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Phase 2 microbiology > Staphylococcus and streptococcus > Flashcards

Staphylococcus and streptococcus Flashcards

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1
Q

Coagulase negative novobiosin sensitive what am I?

A

Staphylococcus epidermidis

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2
Q

Are Staphylococci gram positive or negative?

A

+ve so stain purple

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3
Q

What tests could be used to differentiate between the different kinds of Staphylococci?

A

Coagulase test: +=s.aureus -=use novobiosin

Novobiosin sensitivity test: resistant= s. saprophiticus, sensitive= s.epidermidis

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4
Q

Describe the process of the coagulase test?

A

The coagulase test looks for the enzyme coagulase which is present in Staphylococcus Aureus that causes the convertion of soluable fibrinogen to insoluable fibrin.

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5
Q

How do you differentiate between coagulase negative Staphylococci?

A

Novobiosin test. If sensitive=s.epidermidis if resistant= s.saprophiticus.

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6
Q

Coagulase positive what am I?

A

s.aureus

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7
Q

What does s.aureus cause?

A 
SOFT PAINS 
Skin infections e.g. impetigo
Oseteomyelitis 
Food poisoning 
Toxic shock syndrome 
Pneumonia 
Acute endocarditis
Infective arthritis
Necrotising fascitis
Sepsis
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8
Q

How does s.aureus cause its effects?

A 
PPPET
Pore forming toxin
Proteases 
Protein A= inflames lung tissue, cripples immunity
Exofolatin= blistering 
TSS toxin
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9
Q

Coagulase negative novobiosin resistant what am I?

A

S.saprophiticus

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10
Q

A patient presents with septic arthritis of bacterial origin what do you suspect? and how would you confirm your diagnosis?

A

S.aureus

Swab and coagulase test which would be positive

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11
Q

A patient presents with impetigo what do you suspect is the cause? and how would you confirm your diagnosis?

A

Most commonly s.aureus
Swab and coagulase test which would be positive
Alternatively if coagulase negative Group A strep. Streptococcus pyogenes.

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12
Q

A patient presents with lower leg pain, inflammation, and a fever a month after he fractured his tibia what do you suspect? and how would you confirm your diagnosis?

A

Osteomyelitis due to s.aureus

Swab and coagulase test which would be positive

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13
Q

What does s.saprophiticus cause?

A

Acute cystisis- UTIs.

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14
Q

A patient presents with acute cystisis of bacterial origin what do you suspect? and how would you confirm your diagnosis?

A

S. saprophiticus infection.

Swab and coagulase test which would be negative then novobiosin sensitivity testing which would show resistance.

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15
Q

A patient who has recently had a prosthetic heart valve replacement presents with fever, breathlessness and a high temperature what do you suspect? and how would you confirm your diagnosis?

A

S.epidermidis.

Swab and coagulase test which would be negative then novobiosin sensitivity testing which would be sensitive.

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16
Q

What infections does s.epidermidis cause?

A

Opportunistic infections in debilitated and prosthetics

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17
Q

A patient presents with a sudden onset of fever, rash, hypotension and is going into respiratory failure. She has recently had an abortion. What do you suspect? and how would you confirm your diagnosis?

A

Toxic Sock Syndrome due to s.aureus infection

Swab and coagulase test which would be positive

18
Q

Describe the appearance of a Beta hemolytic stain and the kinds of bacteria in this group.

A

Beta hemolysis is yellow/transparent discolouration of the blood agar (complete hemolysis).
This is due to streptolysin.
Strep. pyogenes
Strep. agalactiae

19
Q

Describe the apperance of Alpha hemolysis and the kinds of bacteria which preform it.

A

Greeny discolouration due to partial hemolysis.
Strep pneumoniae
Strep viridans

20
Q

Compare the structure of a gram positive and a gram negative bacterias cell outer membrane.

