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IMS > Topic 5 - Infection > Flashcards

Topic 5 - Infection Flashcards

Lectures 15-16

1
Q

What are the organisms which cause infection?

A

Helminths, Insects, Protozoa, Fungi, Bacteria, Viruses and Prions

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2
Q

What is a parasite?

A

AN organism which depends on another for its survival to the detriment of its host (traditionally only helminths, insects and protozoa are considered medical parasites)

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3
Q

What is an endoparasite?

A

Lives inside the body, major cause of illness (helminths and protozoa)

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4
Q

What is an ectoparasite?

A

Lives outside the body, minor symptoms but can transmit other infections (insects)

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5
Q

What is a protozoa?

A

Unicellular organisms, some have complex lifecycles involving multiple hosts

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6
Q

What is Entamoeba histolytica?

A

Example of an Amoebae

  • invades large bowel lining
  • causes dysentery (abdomical cramps + bloody diarrhea)
  • excreted with faeces
  • spread vie contaminated food and water
  • due to poor hygiene/sanitation
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7
Q

What is Plasmodium falciparum?

A

Example of Sporozoa, commonly known as Malaria

  • lifecycle in human and mosquito hosts
  • infects RBC and liver
  • symptoms: fever, headaches, joint pains
  • complications: kidney failure, coma, death
  • risk is geographical
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8
Q

What is a Helminth?

A

Worms! Complex organisms, some of which have complex lifecycles involving multiple hosts. Other species have their own helminths hat can accidentally cause human disease

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9
Q

What are the 3 types of helminths?

A
  • Cestodes (tapeworms, flat and segmented)
  • Trematodes (flukes, unsegmented and flat)
  • Nematodes (round worms, cylindrical, have difestive tract with lips, teeth and anus)
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10
Q

What is Taenia saginata?

A

Beef worm. A cestode.

  • intestinal parasite of humans
  • largely asymptomatic (abdominal pain and malnutrition)
  • diagnosed through stool microscopy for eggs
  • cattle are intermediate hosts
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11
Q

What is Schistosoma haematobium (bilharzia)?

A

A trematode.

  • human host, infects the veins around the bladder
  • causes bladder inflammation, bleeding into urine (haematuria)
  • intermediate host is the freshwater snail
  • diagnosed through urine microscopy for eggs
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12
Q

What is Cimex lectularius?

A

The bedbug - an ectoparasite.

  • wingless insect
  • worldwide infestation of human dwellings
  • hides in cracks and furniture
  • emerge at night - blood meal 5-10mins long
  • itchy rash after bite
  • can transmit other infections (protozoa in South America)
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13
Q

What are the two main forms of fungal infections?

A
  • Yeasts (single cells which bud)
  • Moulds (filamentous strands)
  • Some are able to switch (diamorphic fungi)
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14
Q

What is the difference between Tinea Pedis and Tenia Corporsis?

A

Both superficial fungal infections.
Tenia Pedis is athletes foot.
Tinea Corporis is ‘ringworm’ (not a worm)

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15
Q

What is Cryptococcus neoformans?

A

A severe invasive fungal infection

  • infects patients with low resistance due to failing immune system
  • causes meningitis
  • headaches, neck stiffness, confusion, coma, death
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16
Q

What is meningitis?

A

Inflammation of the membranes lining the brain.

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17
Q

What are bacteria?

A
  • Unicellular organisms
  • Cell membrane
  • Cell wall
  • No nucleus
  • Reproduce asexually
  • Move using flagellae and pili
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18
Q

What are the classifications of bacteria?

A

Round - coccus
Rod - Bacillus
They can come in clusters, chains or pairs.

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19
Q

What do Gram Stains mean?

A

Gram positive - Purple
Gram Negative - Pink
The stain allows you to predict which antibiotics would be effective

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20
Q

What is streptococcus pneumoniae?

A

Pneumonia.

  • gram positive cocci in pairs
  • colonise nose and throat
  • invade other sites such as lungs, causing pneumonia
  • cough, dirty sputum, chest pain, breathlessness, fever
  • complications include blood stream infection, meningitis and death
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21
Q

What are viruses?

A
  • dependent on infection of host cell for metabolism anf replication
  • contain DNA or RNA, a protein coat and an outer membrane
  • very small 1/100th size of bacteria
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22
Q

What is an acute viral infection?

A

Norovirus infects host for days, causing diarrhea and vomiting

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23
Q

What is a chronic viral infection?

A

Hepatitis C causes liver inflammation for years

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24
Q

What is a latent viral infection?

A

Herpesviruses can be dormant for decades before reactivating to cause disease

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25
Q

What is the varicella zoster virus?

A

Primary infection causes Chicken Pox (rash and fever)

  • virus becomes dormant in sensory nerve roots
  • reactivates years later as Shingles (same rash, confined to dermatome)
26
Q

Which virus can contribute to cancers?

A

Epstein-Barr virus.

  • usually causes mild illness
  • infects immune B cells and epithelial cells of the nose and mouth
  • 90% of us get it
  • latent lifelong infection
  • contributes to certain cancers with other factors (nasopharyngeal carcinoma esp in Southern China and lymphone in HIV infection)
27
Q

What are prions?

A
  • Smallest infective agents known
  • Proteinaceous Infectious particles
  • Lack nucleic acid - not living
  • Proteins are abnormal and accumulate in neural tissue
  • Difficult to destroy as standard sterilization techniques do not work
28
Q

What are some Prion diseases?

A
  • Creutzfeldt-Jakob disease (rare fatal degenerative neurological disease, transmitted via human growth hormone, surgical instruments and corneal grafts.)
  • Variant CJD typically occurring in younger adults (thought to be derived from bovine spongiform encephalopathy, BSE or mad cow disease)
  • Kuru (similar to vCJD, but occured in 50s in Papua Nwe Guinea through cannibalism)
29
Q

What is endogenous infection?

