ICS - Microbiology (microscopy - do first!)

Question 1

This powerpoint was used as reference. Use as guide if visual reference needed. Mark 5 when read.

Answer 1

https://drive.google.com/file/d/1k6UY2u7nKcj8ot-XU3WikSA2bcIQlNLx/view?ts=627aa1cc

Question 2

Gram positive cocci, what test should be done?

Answer 2

Catalase test
- Positive = staphylococcus (purple clusters)
- Negative = streptococcus (purple pairs/chains)

Question 3

If a catalase test comes back positive, what does this show, and what test should be done next?

Answer 3

Staphylococcus

Coagulase done next
- Positive = Staphylococcus aureus
- Negative = S. epidermidis or saprophiticus

Question 4

Gram positive cocci, catalase positive, coagulase positive, what bacteria is it?

Answer 4

Staphylococcus aureus

Question 5

Gram positive cocci , catalase positive, coagulase negative, what bacteria is it?

Answer 5

S. epidermidis
S. saprophiticus

Question 6

Gram positive cocci are catalase negative. What does this show? What test should be done next

Answer 6

Streptococcus

Haemolysis using blood agar. Results can show:
- alpha (partially) haemolytic
- beta (fully) haemolytic
- Non haemolytic

Question 7

Gram positive cocci, catalase negative what is the genus of the bacteria?

Answer 7

Streptococcus

Question 8

Gram positive cocci, catalase negative, a-haemolytic. What bacteria can it be and how does it show on agar

Answer 8

S. pneumoniae
Viridians streptococcus
(S. oralis
S. sanguinis)

Dark green on agar plate

Question 9

What can be done to further differentiate alpha haemolytic streptococci? What are the results of this?

Answer 9

Optochin sensitivity test.
Sensitive (zone of inhibition) - S. pneumoniae
Resistant - Viridians strep

Question 10

Gram positive cocci, catalase negative, b-haemolytic. What bacteria is it and how does it show on agar

Answer 10

Complete haemolysis

S. pyogenes (Group A strep)
S. agalactiae (Group B strep)

Pale yellow and transparent

(S=Strep)

Question 11

What test can be done to further classify beta haemolytic bacteria?

Answer 11

Lancefield agglutination test

Uses antibodies to determine bacteria using their surface antigens.

Group A - S pyogenes
Group B - S agalactiae

Question 12

Gram positive cocci, catalase negative, non haemolytic. What bacteria is it and how does it show on agar

Answer 12

S. mutans
S. millieri
Enterococcus faecalis

No haemolysis, agar unchanged.

Question 13

What are the gram positive, aerobic bacilli

Answer 13

Cornybacterium (e.g. C.diphtheriae)
Listeria
Bacillus

Question 14

What is the gram positive, anaerobic bacillus species

Answer 14

Clostridium
(e.g. C. difficile, C. tetani)

Question 15

How are mycobacterium stained

Answer 15

Ziehl-Neelsen stain, as their high lipid content means they are acid fast, so can’t be gram stained.

Question 16

How does M. tuberculosis stain?

Answer 16

Stains red with a Ziehl-Neelsen stain

Question 17

The majority of gram negatives are bacilli. What notable species are gram negative cocci?

Answer 17

Neisseria (e.g. N meningitidis)
Moraxella

Question 18

What is the notable anaerobic, gram negative bacilli? (the rest are aerobic)

Answer 18

Bacteroides
e.g. B. fragilis (commonly found in colon)

Question 19

How are gram negative bacilli with simple growth requirements cultured?

Answer 19

Lactose fermenting on MacConkey agar

Question 20

How do lactose fermenters appear on MacConkey agar?

Answer 20

Red/PINK

Question 21

How do non lactose fermenters appear on MacConkey agar?

Answer 21

Pale/ no colour change

Question 22

Gram negative bacilli, appear pink on MacConkey agar, what is it?

Answer 22

Lactose fermenters

Escherichia (E.coli)
Klebsiella

Question 23

A gram negative bacillus grows a pale culture on MacConkey agar. What does this show?

Answer 23

Non lactose fermenters

• Salmonella
• Shigella
• Pseudomonas

Question 24

How can non lactose fermenters (MacConkey pale) be further differentiated?

