeF

What disease is associated with streptococcal pyrogenic exotoxins?

Streptococcal toxic shock syndrome

What exotoxin degrades proteins and mediates the rash in scarlet fever?

Exotoxin B (cysteine protease)

RELATED INFECTIONS AND DISEASES with S. pyogenes

1. BACTERIAL PHARYNGITIS OR TONSILLITIS (STREP THROAT) 2. PYODERMAL INFECTIONS 3. NECROTIZING FASCIITIS 4. STREPTOCOCCAL TOXIC SHOCK SYNDROME 5. SCARLET FEVER (SCARLATINA) 6. POSTSTREPTOCOCCAL SEQUELAE

BACTERIAL PHARYNGITIS OR TONSILLITIS (STREP THROAT)  Incubation period MOT Diagnosis

1 to 4 days spread by droplets and close contact culture of specimen (throat swabs) or direct antigen detection

highly virulent strains can cause sharp outbreaks of sore throats and scarlet fever in schools and camps

BACTERIAL PHARYNGITIS OR TONSILLITIS (STREP THROAT)

BACTERIAL PHARYNGITIS OR TONSILLITIS (STREP THROAT) additional risks when infecting infants and small children

tendency to extend to the middle ear and mastoid

PYODERMAL INFECTIONS

Impetigo Erysipelas Cellulitis

localized skin disease that begins as small vesicles that progress to weeping lesions that crust over after several days usually seen in young children (2 to 5 years)

Impetigo

acute spreading skin lesion that is intensely erythematous with a plainly demarcated but irregular edge rare infection of the skin and subcutaneous tissues observed frequently in elderly patients

Erysipelas

diffuse, spreading infection of subcutaneous skin tissue characterized by defined area of redness (erythema) and the accumulation of fluid (edema) follows infection associated with mild trauma, burns, wounds, or surgical incisions may lead to gangrene

Cellulitis

Cellulitis is Differentiated from erysipelas by two clinical findings

lesion is not raised line between the involved and uninvolved tissue is indistinct

NECROTIZING FASCIITIS is also known as

GALLOPING GANGRENE, FLESH-EATING BACTERIA SYNDROME, SUPPURATIVE FASCIITIS, HOSPITAL GANGRENE, or NECROTIZING ERYSIPELAS

invasive infection characterized by rapidly progressing inflammation and necrosis of the skin, subcutaneous fat, and fascia

NECROTIZING FASCIITIS

Component of S. pyogenes that acts as a superantigen, causing the immune system to contribute to the damage of Necrotizing fasciitis

Exotoxin A

NECROTIZING FASCIITIS type polymicrobial infection from which aerobic and anaerobic bacteria are recovered

Type 1 NF

NECROTIZING FASCIITIS type GAS

Type 2 NF

NECROTIZING FASCIITIS type gas gangrene or clostridial myonecrosis

Type 3 NF

characterized by a precipitous drop in blood pressure, failure of multiple organs, and a very high fever caused by an invasive strep A that produces one or more of the streptococcal pyrogenic exotoxins initial streptococcal infection includes pharyngitis, peritonitis, cellulitis, wound infections

STREPTOCOCCAL TOXIC SHOCK SYNDROME

play a major role in the pathogenesis of the disease (STSS) = superantigens

SpeA

most common strains associated with streptococcal TSS

M1 and M3

punctate exanthem overlying a diffuse erythema that appears initially on neck and upper chest, 1 to 2 days following strep throat rash disappears over the next 5 to 7 days and is followed by desquamation communicable and spread by inhalation of infectious respiratory droplets results from a throat infection with a strain of S. pyogenes that carries lysgenic bacteriophage (T12)- cause by release of streptococcal pyrogenic exotoxins

SCARLET FEVER (SCARLATINA)

SCARLET FEVER (SCARLATINA) cardinal signs

diffuse red rash on the upper chest and spreads to the trunk and extremities, and “strawberry-colored” tongue