A

When normal flora from the skin, gut, upper airways ot genital tract gets in the wrong place. Infection basically comes from ourselves.
(eg, UTI - cystitis)

30
Q

What is Cystitis?

A

UTI.

  • Causes: lower abdominal pain, urgency, dysuria and frequency.
  • Most commonly caused by gut flora bacteria such as E.Coli
31
Q

What is exogenous infection?

A

Caught from someone/something else: another person, animals/insects or the environment.

32
Q

Routes of transmission for endogenous infections?

A

Migration
Perforation
Blood

33
Q

Routes of transmission for exogenous infections?

A 
Contact
Injuries (trauma/bites)
Airborne
Oral (food/water)
Bloodborne
Sex
Mother to baby (vertical)
34
Q

How is Endocarditis spread?

A

Blood - an endogenous infection.

  • dental work may allow mouth flora to enter blood stream
  • invasion can occur in heart valves esp if valve tissue is abnormal
  • causes inflammation ‘vegetation’ and structural damage
35
Q

What is Impetigo?

A

Exogenous infection through direct skin contact.

  • superficial skin infection due to streptococci or staphylococci
  • spreads rapidly between people
36
Q

What is Tetanus?

A

Lockjaw.

  • Clostridium tetani
  • bacteria present in soil
  • contaminates wounds
  • releases tozin causing paralysis
  • prevented by vaccination
37
Q

What is Hepatitis B?

A

Blood-borne infection.

  • liver
  • some viruses spill into blood
  • transmission by blood exposure
38
Q

How does vertical transmission occur?

A
  • During pregnancy (rubella)
  • At the time of birth (herpes)
  • Breast milk (HIV)
39
Q

What are the pathogen factors in infection?

A
  • Infectious dose
  • Direct infection of cells/tissues
  • Virulence factors and toxins
  • Resistance to antibiotics
40
Q

What is the Infectious Dose?

A

Minimum number of organisms required to produce disease

41
Q

What is Cholera?

A
  • Causes severe watery diarrhea
  • bacteria produce toxin
  • binds to gut lining cells
  • massive loss of fluid and electrolytes
  • severe dehydration, kidney failure and death
42
Q

What is the Cholera toxin mechanism?

A
  • cholera toxin enters cells of gut lumen
  • activates adenyl cyclase increasing cAMP
  • reduces Na+ absorption
  • increases Cl- secretion
  • water and electrolytes drawn into bown lumen resulting in diarrhea
43
Q

What are the natural barriers to infection?

A
  • Skin and mucous membranes
  • Stomach acid
  • Native bacteria
  • Immune system
  • Genetics
  • Behaviour
44
Q

What is Dengue fever?

A
  • Viral infection
  • transmitted by Aedes Mosquito
  • Fever and rash and muscle pain
  • Severe form causes bleeding, shock and multi-organ failure
45
Q

What are the four MAJOR pathogenic organism groups?

A

Bacteria
Fungi
Viruses
Parasites

46
Q

What History may patients tell you?

A
  • Non-specific symptoms (sweat, chills, loss of appetite, muscle aches)
  • Specific symptoms (eg, Pneumonia - cough, breathlessness, dirty sputum)
47
Q

What History is important to ask?

A
  • Conditions that may make the patient more susceptible to infection (past medical history & drug history)
  • Lifestyle activities that may bring them in contact with infection (occupation, travel, recreation and contacts)
48
Q

If WBC Neutrophil is elevated?

A

Bacterial infection

49
Q

If WBC Lymphocyte is elevated?

A

Viral infection

50
Q

If WBC Eosinophil is elevated?

A

Parasitic infection

51
Q

What are some basic tests for infection?

A

C-Reactive Protein (CRP) - marker of inflammation.
U&E (Urea and Electrolyte levels - kidney function.
LFT - Liver Function Tests.

52
Q

How do we detect organisms that can’t be grown in lab?

A
  • Identify part of the organism (antigens or DNA/RNA)

- Identify bodys immune response to the infection (antibodies eg IgM or IgG)

53
Q

What is the LgM antibody?

A
  • Initial antibody responce

- Appears within a week, disappears after a few months

54
Q

What is the IgG antibody?

A
  • Later antibody responce
  • Appears 10-14 days
  • Test for rising levels in consecutive samples
  • Persists throughout life
  • Useful in testing immunity to infection
55
Q

What is an antibiotic?

A

A chemical substance derived from a mold or bacterium that can kill microorganisms and cure bacterial infections. Form = of specific therapy.

56
Q

Where does Penicillin come from?

A

Derived from a mould.

57
Q

Where does Mupirocin come from?

A

Produced by Pseudomonas florescens (bacterium)

58
Q

What does an ideal antimicrobial do?

A
  • Has selective toxicity
  • Bacteriocidal rather than bacteriostatic
  • No resistance
  • Good Pharmacokinetics (reaches high levels in body and stays that way, allowing lower doses/day)
  • No side effects
  • Not inactivated by microbes secretory enzymes
59
Q

What are some issues of antimicrobials?

A
  • Broad spectrum of activity
  • Some cannot be given orally
  • Many cause side effects eg. anaphylaxis
  • Bacterial resistance
60
Q

How do we prevent infection spread in hospitals?

A
  • Cleaning wards, rooms and equipment
  • WASHING HANDS
  • Filtered air in operating theatres
  • Using sterile equipment when operating, taking blood etc.
61
Q

What are prophylactic treatments?

A
  • Antimalarials

- Antibiotics given to immunosuppressed patients

IMS (13 decks)

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