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MSE-2019 Medical Microbiology > Lecture 2 GP Bacteria Again but More > Flashcards

Lecture 2 GP Bacteria Again but More Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

Do Steptococci test positive or negative for the catalase test?

A

Negative

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2
Q

What kind aerobe is steptococci?

A

Facultatively anaerobic

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3
Q

Is Streptococci Gram positive or Gram negative?

A

Gram Positive

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4
Q

How is Streptococci found?

A

In pairs and chains

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5
Q

What are the 5 ways to tell apart different Streptococci?

A

Overlapping schemes
Serology- Reactions of antibodies to specific bacterial antigens
Haemolysis- Beta haemolytic streptococci
Cell arrangement
Physiological- Biochemical tests

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6
Q

What are the 3 types of Haemolysis present in Streptococci?

A

Alpha
Beta
Gamma

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7
Q

Which strains show beta haemolysis?

A

Mainly Lancefield groups, strep.pyogenes, strep. agalactiae

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8
Q

Which strains show alpha haemolysis?

A

Strep.pneumoniae and viridans streptococci

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9
Q

Which stains show gamma haemolysis?

A

Enterococci.

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10
Q

What should you see if a bacteria shows gamma haemolysis?

A

Nothing.

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11
Q

What is Lancefield Grouping?

A

A type of serological classification scheme, used to classify catalase-negative gram positive cocci based on the carbohydrate composition of bacterial antigens found on their cells walls.

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12
Q

Why do we use horse blood for blood agar?

A

Allows the detection of Haemolytic reactions
Contains X factory and V factory needed for the growth of many bacterial species e/g haemophilus influenzae

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13
Q

What groups contain the more significant human pathogens in the Lancefield groups?

A

A-G but not E

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14
Q

What is another name for Group A Streptococcus?

A

GAS or S.pyogenes

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15
Q

What are the 4 characteristics of Group A Streptococcus/S.pyogenes?

A

Forms 1-2mm white colonies
Large zone of beta haemolysis on blood agar
Bacitracin sensitive
Pathogenic species often capsulated

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16
Q

What does Protein M do (found in Strep A)?

A

A membrane protein, it destabilises complement interfering with opsonisation and lysis

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17
Q

How does Strep A use hyaluronic acid?

A

Hyaluronic acid forms a capsule that can camouflage the bacteria against WBCs

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18
Q

What is the use of the Streptolysins created by Strep A?

A

Breaks down RBCs, WBCs and platelets.

Interferes with oxygen carrying capacity of RBC, immunity and blood clotting

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19
Q

What happens to the WBC if it eats a Strep A that has produced 2 membrane bound proteins?

A

After being phagocytised, streptolysins are released into the cytoplasm of the phagocyte.
This causes the cell to release its lysosomes, breaking down the phagocyte, releasing more bacteria.

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20
Q

What is the purpose of the 2 Streptokinases that Strep A has?

A

Breaks down blood clot, thus enables rapid spread through infected and damaged tissue

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21
Q

Name the 4 enzymes that Strep A produces?

A

Streptokinases (2)
Distinct deoxyribonucleases (4)
C5a peptidase
Hyaluronidase

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22
Q

What is the purpose of the 4 distinct deoxyribonucleases that Strep A produces?

A

Depolymerise DNA released from dead cells in abscesses
This reduces firmness of pus and increase rate of spread.

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23
Q

What does the enzyme C5a peptidase do?

A

Breaks down C5a complement protein
Acts as a chemotactic factor
Decreases movement of WBCs into infection site

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24
Q

What does the enzyme Hyaluronidase do?

A

Breaks down hyaluronic acid
This increases the spread of Strep A through the tissues

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25
Q

How many pyrogenic toxins are there?

A

3

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26
Q

Explain what pyrogenic toxins can do

A

Stimulates macrophage and T helper lymphocytes
Causes the release of cytokines
This causes fever, rash and shock

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27
Q

Where are toxin genes carried?

A

Found on temperate phages (only lysogenised bacteria can secrete)

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28
Q

Which two genera of bacteria can produce pyrogenic toxins?

A

Staphylococcus and Streptococcus

29
Q

If 1 bacteria goes into the lytic/lysogenic cycle, how many come out?

A

200

30
Q

Where does Streptococci like to infect?

A

Pharynx or skin (resulting in temporary abscesses)

Can invade deeper into tissues and organs through barrier breaks

31
Q

Why does Streptococci cause temporary abscesses?

A

M proteins and streptolysins produced by Strep cause a specific immune response to occur

32
Q

What does GAS do to the gut microbiome?

