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Microbiology > Lecture 4 - Mycobacteria > Flashcards

Lecture 4 - Mycobacteria Flashcards

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Biology 101 flashcards
1
Q

What shape are the mycobacterium

A

Rod shaped

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2
Q

How do the mycobacterium live in regards to oxygen

A

Obligate aerobes

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3
Q

Do mycobacterium produce spores and have a caspsule

A

No

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4
Q

What size are mycobacterium

A

2-4um

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5
Q

What phylum does mycobacteria belong to

A

actinobacteria

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6
Q

What is special about the actinobactera

A

High G and C content and filamontous

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7
Q

How many hours is the generation time

A

15-20hours

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8
Q

How is the cell wall different to gram-/+ bacteria

A

HIGH LIPID CONTENT

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9
Q

How much of the mycobacteria cell wall is lipid

A

60%

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10
Q

What is the main glycolipid part of the membrane

A

MYCOLIC ACID

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11
Q

Name 2 other lipids found in the membrane

A

Surface acyl lipids, lipoarabinomannan, phosphatidyl inositol mannosides (PIM), CORD FACTOR (TDM)

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12
Q

Why is the cell wall structure of mycobacteria important

A

Intracellular survival, confers resistance e,.g many antimicorbials, heat, chemicals, drying STAINS.

Acid fast

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13
Q

What is meant by acid fast

A

Once stained the organisms resist dilute acid or ethanol based de colourisation!!

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14
Q

What is the stain for mycobacteria

A

Ziehl neelson stain

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15
Q

Describe the ziehl neelson stain

A

1- stain with hot concentrated carbol fuschin (all cells pink)
2- de stain with 1% acid-alcohol (HCl/ethanol) or 20% H2SO4 (mycbacteria stay red, others colourless
3- counterstain with methylene blue (mycobacterial cells remain pink others are blue e.g. Wbc are blue)

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16
Q

Name 4 species of mycobacteria

A

M. Tuberculosis, M. Bovis, M. Avium intracellulare, M. Leprae (Hansen’s bacillus)

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17
Q

What disease does M. Avium intracellulare cause and what are the symptoms

A

Disseminated TB in immunocompromised patients e.g. HIV

Symptoms:
Lung infection - spread t bones, joints, blood, meninges, renal system. DEATH

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18
Q

Describe the symptoms of leprosy

A

Folded lesions on face and limbs, disfiguration, loss of peripheral nerves, secondary infection

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19
Q

How can you get M. Bovis and what are the symptoms

A

From unpasteurised milk

Asymptotic often, pneumonia like symptoms. Weight loss, temp. Cough, blood in sputum

SAME AS FOR M.TUBERCULOSIS

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20
Q

How much of world popn have TB

A

1/3

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21
Q

Why was there a huge decrease in HIV patients from the 1950’s (50,000) to mid 1980’s (6000) in the UK

A

Introduction of vaccinations to prevent against TB infection

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22
Q

Why may there be a steady increase once again in the no of TB cases in the UK

A

Antibiotic resistance of bacteria

Also more HIV cases so more risk of infection

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23
Q

What are predisposing factors of TB infection

A
  • close contact with large popn of people I.e schools, nursing homes. Prisons
  • poor nutrition
  • IV drug use
  • alcoholism
  • HIV infection MAIN predisposing factor of TB infection. 10% of all HIV + positive individuals have TB (400x rate associated with general public)
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24
Q

How large are the droplet nuclei

A

5um

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25
Q

How many droplet nuclei are released when someone talks for 5 mins, coughs, sneezes?

A

3,000 for each.

Sneezing 3000 up to ten feet away

26
Q

The droplet nuclei once in the air die within 5 minutes. True or false

A

False

A few hours

27
Q

What does the small size of the droplet nuclei allow for

A

Bypass mucociliary lining

28
Q

What are the 5 stages of a TB infection

A

1- droplet nuclei inhales
2- (7-21 days) MTB multiplies within macrophages (intracellular), macs secrete IL-12 and present MTB antigen on surface, eventually burst through liberating MTB
3- IL-12 stimulates T cells to infiltrate, recognise MTB antigen, become activated (sensitised) and start to release inflammatory factors (IFN gamma); tubercule formation (primary lesion)
4- MTB continues to multiple within unacfivated/poorly activated macs and tubercule expands
5- primary lesion heals - GHON focus (dormant lesion, contains MTB, may reactivate

