Enterobacteriaceae Part 1

• Enterobacteriaceae

  - gram neg bacilli/coccobacilli

  - enterics/coliforms

  - habitants: intestinal tract

  - does not produce cytochrome except: plesiomonas

  - can reduce nitrate to nitrite except: photorhabdus & xenorhabdus

  - all glucose fermenter

  - motile with a presence of peritrichous flagella except:

  • Shigella
  • Klebsiella
  • Yersinia
• H2S

  • blackening of the colony or medium
  • observed on Triple Sugar Iron Agar (TSI)

  S - Salmonella

  P - Proteus

  A - Arizona

  C - Citrobacter

  E - Edwardsiella

  • observed on Lysine Iron Agar (LIA)

  S - Salmonella

  A - Arizona

  C - Citrobacter

  E - Edwardsiella
• Urease

  • Rapid urease producers

  P - Proteus

  P - Providencia

  M - Morganella

  • Slow urease produces

  C - Citrobacter

  K - Klebsiella

  E - Enterbacter

  Y - Yersinia

  S - Serratia
• Deaminase

  P - Proteus

  P - Providencia

  M - Morganella
• Lysine Decarboxylation

  • Positive

  K - Klebsiella

  E - Escherichia

  E - Edwardsiella

  S - Serratia

  S - Salmonella xpt: paratyphi A

  H - Hafnia
• Lysine Decarboxylation

  • Negative

  P - Proteus

  P - Providencia

  M - Morganella

  C - Citrobacter

  Y - Yersinia

  E - Enterobacter

  S - Shigella
• Pathogenic & Spectrum of Diseases

  1. Opportunistic Pathogen

  S - Serratia

  P - Proteus

  E - Enterobacter

  E - E.coli

  C - Citrobacter

  k - Klebsiella
• Pathogenic & Spectrum of Diseases 

  2. Intestinal Pathogens (Primary pathogens)

  S - Salmonella typhi : typhoid/enteric fever

  S - Shigella : dysentry
• Virulence and Antigenic Factors

  1. O antigen/Somatic

  • Heat stable
  • located at cell wall
• Virulence and Antigenic Factors 2. H antigen/Flagella

  • Heat labile
  • located at the surface of flagella
  • responsible for motility
• Virulence and Antigenic Factors 3. K antigen/Capsullar

  • heat labile
  • located at encapsulated spp.
  • E. coli - K1 antigen
  • S. enterica - V1 antigen
• Escherichia coli

  • 1885
  • colon/golden bacillus
  • primary marker of fecal contamination in water quality testing
  • motile: fimbriae & sex pili & O,H,K antigen
  • lactose (+): pink colonies on MAC Agar
  • EMB: green metallic sheen
  • most common cause of nosocomial infection
  • UTI, bacteremia, menigitis
• Uropathogenic Escherichia coli is the most common cause of UTI
• Gastrointestinal pathogen causes diarrhea
• Enterotoxigenic E. Coli

  • Diarrhea in adults and esp in children
  • one of the major causes of infant bacterial diarrhea
  • sometimes reffered to as travelers diarrhea
  • MOT: contaminated food/water
  • Achlorhydria(deficiency in HCL acid): high risk factor
  • heat labile enterotoxin
  • no vomiting/ fever
• Enteropathogenic E. Coli

  • infantile diarrhea
  • Symptoms: low grade fever, vomiting, diarrhea
  • O serogroups - cause of diarrhea
  • H antigenic - intestinal infection
  • Stool: Water with mucus but without blood
• Enteroinvasive E. coli

  • dysentery with direct penetration, invasion, and destruction of intestinal mucosa
  • similar to shigellosis
  • MOT: person to person via faecaloral route
  • Non lactose fermenter
  • do not decarboxylate lysine
• Enterohemorrhage E. coli

  • O 157 : H7 - hemorrhagic diarrhea, colitis hemolytic uremic syndrome (HUS) [ low platelet count and kidney failure]
  • Biochemical test: 4 methylumbelliferyl - B - D - glucuronide assay (MUG)[fluorescent]
  • 2 toxins:
  • verotoxin I - identical to shigatoxins (damage to vero cell)
  • verotoxin II - shigatoxin producing
  • does not ferment sorbitol
  • watery diarrhea, bloody with abdominal cramps
• Opportunistic Pathogens

