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Microbiology: Gram Negative: Enterobacteriaceae: E. Coli, Shigella

Describe enterobacteriaceae
- Gram-negative

- 2-4 uM length Facultative anaerobes

- most motile

- Lactose fermentation to differentiate Generally non-hemolytic
Where do they live?
GIT commensals
contaminte - vegetation, water, soil
What is the result of LF test for E coli?
- very characteristic of E. coli on MAC

- different from NLF

- Ecoli very aggressive LF

- pH drops, ppt dy out and bright! pink
Flow Chart
How is E coli organized and characterized?
1. E. coli Serotypes

2. E coli pathotypes

3. E coli verotypes
How are pathotypes organized of e coli?
- based on virulence mechanism &
process by which disease is caused
What are examples of E coli pathotypes?
• EnteroToxigenic E. coli (ETEC)

• EnteroPathogenic E. coli (EPEC)

• Shiga-Toxin producing E. coli (STEC)

• EXtraintestinal E. coli (ExPEC)
What are varitypes of E coli based on?
Variations in virulence repertoire within Pathotype isolates:

- adhesins (fimbriae) & toxins
E coli Pathotypes
What dz's do ETEC, EPEC, and STEC cause?
- enteritis: diarrhea, scours, colibacillosis
What dz does ExPEC cause?
What is enteritis?
colibacillosis", Diarrhea

seen in:poultry, pigs, ruminants, dogs, cats, horses, and rabbits
What are the strains that cause enteric dz?
typically exogenous
Ehat is ETEC?
Enterotoxigenic E. coli
What are the key components of ETEC?
- - fimbriae & fluid loss (enterotoxins)
What kind of diarreha is seen with ETEC?
- watery
- heavy
What kind of damage does ETEC cause?
- little tissue damage or inflammation
Describe how ETEC affects the enterocyte?
- toxin forces cell to dump Cl ion into GIT lumen

- keeps Na from getting in to cell

- water follows (hydrosecretion) in to lumen because of gradient

- Na, CL, HCO3 accumulate in lumen
What can this diarrhea result in?
dehydation → death
What is Sta? What animals do we see them in?

What is ST? What animals do we see them in?
1. heat stable enterotoxin : piglets, dogs, calves and rabbits

2. piglets and rabbits
Describe ETEC and neonatal diarrhea?
- severe watery diarrhea in neonat

-"white scours"
What can neonatal diarrhea lead to?
dehydration → enddotoxic shock →
terminal septicemia
Can some die before the diarrhea starts?
- yes, because of endotoxin end of LPS

- LPS will be dumped free into microenviro during replication into blood
What can LPS cause?
- if enough can cause :

- hypotension (vasodialtion)

-compromised cardiac ftn,

-bind to TLR-4 macrophage start dumping TNF, ILN 4

- Alveoolar capillaries destroyed → set up of DIC
What are predisposing factors to neonatal diarrhoea?
- no maternal antibodies

- Poor hygiene

- Stressors (air temp)

- Low gastric acidity: bacteria reach intestine
What is the most common cause of E coli diarrhea in neonatal cattle, pigs, dogs and rabbits?
- ETEC!!!
What is ETEC a major cause of in post weaning pigs?

What is a key factor in this?

- weaning stress is a key factor
What are intervention strategies?
block fimbrial attachment

1. Vaccinate pregnant dams/sows → Commercial or Autogenous Vaccines

2. Give anti-pilus antibodies
How can you tx ETEC?
- Abx : Apramycin good for Ecoli and salmonella
- a new tx approach = phage therapy
Does EPEC produce toxins?
Describe EPEC pathogenesis?
1. initial colonization → Type 3 Secretion System (TTSS)

Adhesion bundle forming pilli (BFP)

2. EPEC eject proteins
What are the functions of the proteins EPEC injects?
1. induce pedestal in enterocytes

2. provide host entercyte receptor
What are two types of host eneterocyte receptors?
Intimin → adhesin, remains on bacteria surface

TIR → Translocated Intimin receptor → inserts without host membrane cell and bacteria making ligand at same time for this receptor intimin
What is the result of the colonization and injection of proteins by EPEC?
Attachment/Effacement (AE) Lesions
What is effacement?
- shortening of the enterocyte microvilli and cell death
Describe AE lesions?

