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IMS TEST 2 > L16 & 17 Infection PART 1 > Flashcards

L16 & 17 Infection PART 1 Flashcards

1
Q

Order these organisms from smallest to largest and give examples:

Fungi
Prion
Insect
Virus
Protozoa
Helminth
Bacteria
A 
Prion – Kuru
Virus – influenza
Bacteria – staphylococci
Fungi – candida
Protozoa – malaria
Insect – fleas
Helminths – tapeworm
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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

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3
Q

What is an endoparasite?

A

Lives inside body and major cause of illness eg helminths (worms) and protozoa

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4
Q

What is an ectoparasite?

A

Lives outside body and cause of minor symptoms but can cause other infections eg fleas, lice, bed bugs and ticks

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5
Q

What is a protozoa?

A

Unicellular organism – some have complex lifecycles involving more than 1 host

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6
Q

What is an amoebae?

A

type of protozoa (eg Entamoeba histolytica)
Invades large bowel lining and causes dysentery (abdominal cramps/bloody diarrhoea), is excreted with faeces and spread via contaminated food/water. Poor hygiene/sanitation is a risk

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7
Q

What is a sporozoan?

A

Protozoa (eg Plasmodium falciparum (malaria))
Lifecycle in both humans and mosquitos, infects RBCs and liver. Symptoms include fever, headache, joint pains and complications include kidney failure, coma and death. Geographical risk.

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8
Q

What is the lifecycle of malaria?

A

Mosquito bites human, releasing sporozites into blood. In the liver turns into merozoite. In the blood stages through trophozoite, schizont and back into merozoite or gaetocyte. Gametozyte forms into stages of mosquito eg anopheles spp.

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9
Q

What are helminths?

A

Worms. Complex organisms but Some have complex life cycles with more than one host
Other species have their own helminths which can accidentally cause human disease

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10
Q

Name 3 types of helminths and their structures

A

Cestodes (tapeworm) – segmented, flat
Trematodes (fluke) – unsegmented, flat
Nematodes (round) – cylindrical, have digestive tract with lips, teeth and anus

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11
Q

What are tapeworms?

A

Helminth (eg taenia saginata (beef tapeworm))
Intestinal human parasite – largely asymptomatic but can cause abdominal pain and malnutrition. Cattle are intermediate hosts. Diagnosis made by patient and stool microscopy for eggs

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12
Q

What is the life cycle of a tapeworm?

A
  1. Eggs or gravid proglottids in faeces and passed into environment
  2. Cattle and pigs become infected by ingesting vegetation contaminated by eggs or gravid proglottids
  3. Oncospheres hatch, penetrate intestinal wall, and circulate to musculature. Oncospheres develop into cysticerci in muscle.
  4. Humans infected by ingesting raw or undercooked infected meat
  5. Scolex attaches to intestine
    Adults in small intestine
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13
Q

What is a trematode?

A

Helminth (eg schistosoma haematobium (bilharzia))
Infections of veins around bladder in humans. Causes bladder inflammation, haematuria. Intermediate host is freshwater snail. Diagnosis by urine microscopy for eggs

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14
Q

What is the life cycle of schistosoma spp?

A
  1. Eggs in freshwater
  2. Miracidium hatches from egg. Infects intermediate host – snail
  3. Cercariae leave snail, penetrate skin of human in water
  4. Immature worm enters the blood stream and ends up in veins near intestine or bladder
  5. Worms reach sexual maturity in veins of abdominal cavity, females produce eggs, eggs enter intestinal tract or bladder
    Eggs passed in urine or faeces enter freshwater
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15
Q

what is a bedbug?

A

type of ectoparasite (eg Cimex Lectularius)
wingless insect - hides in cracks in furniture and walls. emerge to feed 5-10 minutes for blood meal. itchy rash after bite and can transmit other infections (protozoa in south america (trypanosomiasis))

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16
Q

what are the 2 main forms of fungus?

