Chapter 1.4 Streptococci Flashcards by Stephanie Wehbe

What type of bacteria is streptococci?

Gram-positive

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What are the differences between streptococci and staphylococci?

Appearance

Enzymes

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What is the appearance of Streptococci vs Staphylococci on a gram-stain?

Streptococci line up one after the other like a strip

Staphylococci appear as a cluster

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What is the enzyme difference between Streptococci and Staphylococci?

Staphylococci have catalase whereas streptococci do not

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How are the 3 groups of Stretococcci categorized?

By their specific hemolytic ability

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What are the characteristics of beta-hemolytic streptococci?

They completely lyse the RBCs and leave a clear zone of hemolysis around the colony

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What are the characteristics of alpha-hemolytic streptococci?

They only partially lyse the RBCs and leave a greenish discoloration of the culture surrounding the colony

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What are the characteristics of gamma-hemolytic streptococci?

They are unable to lyse RBCs

*are non-hemolytic streptococci

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What antigens help classify streptococci based on their antigenic characteristics?

Lancefield antigens- A, B, C, D, E –> S

*but only 5 are significant in human pathogens and 3 of them have Lancefield antigens (A, B, D)

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What are the 2 human significant streptococci that do not have Lancefield antigens?

Stretococcus pneumoniae and Viridans group of streptococci

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What categorizes a streptococci into Group A Streptococci?

Lancefield antigens A and beta-hemolytic

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What is another name for group A streptococci?

Streptococcus pyogenes – which means pus-producing

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What diseases are associated with streptococci pyogenes?

Strep throat, scarlet fever, rheumatic fever, and post-streptococcal glomerulonephritis

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What are the antigenic components of the streptococcal cell?

C carbohydrate, M protein

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What is the M-protein in the streptococcal cell wall?

Major virulence factor for group A Stretococcus

Inhibits activation of complement and protects against phagocytosis

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What are the enzymes associated with group A streptococci?

Streptolysin O- oxygen labile- inactivation by oxygen and destroys red and white blood cells and is antigenic
Streptolysin S- oxygen stable- not antigenic
Pyrogenic exotoxin

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What is the function of pyrogenic exotoxin in some group A streptococci?

Cause scarlet fever

Produce superantigens that super stimulate T cells to cause streptococcal toxic shock syndrome

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What are the 4 types of disease by local invasion and/or exotoxin for group A streptococci?

Streptococcal pharyngitis, streptococcal skin infections, scarlet fever, and streptococcal toxic shock syndrome

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What are the 2 delayed antibody mediated diseases of group A Streptococci?

Rheumatic fever and glomerulonephritis

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What are the characteristics of streptococcal pharyngitis?

Classic strep throat with red, swollen tonsils and pharynx
Purulent exudate from tonsils
High temperature
Swollen lymph nodes
Usually lasts 5 days

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What are the characteristics of skin infections with group A streptococci?

Range from folliculitis (hair follicle infection), cellulitis (deep infection of skin cell), and impetigo (blistered eruption that becomes crusty and flaky)

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What is the mechanism of necrotizing fasciitis in group A streptococci?

“Flesh-eating streptococcus”

They enter through a break in the skin caused by trauma and then follow a path along the fascia between the subcutaneous tissue and muscle

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What are the manifestations of necrotizing fasciitis of group A streptococci?

A day later- Skin color changes from red to purple to blue, large blisters (bullae) form
Later- skin dies and muscle can become infected (myosotis)

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What bacteria can cause necrotizing fasciitis?

Group A streptococcus, staphylococcus, clostridium, gram-negative enterics, or mixed infections with more than one of these

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What are the characteristics of Scarlet fever by group A streptococci?

Production of exotoxin- pyrogenic toxin or erythrogenic toxin that produces fever and scarlet red rash

What is the pattern of the rash associated with Scarlet fever?

Starts on the trunk and neck and then spreads to the extremities, *sparing the face*

What are the characteristics of Streptococcal toxic shock syndrome caused by group A?

Release of pyrogenic toxin

What are the characteristics of rheumatic fever by group A streptococcus?

Usually affects children 5-15 years old | Joint swelling,

What is chorea?

Uncontrolled dance-like movements of the extremities in rheumatic fever

What is erythema marginatum?

Rash with a red margin that spreads from it's center

What makes rheumatic fever antibody-mediated?

There are antigens in the heart that are similar to the antigens of group A streptococci therefore the antibodies that form eradicate cross-react with the antigens of the heart causing myocarditis

What is the most frequently damaged site of the heart in rheumatic fever?

Mitral valve followed by the aortic valve | *occurs 10-20 years later

What are the characteristics of acute post-Stretococcal glomerulonephritis?

Antibody-mediated inflammatory disease of the glomeruli of the kidney Occurs 1 week after infection of either pharynx or skin group A streptococci

What is the patient presentation of an individual with acute post-streptococcal glomerulonephritis?

