Enetrobacteriaceae_Pseudomonas_Acinetobacter

• What is the largest collection of medically important gram-negative rods?

  Family Enterobacteriaceae
• How are the genera of Enterobacteriaceae classified?

  Based on biochemical properties and antigenic structure
• Where are Enterobacteriaceae found worldwide?

  Soil, water, and vegetation
• Which organisms are always associated with disease in Enterobacteriaceae?

  Salmonella typhi, Shigella species, Yersinia pestis
• What type of infections can Escherichia coli cause?

  Opportunistic infections
• What are some common medically important Enterobacteriaceae?

  • Citrobacter freundii
  • Enterobacter aerogenes
  • Escherichia coli
  • Klebsiella pneumoniae
  • Salmonella enterica
  • Shigella sonnei
• What is the size range of enteric bacteria?

  0.3 to 6.0 µm
• How do enteric bacteria move?

  They can be nonmotile or motile with peritrichous flagella
• Do Enterobacteriaceae form spores?

  No, they do not form spores
• What type of anaerobes are Enterobacteriaceae?

  Facultative anaerobes
• What do Enterobacteriaceae ferment?

  They ferment glucose
• What is the Gram stain result for Salmonella typhi?

  Gram-negative
• What is characteristic of the staining of Enterobacteriaceae?

  Bipolar staining is characteristic
• What biochemical property differentiates lactose-fermenting strains from non-fermenters?

  The ability to ferment lactose
• What antigen is associated with the capsule of some Enterobacteriaceae?

  K antigen
• What do fimbriae (F antigen) do in Enterobacteriaceae?

  Mediate adherence to host cell receptors
• What is the major cell wall antigen in Enterobacteriaceae?

  Lipopolysaccharide (LPS)
• How is the serologic classification of Enterobacteriaceae determined?

  Based on somatic O polysaccharides, K antigens, and H proteins
• How are antigens detected in Enterobacteriaceae?

  By reaction agglutination with specific antibodies
• What are the common virulence factors associated with Enterobacteriaceae?

  • Endotoxin (identical to LPS)
  • Capsule (protects from phagocytosis)
  • Antigenic phase variation (K and H antigens)
  • Antimicrobial resistance
• What is the role of endotoxin in gram-negative bacterial infections?

  Initiates systemic manifestations like fever and shock
• What type of bacteria is Escherichia coli?

  Gram-negative, facultative anaerobic rods
• What is the significance of the lipopolysaccharide in E. coli?

  It consists of O polysaccharide, core polysaccharide, and lipid A
• What are the common virulence factors associated with E. coli?

  1. Adhesins (e.g., CFA, AAF, P pili)
  2. Exotoxins (e.g., STa, STb, Shiga toxins)
• What is the most common aerobic, gram-negative rod in the gastrointestinal tract?

  Escherichia coli
• When does E. coli establish infection?

  When the patient's defenses are compromised
• What type of infections are most E. coli infections?

  Endogenous infections
• How are strains causing gastroenteritis typically acquired?

  Generally acquired exogenously
• What are the clinical diseases caused by E. coli?

  1. Bacteremia
  2. Urinary tract infections
  3. Neonatal meningitis
• What is the most common cause of bacterial urinary tract infections?

  Escherichia coli
• What specific serogroups of E. coli are more virulent in UTIs?

  Serogroups producing adhesins
• What is the pathogenesis of neonatal meningitis caused by E. coli?

  Usually with strains carrying K1 capsular antigen
• What are the five major pathogenic groups of E. coli that cause gastroenteritis?

  1. Enteropathogenic (EPEC)
  2. Enterotoxigenic (ETEC)
  3. Enterohemorrhagic (EHEC)
  4. Enteroinvasive (EIEC)
  5. Enteroaggregative (EAEC)
• What is the site of action for Enteropathogenic E. coli (EPEC)?

  Small intestine
• What disease is caused by Enteropathogenic E. coli (EPEC)?

  Infant diarrhea in underdeveloped countries
• What is the pathogenesis of Enteropathogenic E. coli (EPEC)?

  Disruption of normal microvillus structure
• What is the site of action for Enterotoxigenic E. coli (ETEC)?

  Small intestine
• What disease is caused by Enterotoxigenic E. coli (ETEC)?

  Traveler's diarrhea
• What is the pathogenesis of Enterotoxigenic E. coli (ETEC)?

  Heat-stable and/or heat-labile enterotoxins
• What is the site of action for Enterohemorrhagic E. coli (EHEC)?

  Large intestine