122. General characteristics of diseases caused by Escherichia coli. Flashcards
1
Q
Etiology of E coli?
A
Etiology:
- E. coli (Enterobacteriaeceae family)
- Gr(-), lactose (+)
- Antigens:
- O: LPS (181), endotoxin, cell wall antigens (NOT a virulence factor)
- K: polysaccharide (60), capsule antigen
- H: protein (53), flagella antigen
- F: protein (30) - F1-F18, F41, frimbra antigens - species specific
- Normal inhabitant of LI, normal flora, vitamin production
- Pathogenicity: mainly saprophyte (gut flora), some are facultative pathogenic strains
- Virulence factors:
- capsule, endotoxin (LPS, same as cell wall antigens, released when the bacteria breakdown),
- adhesins (frimbrae), toxins, invasive ability (normally cannot invade host cells, some strains can),
- ability of survival in blood
- Adhesins (endotoxin): fimbria -
- human (F2, F3 in newborn children),
- calves (F5, F17, F41),
- pigs (F4 -mostly, F6, F18),
- urogenital (F7-16),
- outer membrane protein of bacteria help with attachment,
- attach to the surface of GI epithelia and damage cells
- Intimin: produced by host cells, but initiated by bacteria
- Fibronectine receptors
2
Q
Toxins of E Coli?
A
Toxins:
- Enterotoxins: produced in gut
- LT: increased cAMP, large molecule, act on AC enzyme of host
- ST: increased cGMP, smaller, dehydration (normally enterocytes absorb water from gut, but damaged from toxins - enterocytes excrete fluid instead = causing diarrhea),
- metabolic acidosis
- Cytotoxins:
- Verotoxins: SLT/VT1/VT2 - inhibition of protein synthesis (endothel damage > edema
- > hemorrhagic, necrosis)
- Cytotoxic necrotic factor (CNF): human strains
- Cytolethal distending toxin (CDT): human strains, urogenital, extra-intestinal
- Alpha-hemolysin: pore-forming toxin
- Invasive ability
- Survival in blood (siderophors): septicemia strain (replicate and spread in blood)
- Genetic variability
3
Q
Pathotypes of E.coli ?
A
Pathotypes of E. coli- Enteric
- Enterotoxigenic ETEC
- produces enterotoxins, fimbria - causes diarrhea in suckling animals,
- newborn children, travellers,
- purely toxic effect that causes diarrhea (NO inflammation)
- Enteropathogenic EPEC
- adhesion from intimin, damage mainly microvilli (decreased absorption)
- causing dyspepsia of newborns
- Enterohemorrhagic/Verotoxigenic EHEC/VTEC
- bind with intimin,
- produce verotoxins (damage endothelial cells) -
- causing hemorrhagic colitis/diarrhea,
- hemolytic-uremic syndrome, purely toxic
- effect that causes diarrhea (NO inflammation)
- Enteroinvasive EIEC
- more in humans, dysentery-like
- Enteroadhesive-aggregative EAEC
- mild enteritis in humans
- Combined types: EHEC/EAEC Germany 2011 (O:104:H4)
4
Q
Extra-intestinal of Ecoli?
A
Extra-intestinal
- Urogenital: adhesin (F7-16), toxins (CNF, CDT, alpha-hemolysin)
- Septicemia, meningitis: newborn children, old people, immune compromised
- Colicin-V plasmid, alpha-hemolysin
- Can survive in blood and spread
5
Q
Diseases of animals caused by E coli ?
A
Diseases of animals caused by E. coli
- Enteric
- Calves: ETEC, VTEC
- Piglets: ETEC, VTEC, EPEC
- Rabbit: EPEC
- Dog, cat: ETEC, VTEC, EPEC
- Septicemic: calves, poultry
- Urinary tract infection, mastitis: cows, sows (MMA)
6
Q
Epidemiology of E coli?
A
Epidemiology
- Infection: bacteria replicate in gut (fast, 4X within 1 hr)
- Faeces (high amount), feed/water contaminated with feces, egg
- (poultry: germinative - infected eggs > infected chickens, can also survive on eggshells)
- Predisposing factors:
- insufficient hygiene,
- insufficient feeding of pregnant cows/weak calves,
- insufficient colostrum,
- overcrowding,
- environment/stable (low temperature, high humidity),
- nutritional deficiencies
7
Q
Pathogenesis of E Coli?
A
Pathogenesis:
- Infection PO: asymptomatic presence in the gut + predisposing factors
- Replicate in gut: production of enterotoxins (act in gut - diarrhea),
- verotoxins (more generalized effects - hemorrhages, edema)
- Septicemia: endotoxin effect, spread in blood and affect different organs
8
Q
Diagnosis of Ecoli ?
A
Diagnosis:
- epidemiology, clinical signs, PM
- Bacteriology:
- Isolation/identification: pure culture (samples from guts, parenchymal organs)
- Identification of serotype (O, K, H, F): certain serotypes produce certain diseases
- Identification of virulence factors:
- adhesins (agglutination, PCR),
- toxins (isolated gut test - inoculate bacteria into the gut, PCR)
- Examination of AB susceptibility
9
Q
Treatment of E coli?
A
Treatment
- Enteric diseases: AB that acts in the gut, not necessary absorbed
- Per os AB: polymyxins, quinolones, aminoglycosides, broad spectrum beta-lactam (amox, cephalosporines)
- Rehydration: fluid therapy
- Septicemia: parenteral, generally too late when see signs caused by endotoxins released when the bacteria die
- Mastitis: quinolones, aminoglycosides
- AB resistance
10
Q
Prevention of E Coli?
A
• Prevention
- Predisposing factors: correct feeding of pregnants, good nutrition and management, hygiene!
- Specific prevention
- Colostrum: received in time, quality (10% of their weight, presence of appropriate AB),
- quantity
- Vaccination: mainly in case of neonatal diseases (vaccination in pregnant animals)
- Probiotics (Gr+): Lactobacillus, Enterococcus, Bifidobacterium - colonize the gut, gut flora will shift to Gr+
- Prebiotics: feed additives