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Medicine Phase 2a Other (Infectious diseases etc) > Microbiology > Flashcards

Microbiology Flashcards

1
Q

On gram stain, what colour will appear if gram positive

A

Purple

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2
Q

Why do gram positive bacteria stain purple

A

Contains peptidoglycan that is stained by crystal violet

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3
Q

On gram stain, what colour will appear if gram negative

A

Pink

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4
Q

Why do gram negative bacteria stain pink

A

Has a lot less peptidoglycan that is not stained, by instead stained by safranin

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5
Q

Appearance of Staphylococcus

A

Gram-positive cocci in clusters

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6
Q

Appearance of Streptococcus

A

Gram-positive cocci in chains

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7
Q

What is another way of distinguishing between staph and strep (not clusters or chains)

A

Catalase test

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8
Q

Describe catalase test

A

Hydrogen peroxide + Staphylococci -> Gas bubbles
+ve for staph
-ve for not staph (or strep)

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9
Q

You know that bacteria is Staphylococcus as positive catalase test. How would you test for Staph.aureus

A

Coagulase test
+ve = staph aureus as it produces coagulase that converts fibrinogen to fibrin
-ve = coagulase -ve staph

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10
Q

Example of a coagulase negative staphylococcus

A

Staph epidermis

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11
Q

You know a bacteria is an Alpha Haemolytic Streptococcus. How would you further differentiate between species

A

Optochin test:
Sensitive means Strep. pneumoniae
Resistant means Viridans strep

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12
Q

How can you tell if a Strep is beta, alpha or gamma haemolytic

A

Blood agar
Beta haemolysis = complete haemolysis
Alpha = partial
Gamme - none

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13
Q

Appearance of Streptococcus pneumoniae on microscopy

A

Gram Positive Diplococci

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14
Q

How would you further differentiate between beta haemolytic streptococci

A

Lancefield test - groups bacteria based on carbohydrate composition of bacterial antigen on cell wall, normally for beta-haemolytic strep

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15
Q

Examples of beta haemolytic streptococci and their group

A

A: Streptococcus pyogenes
B: Streptococcus agalactiae
D: Enterococcus, Strep bovis (group D is not beta-haemolytic)

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16
Q

Examples of gram positive bacilli

A

Listeria monocytogenes
Propionibacterium acne – acne
Clostridium difficile – diarrhoea from antibiotic overuse (those starting with C)

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17
Q

What does MacConkey agar contain

A

Bile salts, lactose and neutral red (pH indicator)

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18
Q

What is the purpose of MacConkey agar

A

Identifies bacteria that can ferment lactose (normally gram -ve bacilli or enteric bugs)

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19
Q

How does MacConkey agar work

A

Ferment lactose -> produce acid -> pH drop <6.8= pink, or if pH>6.8, remains normal colour
Therefore:
Lactose fermenting gram -ve bacilli = pink
Non-lactose fermenting gram -ve bacilli = yellow

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20
Q

Examples of bacteria (bacilli) that appear pink on MacConkey agar

A

(Enterobacteriaceae (coliforms)):
Escherichia coli
Klebisella pneumoniae

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21
Q

Examples of gram -ve non-lactose fermenting bacilli and what colour they appear on MacConkey agar

A

Appear YELLOW

salmonella, shigella, pseudomonas aeruoginosa, proteus mirabilis

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22
Q

Further differentiation between Gram negative non-lactose fermenting bacteria

A

Oxidase test:
Black/purple = +ve = pseudomonas (additional anti-pseudomonal snesitivity tests required to identify this) or Neisseria(note it is cocci not bacilli)

Colourless = -ve = Shigella, salmonella, proteus

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23
Q

How could you specifically identify Proteus mirabilis (Gram-ve bacilli that is oxidase negative and non-fermenting)

A

Urease test

+ve

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24
Q

Examples of gram -ve cocci

A

Neisseria meningitidis, gonorrhoea

Moraxella catarrhalis

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25
Q

Appearance of Vibrio cholera

A

Gram -ve comma/curved shaped

Rice water stool

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26
Q

Examples of Gram-ve bacteria with a HELICAL SHAPE

A

Campylobacter jejuni – bloody diarrhoea

Helicobacter pylori – gastric and duodenal ulcer

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27
Q

Appearance of Haemophilus influenza

A

Gram negative coccobacilli

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28
Q

What is used to identify fastidious bacteria

A

Chocolate agar (Neisseria meningtidis also requires chocolate agar)

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29
Q

What is chocolate agar

A

blood agar but with lysed RBCs due to heating to 80 deg C (haem from factor X)

