W9-ENTEROBACTERIACEAE_PART 1

• General Characteristics


  • Gram negative bacilli/coccobacilli
  • Oxidase Negative (Except Plesiomonas shigelloides)
  • MacConkey Positive
  • Glucose Fermenters
  • Reduces Nitrate to Nitrite
  • All motile at body temperature (37°), except for Klebsiella, Shigella and Yersinia
• Opportunistic Members


  • Escherichia coli
  • Klebsiella
  • Enterobacter
  • Serratia
  • Citrobacter
  • Proteus, Morganella and Providencia
• Primary Intestinal Pathogens


  • Salmonella
  • Shigella
  • Yersinia
  • Plesiomonas
• Escherichia coli


  • UTI, Septicemia, CNS and diarrheal diseases
  • Uropathogenic E. coli
  • Enterotoxigenic E.coli (ETEC)
  • Enteroinvasive E. coli (EIEC)
  • Enterophatogenic E. coli (EPEC)
  • Enterohemorrhagic E. coli (EHEC)
  • Enteroadherent E. coli (EAEC)
• Uropathogenic E. coli (UPEC)


  • Most common cause of UTI in humans
  • Virulence factors: Pili for adherence, Cytolysins, Aerobactin
• Enterotoxigenic E. coli (ETEC)


  • Also known "Montezuma's revenge" or "turista"
  • Causes epidemic (infant) diarrhea and traveler's diarrhea
  • Virulence factors: Fimbria, Heat-labile (LT) and heat stable (ST) enterotoxins
• Enteroinvasive E. coli (EIEC)

  • Virulence factor: Invades enterocytes causing Shigella like infection
  • Causes dysentery and bloody stools
  • Other characteristics: Sereny test (+), can be non-motile or non-lactose fermenter
• Enteropathogenic E. coli (EPEC)


  • Virulence factor: Bundle-forming pilus for attachment to cells of the small bowel
  • Causes infantile diarrhea (watery with mucus but no blood)
• Enterohemorrhagic E. coli(EHEC)


  • Also known as Verotoxic E.coli (VTEC)
  • Virulence factor: Cytotoxin (Verotoxin I & II) similar to Shiga toxin
  • Serotype O157:H7 strain (STEC) (sorbitol-MAC and MUG negative)
  • Causes hemorrhagic colitis and hemolytic uremic syndrome
• Enteroadherent E. coli


  • Diffusely adherent E.coli (DAEC) - associated with UTI and diarrheal disease
  • Enteroaggregative E.coli (EAEC) - adhere to HEp2 in a aggregative "stacked-brick" pattern, produces watery diarrhea
• Klebsiella (Friedlander's bacilli) and Enterobacter

  • Cause respiratory tract (pneumonia), wound, urinary tract, blood (septicemia), and CSF (Meningitis) infections
  • May be encapsulated and appears as mucoid colonies that tend to "string"
  • Klebsiella is Associated with plasmid-mediated ESBL's
• IMVC Reactions for Lactose Fermenters

  Indole, Methyl Red, Voges-Proskauer, Citrate

  
• Decarboxylase Reactions for Lactose Fermenters


  Lysine decarboxylase, Ornithine decarboxylase, Arginine dihydrolase
• Serratia and Citrobacter


  • Nosocomial and opportunistic pathogens causing bacteremia, septicemia, urinary tract, respiratory tract (pneumonias) and wound infections
  • S. marcescens produces a red pigment (prodigiosin) and enzymes like Lipase, Gelatinase and DNase
• Differentiation of Serratia and Citrobacter Species

  TSI, Gas, H2S, Indole, Methyl Red, Voges-Proskauer, Citrate, Lysine decarboxylase, KCN growth
• Proteus, Morganella and Providencia

  • Opportunistic causing bacteremia, septicemia, urinary tract, respiratory tract and wound infection
  • Rapid urease producer, Phenylalanine deaminase positive
  • Proteus produces "Swarming motility" and has a "burnt chocolate odor"
• Differentiation of Tribe Proteeae

