5 virulence gps of E.coli

5 virulence gps of E.coli - FST 3202 Food Microbiology NAME...

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FST 3202 Food Microbiology NAME : ONG POO FEN MATRIC NO. : 130161 PROGRAMME : BSTM TITLE : Description of the 5 Virulence Groups of E.coli & their Virulence Factors. LECTURER : Prof Dr. Son Radu
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Escherichia coli First characterized by Theodor Escherich over a century ago, E. coli is a gram- negative rod and is a member of the family Enterobacteriaceae . Although most strains exist as harmless symbionts, there are many pathogenic E. coli strains that can cause a variety of diseases in animals and humans. Pathogenic E. coli strains differ from those that predominate in the enteric flora of healthy individuals in that they are more likely to express virulence factors — molecules directly involved in pathogenesis but ancillary to normal metabolic functions. Expression of these virulence factors disrupts the normal host physiology and elicits disease. The virulence factors that distinguish the various E. coli pathotypes were acquired from numerous sources, including plasmids, bacteriophages, and the genomes of other bacteria. Over 700 antigenic types ( serotypes ) are recognized based on O, H, and K antigens . Serotyping is still important in distinguishing the small number of strains that actually cause disease. E. coli is responsible for three types of infections in humans: urinary tract infections (UTI) , neonatal meningitis , and intestinal diseases (gastroenteritis) . These three diseases depend on a specific array of pathogenic (virulence) determinants. Based on disease syndromes, laboratory characteristics, particularly their effects on tissue cultures. Five virulence groups are recognized: enteroaggregative (EAEC, EAggEC), enteropathogenic (EPEC), enterotoxigenic (ETEC), enterohemorrhagic (EHEC) and enteroinvasive (EIEC). All cause foodborne infections although some produce active toxins once established in the host. Enteroaggregative E. coli (EAEC) Some indication that EAEC can be foodborne (isolated from infant feeding bottles, in Japan associated an outbreak of school children and school lunches). They carry a 60-MDa plasmid needed for the production of fimbriae and an outer membrane protein that results in their aggregative phenotype. In the laboratory these strains adhere to HEp-2 cells in clumps. EAEC result in a persistent diarrhea that can last for more than 2 weeks especially in children. Also associated with diarrhea and weight loss in HIV- infected individuals. Asymptomatic carriage may occur. Model for pathogenesis involves three stages: 1 ) initial adherence to intestinal mucosa and mucus layer; 2) enhanced
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5 virulence gps of E.coli - FST 3202 Food Microbiology NAME...

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