Human Microbiota Intro (9) Flashcards Preview

EMS - Mechanisms of Disease > Human Microbiota Intro (9) > Flashcards

Flashcards in Human Microbiota Intro (9) Deck (41):
1

What are micro-organisms that cause disease called?

Virulent/pathogenic

2

Akaryote

Without a nucleus

3

Prokaryote

Genetic material in a single DNA chain, not enclosed in a nucleus (bacteria)

4

Eukaryote

Distinct nucleus (protocists, fungi, plants, animals)

5

Koch's postulates

Robert Koch's criteria used to decide if microorganism caused a disease

6

Koch's postulate for genes

Genes encode virulence factors
- The gene encoding the trait of interest should be present and transcribed/translated in a virulent strain and be silent in a strain that does not cause disease; disruption of the gene in a virulent strain should result in the formation of a strain that is incapable of casing disease;

7

Problems with Koch's postulates

- Difficulty of isolation the causative agent
- Impossible to grow some pathogens in artificial culture
- Ethical objections
- Animal models not sufficient/don't behave same as humans

8

What are Viruses?

Obligate intracellular parasites

9

What are viruses comprised of?

Nucleic acid (DNA/RNA) core wrapped in a protein coat (capsomeres), some have a lipid envelope

10

Why are retroviruses unusual?

The virion carries an RNA copy of the genome but upon infection a host cell cDNA copy of virus genome is made using reverse transcriptase

11

Bacteriophage

Attacks bacteria

12

Bacterial shapes

Round, rod-shaped, icosahedral, brick-shaped, bullet-shaped

13

Viroids

Naked, infectious RNA molecules - plants suffer

14

Prions

Causes spongiform encephalopathies e.g. BSE/CZJ

15

Microfungi

Eukaryotic

16

What are most microfungi's cell wall made of?

Chitin (polymer of N-acetyl glucosamine)

17

Where else is chitin found?

Exoskeleton of arthropods e.g. insects

18

Moulds

Fungi that grow in mats of tiny filaments (hyphae), form mats (mycelia), can be subdivided into separate compartments by cross walls (septa), multicellular organisms related to mushrooms

19

What genus is most common fungi?

Cladosporium

20

Yeast

Unicellular fungi e.g. Saccharomyces cerevisiae

21

What diseases do moulds form?

Superficial infections e.g. ringworm and athlete's foot

22

What diseases do yeast form?

Thrush by Candida albicans

23

Protista

Unicellular eukaryotes, many free-living, some cause serious infections, can infect any human tissue

24

How are protista spread?

- Produce cysts to survive outside the body
- Insects
- Sex

25

Classes of protista

1. Apicomplxa (sporozoa)
2. Flagellate protista
3. Ciliate protista
4. Amoebae

26

Examples of infections caused by protists

Toxoplasmosis, amoebic meningitis, malaria, trypanosomiasis, leishmaniasis (Kala-Azar), amoebic dysentery, diarrhoea

27

Protista and vaginal infections

Caused by Trichomonas vaginalis, causes foul-smelling vaginal discharge, men can be asymptomatic carrier/balantis

28

Bacteria

Lack a membrane-bound nucleus/prokaryotes, small minority cause disease

29

Common shape of bacteria

Round/cocci or rod-shaped/bacilli, few are comma-shaped/spiral

30

Gram reaction

Ability to retain crystal violet-iodine dye complex when treated with acetone/alcohol

31

Gram +ve bacteria

30-40 layers of peptidoglycan

32

Gram -ve bacteria

Outer contains lipopolysaccharide, lipid A on surface acts as endotoxin > gram-negative shock

33

How are bacteria motile?

Flagella

34

What are fimbriae?

Hair-like structures that aid adhesion (gram -ve)

35

What are pili?

Tubes the join two cells together during conjugation to exchange genetic material (gram -ve)

36

What is a capsule?

Protects bacterium, even within phagocytes, preventing death

37

Why do some bacteria produce slime?

Helps stick to surface

38

What are endospores?

Resist a range of hazardous environments and protect against heat, radiation and desiccation (only few species have)

39

Spread of infection

- Droplet
- Faecal-oral
- Sexually
- Direct inoculation
- Animals
- Zoonoses (infection through animals being a reservoir)
- Fomites
- Intoxication

40

Examples of diseases acquired through drinking water

Typhoid, cholera, dysentery, hepatitis A and poliomyelitis

41

Virulence factors

Traits used to complete the cycle of infection