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30
Q

What medium is used to culture mycobacteria

A

Lowenstein-Jensen medium

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31
Q

What stain is used to identify mycobacteria

A

Ziehl-Neelsen stain

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32
Q

Antibiotic for MRSA

A

Vancomycin

33
Q

Antibiotic for Entamoeba histolytica or Giardia

A

Metronidazole

34
Q

Antibiotic for Pneumocystis pneumonia

A

Co-trimoxazole

35
Q

Antibiotics that could be used for C. difficile

A

Vancomycin/metronidazole

36
Q

When would you give Metronidazole antibiotic

A

Entamoeba histolytica

Giardia

37
Q

How would you decide on treatment for pneumoniae

A

CURB65 score

38
Q

Modes of action by antibiotics

A

Antibiotics that inhibit cell wall synthesis
Antibiotics that inhibit protein synthesis
Antibiotics which inhibit nucleic acid synthesis

39
Q

Examples of antibiotics that inhibit cell wall synthesis

A

Glycopeptides

Beta lactams

40
Q

Examples of glycopeptides

A

Vancomycin

Teicoplanin

41
Q

Examples of beta lactams

A

Penicillins
Cephalosporins
Carbapenems

42
Q

Examples of penicillins

A

Benzylpenicillin
Flucloxacillin
Amoxicillin

43
Q

Examples of cephalosporins

A 
1st gen - Cephalexin
2nd - Cefuroxime
3rd - Ceftazidime (penetrate CNS)
1st gen more gram positives
3rd gen more gram negatives
44
Q

Example of carbapenems

A

Imipenem

Ertapenem

45
Q

Antibiotics that inhibit protein synthesis

A

Chloramphenicol
Macrolides
Tetracyclines
Aminoglycosides

46
Q

Examples of macrolides

A

Carithromycin

Erythromycin

47
Q

Examples of tetracyclines

A

Tetracycline

Doxycylcine

48
Q

Examples of Aminoglycosides

A

Gentamycin

Streptomycin

49
Q

Antibiotics that inhibit nucleic acid synthesis

A

Inhibit folate synthesis
Inhibit DNA gyrase
Binds to RNA polymerase
DNA strand breaks

50
Q

Antibiotics that break DNA strands

A

Metronidazole (nitroidimazoles)

51
Q

Antibiotics that bind to RNA polymerase

A

Rifampicin

52
Q

Antibiotics that inhibit gyrase

A

Fluoroquinolones:

Ciprofloxacin, Ofloxacin, Levofloxacin

53
Q

Antibiotics that inhibit folate synthesis

A

Trimethoprim
Sulfonamides: Sulfamethoxazole

Co-trimoxazole (trimethoprim and sulfamethoxazole)

54
Q

Examples of fungi

A

Candida albicans
Pneumocystis pneumonia
Aspergilliosis

55
Q

Treatment of candida albicans

A

Treat with antifungal e.g. topical nystatin or oral fluconazole

56
Q

Treatment of pneumocystis pneumonia

A

Co-trimoxazole (fungi treatment)

57
Q

Which patients get infected by aspergilliosis

A

Cystic fibrosis

Bronchiectasis

58
Q

examples of helminths

A

Wucheria bancroftii
Enterobius vermicularis
Schistosomiasis
Hookworm

59
Q

What is pneumocystis pneumonia

A

Fungi

60
Q

What is Wucheria bancroftii

A

Helminth

Filariasis causing lymphoedema

61
Q

What is Enterobius vermicularis

A

Helminth

Common in UK, Itchy bum, spreads in household

62
Q

What can result from schistosmiasis

A

Squamous cell bladder cancer

63
Q

What is the worldwide cause of iron-deficiency anaemia

A

Hookworm

64
Q

*Treatment of hookworm

A

Mebendazole

65
Q

Examples of protozoa

A

Entamoeba histolytica
Malaria
Giardia

66
Q

What is Enterobius vermicularis

A

Helminth

67
Q

What is Entamoeba histolytica

A

Protozoa

68
Q

What is candida albicans

A

Fungi

69
Q

What is schistosmiasis

A

Helminth

70
Q

What is Wucheria bancroftii

A

Helminth

71
Q

What is Giardia

A

Protozoa

72
Q

What is aspergilliosis

A

Fungi

73
Q

What is malaria

A

Protozoa

74
Q

What is Pneumocystis pneumonia

A

Fungi

75
Q

Describe symptoms of Entamoeba histolytica

A

Bloody diarrhoea

Liver abscess

76
Q

*Treatment of Entamoeba histolytica

A

Metronidazole

77
Q

What causes diarrhoea in Giardia

A

Alteration of intestinal villi, reducing absorption

78
Q

*Treatment of Giardia

A

Metronidazole

Medicine Phase 2a Other (Infectious diseases etc) (26 decks)

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