Enterobacteriaceae
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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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Enterobacteriaceae

Enterobacteriaceae


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


Enterobacteriaceae

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


Escherichia coli klebsiella and proteus

Escherichia coli Klebsiella and Proteus


Escherichia coli

Escherichia coli


Enterobacteriaceae

Escherichia coli on ChromID CPS agar


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)


Enterobacteriaceae

EPEC

  • Frequently cause diarrhea in infants

  • Vomiting, fever and prolonged diarrhoea

  • Infants mainly

  • Many serotypes


Enterobacteriaceae

ETEC

  • Enterotoxins that cause watery diarrhoea similar to cholera

  • Infants and adults

  • Traveler diarrhea

  • Many serotypes


Enterobacteriaceae

EIEC

  • Cause a dysentery like infection of the large intestine (similar to shigellosis)

  • Fever and colitis

  • Many serotypes


Enterobacteriaceae

EHEC

  • Produce verocytotoxins and cause a hemorrhagic colitis (damage to vascular endothelia )

  • Causes life-threatening haemorrhagicdiarrhoea

  • All ages


Enterobacteriaceae

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 species

Klebsiella species


Enterobacteriaceae

Klebsiella species


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


Proteus species

Proteus species


Enterobacteriaceae

Proteusspecies on Blood Agar


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 enterobacteria

Other enterobacteria


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


Enterobacteriaceae

UTI

  • Midstream urine

  • Bacterial count

  • CFU/ml

    • ≥105/ml indicate an infection

    • 104/ml doubtful significance

    • ≤103/ml indicate a contamination


Enterobacteriaceae

MacConkey agar showing lactose and non-lactose fermenting colonies


Enterobacteriaceae

Escherichia coli (Gram negative)


Enterobacteriaceae

Oxidase test


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