Puffy face from fluid retention from damaged kidneys Urine is darker than normal (tea or coca-cola colored) from hematuria Patient may say they had sore throat or skin infection a week ago

What is the name for group B streptococci?

Stretococcus agalatiae | *think B for Baby

How can an individual acquire group b streptococci?

A baby can acquire it through vaginal delivery

Who is susceptible to group B streptococci?

Neonates (

What are the signs of meningitis in a neonate?

Nonspecific signs such as fever, vomiting, poor feeding, and irritability

How can a diagnosis of meningitis be made?

Through lumbar puncture

What organisms must be covered in antibiotic treatment for meningitis?

E. Coli, Listeria monocytogenes, and group B stretptococcus

What bacteria are in the Viridans group of streptococci?

Streptococcus salivarius, S. Sanguis, S. Mitis, S. Intermedius, S. Mutans

What are the characteristics of Viridans group streptococci?

Alpha-hemolytic | Normal GI tract flora that are found in nasopharynx and gingiva

What are the 3 main types of infection from Viridans streptococci?

Dental infections, endocarditis, and abscesses

How is dental infection caused by Viridans group streptococci?

The Viridans bind to the teeth and ferment sugar which produces acid and dental caries

How is endocarditis caused by Viridans group streptococci?

Dental manipulation send showers of the organism into the bloodstream and they can implant on the endocardial surface of the heart

Where on the heart is the most likely place where viridan group streptococci implant?

Damaged heart valve

What is the specific result after Viridans implant on the heart?

Subacute bacterial endocarditis

What are the characteristics of subacute bacterial endocarditis?

Slow growth and piling up of bacteria on the heart

What is the patient presentation if they have subacute bacterial endocarditis?

Low-grade fever, fatigue, anemia, and heart murmur secondary to valve destruction

What endocarditis is associated with staphylococcal infection?

Acute infective endocarditis

How does acute infective endocarditis occur?

Staphylococcal infection secondary to IV drug use

What are the characteristics of acute infective endocarditis?

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

What is the difference in heart valve destruction between vidians group streptococci and staphylococcus aureus?

Vidians group streptococci are eating the valve slowly which staphylococcus aureus eats the valve quickly

What 2 streptococci groups are associated with subacute bacterial endocarditis?

Viridans group streptococci and group D streptococci

What subgroup of vidians group streptococci are often found in abscesses?

Streptococci intermedius group | *IMmediately USses (asses) for ABSCESS

What streptococci are in the streptococci intermedius group?

S. Intermedius, S. Constellatus, and S. Angiosus

What are the group D streptococci?

Enterococci and non-enterococci

What bacteria are in the enterococci group of group D streptococci?

Enterococcus faecalis and Enterococccus faecium

What bacteria are in the non-enterococci subgroup of group D streptococci?

Streptococcus bovis and streptococcus equinus

What is the hemolytic patten for group D streptococci?

Alpha-hemolytic

Where do the enterococci (faecalis and faecium) take residence?

Intestines and are considered normal bowel flora

What is the unique characteristic about enterococci?

They grow well in bile and NaCl

Who is the main target for enterococci?

Weak hospitalized patients (nosocomial- hospitally required)

What is the unique characteristic of streptococcus bovis?

Marketable association between S. Bovis and colon cancer | *BOVIS in the BLOOD: Better Beware, CANCER in the BOWEL

What major diseases are associated with Streptococus pneumoniae?

Bacterial pneumonia and meningitis in adults Otitis media in children *Pneumococcus is to Parents what group B Streptococcus is to Babies

What is the shape of pneumococcus?

Lancet-shaped gram + cocci arranged in pairs (diplococci)

What is the major virulence factor of pneumococcus?

Polysaccharide capsule that protects the organism from phagocytosis

What are the 2 important lab tests that identify pneumococcus?

Quellung reaction and Optochin sensitivity

What is the Quellung reaction?

When pneumococci are mixed with antiserum and methylene blue, the capsule will appear to swell

What is the Optochin sensitivity test?

Disc with Optochin is placed in an agar dish- if there is no growth then it is streptococcus pneumoniae but if there is growth present then it is Streptococus Viridans

What is the patient manifestation of pneumocoal pneumonia?

Sudden occurrence, shaking chills (rigors), high fevers, chest pain with respirations, and shortness of breath

What occurs in the lung when exposed with pneumococcal pneumonia?

Lung alveoli or lobe fills with white blood cells (pus), bacteria and exudate *can be detected on X Ray

What is the appearance of the patient's sputum if they have pneumococcal pneumonia?

Yellow-green phlegm

What is the classic sign of meningitis in adults?

Nuchal rigidity (a stiff neck)

What drug is Stretococcus pneumoniae now resistant to?

Penicillins