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Microbiology > Streptococci > Flashcards

Streptococci Flashcards

1
Q

What are some general characteristics of streptococci ?

A
  • gram + cocci (single, pairs, and chains)
  • occurs in pairs and chains microscopically
  • facultative anaerobes
  • catalase (-)
  • normal flora of the skin, mucous membrane, mouth, pharynx and urogenital
  • hemolytic reactions
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2
Q

What is alpha hemolysis ?

A

partial lysis of RBC
- greenish discoloration to agar

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3
Q

What is beta hemolysis ?

A

complete lysis of RBC
- clearing of the agar around colonies

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4
Q

What is gamma hemolysis ?

A

no lysis of RBC
- no change of the agar around the colonies

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5
Q

Which hemolysis have the biggest impact on human health ?

A

alpha & beta

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6
Q

What infections are caused by streptococcus pyogenes ?

A
  • strep throat
  • tonsilitis
  • erysipelas (contagious skin infection)
  • impetigo (around nose, mouth, extremities)
  • septicemia (systemic infection in the blood)
  • pneumonia (respiratory)
  • necrotizing fasciitis (flesh eating bacteria)
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7
Q

What is the function of streptolysin O in strep. pyogenes ?

A
  • SLO exotoxin (rare)
  • oxygen labile (will destroy/inhibit O2)
  • only will perform beta hemolysis in anaerobic conditions
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8
Q

What is the function of streptolysin S in strep. pyogenes ?

A
  • SLS exotoxin (common)
  • oxygen stable
  • hemolysis occurs under aerobic or anaerobic conditions
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9
Q

What is the function of erythrogenic toxin in strep. pyogenes ?

A

rash of scarlet fever
- toxin is absorbed and carried by the blood

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10
Q

What is the function of streptokinase/fibrinolysin in strep. pyogenes ?

A
  • breakdown of fibers
  • helps organism to spread
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11
Q

What is the function of hyaluronidase in strep. pyogenes ?

A

breaks down hyaluronic acid which binds connective fibers

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12
Q

What is the function of exotoxins in strep. pyogenes ?

A

fever and shock

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13
Q

What is the strep bacteria that is a Group A streptococci ?

A

streptococcus pyogenes
- sensitive to bacitracin (won’t grow in it’s presence)

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14
Q

What is the significance of having post-streptococcal diseases ?

A

happen after having Strep A infection
- not the infection that causes the disease but it’s the antigen (antigen-antibody reaction)
- your immune system recognizes the antigen as Strep A (when it isn’t) and your body will start to attack the heart valves and glomerulus of the kidney because the antigen of group A resembles this

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15
Q

What are the 2 post-streptococcal diseases ?

A
  • Rheumatic fever: 10-14 days after (joint issues, myocarditis) caused by the system attacking the heart valves
  • Glomerulonephritis: caused by attack to glomerulus of the kidney (headache, increased BP, low grade fever, weight gain, facial/periorbital edema)
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16
Q

What is impetigo ?

A

one of the most common skin infections among kids
- staph aureus or strep pyogenes
- blisters or sores on face, neck, hands, and diaper area

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17
Q

What are some symptoms of scarlet fever ?

A

rash & tongue may have whitish coating and appear swollen
- reverse strawberry appearance

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18
Q

What are some morphology of Strep. pyogenes ?

A
  • beta hemolytic
  • Lancefield group A
  • bacitracin sensitive (can’t grow in presence of antibiotic bacitracin)
19
Q

What are some characteristics of Strep. agalactiae (group B strep) (GBS) ?

A
  • normal flora especially in urogenital and oral cavity
  • generally harmless and most don’t even know they have it
  • about 25% found in pregnant women
  • bacitracin& SXT resistant
20
Q

What happens if a pregnant person has GBS (group B strep) ?

A

if tested (+) then they are given IV antibiotics during labor to kill the bacteria
- can’t be done before because it grows back quickly

21
Q

What infections are caused by group B strep ?

A
  • meningitis and/or septicemia in newborns
  • infections in post-partum women
  • female urogenital tract
  • wound and skin infections
22
Q

What is some morphology of group B strep ?