What do these lesions result in?
1. effacement

2. PMNs infilitrate

3. Malabsortion of Na and CL

4. mucoid, chronic, diarrhea

5. failure to thrive

no one understand how diarrhea occrus
What is a TTSS?
- like a needle

allows to inject stuff into cells

ie: injects receptor so has more intimate relationship with enetercyte
What is Pig EPEC?
- post weaning diarrhea

- small and large intestine
What is dog EPEC?

What are risk factors for it?
- most likely diarrhea causing E coli isolated

- risk factors:

-kennel and pet stores
- 1-3 month of age
- enteric virus co-infections
What is Rabbit EPEC?
- only important E coli in rabbits

- suckling rabbits: 100% mortality
- weaned rabbits: 0 -50 % mortality
What is STEC?
Shiga toxin producing E coli
What is ED?
- Edema Disease in weaned pigs
How is ED/STEC spread?
fecal oral
Are there AE lesions in ED?
What defines STEC?
- shiga toxins (Stx)euro virulent toxin VTEC

- Stx 1 and Stx2 : ex: two maintypes 1 and 2
- subtypes
Of the shiga toxins, which type is a problem we see in people?
- 2

- see transmision to ppl particulatlry
Describe Stx2e?
- access host cell cytoplasm

- shut down protein synthesis

- cell death
Describe how STx toxins cause problems?
- image

- fimbriae (F18) receptors on intestinal dpi cells

- Stx2e toxins pass thru enterocyte → into blood stream → lots of problems now (enterotoxemia)

- get into cells and shut down protein sysntheis at ribosome

- kills cells and see signs
What cells does Stx toxin like to target?
- vascular endothelical cells
Is STEC zoonotic?
Describe O157: H7?
- from cattle, d/n cause clinical dz

- in ppl huge problem → makes very sick

- get from enviro contamination
Describe the dzO157: H7 causes in ppl?
- mild to life threatening

- dysentary
- +/- uremic

- hemolytic and uremic syndrom
What does ED cause in target tissues?
What is the result of STEC in pigs?

What CS are the most unique for this?
- no diarrhea ****

- no fever ***

- enterotoxemia ***

- sudden daeth

- CNS signs ( ataxia, paddling, confusion)

- edema of eyelids and forehead

- pecular squeal
What is found on PM with STEC in pigs?
- edema of CNS, stomach, larynx and kidney

- not sure why edema

- kidney edmema as Ab/Ag complexes dumped into glomeruli
What do calves and lambs and dogs show for STEC?
- diarrhea, dysentery

- not the edema version

- tend not to see the ureic portion

- different serotupes

- 1/2 dozen that cause dysentary
What CS do humans deveople with STEC?

Why does intravascular hemolysis occur?
What does this result in? 2
- Hemorhagic colitis

- Heamolytic Uremic Syndrom → intravascular hemolysis and renal failure

- receptors on endo cells
- get plt activation and micro thrombi
Describe HUS in ppl?
- Hybrid phenotype

- Enteroaggregative (EAggEC)
- Shiga toxin E coli (STEC)
- aerobactin (siderphore from ExPEC

Multidrug resistant

fenugreek sprouts
walkteron: cow manure: Ecoli: )157:H7
What is ExPEC?
Extraintestinal Pathogenic E Coli
What are subtype abbreviations for ExPEC? 4

What animals does SEPEC affect?
What animals does UPEC affect
- SEPEC → SEPticemia E Coli (pigs, calves, chickens)

- UPEC → Urinary Pathogenic E Coli (dogs)

- Mastitis dairy cow

- Pyometera (dogs)
What is the source of ExPEC?
- endogenous, unlike ETEC,EPEC, STEC

- GIT flora, Mastitis possible
Is there a direct zoonoses with ExPEC?
generally no

exception: UPEC to ppl
Describe the virulence factors of ExPEC? 4

Which ones are FIP's?
- fimbriae and long LPS

- siderphores → host Fe sources, critical to survival

- UPEC and mastitis Ecoli are FIP
ExPEC overview

not best don't go over
What does ExPEC - SEPEC subtype cause in poultry?
- septicemia

- 4-8 weeks old
Describe the pathogenesis of SEPEC subtype in poultry?

