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FP > Infectious Agents: Description of pathogenic microorganisms > Flashcards

Infectious Agents: Description of pathogenic microorganisms Flashcards

1
Q

What groups are microbes classified in? (4)

A

Viruses
Bacteria
Fungi
Parasites

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2
Q

Describe the size of microbes.

A

parasites>bacteria>viruses

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3
Q

What is in the 5 kingdom system?

A 
Animalia 
Plantae 
Protista 
Monera(bacteria)
Fungi
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4
Q

What is the 3 domain system?

A
  1. Bacteria
  2. Eukarya- fungi , animals , plants, protists
  3. Archaea
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5
Q

What are the distinct biological characteristics of all cells?

A
  1. All organisms are cells (except for viruses)
  2. Membranes
  3. Cellular and genome organisation
  4. Single cells
  5. Multiple stages - life cycles
  6. Multicellular
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6
Q

Stata the features of prokaryotes. (3)

A
  1. No nucleus
  2. No mitochondria
  3. Mainly circular DNA e.g. bacteria
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7
Q

State the features of eukaryotes. (2)

A
  1. Chromosome

2. Nucleus

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8
Q

Why is identification essential to understand? (7)

A

For:

  • Biology and microbiology
  • Evolution and phylogenetics
  • Pathogenesis of infectious diseases
  • Life cycles
  • Accurate diagnosis
  • Effective treatments
  • Public health control of infectious diseases
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9
Q

How do we classify pathogenic organisms? (2)

A

Structural and functional and metabolic observations.

Molecular and genetic and genome analysis.

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10
Q

What does the Linnaean classification include? (10)

A
  1. Domain
  2. Kingdom
  3. Phylum
  4. Class
  5. Order
  6. Family
  7. Genus
  8. Species
  9. Strain
  10. Isolate
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11
Q

Compare the genome sizes of microbes and humans.

A

Humans have 6,000,000,000 base pairs but only 19000 are protein coding genes.

Bacteria have 4,000,000 but only 4000 genes code for proteins. (This isn’t an exact number as there are a variety of bases so they have a different sizes of DNA).

Viruses have a genome size of 10,000 but only 9 genes that code for proteins. (Same disclaimer as the bacteria one.)

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12
Q

State which microbes need what type of microscope to be able to see them.

A

Bacteria- Light microscope with x100,000. (some bacteria are smaller and need an electron microscope).

Viruses need electron microscope with x100,000. They are 20-300 nm.

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13
Q

Describe viruses. (6)

A

Size : 20 nm to 300 nm.

Structure:
-DNA or RNA genome
- linear, segmented, single or double stranded
genome size 9Kb- 300Kb

  • protein nucleocapsid - individual capsomeres
  • Helical, cubic or complex arrangement
  • No cytoplasm
  • Enveloped or non-enveloped
    - may have components derived from host cell

-obligate intracellular organism-Obligate intracellular parasites cannot reproduce outside their host cell, meaning that the parasite’s reproduction is entirely reliant on intracellular resources.

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14
Q

Describe bacteria.(10)

A

Size: 0.5 μm to 3 μm

Structure:

  • Prokaryotic.
  • Haploid DNA, circular genome
  • no nucleus (DNA is coiled into nucleoid)
  • usually have rigid cell wall outside cytoplasmic membrane
  • no mitochondria
  • Binary fission (how they divide)
  • can have a capsule which surrounds the cell wall of the bacteria
  • may have pili and flagella (flagellum allows the bacteria to become motile)
  • ribosomes
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15
Q

How are bacteria visualised?

A

With Gram stains they can be either:

  1. Gram positive
  2. Gram negative
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16
Q

Describe how bacteria divide.

A

Bacteria do not have an antisense strand and they are haploid. On the antisense strand they have genes that code for proteins.

When the bacteria divides a septum forms between the 2 new cells which disappears after they split apart.

17
Q

How do bacteria infect people?

A

There are millions of bacteria all of which have different genomes, they are adapted to survive in certain conditions inside the human body.
They can infect via openings present in humans e.g. eyes, ears, skin, genitalia and anus, nose.

18
Q

Describe fungi (pathogenic fungi are known as mycoses).(6)

A

Size: over 2 μm

Structure:
-Eukaryotic

  • Haploid or diploid DNA
  • Single or multiple nuclei
  • Rigid chitinous cell wall outside cytoplasm

-Single or multicellular e.g.
- yeast (spheroid single cells budding and division)
or
- Filamentous form/moulds. – hyphae (e.g. Aspergillus spp) multinucleate branching hyphae forming mycelium

Classification is complex and is based on morphology (growth form), mode of reproduction (sexual or asexual) and disease caused: 70,0000species ~300 human pathogens

19
Q

How are mycoses classified?

A

Easier to consider by type of infection

Superficial mycoses
Skin, nail hair and mucous membranes (dermatophytes) or thrush (Candida albicans)

Cutaneous - e.g. Tanea – aka ringworm

Systemic mycoses
e.g Histoplasmosis

20
Q

Describe oral and yeast infections.

A

most common oral fungal infection
carriage rates 20% - 75% without any symptoms.
Usually Candida albicans

Yeast

  • normal constituent of the digestive and vaginal tracts
  • Generally no problems in healthy people
  • Opportunistic pathogens
21
Q

Explain fungi infections when the person has AIDS.

A

In AIDS the immune system is compromised by conditions such as HIV.
This means that the fungi that the body was capable of overcoming before AIDS now poses a threat to the body.

22
Q

Describe parasites.

A

Eukaryotic organisms – Protozoa and Helminths

Term parasite - sometimes applied to any microbe that lives in or on another animal host , causing it harm.

23
Q

Describe Protozoa.(6)

A
  • Single cells : 5 to 300 μm
  • Single or multiple nuclei
  • Haploid DNA
  • Morphology varies throughout life cycle
  • May have flagella.
  • Trophozoites, cysts and other morphotypes – complex life cycles
24
Q

Describe Helminths. (4)

A
  • These are multicellular parasitic worms
  • Different morphology and sizes at different life cycle stages
  • They can be microscopic or visible to the eye

3 groups:-
Cestodes are tapeworms e.g. Taenia saginata, the beef tapeworm;

Trematodes are flatworms or flukes and include Schistosoma haematobium 
		the cause of bilharzia or schistosomiasis
		filarial worm Onchocerca volvulus – River Blindness 

Nematodes which are roundworms e.g. Ascaris lumbricoides

FP (6 decks)

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