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PHASE 2A (Mine) > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What is the most common cause of UTI’s?

A

E.coli

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2
Q

What is a commensal?

A

Organism that colonises host but causes no disease normally

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3
Q

What is an opportunistic pathogen?

A

Microbe that only causes disease if the host defence is commpromised

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4
Q

What is virulence?

A

The degree to which an organism is pathogenic

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5
Q

What are the stages of gram staining?

A
  1. Fixation of material to microscope slide
  2. Application of primary stain
  3. Application of iodine
  4. Decolourisation step
  5. Application of counterstian
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6
Q

What agent is used as a primary stain and what colour does it stain cells?

A

Crystal violet- turns all cells purple

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7
Q

What is applied after crystal violet and what does it form?

A

Iodine- crystal violet iodine complex formed

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8
Q

What is added in the decolourisatoin step?

A

Acetone or ethanol

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9
Q

What differentiated in the decolourisation step (4)?

A

Gram +ve and Gram -ve bacteria

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10
Q

What colour do gram positive bacteria stain?

A

Purple

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11
Q

What colour to gram negative bacteria stain?

A

Pik

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12
Q

What is added as a counterstain to make gram -ve’s pink?

A

Safranin

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13
Q

Pneumonic to remember order of stains?

A 
Come In And Stain
Crystal violet
Iodine
Alcohol
Safranin
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14
Q

What is the differene between gram positive and gram negative bacteria?

A

Gram +ve: Thick cell wall (thick layer of peptigoglycan)

Gram -ve: Thin layer of peptidoglycan (thin cell wall), high lipid content

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15
Q

What are the two types of gram positive cocci?

A

Staphylococcus

Streptococcus

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16
Q

What are the types of gram positive rods?

A

Corneybacteria, mycobacteria, isteria, bacillus, nocardia

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17
Q

What test can be done to differentiate staphylococcus?

A

Coagulase test

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18
Q

What organism would a positive coagulase test indicate?

A

Staph, aureus

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19
Q

What would a negative coagulase test indicate?

A

Coagulase negative staphylococcus (epidermis, saprophiticus)

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20
Q

What happens in a coagulase test and what is it used for?

A

Used to differentiate staph. aureus from other types of staph.
Coagulase is an enzyme produced by S. aureus that converts soluble fibrinogen to insoluble fibrin, causing clumping.

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21
Q

What test is done to differentiate gram positive cocci?

A

Catalase test

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22
Q

What bacteria are present if it is catalase positive?

A

Staphylococcus

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23
Q

What bacteria are present if it is catalase negative?

A

Streptococcus

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24
Q

What is a catalase test?

A

Catalase is an enzyme that converts hydrogen peroxide to water and oxygen gas. Bacterial isolate is added to hydrogen peroxide and if positive, bubbles of oxygen are observed

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25
Q

How can streptococcus be differentiated?

A

Haemolysis on blood agar

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26
Q

What is blood agar and what does it test?

A

Agar plate that contains sheeps blood:

Tests the ability of an organism to produce hemolysins, enzymes that break down red blood cells

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27
Q

What are the three outcomes of haemolysis on blood agar?

A

Alpha
Beta
Gamma

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28
Q

What does alpha haemolysis look like?

A

Partial lysis–> Green on red plate

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29
Q

What does beta haemolysis look like on a blood agar plate?

A

Complete lysis–> Clear

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30
Q

What does gamma haemolysis look like on a blood agar plate?

A

No lysis–> Remains red.

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31
Q

What organism is present is there is greening of the BAP?

A

Alpha haemolytic strep

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32
Q

How are alpha haemolytic streps differentiated?

A

Optochin test

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33
Q

What is the optochin test?

A

Optochin antibiotic disk is placed on plate, which will inhibit growth of susceptible bacteria

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34
Q

What bacteria are optochin resistant?

A

Viridans strep

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35
Q

What bacteria are optochin sensitive?

A

S. Pneumonia

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36
Q

What bacteria are present if there is complete lysis (clear) BAP?

A

S. pyogens

Lancefield groups A, B, C, G

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37
Q

What bacteria are present if there is no lysis (red BAP)?

A

Lancefield D: S. bovis, enterococcus.

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38
Q

What kind of bacteria is S. aureus and what kind of infections does it usually cause?

A

Gram +ve, Coagulase +, catalase + Staphylococcus (cluster)

Skin infection

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39
Q

What kind of bacertia is MRSA?

