Escherichia Flashcards
What is the structure of Escherichia coli? In what oxygen conditions does it live in? What is it able to ferment?
Gram-negative rodes with peritrichous flagella
facultative anaerobes
glucose and lactose —> pink on MacConkey
How does E. coli respond to oxidase and catalase tests?
oxidase negative
catalase positive
What is E. coli’s most common habitat? Is it antimicrobial resistant?
normally live harmlessly in the intestinal tract of all mammals
yes - β-lactams and fluoroquinolones
What surface antigens are used to serotype E. coli? What 2 serotypes of E. coli are known to be extremely dangerous?
- fimbrial antigens (F)
- capsular antigens (K)
- flagellar antigens (H)
- somatic/LPS antigen (O)
- E. coli O157:H7
- E. coli O18:K1:H7
What are the main 4 intestinal (diarrheagenic) E. coli and where are they found?
SMALL BOWEL
1. enterotoxigenic E. coli (ETEC)
2. enteropathogenic E. coli (EPEC)
LARGE BOWEL
3. enterohemorrhagic E. coli (EHEC)
4. enteroinvasive E. coli (EIEC) - human pathogen
(enteritis + diarrhea)
What fimbrial adhesins are present in Enterotoxigenic E. coli? What is their function?
F4*, F5, F6, F41
attachment to the small intestine
What 2 enterotoxins do enterotoxigenic E. coli secrete? What do they do?
- heat-labile enterotoxin (LT)
- heat-stable enterotoxin (ST)
increase cGMP and cAMP levels within small intestine epithelial cells, causing water and electrolytes to secrete from the cell —> watery diarrhea
What pathogen causes neonatal diarrhea? What is the most common host? What are 3 symptoms?
enterotoxigenic E. coli
newborn calves, lambs, and piglets within the first week of life (receptors aren’t resistant to ETEC yet)
- diarrhea
- severe dehydration
- death
How is enteric colibacillosis treated? Controlled?
enterotoxigenic E. coli —> neonatal diarrhea
- milk with fluids containing electrolytes
- feeding ample amounts of colostrum shortly after birth for resistance (antibiotics not recommended)
What pathogen(s) cause post-weaning diarrhea? What is the most common host? What are 3 symptoms?
enterotoxigenic E. coli or enteropathogenic E. coli
pigs within 1-2 weeks after weaning
- watery diarrhea
- loss of appetite
- purplish discoloration of the skin
In what 3 ways is post-weaning diarrhea controlled/treated?
- vaccination
- breeding for disease resistance
- antibiotics following a susceptibility test
What adhesin is present in enteropathogenic E. coli? How is it able to translocate internal toxins and proteins into host cells?
intimin
type 3 secretion system
How does enteropathogenic E. coli cause watery diarrhea?
pedestal formation on small intestine epithelium leads to the loss of microvilli and causes attaching and effacing lesions
What surface structures contribute to enterohemorrhagic E. coli virulence? Where does it colonize?
- intimin (ahesion)
- T3SS
- attaching and effacing lesions
(like EPEC)
large bowel (colon)
What toxin is unique to enterohemorrhagic E. coli? What does it do?
Shiga toxin - causes hemorrhagic diarrhea and kidney failure
- EHEC = Shiga toxin-producing E. coli (STEC) = verocytotoxin-producing E. coli (VTEC)
Cattle are the primary reservoir of EHEC E. coli O157:H7, but they remain healthy. Why?
Shiga toxins bind to globotriaosylceramides (Gb3) found in the kidneys and intestine of humans, but are absent in cattle
What kind of disease does enterohemorrhagic E. coli cause? How is it able to do this?
edema disease in pigs within 1-2 weeks after weaning
Shiga toxin-producing (O138, O139, O141, O147) that binds to Gb4
What are 5 symptoms of enterohemorrhagic E. coli-caused edema disease in pigs?
- swelling (edema) of eyelids
- muscle tremors
- unusual squeal or snoring sounds
- neurological dysfunction
- flaccid paralysis and death within 36 hrs onset of clinical symptoms
What is enteroinvasive E. coli? What allows it to colonize the large bowel?
flagella lacking intracellular pathogen in the colon
ipaH (invasive) gene and T3SS
What are the 2 most common signs of enteroinvasive E. coli infection? What is the most common host?
- inflammation, necrosis, and ulceration of the bowel
- watery to bloody diarrhea (dysentery) with fever
humans —> dogs and cats resistant
What are the 4 most common extraintestinal pathogenic E. coli (ExPEC)?
