Chapter 4: Streptococci Flashcards by Jourdan Harkless

What cocci gram-positive bacteria does not have catalase?

Streptococci

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What cocci gram positive bacteria are round in clusters and have catalase?

Staphlococci

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Beta-hemolytic streptococci

Completely lyse RBC, leaving a clear zone of hemolysis around the colony

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Alpha-hemolytic Streptococci

Partially lyse the RBCs, leaving a greenish discoloration

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Gamma-hemolytic streptococci

unable to hemolyze the RBCs

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Lancefield antigens

C carbohydrate found on the cell wall of streptococci

A,B,D most important

Strep pneumoniae and viridans do not have lancefield antigens

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Group A beta-hemolytic streptococci

Streptococcus pyogenes
Pus-producing
Strep throat, scarlet fever, rheumatic fever, poststreptococcal glomerulonephritis

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What are the components of the cell wall of Group A beta-hemolytic streptococci that are antigenic?

C carbohydrate Group A

M protein - Major source of virulence, inhibits complement and protects from phagocytosis

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What are the enzymes that contribute to Group A beta-hemolytic streptococci pathogenicity ?

Streptolysin O
Streptolysin S
Pyrogenic Exotoxin
Streptokinase

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Streptolysin O

Inactivated by oxygen, destroys red and white blood cells
Reason for Group A beta-hemolytic streptococci hemolytic ability
antigenic

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Streptolysin S

Oxygen stabile
Responsible for beta-hemolhysis
Not antigenic

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Pyrogenic exotoxin

Only found in a few strands of Group A beta-hemolytic streptococci
leads to scarlet fever
Directly superstimulate T cells to pour out inflammatory cytokines –>streptococcal TSS

Acquired by lysogenic conversion

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Streptokinase

Activates the proteolytic enzyme plasmin which breaks up fibrin blood clots

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Group A beta-hemolytic streptococci causes what four diseases by local invasion and/or exotoxin release?

Streptococcal pharyngitis
Streptococcal skin infections
Scarlet fever
Streptocococcal TSS

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Group A beta-hemolytic streptococci causes what 2 Delayed antibody mediated diseases?

Rheumatic Fever

Glomerulonephritis

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streptococcal pharyngitis

Strep throat with red swollen tonsils and pharynx, purulent exudate on the tonsils, high temp, and swollen LNs

Group A beta-hemolytic streptococci

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Streptococcal Skin infections

Folliculitis,
pyoderma: Pustule on extremity or face, forms thick crust, heals slowly, leaves depigmented area
erysipelas: superficial skin, dermis only (raised, bright red rash with sharp border)
cellulitis,
Impetigo: vesicular, blistered, eruption (most common in children) crusty and flaky around mouth

Group A beta-hemolytic streptococci

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Necrotizing Fasciitis

Flesh-eating
M-proteins block phagocytosis
Follow path along fascia btwn subQ and muscle
Swelling, heat, redness moves rapidly
Red–>blue skin change 24 hours later with large blisters

Group A beta-hemolytic streptococci

Fournier’s Gangrene

Necrotizing fasciitis involving the male genital area and perineum

Often caused by mixed organisms or by streptococcus pyogenes

Scarlet Fever

Group A beta-hemolytic streptococci
pyrogenic toxin/erythrogenic toxin

Fever, scarlet-red rash
Rash begins on trunk and neck then spreads to extremities

FACE is spared

Streptococcal TSS

Pyrogenic toxin
Similar to scarlet fever
TSS is similar to the one caused by staphylococcus aureus
Group A beta-hemolytic streptococci

Rheumatic fever

Uncommon
Usually strikes children 5-15
Follows untreated pharyngitis by Group A beta-hemolytic streptococci
Fever, myocarditis, joint swelling (acute migratory polyarthritis)
chorea (dance-like moves)
Subcutaneous nodules
Rash - erythema marginatum

Ags in heart similar to Ags of strep

Acute post-streptococcal glomerulonephritis

Occurs one week after infection of pharynx or skin by nephritogenic strains of Group A beta-hemolytic streptococci

Puffy face (retention of fluids)
Darker urine (hematuria - tea)
Hypervolemia (cause HTN)
Sore throat or skin infection one week prior

Group B Streptococci

Streptococcus agalactiae
Acquired during delivery

Neonatal meningitis, pneumonia, spesis
Symptoms of meningitis: fever, vomiting, poor feeding and irritability

Pregnant women - bacteremia and sepsis

What are the three bacteria that are responsible for most meningitis acquired by the baby coming out of the birth canal within the first 3 months of age?

Listeria monocytogenes E coli Group B streptococcus

What are the two bacteria that cause meningitis later in life after the maternal Abs passively given to fetus wane?

Neisseria meningitides and Haemophilus influenzae

Viridans group Streptococci

Big, heterogeneous group of streptococci that are not identified based on one Lancefield group Most alpha-hemolytic causing greenish-yellow discoloration Normal human GI tract flora found in nasopharynx and gingival crevices

Viridans streptococci cause what 3 main types of infections?

Dental infection: cavities Endocarditis Abscesses

What causes subacute bacterial endocarditis?

viridans Streptococcus and Group D Streptococci Settle on heart valves, especially valves that are previously damaged

What causes acute bacterial endocarditis ?

Staphylococus aureus

Group D streptococci

Can be alpha or gamma hemolytic | Two subgroups: enterococci and non-enterococci

Enterococcus

Faecalis and faecium Normal flora Variably hemolytic UTI, biliary tract infection, bacteremia, subacute bacterial endocarditis 2nd-3rd most common cause of HA-infection

Non-enterococci

Streptococcus bovis and Equinus | Grows better in bile, can lead to Colon cancer

Streptococcus pneumoniae

No Lancefield antigen; MAJOR cause of pneumonia and meningitis in adults and otitis media in children Pneumococci Major virulence: polysaccharide capsule

What are the two lab tests for Streptococcus pneumoniae?

Quellung reactions -> pneumococci on a slide smear are mixed with a small amount of anti-serum and methylene blue, capsule will swell Optochin sensitivity ->Optochin is added, Strep pneumoniae will be inhibited; Strep viridans will continue to grow

What are the symptoms of Streptococcus pneumoniae

Shaking and chills, high fevers, chest pain with respirations, shortness of breath

What is Otitis Media caused by?

Streptococcus pneumoniae, haemophilus influenzae, moraxella (decreasing order of infection)

What bacteria is associated with colonic malignancies?

S. Bovis | non-enterococci

What is the major virulence factor for group A streptococcus?

M protein

What is the major virulence factor of pneumococcus?

Polysaccharide capsule

What are the major virulence factors of Strep viridans and Lancefield group D?

Extracellular dextran - helps them bind to heart valves

What is subacute bacterial endocarditis?

SBE is the slow growth and piling up of bacteria on the heart valve Slowly develops low-grade fever, fatigue, anemia, and heart murmurs secondary to valve destruction

What is acute infective endocarditis?

Abrupt onset of shaking chills, high spiking fevers, and rapid valve destruction

What are the Anginosus species group?

Streptococcus intermedius group part of normal GI tract flora Hate oxygen Found in abscesses in brain or abdominal organs If in blood, suspect there is an abscess hiding somewhere