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Topic 6: Infection & Forensic > TB and HIV > Flashcards

TB and HIV Flashcards

1
Q

What is tuberculosis (TB)? What is it caused by? Where is it usually found? What does the bacterium have?

A
  • Tuberculosis is a contagious disease caused by bacterium Mycobacterium tuberculosis
  • it can be found in many parts of the body but usually found in the lungs (pulmonary or respiratory)
  • the bacterium has a thick waxy cell wall making it difficult to break down
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2
Q

What are antibiotics? From what are they produced? What are they used for?

A
  • antibiotics are chemical substances produced by living organisms, generally microorganisms which are used to treat bacterial infections
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3
Q

What is a tubercle/ granuloma?

A
  • a tubercle/ granuloma is a tissue mass formed by the immune system attempting to wall off a foreign substance it can’t eliminate
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4
Q

What is an obligate aerobe?

A
  • an obligate aerobe is an aerobe that requires oxygen for aerobic respiration
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5
Q

What is the course of the disease (TB)?

A

course of the disease:
- bacterium enters the body
- primary infection
- latent phase (live bacteria inactive but dormant inside tubercle)
- active tuberculosis (secondary infection)
- death

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6
Q

What is the primary infection of TB? What happens during this phase? What forms at the end?

A
  • primary infection is the first phase, it can last for several months and may have no symptoms
  • during this phase, the body first mounts a non-specific immune response against the bacterium
  • macrophages engulf the bacteria
  • a granuloma/ tubercle forms
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7
Q

How does the bacterium enter the body? What is the likelihood of infection? What is the percentage of people exposed who become infected?

A
  • M. Tuberculosis bacteria are inhaled and lodge in the lungs, where they start to multiply
  • relatively low likelihood of infection - only 30% of people exposed become infected and only 5-10% of those will develop symptoms
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8
Q

When does active tuberculosis occur? What does the bacteria do to the lung?

A
  • active tuberculosis occurs after primary infection if there are too many bacteria for the immune system to tackle, or if the immune system is weakened
  • the bacteria multiply rapidly and destroy the lung, creating holes or cavities
  • the lung damage will eventually kill the patient, unless treated with appropriate antibiotic
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9
Q

What is the difference between active TB and latent TB?

A

active TB:
- TB bacteria are ‘awake’
- you will feel unwell
- you could pass TB to others
latent TB:
- Tb bacteria are ‘asleep’
- you do not feel unwell
- you cannot pass TB to others

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10
Q

What are some of the symptoms of TB?

A

symptoms:
- cough/ coughing up blood
- shortness of breath
- fever and extreme fatigue
- weight loss
- loss of appetite
- night sweats
- tiredness

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11
Q

How can TB be treated?

A
  • active TB can be killed by antibiotics
  • usually combination of four antibiotics for 2 months, then 2 for four months - ensures dormant bacteria is killed
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12
Q

What was the first TB antibiotic to be discovered? What is the issue with this antibiotic now?

A
  • Streptomycin first TB antibiotic discovered by Albert Schatz in the lab of Selman Waksman in 1932
  • problem of drug-resistant TB bacteria - now widespread resistance to streptomycin
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13
Q

What effect does TB have on the immune system?

A
  • phagocytosis impaired - TB bacteria can prevent lysosomes from fusing with vacuole containing bacterium (phagosome)
  • TB bacteria can suppress T-helper cells:
  • less cytokine production so less activation B and T- killer cells
  • reducing antibody production and attack by T-killer cells
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14
Q

How is TB diagnosed?

A
  • doctors take patients history (symptoms)
  • skin test = TB proteins (tuberculin) injected under skin - inflamed skin suggest TB infection although risk of false positives
  • newer blood tests detect presence of T-cells specific to TB antigens
  • sputum sample taken and cultured to see whether mycobacterium bacteria grow in lab
  • chest x-rays
  • family, friends, work colleagues may be tested if patient is positive for TB
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15
Q

What can TB also effect (glandular TB)?

A

TB can also effect:
- bones
- lymph nodes
- central nervous system

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16
Q

How does TB spread?

A
  • TB is transmitted by droplet infection
  • bacterium is carried in droplets and mucus and saliva, released into air when person talks, coughs or sneezes
  • droplets can remain suspended for several hours in poorly ventilated areas
17
Q

Why has TB declined in industrialised nations?

A
  • improved housing and living conditions
  • development of antibiotics
  • vaccination programmes
  • pasteurisation of milk
  • programmes to reduce transmission of TB in cows- infected meat no longer eaten
18
Q

What is HIV? What does it stand for? What does the virus consist of? What is it surrounded by?

A

HIV (Human Immunodeficiency Virus) is a structurally complex virus, an example of an enveloped virus
- the virus consists of RNA surrounded by a 20-sided (icosahedral) protein capsid (coat) enclosed in a layer of viral protein

19
Q

What is a virus?

A
  • a virus is a chain of nucleic acids, which lives in a host cells, uses parts of the cellular machinery to reproduce, and release the replicated nucleic acid chains to infect more cells
20
Q

What is AIDS caused by? What does it stand for?

A
  • AIDS (Acquired Immune Deficiency Syndrome)
  • is caused by infection with the human immunodeficiency virus, HIV
21
Q

What is the structure of a glycoprotein?

A
  • proteins with carbohydrate side chains, that are exposed in the surface of the envelope
22
Q

t helper cells

A
23
Q

reverse transcriptase

A
24
Q

integrase

A
25
Q

acute

A
26
Q

chronic

A
27
Q

opportunistic infection

A
28
Q

How can HIV be spread? What is the preventative measure?

A
  • unprotected sex with infected person = condoms
  • sharing needles (intravenous drugs) = needle exchange programmes
  • mother-foetus (childbirth) = c-section
  • breastfeeding = avoid breast-feeding
  • blood transfusion/ operations = blood screening methods
29
Q

What are the stages of the HIV life cycle?

A
  1. once RNA is inside the T helper cell/ macrophage, the enzyme reverse transcriptase converts viral RNA into viral DNA
  2. the enzyme integrase inserts the viral DNA into the host DNA
  3. the host cell reads the viral DNA, produces viral mRNA which is translated into viral proteins (envelope glycoproteins = enzymes)
  4. the envelope proteins incorporate themselves in the cell membrane
  5. these, together with the RNA assemble into new viruses
  6. as the virus bud off the host cell’s cell surface membrane, they cover themselves in it, which becomes the viral envelope
30
Q

What happens in the acute phase of HIV?

A
  • HIV antibodies appear in blood after 3-12 weeks
  • the infect person may experience symptoms such as fever, sweats, headaches, sore throat and swollen lymph nodes or no symptoms
  • there is rapid replication of the virus and loss of T helper cells
  • after a few weeks, infected T help cells are recognised by T killer cells, which start to destroy them. This reduces the rate of virus replication, but does not totally eliminate it
31
Q

What happens in the chronic phase of HIV?

A
  • sometimes called the laten phase
  • virus continues to reproduce rapidly but the numbers are kept in check by the immune system
  • there may be no symptoms during this phase, but there can be an increasing tendency to suffer colds or other infections, which are slow to go away
  • dormant disease like TB and shingles can reactivate
  • last for many years especially combined with drug treatment
32
Q

What happens in the disease phase of HIV?

A
  • eventually, increased number of viruses in circulation and a declining number of T helper cells indicates the onset of AIDS, the disease phase
  • the decrease in the number of T helper cells leaves the immune system vulnerable to other diseases. A normal T helper cell count is over 500 per mm3. Below 200 per mm3, there is high risk of infections by opportunistic infections

Topic 6: Infection & Forensic (8 decks)

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