  • Part of the intestinal microbiota of humans and animals
• Intestinal pathogens

  • referred to as the primary pathogens
• Properties of Enterobacteriaceae

  • Fermentation of glucose, lactose, trehalose, and xylose
  • production of indolent from tryptophan
  • does not produce H2S
  • cannot use citrate as a sole carbon source
• Uropathogenic E. coli

  • most common cause of UTI in humans
  • Usually, these strains that causes UTI allows them to attach to the epithelial urinary mucosa
• Enteroadherent E. coli

  • Diarrheal syndrome and UTIs - DAEC (diffusely adherent E. coli)
  • EAEC (enteraggregative E. coli) -diarrhea by adhering to the surface of intestinal mucosa
  • Most common causes of septicemia and meningitis among neonates
• Escherichia hermanii

  • yellow pigmented
  • isolated from CSF, wounds, and blood
• Escherichia vulneris

  • yellow pigmented
  • isolated from humans with infected wounds
• Escherichia albertii

  • associated with diarrheal disease in children
• Klebsiella and Raoutella ( - - + + )

  • most grow on Simmons citrate and in potassium cyanide broth
  • None H2S producing
  • A few hydrolyze urea slowly
  • all (-) in methyl red test
  • all (+) in Voges proskauer test
  • no indole is produced from tryptophan
  • motility is variable
  • associated w/ opportunistic and hospital infections
• Klebsiella and Raoutella ( - - + + )

  • Klebsiella pneumoniae - most commonly isolated species; large polysaccharide capsule
  • Capsule: provide protection against phagocytosis (responsible for moist and mucoid colonies) (tend to string)
  • Friedlanders bacillus
  • able to cause pneumonia which is very necrotic and hemorrhagic- currant jelly is sputum
• Klebsiella oxytoca

  • the only indole (+) among Klebsiella spp.
  • Isolated in stool and blood cultures
  • ornithine positive
  • linked to antibiotic associated hemorrhagic colitis
• Klebsiella pneumoniae subsp. ozaenae

  • highly associated with the presence of plasmid mediated ESBLs
  • isolated from nasal secretions and cerebral abscesses
• Klebsiella pneumoniae subp. rhinoscleromatis

  • isolated from patients with rhinoscleroma
  • infection in the nasal cavity
  • intense swelling and malformation of the entire face and neck
• Raoutella (klebsiella) ornithinolytica

  • indole and ornithine decarboxylase positive
• Raoutella (klebsiella) planticola

  • isolated from urine, RT, and blood
• Klebsiella variicola

  • isolated from primarily sterile sites
• Enterobacter, Cronobacter, & Pantoea ( - - + +)

  • motile
  • resembles klebsiella when growing on MAC agar
  • grow on Simmons citrate medium and potassium cyanide broth
  • (-) methyl red test
  • (+) voges proskauer test
  • usually produce ornithine decarboxylase
  • lysine decarboxylase is produced by most spp. but not by E. gergoviae or E. cloacae
  • Considered as slow urease producer except: E. gergoviae
• Enterobacter taylorae

  • lactose (-)
  • ONPG (+)
• Enterobacter gergoviae

  • resembles enterobacter aerogenes
  • rapid urease produces (RUP)
  • causes infection of urinary tract and blood
• Cronobacter sakazakii

  • Biochemically similar to E. cloacae
  • Yellow pigment
  • Pathogen in neonates - meningitis an bacteremia
  • Often coming from powdered infant formula
• Pantoea agglomerans

  • Triple decarboxylase negative
  • Lysine, ornithine, arginine
  • (+) indole
  • (-) mannitol, raffinose, salicin, sucrose, maltose, xylose
• Serratia ( - V + + )

  • opportunistic pathogen
  • associated with outbreaks in HC settings
  • Ferment lactose slowly
  • (+) for o -nitrophenyl - B - D - galactopyranoside (ONPG) test except: S. fonticola
  • Ability to produce extracellular DNase
  • S. marcescens, S. rubidaea, S. plymuthica produce a pink to red pigment, prodigiosin especially when incubated at room temperature