A
  • beta hemolytic
  • Lancefield Group B
  • CAMP test (+)
23
Q

What is the group B streptococci ?

A

streptococci agalactiae

24
Q

What is Lancefield grouping ?

A

method of grouping catalase-negative & coagulase-negative bacteria based on carb composition of bacterial antigens found on their cell walls

25
Q

What is the CAMP test ?

A

test to identify group B beta-streptococci based on their formation of a substance (CAMP factor) that enlarges the area of hemolysis formed by beta hemolysin from staph. aureus
- read at 24 hr mark
- make sure aureus and agalactiae don’t touch
- make a line of staph. aureus and do strep. agalactiae perpendicular to it

26
Q

Is strep group A CAMP + or - ?

A

-

27
Q

Is strep group B CAMP + or - ?

A

+

28
Q

What are some general characteristics of Group D strep and enterococcus ?

A
  • hemolytic reaction (can be alpha, beta, or gamma)
    • gamma most isolated
  • normal intestinal flora
  • bile esculin +
29
Q

What infections are caused by group D strep and enterococcus ?

A
  • wounds
  • endocarditis
  • urinary tract infections
30
Q

how can you differentiate enterococcus from streptococci ?

A

can tolerate wide range of temps (10-45) and high NaCl concentrations

31
Q

How do you know if a species is a Vancomycin Resistant Enterococcus (VRE) ?

A

can grow in the vancomycin agar
- more common in nosocomial or hospital acquired infections

32
Q

What are some characteristics of enterococcus ?

A
  • 90% gamma hemolytic
  • susceptibility to penicillin low (typically resistant)
  • identify using: bile esculin +, 6.5% salt+ (growth occurs)
33
Q

What is the bile esculin test ?

A

seeing if the species hydrolyze esculin to products that react with ferric citrate in the bile esculin agar medium to produce insoluble iron salts which results in the blackening of the medium
- if it turn black then (+)
- enterococci are bile esculin +

34
Q

What are the group D streptococcus ?

A
  • strep. bovis
  • strep. equinus
  • susceptible to penicillin (will work)
  • Identification: bile esculin +, 6.5% NaCl (-) won’t grow in salt broth
35
Q

What are the alpha hemolytic streptococcus ?

A
  • pneumoniae
  • viridans
36
Q

What are the beta hemolytic streptococcus ?

A
  • pyogenes
  • agalactiae
37
Q

What are the gamma hemolytic streptococcus ?

A

enterococcus
- E. faecalis
- E. faecium

38
Q

What are the general characteristics of streptococcus pneumoniae

A
  • gram (+) cocci in pairs (diplococci), slightly enlongated (lancet-shaped)
  • common oropharyngeal (mouth and pharynx) flora
  • need increased CO2 for better growth
  • alpha hemolytic
  • optochin sensitive
38
Q

What are infections caused by strep. pneumoniae ?

A
  • common cause of community acquired pneumonia
  • meningitis
  • septicemia
  • pericarditis
  • pleuritis
  • otitis media
  • sinusitis
39
Q

How do we identify strep. pneumoniae ?

A
  • alpha hemolysis
  • lysed by bile salts (rarely used test)
  • serological (latex coated beads-look for agglutination)
  • optochin sensitive
40
Q

What are some general characteristics of strep viridans ?

A
  • normal flora of urogenital, mouth, nose, pharynx, skin
  • not normally pathogenic (under certain circumstances)
    • Ex.) bacterial endocarditis, streptococcus mutans (dental caries)
41
Q

What is the clinically significant strep pyogenes infection ?

A

strep throat

42
Q

What bacteria cause impetigo ?

A

Staph aureus or strep pyogenes
- common skin infection among kids (blisters/sores on face, neck, hands, diaper areas)

43
Q

How do we differentiate between enterococcus and strep group D with a 6.5% NaCl (salt) test ?

A
  • enterococcus can tolerate high salt concentrations while strep D can’t

Microbiology (18 decks)

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