A

Gram +ve, Coagulase +ve Staphylococcus

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40
Q

What kind of bacteria is S.pneumonia and where does it usually affect?

A

Gram +ve, Catalase -ve, alpha haem Streptococcus

Affects ENT

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41
Q

What kind of bacteria is S. pygones and where does it usually affect?

A

Group A streptococcus

Throat + skin

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42
Q

How are gram negative bacilli differentiated?

A

By their appearance on MacConkey agar

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43
Q

What is MacConkey agar and how does it differentiate gram negative bacteria?

A

Inhibits Gram-positive organisms and differentiates Gram-negative organisms by lactose fermentation.

44
Q

What colour will lactose fermenting bacteria turn MacConkey agar?

A

Pink

45
Q

What colour will non-lactose fermenting bacteria stain MacConkey agar?

A

White/ clear

46
Q

What are the main lactose fermenting bacteria?

A

E.Coli

Klebsiella

47
Q

What are the main non lactose fermenting bacteria?

A

Shigella
Salmonella
Pseudomonas
Proteus

48
Q

How are lactose fermenting bacteria further differentiated?

A

Biochemical identification (API strip) + Sensitivity tests

49
Q

How are non lactose fermenting bacteria further differentiated?

A

Oxidase test

50
Q

What bacteria tests positive in the oxidase test?

A

Pseudomonas

51
Q

What non lactose fermenting bacteria tests negative in an oxidase test?

A

Shigella, Salmonella, Proteus

52
Q

What type of bacteria is E.Coli and what are the main infections it causes?

A

Lactose fermenting Gram -ve bacteria:
UTI’s
Travellers diarrhoea

53
Q

What type of bacteria is Klebsiella and what are the main infections it causes?

A

Lactose fermenting gram -ve bacilli:

Pneumonia, meningitis

54
Q

What type of bacteria is pseudomonas and what infections does it commonly cause?

A

Non-lactose fermenting, Oxidasae +ve gram negative bacilli:

Pneumonia

55
Q

What type of bacteria is Shigella and what infections does it commonly cause?

A

Non-lactose fermenting, Oxidasae -ve gram negative bacilli:

Shigellosis (diarrhoea/ fever)

56
Q

What type of bacteria is Salmonella and what infections does it commonly cause?

A

Non-lactose fermenting, Oxidasae -ve gram negative bacilli:

Salmonellosis (diarrhoea)

57
Q

What type of bacteria is Neisseria and what infections does it commonly cause?

A

Gram negative cocci:

Gonorrhoea, meningitis

58
Q

What are the most common gram positive rods?

A

Corneybacteria, Mycobacteria, Listeria, Bacillus, Nocardia

59
Q

What are the most common gram negative cocci?

A

Neisseria (gonorrhoea), Moraxella

60
Q

What are the two most common causes of meningitis and what type of bacteria are they?

A

N. meningitidis (meningococcus)–> Gram negative cocci
S. pneumonia–> Gram positive cocci
(Diplococci)

61
Q

Which Hepatis is the only DNA virus (instead of RNA)?

A

Hep B

62
Q

Which forms of hepatitis are spread by faecal-oral transmission?

A

Hep A & E

63
Q

Which forms of hepatitis are spread by blood-blood transmission?

A

B, C, D

64
Q

How does acute non-inflammatory diarrhoea present?

A

Watery and non-bloody with no fever

65
Q

How does acute inflammatory diarrhoea present?

A

Bloody, possibly with pus and fever

66
Q

What is bloody diarrhoea also known as?

A

Dysentry

67
Q

What are the two ways bacterial toxins can enter the body?

A

Secrete exotoxins directly into food

Enter the body and secrete enterotoxins

68
Q

What bacteria produce preformed exotoxins?

A

Staph. aureus

Bacillus cereus

69
Q

What are the main pathogens that cause noninflammatory acute diarrhoea?

A 
E.coli (ETEC)
Vibrio cholerae
Staph. aureus
Bacillus cereus
Listeria
Norovirus
Giardia lamblia
70
Q

What are the main pathogens that cause inflammatory diarrhoea?

A 
Salmonella
Shigella
Campylobacter
C.Diff
STEC
71
Q

What does a presentation of diarrhoea with vomiting suggest?

A

S.aureus food poisoning or viral gastroenteritis

72
Q

What should be suspected if symptoms come on within 6 hours of ingesting food?