How is it transmitted?
- Respiratory initially → caseous air sacculitis

- ingested/ inhaled

- septicemia → air sacculitis → pericarditis and perihepatitis and polyserositis
Why are air sacs affected?
they lack innate immune protection, great place to live
What are risk factors for birds for SEPEC?
- resp. virus → Mycoplasma spp,

- ammonia → also compromises cilia
What virulence factors aid in SEPEC in birds?
- four Fe acquisition systems:

aerobactin - siderphore (free Fe)

- critical for them to replicate
Describe SEPEC in neonatal pigs, calves and lambs?

Why does endotoxic shock occur?
- typical acute septicaemia → endotoxic shock → because of LPS

- leads to death
What are risk factors of SEPEC in neonatal pigs and calves?
- inadequate colostrum

- poor sanitation
What is a common entry point for SEPEC in these neonates?
- navel ill

- umbilical stump
Describe EXPEC - UPEC in dogs and cats?
- more in dogs then cats

- the most frequently isolated bug cause of UTI*****
What is the source of EXPEC - UPEC?
- fecal source: typically cystitis

- usually endogenous → GIT flora
What are virulence factors of EXPEC - UPEC? 6

What does the fimbrae allow?
What is the function of the flagella?
What is the function of the LPS?
What is the function of the alpha hemolysin?

What does the fact that they are a FIP allow for?
1. fimbriae (P): colonize UT epithelium

2. Flagella - ascending UTI

3. LPS : endotoxin, resists compliment

4. alpha hemolysin damages uroepithelium

5. siderphores: aerobactin, 5 others

6. FIP → chronicity
Where does the bug remain most of the time even though it has flagella?
- 99% time stay in bladder to cause cystitis

- sometimes goes up to kidney
Describe the zone of hemolysis of EXPEC UPEC?
small zone
Is UPEC zoonotic?
potential from dog
What are two times of greatest risk for mastitis in cattles?
1. 2 weeks before and 1 week after partitions

2. 2 weeks after dry off
What does EXPEC cause in cattle?
coliform mastitis, which could occur in any app but cattle are prone at certain times of lacation
Why are cattle prone to coliform mastitis during these times?
- neutrophls not working up to par at these times
Are they likely to get mastitis as dry off?
?? no, because dry off udder has lots of stuff there to prevent infections

- lactoferrins → bind Fe, keeping it away from bugs
What kind of organism is EXPEC in cattle causing mastitis?
Is there a Vx to provent coliform mastitis?

What does this Vx prevent?
- yes, only one out there

- without saccharine portion , protect animal from systemic effects not from infection
What are Clinical manifestations of coliform mastitis?
- peracute illness

- endotoxic shock → so can develop fast

- death

- acute and chronic possible
What are risk factors for EXPEC in cattle causing coliform mastitis?
- perpartum

- dry off time

- on pasture

- heavily manure contaminated environ

- low SCC
Why does having a low SCC pose a risk?
- less optimal greater risk of E coli

not complete protection
If it is chronic, what complications can arise?
- penetrate epith. cells of mammary glands and hangout
What are interventions of coliform mastitis?
- manure mgt

- Vx

- teat dip

- watch bedding

- wash hands

- its is transmissible by the environment
What is pyrometer in dogs >cats?

What is the common pathogen involved?
- pus in uterus

- most common genital tract infection in dogs

- E Coli most common pathogen
What is the pathogenesis of pyometra?
- metestrus and progesterone production

- endogenous source from GIT flora

- gets into cervix at this time

- massive PMN recruitment
What are CS of pyometra?
- abdominal enlargement

- purulent vaginal discharge

- Fever → LPS

- hypotension

- PU/PD due to Ag/Ab complex destruction of renal tubules
What other bacteria has been associated with pyometras?