2 EnterobacteriaceaeThe most important bacterial family in human medicineWell-defined diseases with typical clinical symptoms:Typhoid fever, dysentery and plagueNosocomial infections:Urinary tract infections, pneumonias, wound infections and sepsisThe most important bacterial family in human medicine is the Enterobacteriaceae.This family includes genera and species that cause well-defined diseases with typical clinical symptoms (typhoid fever, dysentery, plague) as well as many opportunists that cause mainly nosocomial infections (urinary tract infections, pneumonias, wound infections, sepsis). Enterobacteriaceae are Gram-negative, usually motile, facultatively anaerobic rod bacteria.The high levels of metabolic activity observed in them are made use of in identification procedures. The species are subdivided into epidemiologically
3 Definition and significance 41 genera with hundreds of speciesGram-negative, facultatively anaerobic rodNatural habitat: intestinal tract of humans and animals
4 The Most Important Genera/Species/Vars of Enterobacteriaceae and the Corresponding Clinical Pictures
6 Virulence and pathogenicity The most important pathogenicity factors:Colonizing factorsInvasinsEndotoxinExotoxinsEnterobacteriaceae are the most significant contributors to intestinal infectionsThe most important pathogenicity factors of Enterobacteriaceae are colonizing factors, invasins, endotoxin, and various exotoxins. Enterobacteriaceae are the most significant contributors to intestinal infections, which are among the most frequent diseases of all among the developing world populace.
7 Identification of Enterobacteriaceae Gram-negative rodUsually motile (with few exceptions)Facultative anaerobesGrow on simple nutrient mediaOxidase test negativeFerment glucose with acid or acid and gas
8 Sero-typing based on antigenic structure O antigens: Somatic antigens (polysaccharide)H antigens: Flagellar antigens (protein)K antigens: Capsular antigens (carbohydrate)e.g., serovar O18:K1:H7O antigens. Specific polysaccharide chains in the lipopolysaccharide complex of the outer membrane.H antigens. Flagellar antigens consisting of protein.K antigens. Linear polymers of the outer membrane built up of a repeated series of carbohydrate units (sometimes proteins as well). They can cover the cell densely and render them O inagglutinable.F antigens. Antigens of protein attachment fimbriae.
12 Natural habitat Intestinal tract of humans and animals indicator organism for fecal contamination of water and foodsThe natural habitat of E. coli is the intestinal tract of humans and animals.It is therefore considered an indicator organism for fecal contamination ofwater and foods.
13 Infections Extraintestinal infections Intestinal infections (Diarrhoeal diseases)The natural habitat of E. coli is the intestinal tract of humans and animals.It is therefore considered an indicator organism for fecal contamination ofwater and foods.
14 Extraintestinal infections Urinary tract infectionsWound infectionsPeritonitisCholecystitisAppendicitisSepsis and endotoxin induced shockNeonatal meningitisE. coli is the most frequent causative pathogen in humanbacterial infections. Extraintestinal infections include urinary tract infections,which occur when the tract is obstructed or spontaneously causedby the pathovar UPEC. The most important other coli infections are cholecystitis,appendicitis, peritonitis, postoperative wound infections, and sepsis.
15 Diarrheagenic pathovars Enteropathogenic E. coli (EPEC)Enterotoxigenic E. coli (ETEC)Enteroinvasive E. coli (EIEC)Enterohaemorrhagic E. Coli (EHEC)Enteroaggressive E. coli (EaggEC)Intestinal infections are caused by the pathovars EPEC, ETEC, EIEC, EHEC,and EAggEC. EPEC and EAggEC frequently cause diarrhea in infants. ETECproduce enterotoxins that cause a choleralike clinical picture. EIEC cause adysenterylike infection of the large intestine. EHEC produce verocytotoxinsand cause a hemorrhagic colitis as well as the rare hemolytic-uremic syndrome.E. coli bacteria infections are diagnosed by means of pathogen identification.
16 EPEC Frequently cause diarrhea in infants Vomiting, fever and prolonged diarrhoeaInfants mainlyMany serotypes
17 ETEC Enterotoxins that cause watery diarrhoea similar to cholera Infants and adultsTraveler diarrheaMany serotypesPlasmid mediated toxin (HS, HL)
18 EIECCause a dysentery like infection of the large intestine (similar to shigellosis)Fever and colitisMany serotypes
19 EHECProduce verocytotoxins and cause a hemorrhagic colitis (damage to vascular endothelia )Causes life-threatening haemorrhagic diarrhoeaAll ages
20 EHEC No pus cells and no fever It can progress to Haemolytic Uremic Syndrome → Renal failureO157:H7 or verocytotoxin-producing E. coliContaminated meat products, unpasteurized milk and diary products
21 EaggECChronic watery diarrhoeaMainly in children
30 Medically important Proteus species P. mirabilisUTIWound infectionSepticeamiaOccasionally meningitis and chest infectionsP. vulgarisUTI and wound infectionsAlkaline reactionCommon cause of male UTI specially those with catheter or cytoscopy