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SJ Phase 2a > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Define commensal

A

Organism which colonise the host but cause no disease in normal circumstances

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2
Q

Define oppurtunist pathogen

A

Microbe that only causes disease if host defences are compromised

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3
Q

Define asymptomatic carriage

A

Pathogen is carried harmlessly at tissue site without causing disease

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4
Q

What is the relationship between gram stain and membrane of bacteria?

A

Gram +ve = single membrane
Gram -ve = double membrane

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5
Q

Describe the process of gram staining

A

Come In And Stain
1. Crystal violet
2. Iodine
3. Alcohol/acetone
4. Safranin

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6
Q

How do gram +ve and gram -ve bacteria appear?

A

Gram +ve - purple
Gram -ve - pink

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7
Q

When would Ziehl-Neelsen stain be used?

A

Mycobacteria
-acid-fast bacilli do not take up gram stain

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8
Q

How do Ziehl-Neelsen stain?

A
  • Acid-fast bacilli = Red (mycobacterium)
  • Non acid-fast bacilli = Blue
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9
Q

What is the catalase test?

A
  1. Add peroxide to bacteria and see for bubbling reaction
  2. Used to differentiate between staphylococci (+ve) and streptococci (-ve)
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10
Q

What is a haemolysis test?

A
  1. Haemolysis = ability of bacteria to break down RBCs in blood agar
  2. Expression of haemolysin dependent
  3. Used to classify streptococci
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11
Q

What is alpha haemolysis?

A
  1. Indistinct zone of partial destruction of RBC
  2. Medium discolouration to greenish brown
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12
Q

Give some examples of alpha haemolytic bacteria

A
  1. Strep. Pneumoniae
  2. Strep. Viridans
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13
Q

What is beta haemolysis?

A
  1. Clear colourless zone appears around colonies; RBCs have undergone complete lysis
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14
Q

Give some examples of beta haemolytic bacteria

A
  1. Strep. pyogenes
  2. Staph. aureus
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15
Q

How can you differentiate between strep. and staph. aureus in beta haemolysis?

A

Staph aureus beta haemolysis will appear creamy yellow on blood agar

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16
Q

What is gamma haemolysis?

A

No haemolysis occurs

17
Q

What is the Optochin test?

A
  1. Tests to differentiate between Strep. pneumoniae and viridans strep. and other alpha haemolytic strep.
  2. Optochin soaked disc placed in agar, growth observed
18
Q

How does the Optochin test?

A

-Sensitive = strep. pneuomniae = clear zone of no growth around disc
-Resistant = Viridans strep. and other alpha haemolytic strep. grow around disc

19
Q

How does the oxidase test?

A
  • oxidase +ve = blue (aerobic) = V. cholerae
  • oxidase -ve = no colour change = bacteria may be aerobic or anaerobic
20
Q

What is the use of Macconkey agar?

A
  1. Only grows gram -ve bacilli
  2. Useful to differentiate between lactose fermenting and non-lactose fermenting gram -ve bacilli
  3. pink/red = lactose fermenting = E.Coli
  4. White/transparent = non lactose fermenting = Salmonella
21
Q

What is the use of XLD agar?

A
  1. Differentiate salmonella vs shigella
  2. Red/pink colonies with some black spots = Salmonella
  3. Red/pink colonies = Shigella
22
Q

How to find, diagnose and treat Staph. aureus

A

Clinical presentation
- Pain in shoulder
- Elevated temperature
- Osteomyelitis (bone infection) C6 & C7
Diagnose
- Blood culture shows staph. aureus
- Coagulase +ve
Treat
- FLUCLOXACILLIN 3 MONTHS

23
Q

What is the cause,test and treatment of impetigo, boils, cellulitis, endocarditis, toxic shock syndrome?

A

CAUSE - Strep. Aureus
TEST - Gram +ve, Coagulase +ve
TREAT - Flucloxacillin, co-amoxiclav, macrolides

24
Q

What is the cause,test and treatment of MRSA?

A

CAUSE - Staph. Aureus
TEST - Gram +ve, Coagulase +ve
TREAT - Gentamicin, vancomycin

25
Q

What is the cause,test and treatment of surgical wound infections, septicaemia, endocarditis?

A

CAUSE - Strep. epidermidis
TEST - Gram +ve, Coagulase -ve
TREAT - Co-Amoxiclav

26
Q

What is the cause,test and treatment of acute cystitis?

A

CAUSE - Strep. saphrophiticus
TEST - Gram +ve, Coagulase -ve
TREAT - Nitrofurantoin, Trimethoprim

27
Q

What are the key differences between gram +ve and -ve bacteria?

A
  • Gram +ve = single cytoplasmic membrane, large amount of peptidoglycan, no endotoxin, STAIN PURPLE
  • Gram -ve = Inner & outer membrane, small amount of peptidoglycan, endotoxin present, STAIN PINK
28
Q

State the different types of antibiotics

A
  1. Beta lactams glycopeptides
  2. Metronidazole and Rifampicin
  3. Fluroquinolones
  4. Aminoglycosides,Tetracyclines, Macrolides, Chloramphenicol
  5. Sulphonamides, Trimethoprim
29
Q

How do beta lactam gylcopeptide antibiotics work?

A
  1. Bind to bacterial cell wall
  2. Inhibition of cell wall synthesis
30
Q

How do Metronidazole and Rifampicin antibiotics work?

A

Interfere with nucleic acid synthesis or function

31
Q

How do Fluroquinolones antibiotics work?

A

Inhibit DNA gyrase

32
Q

How do Aminoglycosides, Tetracyclines, Macrolides, Chloramphenicol antibiotics works?

A

Inhibit ribosomal activity and protein synthesis

33
Q

How do Sulphonamides and Trimethoprim antibiotics work?

A

Inhibit folate synthesis

34
Q

What are the 4 species of protazoa responsible for malaria?

A
  1. P. falciparum
  2. P. Ovale
  3. P. vivax
  4. P. malariae
35
Q

Which mosquito is responsible for malaria?

A

Female ANOPHELES mosquito

36
Q

What is the pathology of malaria?

A
  1. Anaemia
  2. Cytokine release
  3. Widespread organ damage due to impaired microcirculation
37
Q

What are the clinical features of malaria?

A
  1. Incubation period = 10-21 days
  2. Chills & sweats
  3. Myalgia (muscle pain)
  4. Fatigue
  5. N,D&V
38
Q

What is the life cycle of malaria?

A

Mosquito > sporozoites > human blood > liver > merozoites > RBC > gametocytes > mosquito

SJ Phase 2a (13 decks)

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