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Belle Phase 2a > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What does an application of safranin do in gram staining?

A

Stains gram negative bacteria PINK

gram positive remain PURPLE

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2
Q

Why does gram positive bacteria remain purple after decolorisation?

A

Thick layer of peptidoglycan in cell wall

Gram negative bacteria have a thin layer of peptidoglycan and a high lipid content

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3
Q

What are the four steps of gram staining?

A

Come In And Stain

Crystal violet (turns all cells purple)
Iodine
Alcohol (decolourisation)
Safranin (gram negative turn pink)

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4
Q

Which gram positive cocci produces an enzyme that converts fibrinogen to fibrin?

A

Staphylococcus aureus and MRSA: produce coagulase

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5
Q

Which test differentiates clusters vs chains in gram positive cocci?

A

Catalase test
Positive: Staphylococcus (clusters)
Negative: Streptococcus (chains)

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6
Q

Which groups does a haemolysis test differentiate streptococcus into?

A

Alpha: partial lysis (green)
Beta (Lancefield A, B,C + G): complete lysis (clear)
Gamma (Lancefield D): no lysis (non haem)

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7
Q

Which test can be used to differentiate alpha haemolytic streptococci?

A

Optochin test
Resistant: viridans strep
Sensitive: s. pneumoniae

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8
Q

Name two alpha haemolytic streptococci

A

Streptococcus pneumoniae

Viridans group streptococci

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9
Q

Which gram positive bacteria is beta haem group A?

A

Streptococcus pyogenes

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10
Q

Which gram positive bacteria are non-haem Group D?

A

Streptococcus bovis

Enterococcus

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11
Q

Infections associated with staphylococcus epidermidis

A

Surgical wound infections
Septicaemia
Endocarditis (prosthetic valve)

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12
Q

Infections associated with streptococcus pneumoniae

A

Pneumonia
Meningitis
Otitis media
Sinusitis

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13
Q

Treatment of MRSA infection

A

Vancomycin

Methicillin resistant s. aureus = MRSA

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14
Q

Test to initially differentiate gram negative bacilli

A

MacConkey Agar
Lactose fermenting: pink
Non lactose fermenting: white

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15
Q

Lactose fermenting gram negative bacilli

A

E. Coli

Klebsiella

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16
Q

Non lactose fermenting gram negative bacilli

A

Shigella
Salmonella
Pseudomonas

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17
Q

Oxidase positive non lactose fermenting gram negative bacilli

A

Pseudomonas

Produce cytochrome c oxidases

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18
Q

Oxidase negative non lactose fermenting gram negative bacilli

A

Shigella

Salmonella

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19
Q

Infections associated with E. Coli

A

UTIs (causes the majority)
Travellers diarrhoea
Cholecystitis
Cholangitis

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20
Q

Infections associated with pseudomonas and treatment

A

Skin infections
Pneumonia

Treatment: gentamicin, quinolones

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21
Q

Infections associated with shigella and treatment

A

Shigellosis (diarrhoea, fever)

Treatment: quinolones, azithromycin

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22
Q

Infections associated with neisseria and treatment

A

Gonorrhoea
Meningitis

Treatment: cephalosporins

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23
Q

Two examples of mycobacteria

A

TB

Leprosy

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24
Q

Stain used for mycobacteria

A

Ziehl-Nielsen stain
Acid fast bacteria: red
Non-acid fast: blue

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25
Q

Four different ways viruses can cause disease and examples of diseases for each

A

Direct destruction e.g. polio
Modification e.g. rotavirus
Over-reactivity e.g. hepatitis B
Cell proliferation e.g. HPV

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26
Q

3 tests used for identification of viruses

A

PCR
Nucleic acid amplification tests (NAAT)
Serology (acute: IgM, IgG appears later)

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27
Q

Worms

A

Common worldwide but rare in the UK
3 groups: roundworms (nematodes), flatworms (trematodes), tapeworms (ceratodes)
Mainly IgG and IgE mediated
Example: hookworm

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28
Q

Listeria monocytogenes

A

Gram positive bacilli

Pregnant women at high risk of this cause of MENINGITIS 🤰🏼

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29
Q

Haemophilus influenza

A

Gram negative coccobacilli

Aerobic

30
Q

Mechanism of action of glycopeptides and example AB

A

Inhibit cell wall synthesis

Vancomycin

31
Q

Mechanism of action of beta lactams and example groups

A

Inhibit cell wall synthesis

Penicillins, cephalosporins

32
Q

Three examples of penicillins

A

Amoxicillin
Benzylpenicillin
Flucloxacillin

33
Q

Example of cephalosporins

A

Cephalexin
Cefotaxime
Ceftriaxone

34
Q

Alternative AB used in the case of penicillin allergy

A

Macrolides e.g. erythromycin

35
Q

Mechanism of action of macrolides

A

Inhibit protein synthesis by targeting bacterial ribosome (50S subunit)