  Indole, Methyl Red/Voges-Proskauer, Citrate, Urease, H2S, Ornithine decarboxylase, Motility
• Salmonella enterica subsp. enterica

  • Salmonella has 7 subspecies (1, 2, 3a, 3b, 4, 5, 6)
  • Almost all clinical isolates are of Subgroup I (S. enteritidis, S. choleraesuis and S. typhi)
• "Swarming motility"


  Characteristic of P. mirabilis and P. vulgaris
• "Burnt chocolate odor"


  Characteristic of P. mirabilis and P. vulgaris
• Organisms in Tribe Proteeae

  • P. mirabilis
  • P. vulgaris
  • Prov. stuartii
  • Prov. retgerri
  • M. morganii
• Biochemical tests for Tribe Proteeae

  • Indole
  • MR/VP
  • Citrate
  • Urease
  • H2S
  • ODC
  • Motility
• Opportunistic members of Enterobacteriaceae

  • Escherichia coli
  • Klebsiella
  • Enterobacter
  • Serratia
  • Citrobacter
  • Proteus, Morganella and Providencia
• Primary Intestinal Pathogens


  • Salmonella
  • Shigella
  • Yersinia
  • Plesiomonas
• Salmonella


  Has 7 subspecies (1, 2, 3a, 3b, 4, 5, 6)
• Salmonella subspecies I serotypes

  • S. enteritidis
  • S. choleraesuis
  • S. typhi
• Biochemical tests for Salmonella subspecies

  • Citrate
  • Gas
  • H2S
  • LDC
  • ODC
• Salmonella virulence factors


  • Fimbriae, ability to transverse intestinal mucosa, enterotoxin (gastroenteritis)
• Clinical infections caused by Salmonella

  • Acute gastroenteritis or food poisoning
  • Enteric Fever (Typhoid fever)
  • Bacteremia
  • Carrier state
• Salmonella appears as metallic colonies with a black ring in Bismuth sulfite agar
• Salmonella is diagnosed with Widal's test in reference laboratories
• Differences between Salmonella and Shigella

  • Motile (Salmonella) vs Non-motile (Shigella)
  • H2S (+) (Salmonella) vs H2S (-) (Shigella)
  • Lysine Decarboxylase (+) (Salmonella) vs Lysine Decarboxylase (-) (Shigella)
  • Infectious Dose: 106 (Salmonella) vs 100-200 (Shigella)
• Biochemical tests for Shigella species

  • Mannitol
  • ONPG
  • ODC
  • Serogroup
• Shigella virulence factors


  • Mediate attachment and invasion of mucosal cells, S. dysenteriae produces neurotoxin and enterotoxin, other species produce only enteroxin
• Clinical stages of Shigellosis


  • First Stage involves watery diarrhea
  • Dysenteric phase - Bloody and mucoid stools
• Yersinia species


  • Yersinia pestis
  • Yersinia enterocolitica
  • Yersinia pseudotuberculosis
• Yersinia pestis


  Causes Bubonic (Glandular) and Pneumonic Plague, exhibits bipolar staining "safety pin appearance", cauliflower appearance at 48 hrs in SBA, "stalactite pattern" in broth culture, preferential growth at 25°C to 30°C
• Yersinia enterocolitica


  Causes acute enteritis (enterocolitis) and arthritis/erythema nodosum, exhibits bipolar staining "safety pin appearance", bull's eye colonies in CIN agar in 48 hours, preferential growth at 25°C to 30°C, motile at 25°C
• Yersinia pseudotuberculosis


  Causes pseudotubercles, exhibits bipolar staining "safety pin appearance", motile at 18°C to 22°C
• Biochemical tests for Yersinia species

  • TSI
  • Christensen Urea
  • Motility at 25°C
  • ODC
  • Sucrose