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Escherichia coli (General features (Gram negative, Family:…
Escherichia coli
Pathogen and commensal
Versatile pathogen
Infection may be opportunistic or caused by specific pathotypes
Can be broadly grouped into:
Intestinal (Diarrheagenic)
Extra-intestinal
Major pathotypes and virulence factors (that underlie disease)
Pathotypes
Diarrheagenic E.coli
Enterotoxinogenic E.coli
Enteropathogenic E.coli
Enterohaemorrhagic/Shiga toxin producing E.coli
Enteroaggregative E.coli
Diffusely-adherent E.coli
Enteroinvasive E.coli
Extra-intestinal pathogenic E.coli
Virulence factors
Adhesins such as pili and fimbriae that allow attachment to host cells & tissues
Nutrient scavenging systems to cope with hostile environments (iron scavenging elements key factor)
Toxins that act on the gut or systemically
Secretion systems that deliver host proteins to alter function/structure of host cells
Bacterial components that activate innate immunity
Lipopolysaccharide (LPS) from E.coli is a potent stimulator of inflammation
Role of horizontal gene transfer in virulence development
Transformation
Uptake and incorporation of free floating DNA
Transduction
Phage incorporates host with new DNA (phage DNA or transferred DNA from another bacterium)
Conjugation
Sex pillus transfers DNA (usually plasmid)
Evolution of virulence
Pathogenicity islands encode for factors such as T33
Pathogenicity islands incorporated into bacterial DNA
General features
Gram negative
Family: Enterobacteriaceae
Motile via peritrichous flagella
Rod shaped
Facultative anaerobe (grow with or without oxygen)
Energy from oxidation and reduction of organic sources
Common inhabitant of intestines of warm-blooded mammals
E.coli as part of microbiome
10 x bacterial cells than mammalian cells
Intestinal microbiome is essential for development, homeostasis, digestion and immune development
E.coli can be used as indication of faecal contamination
Role in biosynthesis of vitamin K
Toxins
Enterotoxins
Damage enterocytes leading to diarrhoea
May damage kidneys when in renal capillaries
E.coli that carry STX referred to as STEC
EHEC a type of STEC
Can cause bloody diarrhoea in humans and renal failure
Can cause severe neurological problems in pigs
Secretion systems
Bacteria can inject secretions into host cell or surrounding environment
Can change how host cell behaives
Extra-intestinal disease caused by ExPEC
Includes neonatal meningitis (NMEC)
Urinary tract (UPEC)
Avian pathogenic (APEC) pathotypes
No distinct genotypes or virulence factors - generally want to survive in blood/attach to cells
APEC
2-4% mortality in UK broiler flock (20-40 million birds/year)
Reproductive tract infection in mature layers
Clinical signs
Respiratory distress (inflammation of airsacs)
Fibrinous or caseous deposits around visceral organs
Reproductive tract infection with deposits on ovaries
Peritonitis and ascites
Cellulities
E.coli mastitis
Particular problem in housed dairy cattle over winter
Bacteria infect udder and strong inflammatory response