36
Q

Mechanism of action of aminoglycosides and example

A

Inhibit protein synthesis by targeting bacterial ribosome (30S)

Gentamicin

37
Q

Mechanism of action of tetracyclines and example

A

Inhibit protein synthesis by targeting bacterial ribosome (30S)

Doxycycline

38
Q

When is trimethoprim contraindicated

A

Pregnancy (folate is important in preventing spina bifida)

39
Q

Mechanism of action of trimethoprim

A

Inhibit folate synthesis (inhibits nucleic acid synthesis)

40
Q

Mechanism of action of fluroquinolones and example

A

Inhibit DNA gyrase (inhibits nucleic acid synthesis)

Ciprofloxacin

41
Q

Gold standard treatment for Staphylococcus infection

A

Flucloxacillin

42
Q

Two first line treatments for lower UTIs

A

Nitrofurantoin

Trimethoprim

43
Q

Two important bacterial resistance types

A

MRSA (methicillin)

VRE (vancomycin)

44
Q

Hepatitis B testing

A

1) Total anti-HB total core antibody = IgM + IgG
- Exposed to virus

2) Hepatitis B surface antigen (sAg)
- Exposed to virus AND it’s still active

3) Anti-HB surface antibody (sAb)
- Immunity to virus

45
Q

Which hepatitis viruses have a vaccine?

A

A and B

THERE IS NO VACCINE FOR HEPATITIS C

46
Q

Hepatitis C treatment

A

Direct acting antiviral therapy (successfully cure 90% of patients)

47
Q

Streptococcal treatment

A

E.g. Strep throat

Penicillin e.g. amoxicillin

48
Q

Enteric infection

A

Microorganisms that cause intestinal illness

49
Q

Causative organism of osteomyelitis

A

staphylococcus aureus

50
Q

Endocarditis symptoms

A

Fever, anaemia, murmur, breathlessness, chest pain

51
Q

Uncomplicated UTI criteria

A

Non-pregnant women

52
Q

Pyelonephritis triad

A

Loin pain + fever + pyuria (WCC)

53
Q

Complicated UTIs Mx

A

Empirical antibiotics first
Urinalysis
Blood culture

54
Q

Skin and soft tissue infection causative organisms and Tx

A

Beta haemolytic strep (Strep pyogenes): amoxicillin

Staph Aureus: flucloxacillin

55
Q

Three major classes of antibiotics

A

Inhibit cell wall synthesis
Inhibit nucleic acid synthesis (folate, DNA, RNA)
Inhibit protein synthesis (30S and 50S ribosomal subunits)

56
Q

Mechanism of antimicrobial resistance in MRSA

A

Flucloxacillin and methicillin are no longer able to bind to the PBP (penicillin binding protein) of staphylococci

57
Q

Mechanism of antimicrobial resistance in VRE

A

change in cell wall components reduce vancomycin binding

58
Q

Which type of bacteria are intrinsically resistant to metronidazole and why

A

Aerobic bacteria

Unable to convert it to its active form

59
Q

Which type of bacteria are intrinsically resistant to vancomycin and why

A

Gram negative bacteria

Vancomycin cannot penetrate its outer membrane

60
Q

Streptococcal pharyngitis

A

Throat inflammation caused by streptococcus pyogenes (strep throat)
- Group A Beta-haemolytic

61
Q

Streptolysin

A

Enzyme that completely lyses RBC (Beta haemolysis)

62
Q

RBCs in alpha haemolysis

A

Damaged RBCs (NOT ruptured)

63
Q

Rheumatic fever microbiology/pathophysiology

A

Group A Beta-haem streptococci

M protein (antibody) from the strep cell wall cross reacts with tissue causing inflammation and damage E.g. to heart valves

64
Q

Rheumatic fever symptoms

A 
Fever
Arthritis (painful, tender joints)
Chest pain
SoB
Fatigue 
Chorea
65
Q

AB table

66
Q

Cell wall synthesis disruption two mechanisms

A 
Peptidoglycan cross-linking (Beta lactams)
Peptidoglycan synthesis (Glycopeptides e.g. vancomycin)
67
Q

Folic acid synthesis disruption example Ab

A

Trimethoprim

68
Q

Pseudomembranous colitis is a complication of which microorganism?

A

Clostridium Difficile

local inflammation of large intestine = significant diarrhoea

69
Q

Treatment given to patients with suspected meningococcal septicaemia in the COMMUNITY

A

Benzylpenicillin IM

70
Q

Meningitis hospital Tx

A

Cefotaxime IV

71
Q

TB risk factors

A 
Ethnicity 
IVDU
homeless 
Immunosuppression
Alcoholic 
Close contact with infected
72
Q

Prophylaxis against meningococcal meningitis for close contacts

A

Ciprofloxacin

Belle Phase 2a (14 decks)

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