TEST FOR SCARLET FEVER

a. DICK’S TEST b. SCHULTZ- CHARLTON TEST

susceptibility test for scarlet fever

DICK’S TEST

DICK’S TEST  Test arm:  Control arm: :  Read reaction after

 Test arm: 0.1 ml of Dick’s toxin (Eryhtrogenic Toxin)  Control arm: : 0.1 ml of Dick’s toxoid  Read reaction after 24 hours

DICK’S TEST  (+) reaction Interpretation

Eythema or redness in the test site Susceptible to scarlet fever

based on neutralization of eryhtrogenic toxins when anti-toxin is injected on the skin of patient with scarlet fever diagnose whether rashes of patient is due to scarlet fever or not

SCHULTZ- CHARLTON TEST

SCHULTZ- CHARLTON TEST (+) reaction:

“BLANCHING PHENOMENON” – fading of the rashes

POSTSTREPTOCOCCAL SEQUELAE diseases

RHEUMATIC FEVER ACUTE GLOMERULONEPHRITIS

follows S. pyogenes pharyngitis autoimmune disease characterized by fever and inflammation of the heart, joints, blood vessels, and subcutaneous tissues mediated by antibodies produced against S. pyogenes M protein that cross-react with human heart tissue

RHEUMATIC FEVER

Rheumatic fever most serious result

chronic, progressive damage to the heart valves

most common cause of permanent heart valve damage in children

RHEUMATIC FEVER

ACUTE GLOMERULONEPHRITIS is also known as

BRIGHT’S DISEASE

 inflammatory disease of the renal glomeruli  develops 1–4 weeks after S pyogenes skin infection (pyoderma, impetigo) or respiratory infection deposition of antigen-antibody complexes, possibly involving the streptococcal M protein  Type III hypersensitivity reaction

ACUTE GLOMERULONEPHRITIS

Specimen of choice for diagnosing S. pyogenes

Pharynx and Tonsillar Swabs (Throat Swabs)

Laboratory diagnosis methods for S. pyogenes

1. Culture Medium 2. Bacitracin Susceptibility Test/Taxo A (0.02-0.04 U) 3. Pyrrolidonyl-α-Naphthylamide Hydrolysis Test 4. Sulfamethoxazole and Trimethoprim Test 5. Serologic Test: ASO TEST 6. Anti-DNase B Testing

Culture Medium choice and appearance of S. pyogenes in media

BAP: colonies are transparent to translucent, convex or domed entire, circular, shiny and surrounded by wide zone of βhemolysis

presumptive identification of S. pyogenes (S) screening for GAS in throat cultures groups C and G are also susceptible

Bacitracin Susceptibility Test/Taxo A (0.02-0.04 U)

Bacitracin Susceptibility Test/Taxo A (0.02-0.04 U) result for S. pyogenes

Susceptibility or any zone of inhibition

Which species is resistant to Bacitracin Susceptibility Test/Taxo A (0.02-0.04 U)

S. agalactiae

detects L-pyrrolidonyl arylamidase more specific for S. pyogenes than bacitracin  S. pyogenes is the only species of Streptococcus that is positive with PYR test

Pyrrolidonyl-α-Naphthylamide Hydrolysis Test

Pyrrolidonyl-α-Naphthylamide Hydrolysis Test detects what

L-pyrrolidonyl arylamidase

Other PYR(+) species

Enterococcus, Aerococcus, and Gemella

Positive result for S. pyogenes when using Pyrrolidonyl-α-Naphthylamide Hydrolysis Test

Cherry Red color

Sulfamethoxazole and Trimethoprim Test resistant groups (positive result)

Group A and B streptococci

Sulfamethoxazole and Trimethoprim Test susceptible groups (negative result)

Group C

interfering respiratory microbiota will be inhibited by SXT (+) result: Resistance

Sulfamethoxazole and Trimethoprim Test

 Serum is added with measured amount of SLO reagent and incubated  Reagent RBC are added  indicator  Enough antibody is present: SLO neutralized and no hemolysis occurs

Serologic Test: ASO TEST

reciprocal of the highest dilution demonstrating no hemolysis expressed in TODD units

Titer

neutralize reagent DNase B, preventing it from depolymerizing DNA

Anti-DNase B Antibodies

DNase measured by its effect on a DNA methyl-green conjugate

Anti-DNase B Testing