A

S. aureus of B. cereus (preformed exotoxin) infection

73
Q

What is the main cause of travellers diarrhoea?

A

Enterotoxigenic E. coli (ETEC)

74
Q

What is the most common cause of Osteomyelitis?

A

Staph. aureus

75
Q

What is the most common cause of septic arthritis?

A

S. aureus

Young sexually active adults: Neisseria gonorrhoea

76
Q

What is the most common bacterial STI?

A

Chlamydia

77
Q

What are the main symptoms of chlamydia?

A

70% asymptomatic
Men: Urethritis, Testicular pain
Women: Vaginal discharge, lower abdominal/ pelvic pain

78
Q

What is the first line investigation for STI?

A

NAAT (Nucleic acid amplification test)

79
Q

How is chlamydia treated?

A

Doxycycline/ Azithromycin antibiotics

80
Q

What is the second most common STI in the UK?

A

Gonorrhea (Niesseria gonorrhoea)

81
Q

How does gonorrhea present?

A

Usually asymptomatic
Men: Urethritis with purulent discharge and dysuria
Women: Pelvic pain with vaginal discharge, itch and dysuria

82
Q

What is the most common cause of viral meningitis?

A

Enteroviruses

Herpes simplex

83
Q

What pathogen causes TB?

A

Mycobacterium tuberculosis

84
Q

What kind of antibiotic is usually used to treat gram positive bacteria and why?

A

Those that inhibit cell wall synthesis as gram positive bacteria have thick cell walls

85
Q

What are the different types of antibiotic that inhibit cell wall synthesis?

A

Penicillins
Glyopeptides
Cephalosporins
Carbapenems

86
Q

What are the main types of glyopeptides/

A

Vancomycin

Teicoplanin

87
Q

What are the main types of penicillins?

A

Benzylpenicillin
Amoxicillin
Flucloxacillin

88
Q

What are the main types of cephalosporins?

A

Cephalexin
Cefotaxime
Ceftriaxone

89
Q

What are the main types of carbapenems?

A

Imipenem

Estapenem

90
Q

When are Carbapenems usually used?

A

For the treatment of severe infections or infection caused by multiple resistant bacteria

91
Q

What types of antibiotic inhibit protein synthesis?

A

Cholaramphenicol
Macrolides
Tetracyclines
Aminoglycosides

92
Q

What would be used instead of penicillin in those with a penicillin allergy?

A

Macrolides (e.g. Clarithromycin, Erythromycin)

93
Q

What are the different ways antibiotics can inhibit nucleic acid synthesis?

A

Inhibit folate synthesis
Inhibit DNA Gyrase
Bind to DNA polymerase
Break DNA strands

94
Q

What are the main types of antibiotic that inhibit nucleic acid synthesis?

A 
Rifamipcin
Fluroquinolones
Ciprofloxacin
Trimethoprim
Sulphonamids
Sulphamethoxazole
Metronidazole
95
Q

Why should you never give the antibiotic Trimethroprim to pregnant women?

A

It inhibit folate synthesis and folate is very important during pregnancy to prevent spina bifida

96
Q

What antibiotic is the first line in staph infections?

A

Penicillins e.g. Flucloxacillin

97
Q

What is the main antibiotic used for UTI’s?

A

Nitrofurantoin or Trimethoprim

98
Q

What antibiotic is used to treat MRSA?

A

Vancomycin

99
Q

What are mycobacteria?

A

Aerobic, non-spore forming bacilli

100
Q

What are the two main types of mycobacteria?

A

TB + Leprosy

101
Q

How are Mycobacteria investigated?

A

Zeihl-Neelsen stain instead of gram staining

102
Q

What are the two outcomes of Zeihl-Neelsen staining?

A

Acid-fast bacteria stain red

Non acid-fast bacteria stain blue

103
Q

How can viruses be identified>

A

PCR
Nucleic acid amplification tests (NAAT)
Serology: look for antibodies in response

104
Q

What can be given to treat severe viral infections?

A

Antivirals: End in ‘vir’ e.g. Acyclovir

105
Q

What are protozoa?

A

Microscopic unicellular eukaryotes

106
Q

How are protozoa classified?

A

Based on movement: ameoiboids, ciliates, sporozoan, flagellates

107
Q

What are the most common types of protozoa?

A

Malaria
Giardia Lamblia
Toxoplasmiosis
Trichomonas vaginalis

PHASE 2A (Mine) (15 decks)

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