bacterial genetics and bacterial pathogenesis

Question 1

what are the three ways the bacteria can do horizontal gene transfer

Answer 1

transduction
conjugation
transformation

Question 2

transformation

Answer 2

DNA is taken up directly by cells

• competent cells
• naturally competent (transform a lot)
• DNA taken up is mostly linear, not plasmids or phage DNA

Question 3

transduction

Answer 3

viruses replicate in bacteria
lytic or lysogenic phases
-occurs when bacterial genes are packaged by phage and subsequently transferred to other bacteria

Question 4

what is a prophage

Answer 4

the phage genome once it is incorporated into bacteria genome

Question 5

generalized transduction

Answer 5

any random bit of bacterial DNA can be excised with the prophage

Question 6

specialized transduction

Answer 6

that phage has a specific loci and thus the phage will always have the same bit of DNA from the bacteria with it

Question 7

conjugation

Answer 7

bacterial sex via pilus

Question 8

transposable elements

Answer 8

DNA elements that move from one place in bacterial DNA to another

• can transfer genes to a new location or disrupt genes when they insert
• can carry virulence and ABX resistance genes

Question 9

direct transposons

Answer 9

moves the transposon to a new site

Question 10

replicative transpostions

Answer 10

transposon leaves a copy in place upon movement

Question 11

pathogenicity islands (PAIs)

Answer 11

virulence genes compact in distinct genomic islands

• acquired by horizontal gene transfer
• differ in GC content from rest of bacterial chromosome

Question 12

mutualistic symbiosis

Answer 12

host receives goods and or services while bacteria may receive goods in return
-both benefit

Question 13

commensalism

Answer 13

bacteria benefit while host is unaffected

Question 14

disease (pathogens)

Answer 14

due to interactions that damage the host directly or indirectly via stimulation of host inflammatory response

Question 15

opportunists and pathobionts

Answer 15

an organism which under normal circumstances does not cause disease, but can be pathogenic under some conditions

Question 16

as you go further down the GI tract what happens to the number of bacteria?

Answer 16

it increases

• helps extract nutrients
• required for proper immune system development
• affect metabolism of some drugs
• protects against pathogens

Question 17

coloniziation resistance

Answer 17

microbiota inhibits colonization by newcomers

• high diversity
• high density
• high colonization resistance

Question 18

Clostridium difficile

Answer 18

gram positive anaerobe found in GI tract

-only causes pathogenesis following antibiotic tx that depresses the rest of the microbiota of the gut

Question 19

psuedomembranous colitis

caused by C. difficile

Answer 19

severe ulceration of the colon

• initially associated with clindamycin, now associated with other ABX
• can be acquired in hospital as spores

Question 20

symptoms of psuedomembranous colitis

Answer 20

use of broad spectrum ABX
diarrhea
abdominal pain
fever

Question 21

how does C. difficile survive antibiotics

Answer 21

resistance genes
biofilm formation
spore formation

Question 22

how can C. difficile be spread?

Answer 22

via spores that are excreted by infected pts

-the spores can persist in the environment and are highly resistant to commonly used disinfectants and ABX

Question 23

spore components (5) of C. difficile

Answer 23

cell membrane
thick peptidoglycan mesh
another cell membrane
wall of keratin like protein
outer layer called exosporium

Question 24

how do you get rid of spores?

Answer 24

via autoclave
121 C for 15 min
-most ABX and hand sanitizers will not kill spores

Question 25

factors that facilitate bacterial infection and survival within a host

Answer 25

- outcompete commensals - attachment to host cells and tissues via -adhesins - evasion of innate and adaptive immune sys - acquisition of limiting nutrients eg: Fe, AAs - dissemination within a host and transmission to new host eg: ability to break down or cross tissue barrier)

Question 26

how to pathogens defend against phagocytosis?

Answer 26

capsules

Question 27

survival strategies within extracellular environments?

Answer 27

- capsules - vary surface exposed antigens - secret molecules that interfere with host defenses eg: toxins, enzymes

Question 28

survival strategies within intracellular environments

Answer 28

- resistance to ROS and NO eg: superoxide dismutase, suppression of host NO synthase expression - neutralized phagolysosome contents - prevent phagolysosome fusion - escape phagolysosme

Question 29

toxins

Answer 29

virulence factors excreted or not that are toxic to human or animal or plant cells

Question 30

what are some toxin types

Answer 30

endotoxin super antigens action on host cell membrane A-B type toxins

Question 31

staphylococcus aureus

Answer 31

1/3 of population colonized survives on skin, surfaces, environment -can cause food poisoning, bacteremia/sepsis, toxic shock syndrome, abscesses and cellulitis

Question 32

what is Hospital acquired methicillin resistant S. aureus

Answer 32

HA-MRSA is when a patient gets MRSA from a staff at a hospital

Question 33

what is community acquired MRSA

Answer 33

MRSA from the environment eg: daycare, wrestlers | -colonizes in the skin more than nose

Question 34

how many death are HA-MRSA and CA-MRSA responsible for per year?

Answer 34

20,000

Question 35

A/B toxins

Answer 35

a two component toxin

Question 36

A subunit of A/B toxin

Answer 36

responsible for the enzymatic activity of the toxin

Question 37

B subunit of A/B toxin

Answer 37

mediates binding to a specific receptor and transfer of the A subunit across the membrane **B subunit Breaks cell membrane