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Understanding Opportunistic Enterobacteriaceae Infections

Learn about gram-negative sepsis, UTI, pneumonia, abdominal sepsis, meningitis, SBP, endocarditis. Pathogenesis, diagnosis, virulence factors, and more.

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Understanding Opportunistic Enterobacteriaceae Infections

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  1. Opportunistic Enterobacteriaceae

  2. OPPORTUNISTIC INFECTIONS OF ENTEROBACTERIACEAE • GRAM NEGATIVE SEPSIS • URINARY TRACT INFECTIONS • PNEUMONIA • ABDOMINAL SEPSIS • MENINGITIS • SPONTANEOUS BACTERIAL PERITONITIS • ENDOCARDITIS

  3. OPPORTUNISTIC INFECTIONS (cont.) • GRAM NEGATIVE SEPSIS • Life-threatening • Usually nosocomial • Commonly caused by E. coli • PATHOGENESIS: • Early Phase (REVERSIBLE) • Decreased arterial resistance; Increased cardiac output • Kinins (protein vasodilators & mediators of inflammation) in plasma due to tissue damage, endotoxin, AG-AB complexes • Second Phase (REVERSIBLE) • Increased arterial resistance; Decreased cardiac output • Third Phase (IRREVERSIBLE) • Vascular collapse with organ failure • Endotoxin induced DIC, hemorrhage and death

  4. OPPORTUNISTIC INFECTIONS (cont.) • URINARY TRACT INFECTIONS • Usually ascending infection, not hematogenous route • Greatest incidence in young & middle-aged females • Incidence increases with age in males • Most commonly caused by E. coli • Diagnosis by microscopic & cultural exam of urine • Obtain urine by catheter through urethra into bladder, clean catch midstream (CCMS) or suprapubic tap PNEUMONIA • Nosocomial; Spread by personnel and equipment • Frequently caused by K. pneumoniae • Often in middle-aged males who abuse alcohol • Difficult to diagnose due to commensals in sputum

  5. OPPORTUNISTIC INFECTIONS (cont.) • ABDOMINAL SEPSIS • Caused by flora of the GI tract • Infections usually polymicrobial • MENINGITIS • Usually nosocomial • Frequently caused by E. coli • Diagnosis by microscopic & cultural exam of CSF

  6. OPPORTUNISTIC INFECTIONS (cont.) • SPONTANEOUS BACTERIAL PERITONITIS • Usually in patients with liver ailments • Commonly caused by E. coli, but also anaerobes & Gram-positive cocci (S. pneumoniae) • ENDOCARDITIS • Vascular endocardial surface inflammation • Mostly caused by Gram-positive cocci, but 1-3% caused by aerobic Gram-negative rods • Diagnosis by blood culture • Difficult to treat; Treatment is of long duration

  7. Virulence Factors Associated with Enterobacteriaceae • Common Virulence Factors • Endotoxin • Capsule • Antigenic phase variation • Sequestration of growth factors • Resistance to serum killing • Antimicrobial resistance • Factors Associated with Specific Pathogens • Exotoxin production • Expression of adhesion factors • Intracellular survival and multiplication

  8. Endotoxin-Mediated Toxicity • Fever • Leukopenia (reduced # of WBCs) (<5000/mm3) followed by leukocytosis (increased # of WBCs)(>10-12,000/mm3) • Activation of complement • Thrombocytopenia (reduced # of platelets) • DIC (Disseminated intravascular coagulation) • Decreased peripheral circulation and perfusion (blood flow) to major organs • Shock • Death

  9. See Handout on Enterobacteriaceae General Information

  10. Summary of Escherichia coli Infections

  11. Summary of Escherichia coli Infections(cont.)

  12. Gastroenteritis Caused by E. coli

  13. Specialized Virulence Factors Associated with E. coli Type 1 pili ETEC EAEC UPEC EPEC UPEC EIEC UPEC ETEC EHEC UPEC ETEC

  14. Fimbriated Bacterial Cell F = Flagellum Note: All other appendages are fimbriae (a.k.a., pili)

  15. Afimbriated Bacterial Cells Nonadherent Afimbriated Bacterial Cells and Buccal Cells

  16. Fimbriated Bacterial Cells Adherent Fimbriated Bacterial Cells and Buccal Cells

  17. Heparin-binding epidermal growth factor on heart & nerve surfaces (ETEC) (EHEC)

  18. REVIEW

  19. OPPORTUNISTIC INFECTIONS OF ENTEROBACTERIACEAE • GRAM NEGATIVE SEPSIS • URINARY TRACT INFECTIONS • PNEUMONIA • ABDOMINAL SEPSIS • MENINGITIS • SPONTANEOUS BACTERIAL PERITONITIS • ENDOCARDITIS REVIEW

  20. Virulence Factors Associated with Enterobacteriaceae • Common Virulence Factors • Endotoxin • Capsule • Antigenic phase variation • Sequestration of growth factors • Resistance to serum killing • Antimicrobial resistance • Factors Associated with Specific Pathogens • Exotoxin production • Expression of adhesion factors • Intracellular survival and multiplication REVIEW

  21. See Handout on Enterobacteriaceae General Information REVIEW

  22. Endotoxin-Mediated Toxicity • Fever • Leukopenia (reduced # of WBCs) (<5000/mm3) followed by leukocytosis (increased # of WBCs)(>10-12,000/mm3) • Activation of complement • Thrombocytopenia (reduced # of platelets) • DIC (Disseminated intravascular coagulation) • Decreased peripheral circulation and perfusion (blood flow) to major organs • Shock • Death REVIEW

  23. Summary of Escherichia coli Infections REVIEW

  24. Summary of Escherichia coli Infections(cont.) REVIEW

  25. Gastroenteritis Caused by E. coli REVIEW

  26. Fimbriated Bacterial Cell F = Flagellum Note: All other appendages are fimbriae (a.k.a., pili) REVIEW

  27. Afimbriated Bacterial Cells Nonadherent Afimbriated Bacterial Cells and Buccal Cells REVIEW

  28. Fimbriated Bacterial Cells Adherent Fimbriated Bacterial Cells and Buccal Cells REVIEW

  29. REVIEW

  30. Heparin-binding epidermal growth factor on heart & nerve surfaces (ETEC) (EHEC) REVIEW

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