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Microbiology > Lecture 4 - Mycobacteria > Flashcards

Lecture 4 - Mycobacteria Flashcards

(61 cards)

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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
How many droplet nuclei are released when someone talks for 5 mins, coughs, sneezes?
3,000 for each. | Sneezing 3000 up to ten feet away
26
The droplet nuclei once in the air die within 5 minutes. True or false
False | A few hours
27
What does the small size of the droplet nuclei allow for
Bypass mucociliary lining
28
What are the 5 stages of a TB infection
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
What in healthy people 'heals ' primary lesion
Cell mediated response
30
What are the symptoms of primary tuberculosis
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
How many people experience primary tuberculosis and how is the body prepared for attacking re exposure
10% and patients hypersensitised e,g, CMI (T- lymphocytes)
32
How many people are asymptomatic due to cell mediated response keeping the infection under control
90%
33
What is secondary tuberculosis
Reactivation
34
Give examples of how secondary tuberculosis is associated with impairment of CMI
Steroid therapy, immunosuppressive drugs, cancer chemotherapy, old age, HIV.
35
What happens to the dormant primary focus during secondary tuberculosis
Dormant primary focus becomes necrotic (cheesy) and liquefies distributing thousands of M, tuberculosis MTB into the lungs
36
What is the appropriate clinical sample for lab diagnosis of pulmonary (respiratory) TB?
Sputum
37
What category microorganism is m.tuberculosis
Category 3
38
What are category 3 microorganisms
Cause severe human diseases, serious hazard to employees, risk of spread in community BUT EFFECTIVE TREATMENT.
39
How is the sputum processed in a lab diagnosis of pulmonary (respiratory) TB?
Class 3 lab under a class 1 safety cabinet, under negative pressure, 0.74m3/sec
40
When was consumption first described and who by
1970- Benjamin Martin | "Wonderfully minute living creatures"
41
When was the cause of consumption discovered
1882 - caused by infectious agent Kochs bacillus
42
Recently UCL proved that Granvilles mummy had TB instead of ovarian cancer by finding what
TB DNA in lung, femur, gall bladder
43
What magnification is used to view sputum smears stained by ZN
1000x light microscopy
44
How many microbes per ml is required to visualise one organism
10^4 microbes in 1ml
45
What is the incredibly specialist agar that sputum is culture on
Lowenstein-Jensen slopes (LJ slopes)
46
What does LJ slopes contain
Egg, glycerol, minerals, potato flour, antibiotics, malachite green
47
How many weeks and what temp do you incubate the sputum
37deg for up to 12 weeks
48
Describe the colonies in m.tuberuclosis
Generally grown 4-6 weeks, - yellow/buff coloured colonies, irregular in shape - colonies ZN positive - form distinctive serpentine cords when stained.
49
Who discovered the serpentine cords
Robert Koch.
50
What makes the cells to grow in serpentine cords
Cord factor - trehalose 6,6' dimycolate
51
How long is the treatment regime for TB
six months - toxic anti mycobacterial drugs
52
What is the combo of drugs
Isoniazid Rifampicin Pyrazinamide Ethambutol
53
What are side effects of TB treatment
Hepatitis (inflammation of liver), gastrointestinal disturbances
54
What vaccination is used to prevent TB
BCG vaccination (1953)
55
What is the vaccination made of and how is it obtained
Live attenuated form of m.bovis. | 230 passages over glycinerated bile potato medium in vitro.
56
How effective is the vaccination and how long does it last
50-80% effective, last 10-15 years
57
What changed about the vaccine from 2005
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
What is the principle of the Mantoux test ( tuberculin skin testing)
TST detects delayed type 4 hypersensitivity. If previous infection, sensitised T cells circulate that respond to re- exposure to TB antigen
59
What is the procedure of the Mantoux test
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
What is the interpretation of the TST
Examined between 48 and 72 hours,measure induration (mm); positive if induration is >10mm VACCINATION GENERATE POSITIVE RESPONSE
61
Are mycobacterium multicellular or unicellular?
Unicellular

Microbiology (5 decks)

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