A

Gram positive bacteria have one membrane surrounded by a thick layer of peptidoglycan
Gram negative bacteria have 2 membranes with a thin layer of peptidoglycan between the two and a periplasmic space. The outer membrane of Gram -ve bacteria has lipopolysaccharides LPS= endotoxin.

21
Q

How would you differentiate between Alpha hemolytic varieties?

A

Test for sensitivity to optchin.
Sensitive: strep. pneumoniae
Resistant: viridans strep

22
Q

How are the different kinds of Streptococcus differentiated?

A

Hemolysis test on blood agar groups into Beta and Alpha hemolytic strep.
Alpha hemolytic strep are tested for sensitivity to optchin
Beta hemolytic strep are grouped into A and B depending of type of streptolysin present.

23
Q

What colour are gram positive bacteria on gram stains and why?

A

Purple as they have a think peptidoglycan layer and are therefore able to absorb more of the gram stain.

24
Q

Beta hemolytic, SLS what am I?

A

Streptococcus agalactiae

25
Q

Alpha hemolytic optchin sensitive what am I?

A

s. pneumoniae

26
Q

How would you differentiate between beta hemolytic varieites of bacteria?

A

Different types of streptolysin
Group A strep has Streptolysin O (SLO) which is oxygen sensitive and therefore hemolysis will only occur bellow the surface of the blood agar. S.pyogenes
Group B strep has Streptolysin S (SLS) which is oxygen resistant and therefore hemolysis will occur on the surface of the blood agar. S. agalactiae

27
Q

Beta hemolytic, SLO what am I?

A

Streptococcus pyogenes

28
Q

Alpha hemolytic optchin resititant what am I?

A

Viridans strep

29
Q

A yellowy stain on blood agar what am I?

A

Beta hemolytic strep.

Analysis of streptolysin needed to determine between Group A (s.pyogenes) and Group B (s.agalactiae).

30
Q

A greeny stain on blood agar with partial white covered disc what am I?

A

Alpha hemolytic strep becuase of greenish discolouration (partial hemolysis) and optchin resistant as optchin disc partially covered.
Therefore Viridans strep

31
Q

What does s.pyogenes cause?

A 
NIPPLES
Nectrotising fascitis 
Impetigo 
Pharyngitis
Pneumonia 
Lymphangitis 
Erysipelas 
Scarlet fever/TSS
32
Q

How does s. pyogenes cause damage?

A

ON surface it has M protien that degrades complement.
Streptolysin O and S destroy RBC and WBC
Erythrogenic toxin causes increased nonspecific T cell activation and therefore damage to plasma membranes of blood capillaries.

33
Q

Greeny stain on blood agar with white uncovered disc what am I?

A

Alpha hemolysis with optchin sensitivity.

Therefore s. Pneumoniae

34
Q

Impetigo with coagulase negative test what am I?

A

Group A strep. Streptococcus pyogenes.

As coagulase negative so not s.aureus

35
Q

Necrotising fascitis what do you suspect is the cause? and how would you confirm your diagnosis?

A

Group A strep: s.pyogenes= Beta hemolysis
Or S.aureus = coagulase +ve
Tests

36
Q

What does viridans strep cause?

A

DID
Dental cavities
Infective endocarditis
Deep organ absess

37
Q

A patient presents with pneumonia and cultures show greeny hemolysis on blood agar with opthchin sensitivity what has caused this?

A

Strep pneumonia

38
Q

What does s.pnuemonia cause?

A 
MOPS
Meningitis
Otitis media
Pneumonia
Sinusitis
39
Q

Hows does s. pneumoniae cause its effect?

A

Capsule inhibits complement
IgA protease breaks down Iga
(IgA is the main antibodiy of mucosal surfaces)

40
Q

A patient presents with a central rash what has caused it?

A

s.pyogenes causing scarlet fever

41
Q

A child presents feeling ill and having a slight fever, they also have an ear ache. what has caused this? and how would you check?

A

This child has otitis media caused by s.pneumoniae which is a Alpha hemolytic optichin sensitive form of streptococcus.

Phase 2 microbiology (1 decks)

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