A

yeasts which are single cells which bud

moulds which are filamentous strands

some can switch between yeast + mould (dimorphic fungi)

17
Q

what is a superficial fungal infection?

A

infection of skin and related structures eg tinea pedis (athlete’s foot), tinea corporis (ringworm). usually due to 3 common species of mould

18
Q

what is a severe invasive fungal infection?

A

eg cryptococcus neoformans (yeast)
infects patients with low resistance due to failing immune system eg HIV.
causes meningitis. other symptoms: headaches, neck stiffness, confusion, coma, death

19
Q

what is bacteria and what structures does it contain?

A

unicellular organism - prokaryote. has a cell membrane, cell wall, no nucleus, reproduce asexually and are able to move using flagellae and pili

20
Q

which common severe infections in developed countries is bacteria responsible for?

A
  • pneumonia
  • UTI
  • cellulitis
  • meningitis
  • clolecystitis
  • diverticulitis
  • appendicitis
21
Q

what different forms can bacteria take up?

A 
round - coccus
rod - bacillus
clusters
chains
pairs (diplococci)
22
Q

how is bacteria classified?

A

using a gram stain. some retain crystal violet stain, others do not. gram-positive (purple), gram-negative (pink)

23
Q

what is streptococcus pneumoniae aka pneumococcus?

A

bacterial infection. gram +ve coccus in pairs. colonise nose + throat. cause pneumonia when invade other sites eg lungs. symptoms: dirty sputum, chest pain, breathlessness, fever. complications: blood stream infection, meningitis, death

24
Q

what is a virus?

A

it is dependent on infection of host cell for metabolism and replication. contains protein core surrounding genetic material (DNA or RNA), protein coat and maybe outer membrane. small - 1/100th size of bacteria. can only be seen by electron microscope

25
Q

what is the life cycle of HIV?

A 
GP120 protein on surface of HIV.
HIV infects cell.
HIV binds to CCR5 protein on cell surface membrane.
CD4 cascade
reverse transcriptase
DNA integrase into cell DNA
protease

CHECK AND UPDATE DETAILS

26
Q

what spectrum of disease can viruses cause?

A
  • trivial infections eg rhinovirus (common cold)
  • severe chronic disease eg HIV
  • acute life threatening disease eg ebola - viral haemorrhagic fever
27
Q

how long do viruses infect host cells for in acute infection, chronic infection and latent infection?

A

Acute infection: norovirus infects hosts for days, causing diarrhoea and vomiting (gastroenteritis)

Chronic infection: hepatitis C virus causes liver inflammation for years

Latent infection – herpes viruses can be dormant for decades before reactivating to cause disease

28
Q

what is viracella zoster virus?

A

primary infection causes chicken pox. virus becomes dormant in sensory nerve roots. reactivates years later as shingles (same rash but confined to dermatome (area supplied by single sensory nerve))

29
Q

what is the epstein-barr virus?

A

usually carries mild illness eg glandular fever. infects immune system (B cells) and epithelial cells of nasopharynx. common (90%) and causes latent lifelong infection. contributes to certain cancers:

  • nasopharyngeal carcinoma esp in southern china
  • lymphoma in HIV infection
30
Q

what is a prion?

A

Smallest infective agents known. PROteinaceous INfectious particles
Lack nucleic acid, ie not a living organism. Proteins are abnormal and accumulate, mainly in neural tissue
They are very difficult to destroy. Standard sterilisation techniques e.g. disinfectants and heating do not work

31
Q

which 3 diseases are caused by prions?

A

CJD = Creutzfeldt-Jakob Disease. rare fatal, degenerative neurological disease transmitted via human growth hormone, surgical instruments and corneal grafts

Variant CJD - typically in yound adults. thought to be derived from bovine spongiform encephalopathy (BSE or mad cow disease)

Kuru - similar to vCJD
first in Papua New Guinea in 1950s. spread by cannibalism (esp brains of deceased relatives)

IMS TEST 2 (14 decks)

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