Escherichia Coli Flashcards
What are some general features of Ecoli
Gram negative family - enterobacteriaceae
Motile by peritrichous flagella
Rod shaped - 2um long and 0.5um diameter
Facultative anaerobe
Energy by oxidation and reduction of organic substances
Inhabitant of intestines or warm blooded animals
Frequently commensal some cause disease
What are true commensal
Symbionts
What biosynthesis role does Ecoli play
Biosynthesis of vitamin K
What groups can infections of Ecoli be
Intestinal - caused by diarrhoeagenic Ecoli
Extra intestinal - caused by extra intestinal pathogenic Ecoli
Pathogenic Ecoli can be grouped further into pathotypes on basis of clinical features and bacterial properties
What are the intestinal pathotypes of Ecoli
Enterotoxigenic
Enterohaemorrhagic
Enteropathogenic
Enteroaggregative
Diffusely adherent
Enteroinvasive
What are extra intestinal pathotypes of Ecoli
Neonatal meningitis associated Ecoli
Uropathogenic Ecoli
Avian pathogenic Ecoli
Sepsis associated Ecoli
Some cant be grouped e.g. mastitis or pyometra causing
What are Ecoli virulence factors
Adhesins - pili or fimbriae
Nutrient scavenge system
Toxins - can act on gut or systemic
Secretion systems - deliver host proteins to alter function or structure of cells
Bacterial components that activate innate immunity- Lipopolysaccharide from Ecoli is potent stimulator or inflammation
What can flagella pili and fimbriae act as
Adhesins
Flagella - motility
Some fimbrial types associated with increased virulence
What is a major driver of pathogenic diversity in Ecoli
Horizontal gene transfer
What are pathogenicity islands
Regions of DNA acquired into genome encoding virulence factors e.g. T3SS regonised by flanking genome repeats and different GC content
What can bacteriophages do
Transfer of toxin genes - Stx or Shinga like toxins
What are enterotoxins important in and what do they do
Important in ETEC
Damage erythrocytes leading to diarrhoea
What do Shiga like toxins do
Act on blood vessels and endothelial cells
Encoded by bacteriophages (Stx1 and Stx2)
What are Ecoli that carry Stx referred to as
STEC
EHEC are a class of STEC
EHEC are carried asymptomatically in cattle
Main source from beef or faecal contamination of veg/fruit
Toxin during human infection may cause haemorrhage in gut or damage kidneys
What serotypes are pigs affected by
O138, O139, O141 serotypes distinct from human/cattle EHEC STEC
Toxin has range of effects in pigs - neurological damage
Toxins may lead to fluid accumulation or lesions I’m range of tissues - gut, cardio-pulmonary, brain
Oedema of face and eyelids common sign
What does LEE stand for
Locus of enterocyte effacement
What does LEE do
The T3SS encoded on the LEE operon is associated with colonisation of gut in cattle and enteritis in humans
Unlike salmonella SPI1 T3SS, LEE doesn’t mediate cell invasion but translocates its own receptor enterocytes - allows tight binding to gut
Effectors then inject into host cell cause actin filamentation - in distinct attaching : effacing lesions with bacterium sitting on pedestal
What virulence factors are needed for disease with EHEC system
Adhesins
LEE T3SS secures EHEC to gut epithelium and elicits formation of lesions
Action of Stx-haemolytic Uremic syndrome
What is the German 2011 bean sprout Ecoli outbreak
O104 is EAEC usually causes persistent diarrhoea
The German isolate acquired Stx toxin genes so because persistent
Infection common in women 15-50 unusual as EHEC is usually an infection of children and elderly
Cucumbers wrongly identified as source but did have EHEC contamination
What is the extra intestinal disease caused by and what does it include
Caused by ExPEC
Includes neonatal meningitis, urinary tract and avian pathogenic pathotypes
Has distinct but variable virulence factors including invasion and systemic survival
No distinct genotype or virulence factor associated with pathotypes
What is APEC
Important endemic disease in layer and broiler sector
Major cause of mortality in young broiler respiratory and systemic disease
Cause 2-4% mortality in UK broiler flock
Reproductive tract infection in mature layers
Disease from APEC pathotypes and opportunistic infection from strains in microbiota
What do clinical presentations of avian colibacillosis include
Foamy air sacs (airsacculitis)
Fibrinous or caseous deposits around visceral organs including heart and liver (sometimes called Ecoli peritonitis)
What is salpingo-peritonitis syndrome
Reproductive tract infection of mature layers with inflammation and fibrinous/frequently caseous deposits on ovaries or egg peritonitis
What else may be seen in clinical presentations of avian colibacillosis
Peritonitis / accumulation of fluid in abdomen - ascites
Cellulitis
Septicaemia
May manifest as reduced intake of food and water, hunched posture, depression, ataxia, respiratory distress, reduced productivity