- septicemic E. coli (SEPEC)
- avian pathogenic E. coli (APEC)
- uropathogenic E. coli (UPEC)
- mammary pathogenic E. coli (MPEC)
What type of E. coli causes colisepticemia? What are the most common hosts? How does it cause disease?
septicemic E. coli
newborn calves, lambs, and poultry, or immunocompromised animals
invades the bloodstream to cause systemic infection
What are 5 virulence factors of septicemic E. coli?
- serum resistance (necessary to avoid complement and leukocytes in the blood)
- fimbrial adhesins
- aerobactin iron uptake system
- LPS
- cytotoxic necrotizing factors (CNF)
What are the most common signs of colisepticemia in calves, lambs, and horses/dogs/cats?
CALVES: pyrexia, depression, weakness, hypothermia, prostration, meningitis, pneumonia, arthritis
LAMBS: watery mouth disease, death
HORSES/DOGS/CATS: pneumonia
What is septicemic E. coli the most common cause of?
- meningitis
- pneumonia
- arthritis
able to invade bloodstream and spread
What pathogen causes avian colisepticemia?
(systemic disease of birds and poultry)
avian pathogenic E. coli
- serotype O1, 2, 18, 35, 36, 78, 111
What are the 4 major virulence factors of avian pathogenic E. coli?
- type 1 (F1) and P fimbriae
- LPS
- serum resistance
- aerobactin iron uptake system
What are 4 common signs of avian colisepticemia?
- septicemia
- salpingitis
- pneumonia and airsacculitis
- egg yolk peritonitis
What are 2 common signs of uropathogenic E. coli infection?
- cystitis
- pyelonephritis
What 6 virulence factors are present in uropathogenic E. coli?
- type 1 pili - attachment to uroepithelium
- hemolysin A
- LPS
- CNF1
- aerobactin - kidney infection
- capsule - kidney infection
How is uropathogenic E. coli able to evade host defense and antimicrobials?
undergo the formation of intracellular bacterial communities or quiescent intracellular reservoirs
What are 4 common conditions in dogs caused by uropathogenic E. coli? Why are females more likely to become infected?
- cystitis - inflammation of the bladder
- pyelonephritis - inflammation of the kidney
- pyometra - inflammation of the uterus
- prostatitis - inflammation of the prostate
females have shorter urethras, making it easier for the bacteria to reach the bladder
Does uropathogenic E. coli have zoonotic potential?
YES
What does mammary pathogenic E. coli commonly cause? What are the 2 most common sources of infection?
infection of the mammary glands of cows and sows —> mastitis
- fecal contamination of the skin of the mammary gland
- relaxation of the teat sphincter following milking
What are the 3 most common pathogens causing mastitis in cattle? What are 3 clinical signs?
E. coli, Steptococcus uberis, Staphylococcus aureus
- swelling of the udder, pain, redness
- fever
- reduced milk production and quality
What are 2 ways to treat mastitis in cattle?
- broad spectrum intramammary antibiotic tubes
- nonsteroidal anti-inflammatories (NSAIDs)
What specimen can be collected for E. coli isolation?
- cervical swabs, vaginal discharge (pyometra)
- milk (mastitis)
- urine (cystitis)
- blood (septicemia)
- feces (enteritis with diarrhea)
How does E. coli grow in blood agar, MacConkey agar, EMB agar, and chromogenic agar?
BLOOD: hemolytic
MACCONKEY: pink (lactose and glucose fermentation)
EMB: metallic sheen
CHROMOGENIC: dark blue
How does E. coli respond to the IMViC test?
indole +
methyl red +
Voges-Proskauer -
citrate -
How are ETEC and EPEC strains of E. coli specifically identified?
ETEC
- enterotoxin: ELISA
- virulence genes LT, ST, EAST, F4: PCR
- fimbrial antigens: latex agglutination test
EPEC
- urease +
- virulence gene eae: PCR
- histopathological examination: effacement of mucosal surface
How are STEC (edema disease), SEPEC, and UPEC strains of E. coli specifically identified?
STEC
- clinical and PM findings: bloody/watery diarrhea
- hemolytic on blood agar
- serotype O139 and 141
- virulence genes eae, stx2e
SEPEC
- isolation from blood
- colicin V plasmids for serum resistance
UPEC
- isolation from urine
- type 1 pili (fimH)
What is the recommended treatment for E. coli infection? How is infection controlled?
- rehydration + electrolytes
- antibiotic therapy if infection is severe or systemic
~ feeding colostrum after birth
~ reduce stress during weaning
~ hygiene
~ vaccines for enteric disease in piglets and mastitis in dairy cows
E. coli summary: