4.0 Bacteriology Flashcards Preview

MedST IB: Biology of Disease (BoD) > 4.0 Bacteriology > Flashcards

Flashcards in 4.0 Bacteriology Deck (36)
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1

What four criteria are needed to identify the causative agent of a particular disease (Koch's postulates)?

1. Bacterium must be present in every case of the disease
2. Bacterium must be isolated from the disease and grown in pure culture
3. Bacterium from pure culture must cause disease when inoculated into a healthy, susceptible host
4. Bacterium must be reisolated from the new host

2

Define endemic:

Occurs regularly
At low or moderate levels

3

Define epidemic:

Sudden appearance of disease (or ↑ above endemic levels)

4

Define pandemic:

Global epidemic

5

Define point source outbreaks:

Bacterial infections arising from single origin

6

Define continuous source:

Point source outbreaks can be continuous outbreaks if source is not eradicated

7

Define propagated outbreaks:

Host-to-host transmission → even greater numbers of infections

8

Cell size range for bacteria:

0.5 - 3 um

9

Comment on the genome of bacteria:

Haploid
Single + circular
Plasmids
Bacteriophage

10

What colour are gram positive bacteria?

Violet/blue

11

What colour are gram negative bacteria?

Pink

12

What bacteria do not gram stain well?

1) Treponema
2) Mycobacterium
3) Mycoplasma
4) Leigonella pneumoniae
5) Rickettsia
6) Chlamydia

13

What is bacterial cell wall made up of?

Peptidoglycan

Alternating NAG + NAM sugars with oligopeptide cross-links

14

Functions of bacterial cell membrane:

1) Osmotic barrier
2) Signal transduction
3) Nutrient transport
4) Respiration

15

Differences between Gram +ve and Gram -ve cell envelope:

Gram +ve
Thicker cell wall

Gram -ve
Thinner cell wall
Periplasm
Outer membrane (with porins and LPS)

16

What enzymes are found in the gram -ve periplasm?

Hydrolytic enzymes:
1) Proteases
2) Lipases
3) Phosphatases
4) β lactamases

17

What does the Gram -ve outer membrane?

1) Porins
2) Lipopolysaccarhide (LPS)
- O-antigen (v. variable)
- Lipid A = endotoxin → TNF and IL-1

18

What is the bacterial capsule made out of?

Role of bacterial capsule?

Polysaccharides

Prevents drying out and provides protection

19

How are proteins secreted across the cell membrane (inner membrane)?

Use N-terminal secretion signal + Sec pathway

20

Complete the blanks:

Bacteria use _____ for mobility. Receptors on the bacterial nose sense chemicals and move towards ______ and away from _________.

__________ rotation of the _______ causes _________ movement. __________ rotation of the _______ causes ___________________

Bacteria use flagella for mobility. Receptors on the bacterial nose sense chemicals and move towards nutrients and away from toxic chemicals.

Counter-clockwise (CCW) rotation of the falgella causes forward movement. Clockwise (CW) rotation of the flagella causes tumbling + changing of direction

21

What is the signal transduction pathway used by bacteria to sense the environment?

Histidine-aspartate phosphorelay (HAP)

22

What is Quorom Sensing?

Sensing cell density
Some pathogens switch on their virulence only when cell population is high
Bacteria recognise a 'quorum' by secreting small signal molecules and sensing its concentration (communication)

23

Define transposons:

Segment of DNA containing useful genes that benefit bacteria

24

Define plasmids:

Extra-chromosomal genetic elements

(may contain transposons)

25

Define pathogenicity islands:

Genes required for survival and virulence are usually in pathogenicity islands (higher G+C content)

26

What are 3 techniques by which bacteria can acquire and transfer DNA?

1) Transduction
- From bacteriophage (bacterial virus)

2) Transformation
- Uptake from dead (lysed) bacteria

3) Conjugation
- Direct transfer between 2 bacteria

27

Direct vs indirect damage:

Direct damage = caused by toxins/bacterial invasion

Indirect damage = caused by host response

28

What do UPEC use to bind to bladder receptors?

Common (type I) pili

29

What do UPEC use to bind to kidney receptors?

Pap (p-pilli)

30

Why are UTIs from UPEC recurrent?

Acute infection → superficial bladder cells exfoliate → allows UPEC to invade underlying epithelial cells where they can persist in a quiescent reservoir + are protected from Abs → resurge and cause recurrence