E. Coli

Question 1

Enterobacteriaceae members/genera

Answer 1

Eschericia
Salmonella
Shigella
Yersinia
Klebsiella
Proteus

Question 2

Enterobacteriaceae importance

Answer 2

Cont many important pathogens
Many carry plasmids with antibio res
Can lead to multi antibio res strains

Question 3

Enterobacteriaceae description in general

Answer 3

G-ve
Non-sporing
Rods
Facultative anaerobes
Motile via flagella
Don't cont cytochrome C/oxidase so test oxidase -ve

Question 4

E. Coli strain IDing

Answer 4

Classically by surface antigens
Somatic O antig
Capsule antig
Flagella antig
Being replaced by sequencing

Question 5

When E.Coli get into body

Answer 5

Colonise most mammals shortly after birth

Diff strains displace each other as commensal intestinal flora some strains are pathogenic

Question 6

E. Coli colibacillary diarrhoea

Answer 6

Multiple hosts (calves lambs piglets)
1-3d post birth
ETEC assoc
Large ETEC no bind to L and S intestine mucosa 
Release ST and LT toxins

Question 7

E. Coli diarrhoea

Answer 7

In older animals

ETEC and other types eg EPEC and VTEC

Question 8

E. Coli systemic colibacillosis

Answer 8

Multi host (calves lambs poultry)
Bact invade through GIT cause generalised infect
More likely if colostrum deprived
Diff E. Coli types but often expr serum res capsule

Question 9

E. Coli colibacillary toxaemia

Answer 9

Pigs
Oedema 1-2wk post weaning
VTEC with special VT toxin variant
Aka ‘shock weaner syndrome’ ‘haemorrhagic colitis’

Question 10

E. Coli UTI

Answer 10

Esp cat dog human

UPEC

Question 11

E. Coli enviro mastitis

Answer 11

Common

Usually mild

Question 12

Why diff diseases by same organism

Answer 12

Diff strains carry diff virulence assoc genes

key diff virulence factors are toxins, adhesins, secreted effector pros

Question 13

Why some animals more prone to UPEC UTIs

Answer 13

Anatomical differences

Genetic susceptibility

Question 14

UTI causing UPEC origin

Answer 14

Strains present in GIT

Question 15

UPEC UTI symptoms

Answer 15

Some asymptomatic
Some cause much inflam in UT so cause pain and discomfort
Bladder inflam caused (cystitis)
If kidneys are involved (pyelonephritis)

Question 16

How UPEC adhere to cause UTIs

Answer 16

Strains must bind and persist in UT
Use P pili or type 1 fimbr to adhere to epi or bladder cells
Flagella aid colonisation

Question 17

UPEC strain differences that allow inflam to be caused in UTIs

Answer 17

Some strains secrete toxins, potentially to release nutrients from cells to aid invasion
More dam caused - more likely strong inflam response

Question 18

UPEC toxins that dam cells

Answer 18

Haemolysins

Cytotoxic necrotising factor

Question 19

How UPEC can evade imm resp

Answer 19

Carries multiple adhesins that are phase variable (antigenic shift) can be switched on and off at single cell level

Question 20

How ETEC adhere and where

Answer 20

Adgere mainly to small intestine and multiply to high numbers
Adhere via F4 (mainly pig assoc) and F5 (mainly calf assoc) fimbriae

Question 21

Key factors assoc with the diarrhoeal dis

Answer 21

Enterotoxins
LT - heat. Labile tox
ST - heat stable toxin

Question 22

LT found, comp and action

Answer 22

Porcine and human strains
AB tox
B bind to GM1 ganglioside rec allow A entry that ADP-ribosylates some small Gpros - prev adenylate cyclase shut down
Cause ion efflux and influx disreg and loss of fluid to gut

Question 23

ST comp and action

Answer 23

Single pp

Once internalised act on guanylate cyclase activity also impact ion transfer and cause water loss

Question 24

EPEC pathology

Answer 24

Induce form of attaching and effacing lesions in GIT cause reduced epit integrity and diarrhoea
Inject their own rec (Tir) into host cell via type 3 secr syst, binds intimin on bact surface causing intimate attachment
More effector pros secr can interfer with cell water uptake and cause diarrhoea or alter cell signalling and lead to apoptosis of epi cells inducing inflam and neutro influx to try and control infection

Question 25

D against pathogens colonising GI epi

Answer 25

Incr mucus secr and sloughing off epi cells

Question 26

VTEC/STEC formation

Answer 26

E. Coli strain infected with phage carrying toxin and phage become lysogenic (enters chrom) then strain becomes VTEC or STEC

Question 27

Where are shiga toxin carrying phages common

Answer 27

In ruminants and toxin provide STEC advantage in colonising GI epi in ruminant

Question 28

EHEC formation

Answer 28

Shiga toxin carrying phage enters EPEC strain

Strain is v pathogenic to humans as has T3 secr system and shiga tox

Question 29

Why EHEC O157:H7 affects hunans not cattle

Answer 29

Infect terminal cattle rectum, but cattle dont expr Gb3 rec for toxin in endo cells, humans do so if EHEC colonises human gut and shuga tox is released can cause bloody diarrhoeafollowed by kidney and brain dam as there is capillary dam at these sites