29
Q

What in healthy people ‘heals ‘ primary lesion

A

Cell mediated response

30
Q

What are the symptoms of primary tuberculosis

A

LRTI- cough (sputum with blood), weight loss, night sweats, fatigue, fever

May spread to other body parts: meningitis, blood poisoning, kidney infection, joint infection

31
Q

How many people experience primary tuberculosis and how is the body prepared for attacking re exposure

A

10% and patients hypersensitised e,g, CMI (T- lymphocytes)

32
Q

How many people are asymptomatic due to cell mediated response keeping the infection under control

A

90%

33
Q

What is secondary tuberculosis

A

Reactivation

34
Q

Give examples of how secondary tuberculosis is associated with impairment of CMI

A

Steroid therapy, immunosuppressive drugs, cancer chemotherapy, old age, HIV.

35
Q

What happens to the dormant primary focus during secondary tuberculosis

A

Dormant primary focus becomes necrotic (cheesy) and liquefies distributing thousands of M, tuberculosis MTB into the lungs

36
Q

What is the appropriate clinical sample for lab diagnosis of pulmonary (respiratory) TB?

A

Sputum

37
Q

What category microorganism is m.tuberculosis

A

Category 3

38
Q

What are category 3 microorganisms

A

Cause severe human diseases, serious hazard to employees, risk of spread in community BUT EFFECTIVE TREATMENT.

39
Q

How is the sputum processed in a lab diagnosis of pulmonary (respiratory) TB?

A

Class 3 lab under a class 1 safety cabinet, under negative pressure, 0.74m3/sec

40
Q

When was consumption first described and who by

A

1970- Benjamin Martin

“Wonderfully minute living creatures”

41
Q

When was the cause of consumption discovered

A

1882 - caused by infectious agent Kochs bacillus

42
Q

Recently UCL proved that Granvilles mummy had TB instead of ovarian cancer by finding what

A

TB DNA in lung, femur, gall bladder

43
Q

What magnification is used to view sputum smears stained by ZN

A

1000x light microscopy

44
Q

How many microbes per ml is required to visualise one organism

A

10^4 microbes in 1ml

45
Q

What is the incredibly specialist agar that sputum is culture on

A

Lowenstein-Jensen slopes (LJ slopes)

46
Q

What does LJ slopes contain

A

Egg, glycerol, minerals, potato flour, antibiotics, malachite green

47
Q

How many weeks and what temp do you incubate the sputum

A

37deg for up to 12 weeks

48
Q

Describe the colonies in m.tuberuclosis

A

Generally grown 4-6 weeks,

  • yellow/buff coloured colonies, irregular in shape
  • colonies ZN positive
  • form distinctive serpentine cords when stained.
49
Q

Who discovered the serpentine cords

A

Robert Koch.

50
Q

What makes the cells to grow in serpentine cords

A

Cord factor - trehalose 6,6’ dimycolate

51
Q

How long is the treatment regime for TB

A

six months - toxic anti mycobacterial drugs

52
Q

What is the combo of drugs

A

Isoniazid
Rifampicin
Pyrazinamide
Ethambutol

53
Q

What are side effects of TB treatment

A

Hepatitis (inflammation of liver), gastrointestinal disturbances

54
Q

What vaccination is used to prevent TB

A

BCG vaccination (1953)

55
Q

What is the vaccination made of and how is it obtained

A

Live attenuated form of m.bovis.

230 passages over glycinerated bile potato medium in vitro.

56
Q

How effective is the vaccination and how long does it last

A

50-80% effective, last 10-15 years

57
Q

What changed about the vaccine from 2005

A

Targeted vaccination introduced to high risk e,g,

Babies born in areas of uk where TB prevalence is high e.g, London

At risk employees e,g. Healthcare workers

58
Q

What is the principle of the Mantoux test ( tuberculin skin testing)

A

TST detects delayed type 4 hypersensitivity. If previous infection, sensitised T cells circulate that respond to re- exposure to TB antigen

59
Q

What is the procedure of the Mantoux test

A

Inject 0.1ml of tuberculin purified protein derivative (PPD) into inner surface of forearm. (intradermal injection). Injection produce pale elevation of skin (wheal) 6-10mm diameter.

60
Q

What is the interpretation of the TST

A

Examined between 48 and 72 hours,measure induration (mm); positive if induration is >10mm

VACCINATION GENERATE POSITIVE RESPONSE

61
Q

Are mycobacterium multicellular or unicellular?

A

Unicellular

Microbiology (5 decks)

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