Staphylococcus and streptococcus

Question 1

Coagulase negative novobiosin sensitive what am I?

Answer 1

Staphylococcus epidermidis

Question 2

Are Staphylococci gram positive or negative?

Answer 2

+ve so stain purple

Question 3

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

Answer 3

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

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

Question 4

Describe the process of the coagulase test?

Answer 4

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

Question 5

How do you differentiate between coagulase negative Staphylococci?

Answer 5

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

Question 6

Coagulase positive what am I?

Answer 6

s.aureus

Question 7

What does s.aureus cause?

Answer 7

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

Question 8

How does s.aureus cause its effects?

Answer 8

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

Question 9

Coagulase negative novobiosin resistant what am I?

Answer 9

S.saprophiticus

Question 10

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

Answer 10

S.aureus

Swab and coagulase test which would be positive

Question 11

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

Answer 11

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

Question 12

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?

Answer 12

Osteomyelitis due to s.aureus

Swab and coagulase test which would be positive

Question 13

What does s.saprophiticus cause?

Answer 13

Acute cystisis- UTIs.

Question 14

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

Answer 14

S. saprophiticus infection.

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

Question 15

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?

Answer 15

S.epidermidis.

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

Question 16

What infections does s.epidermidis cause?

Answer 16

Opportunistic infections in debilitated and prosthetics

Question 17

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?

Answer 17

Toxic Sock Syndrome due to s.aureus infection

Swab and coagulase test which would be positive

Question 18

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

Answer 18

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

Question 19

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

Answer 19

Greeny discolouration due to partial hemolysis.
Strep pneumoniae
Strep viridans

Question 20

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

Answer 20

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.

Question 21

How would you differentiate between Alpha hemolytic varieties?

Answer 21

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

Question 22

How are the different kinds of Streptococcus differentiated?

Answer 22

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.

Question 23

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

Answer 23

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

Question 24

Beta hemolytic, SLS what am I?

Answer 24

Streptococcus agalactiae

Question 25

Alpha hemolytic optchin sensitive what am I?

Answer 25

s. pneumoniae

Question 26

How would you differentiate between beta hemolytic varieites of bacteria?

Answer 26

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

Question 27

Beta hemolytic, SLO what am I?

Answer 27

Streptococcus pyogenes

Question 28

Alpha hemolytic optchin resititant what am I?

Answer 28

Viridans strep

Question 29

A yellowy stain on blood agar what am I?

Answer 29

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

Question 30

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

Answer 30

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

Question 31

What does s.pyogenes cause?

Answer 31

``` NIPPLES Nectrotising fascitis Impetigo Pharyngitis Pneumonia Lymphangitis Erysipelas Scarlet fever/TSS ```

Question 32

How does s. pyogenes cause damage?

Answer 32

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.

Question 33

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

Answer 33

Alpha hemolysis with optchin sensitivity. | Therefore s. Pneumoniae

Question 34

Impetigo with coagulase negative test what am I?

Answer 34

Group A strep. Streptococcus pyogenes. | As coagulase negative so not s.aureus

Question 35

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

Answer 35

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

Question 36

What does viridans strep cause?

Answer 36

DID Dental cavities Infective endocarditis Deep organ absess

Question 37

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

Answer 37

Strep pneumonia

Question 38

What does s.pnuemonia cause?

Answer 38

``` MOPS Meningitis Otitis media Pneumonia Sinusitis ```

Question 39

Hows does s. pneumoniae cause its effect?

Answer 39

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

Question 40

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

Answer 40

s.pyogenes causing scarlet fever

Question 41

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?

Answer 41

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