Answer 24

Oxidase test

Positive = Pseudomonas aeruginosa
Negative = Salmonella, shigella

Question 25

How can salmonella and shigella be differentiated between?

Answer 25

Culture on XLD agar. Salmonella - red with black centres Shigella - Just red All others turn it yellow

Question 26

What agar is used to detect bacteria with fastidious growth requirements

Answer 26

Chocolate agar

Question 27

What bacteria have fastidious growth requirements, so must be cultured on chocolate agar?

Answer 27

Helicobacter H. Influenza Legionella. pneumophilia Bordatella pertussis

Question 28

How is Campylobacter jejuni cultured

Answer 28

On CCDA charcoal plate

Question 29

How is H influenzae cultured and how is it treated

Answer 29

Factors X and V added to chocolate agar Treated with amoxicillin and doxycycline

Question 30

Viridians streptococci properties, examples, infection

Answer 30

A-haemolytic and optochin resistant. S. sanguinis, S. oralis Found in mouth, cause deep organ abscesses (IE, brain, liver)

Question 31

What are group A Strep and what do they cause

Answer 31

A = S. pyogenes Tonsilitis, pharyngitis, skin infections

Question 32

What are group B Strep and what do they cause

Answer 32

B = S. agalacticae Neonatal sepsis and neonatal meningitis 15 mins in

Question 33

Give the properties of H pylori

Answer 33

Curved, motile bacilli with flagella.

Question 34

What classes of antibiotics inhibit cell wall synthesis

Answer 34

- Beta lactams (penicillins, cephalosporins) - Glycopeptides (vancomycin)

Question 35

Give the types of penicillin, with the infections they are indicated in

Answer 35

Flucloxacillin - Staph aureus, strep pyogenes (group A) Benzylpenicillin - Strep, pneumococcal pneumonia, meningitis Amoxicillin - UTI, listeria, enterococci

Question 36

Give the types of cephalosporin

Answer 36

1st gen - Cephalexin 2nd gen - Cefuroxime 3rd gen - Ceftriaxone

Question 37

Side effects of vancomycin

Answer 37

- nephrotoxicity Avoid in pregnancy

Question 38

What syndrome can be caused by Cephalosporins

Answer 38

Stephens-Johnson syndrome (epidermal necrosis- itchy skin, sore throat, sore eyes, rash, blister) - can kill

Question 39

What Antibiotics inhibits nucleic acid synthesis

Answer 39

Folate synthesis: Trimethoprim Sulfonamides (co trimoxazole) / DNA Gyrase: Fluoroquinolones (-foxacin) / RNA polymerase: Rifampicin / Metronidazole

Question 40

Give the class of ciprofloxacin with their MoA

Answer 40

Fluoroquinolones (basically any -floxacin) Inhibit DNA gyrase

Question 41

What antibiotics inhibit folate synthesis

Answer 41

Trimethoprim Sulfonamides (Including co-trimoxazole) (inhibit dihydrofolate reductase)

Question 42

What is the MoA of Rifampicin

Answer 42

Binds to RNA polymerase

Question 43

What is the MoA of metronidazole, and what is it indicated in?

Answer 43

Breaks the DNA Strand Indicated in anaerobic parasites, and prophylaxis in GI surgery

Question 44

When is Rifampicin contraindicated

Answer 44

Jaundice

Question 45

When is metronidazole contraindicated

Answer 45

Interactions with alcohol - causes profuse vomiting

Question 46

What antibiotic classes inhibit protein synthesis

Answer 46

- Tetracyclines (doxycycline) - Aminoglycosides (gentamicin) - Chloramphenicol - Macrolides (clarithromycin, azithromycin, erythromycin)

Question 47

What antibiotics inhibit 30s protein synthesis

Answer 47

Tetracyclines (doxycycline) Aminoglycosides (streptomycin, gentamicin)

Question 48

What antibiotics inhibit 50s protein synthesis

Answer 48

Macrolides - Azithromycin

Question 49

What does doxycycline do

Answer 49

It is a broad spectrum antibiotic

Question 50

When is gentamycin contraindicated

Answer 50

Myasthenia gravis