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

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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?

Septicemia
Mastitis
Pyometritis
UTI

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?

Diarrhea

- 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
orally

How can you tx ETEC?

- Abx : Apramycin good for Ecoli and salmonella
- a new tx approach = phage therapy

Does EPEC produce toxins?

no

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?

no

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?

yes

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?

edema

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

diagram

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?

FIP

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?

Klebsiella

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