E. Coli Flashcards
Enterobacteriaceae members/genera
Eschericia Salmonella Shigella Yersinia Klebsiella Proteus
Enterobacteriaceae importance
Cont many important pathogens
Many carry plasmids with antibio res
Can lead to multi antibio res strains
Enterobacteriaceae description in general
G-ve Non-sporing Rods Facultative anaerobes Motile via flagella Don't cont cytochrome C/oxidase so test oxidase -ve
E. Coli strain IDing
Classically by surface antigens Somatic O antig Capsule antig Flagella antig Being replaced by sequencing
When E.Coli get into body
Colonise most mammals shortly after birth
Diff strains displace each other as commensal intestinal flora some strains are pathogenic
E. Coli colibacillary diarrhoea
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
E. Coli diarrhoea
In older animals
ETEC and other types eg EPEC and VTEC
E. Coli systemic colibacillosis
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
E. Coli colibacillary toxaemia
Pigs
Oedema 1-2wk post weaning
VTEC with special VT toxin variant
Aka ‘shock weaner syndrome’ ‘haemorrhagic colitis’
E. Coli UTI
Esp cat dog human
UPEC
E. Coli enviro mastitis
Common
Usually mild
Why diff diseases by same organism
Diff strains carry diff virulence assoc genes
key diff virulence factors are toxins, adhesins, secreted effector pros
Why some animals more prone to UPEC UTIs
Anatomical differences
Genetic susceptibility
UTI causing UPEC origin
Strains present in GIT
UPEC UTI symptoms
Some asymptomatic
Some cause much inflam in UT so cause pain and discomfort
Bladder inflam caused (cystitis)
If kidneys are involved (pyelonephritis)
How UPEC adhere to cause UTIs
Strains must bind and persist in UT
Use P pili or type 1 fimbr to adhere to epi or bladder cells
Flagella aid colonisation
UPEC strain differences that allow inflam to be caused in UTIs
Some strains secrete toxins, potentially to release nutrients from cells to aid invasion
More dam caused - more likely strong inflam response
UPEC toxins that dam cells
Haemolysins
Cytotoxic necrotising factor
How UPEC can evade imm resp
Carries multiple adhesins that are phase variable (antigenic shift) can be switched on and off at single cell level
How ETEC adhere and where
Adgere mainly to small intestine and multiply to high numbers
Adhere via F4 (mainly pig assoc) and F5 (mainly calf assoc) fimbriae
Key factors assoc with the diarrhoeal dis
Enterotoxins
LT - heat. Labile tox
ST - heat stable toxin
LT found, comp and action
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
ST comp and action
Single pp
Once internalised act on guanylate cyclase activity also impact ion transfer and cause water loss
EPEC pathology
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
D against pathogens colonising GI epi
Incr mucus secr and sloughing off epi cells
VTEC/STEC formation
E. Coli strain infected with phage carrying toxin and phage become lysogenic (enters chrom) then strain becomes VTEC or STEC
Where are shiga toxin carrying phages common
In ruminants and toxin provide STEC advantage in colonising GI epi in ruminant
EHEC formation
Shiga toxin carrying phage enters EPEC strain
Strain is v pathogenic to humans as has T3 secr system and shiga tox
Why EHEC O157:H7 affects hunans not cattle
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