A

GAS will compete with your microbiota until its all depleted. Large numbers can easily take over the gut microbiome before antibodies are formed.
Immunocompromised patients would not survive this.

33
Q

How is Strep transmitted?

A

Normally through respiratory droplets, helps if its crowded

34
Q

List the 7 things that GAS can cause?

A

Pharyngitis
Scarlet fever
Pyoderma and Erysipelas
Streptococcal Toxic Shock Syndrome
Necrotizing fasciitis
Rheumatic fever
Glomerulonephritis

35
Q

What does the ASOT/ASLO blood test do?

A

Looks for antibodies to the Strep A bacteria.
If abnormal results or positive then it shows that you have recently had a strep infection even with no symptoms

36
Q

What 3 antibiotics can you give if someone has a Strep A infection?

A

Penicillin
Erythromycin
Cephalexin

37
Q

What is another name for Strep B?

A

S.agalactiase

38
Q

The 4 stats of Strep B

A

Bacitracin resistant
Produces capsules (doesn’t protect from antibodies)
Predilection for newborns
Produces proteases and haemolysins

39
Q

What are the two enzymes that Strep B produces?

A

Proteases and haemolysins

40
Q

Where does Strep B like to infect?

A

Lower GI tract
Genitals
Urinary tract

41
Q

What is the morality rate of Strep B?

A

Over 50%

42
Q

What does GAS mean?

A

Group A Strep

43
Q

How is Group B Strep treated?

A

Penicillin
Sometimes streptomycin as some Group B Streps can tolerate a Pen conc x10

44
Q

How is Group B Strep treated in newborns?

A

Prophylaxis

45
Q

Is vaccination viable against Group B Strep?

A

Vaccinations would be nice if we had any :/

46
Q

Name the two other beta haemolytic streptococci

A

S.equisimilis
S.anginosus

47
Q

What does S.equisimilis cause?

A

Pharyngitis

48
Q

What does S.anginosus cause?

A

Purulent abscesses

49
Q

Where is Viridans Streptococci found?

A

Mouth (apart of our gut flora)
Pharynx
GI tract
Urinary Tract (of humans)

50
Q

What symptoms can Viridans Streptococci cause?

A

Purulent abdominal infections
Dental caries (dextran)
Biofilm (dental plaque)
Meningitis (if gets into blood)
Endocarditis

51
Q

What is Strep Pneumoniae sensitive to?

A

Optochin

52
Q

What type of haemolysis does Strep Pneumoniae do?

A

Alpha

53
Q

What does Strep Pneumoniae look like on blood agar?

A

Dimpled colony due to death of older cells

54
Q

Where can you find Strep Pneumoniae?

A

Normal flora of the pharynx
Can colonise the lungs, sinuses and middle ear

55
Q

What causes virulence in Strep Pneumoniae?

A

Polysaccaride capsule

Unencapsulated strains are avirulent

56
Q

What does Strep Pneumoniae produce?

A

Produces phosphorylecholine

57
Q

What does phosphorylecholine do?

A

Stimulates cell receptors within the lungs/meninges/blood vessels to engulf and hide itself (Strep Pneumoniae)

58
Q

What does IgA do?

A

Can limit migration of bacteria into the lungs.
By binding to the organism and then binding to the mucous so that it can be swept up and away from the ciliated epithelium

59
Q

What is a countermeasure the pathogen can do against IgA?

A

Produces IgA protease.

60
Q

What is Pneumolysin?

A

A type of pore-forming toxin (can create small holes/pores in host cell cell membrane)

61
Q

Which bacteria produces pneumolysin?

A

Streptococcus pneumoniae

62
Q

Where does Streptococcus pneumoniae infect?

A

Causes lung infections

63
Q

What demographic does Streptococcus pneumoniae affect the most?

A

The young and elderly because their immune systems are not fully active

64
Q

List the 6 diseases that can be caused by an infection of Streptococcus pneumoniae

A

Pneumonia
Sinusitis
Otitis media
Bacteremia
Endocarditis
Meningitis (affects children more because they haven’t been vaccinated yet)

65
Q

How is Strep Pneumoniae treated?

A

Penicillin

66
Q

Why can’t we use Cephalosporin, Erythromycin and Chloramphenicol to treat Strep Pneumoniae?

A

1/3 of Strep Pneumoniae are resistant

67
Q

Is there a vaccine for Strep Pneumoniae?

A

Yes, against the 23 most common pneumococcal strains

68
Q

Name 5 other gram positive bacteria

A

Enterococci
Bacillus sp
Listeria
Corynebacteria
Mycobacteria

MSE-2019 Medical Microbiology (6 decks)

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