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Enterobacteriaceae. Enterobacteriaceae. The most important bacterial family in human medicine Well-defined diseases with typical clinical symptoms: Typhoid fever, dysentery and plague Nosocomial infections: Urinary tract infections, pneumonias, wound infections and sepsis.

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enterobacteriaceae1
Enterobacteriaceae
  • The most important bacterial family in human medicine
  • Well-defined diseases with typical clinical symptoms:
    • Typhoid fever, dysentery and plague
  • Nosocomial infections:
    • Urinary tract infections, pneumonias, wound infections and sepsis
definition and significance
Definition and significance
  • 41 genera with hundreds of species
  • Gram-negative, facultatively anaerobic rod
  • Natural habitat: intestinal tract of humans and animals
slide4

The Most Important Genera/Species/Vars of Enterobacteriaceae and the Corresponding Clinical Pictures

virulence and pathogenicity
Virulence and pathogenicity
  • The most important pathogenicity factors:
    • Colonizing factors
    • Invasins
    • Endotoxin
    • Exotoxins
  • Enterobacteriaceae are the most significant contributors to intestinal infections
identification of enterobacteriaceae
Identification of Enterobacteriaceae
  • Gram-negative rod
  • Usually motile (with few exceptions)
  • Facultative anaerobes
  • Grow on simple nutrient media
  • Oxidase test negative
  • Ferment glucose with acid or acid and gas
sero typing based on antigenic structure
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:H7
natural habitat
Natural habitat
  • Intestinal tract of humans and animals
  • indicator organism for fecal contamination of water and foods
infections
Infections
  • Extraintestinalinfections
  • Intestinal infections (Diarrhoealdiseases)
extraintestinal infections
Extraintestinal infections
  • Urinary tract infections
  • Wound infections
  • Peritonitis
  • Cholecystitis
  • Appendicitis
  • Sepsis and endotoxin induced shock
  • Neonatal meningitis
diarrheagenic pathovars
Diarrheagenicpathovars
  • EnteropathogenicE. coli (EPEC)
  • EnterotoxigenicE. coli (ETEC)
  • EnteroinvasiveE. coli (EIEC)
  • EnterohaemorrhagicE. Coli (EHEC)
  • EnteroaggressiveE. coli (EaggEC)
slide16
EPEC
  • Frequently cause diarrhea in infants
  • Vomiting, fever and prolonged diarrhoea
  • Infants mainly
  • Many serotypes
slide17
ETEC
  • Enterotoxins that cause watery diarrhoea similar to cholera
  • Infants and adults
  • Traveler diarrhea
  • Many serotypes
slide18
EIEC
  • Cause a dysentery like infection of the large intestine (similar to shigellosis)
  • Fever and colitis
  • Many serotypes
slide19
EHEC
  • Produce verocytotoxins and cause a hemorrhagic colitis (damage to vascular endothelia )
  • Causes life-threatening haemorrhagicdiarrhoea
  • All ages
slide20
EHEC
  • No pus cells and no fever
  • It can progress to Haemolytic Uremic Syndrome → Renal failure
  • O157:H7 or verocytotoxin-producing E. coli
  • Contaminated meat products, unpasteurized milk and diary products
eaggec
EaggEC
  • Chronic watery diarrhoea
  • Mainly in children
klebsiella pneumoniae
Klebsiellapneumoniae
  • Four subspecies:
    • K.p.pneumoniae
    • K.p. aerogenes
    • K.p. ozaenae
    • K.p. rinhoscleromatis
infections caused by klebsiella species
Infections caused by Klebsiellaspecies
  • UTI
  • Wound infections
  • Chest infections
medically important proteus species
Medically important Proteus species
  • P. mirabilis
    • UTI
    • Wound infection
    • Septiceamia
    • Occasionally meningitis and chest infections
  • P. vulgaris
    • UTI and wound infections
other enterobacteria1
Other enterobacteria
  • Enterobacter
  • Citrobacter
  • Serratia
  • Opportunistic pathogens:
    • UTI
    • Wound infections
    • Septiceamia
    • Pulmonary infections
laboratory diagnosis
Laboratory diagnosis
  • Specimens:
    • Urine, pus, faeces, CSF, blood, sputum
  • Direct examination:
    • Gram –ve bacilli
    • Few capsulated
  • Culture aerobically at 36-37° C:
    • Blood agar
    • MacConkey agar
    • CLED
    • XLD and DCA
slide34
UTI
  • Midstream urine
  • Bacterial count
  • CFU/ml
    • ≥105/ml indicate an infection
    • 104/ml doubtful significance
    • ≤103/ml indicate a contamination
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