CHAPTER 05- INFECTION.txt

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scottmreis
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CHAPTER 05- INFECTION.txt
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2012-01-07 17:55:22
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  1. what is the most common immune deficiency?
    malnutrition
  2. Microflora:

    Stomach:
    Proximal small bowel:
    Distal small bowel:
    Colon:
    • Stomach: virtually sterile; some GPC, some yeast
    • Proximal small bowel:105 bacteria, mostly GPC
    • Distal small bowel: 107 bacteria, GPCs, GPRs, GNRs
    • Colon: 1011 bacteria, almost all anaerobes, some GNRs, GPCs
  3. Anaerobes in the colon:
    • 1) most common organism in the GI tract
    • 2) More common than bacteria in the colon (1,000:1)
    • 3) bacteriodes fragilis- most common anaerobe in the colon
  4. Whats the most common anaerobe in the colon?
    What the most common aerobe?
    • Bacteriodes fragilis- most common anaerobe in the colon
    • Escherichia coli- most common aerobic bacteria in the colon
  5. Gram negative sepsis:
    • 1) E. coli most common
    • 2) Endotoxin (lipopolysaccharide lipid A) is released
    • 3) Triggers the release of TNF-alpha (from macrophages), activates complement and coagulation cascade
    • 4) Early gram negative sepsis:- decreased insulin, increased glucose (impaired utilization)
    • 5) Late gram-negative sepsis- increased insulin, increased glucose secondary to insulin resistance
    • 6) Hyperglycemia- often occurs just before the patient becomes clinically septic
    • 7) Optimal glucose level in a septic patient- 100-120mg/dL
  6. Clostridium difficile colitis
    • 1) Dx:
    • 1- fecal leukocytes in stool
    • 2- C. difficile toxin
    • 2) Tx:
    • 1- oral vancomycin or flagyl
    • 2- IV- flagyl
    • 3- lactobacillus can also help
    • 3) Stop other antibiotics or change them
  7. Abscesses
    • 1) 90% of abdominal abscesses have anaerobes
    • 2) 80% of abdominal abscesses have both anaerobic and aerobic bacteria
    • 3) abscesses are treated by drainage
    • 4) usually occur 7-10 days after an operation
    • 5) Antibiotics need to be started in patients w/diabetes, cellulitis, clinical signs of sepsis, fever, elevated WBC, or who have biprosthetic hardware (e.g. mechanical valves, hip replacement)
  8. Rates of wound infection:
    • Clean (hernia)- 2%
    • Clean contaminated (elective colon resection with prepped bowel): 3-5%
    • Contaminated (gunshot wound to colon with repair): 5-10%
    • Gross contaminated (abscess): 30%
  9. staphylococcus aureus
    • 1) coagulase positive
    • 2) most common organism overall in surgical wound infections
  10. staphylococcus epidermidis
    coagulase negative
  11. Exoslime
    released by staph species is an exopolysaccharide matrix
  12. What is the most common GNR in surgical wound infections?
    E. Coli
  13. What is the most common anaerobe in surgical wound infections?
    • 1) B. fragilis
    • 2) Recovery from tissues indicates necrosis or abscess (only grows in low redox states)
    • 3) also implies translocation from the gut
  14. What bacteria count is needed for wound infection?
    >105 bacteria needed for wound infection; less bacteria needed if foreign body present
  15. Risk factors for wound infection:
    • 1) long operations
    • 2) hematoma or seroma formation
    • 3) advanced age
    • 4) chronic disease (COPD, renal failure, liver failure, diabetes mellitus)
    • 5) malnutrition
    • 6) immunosuppressive drugs
  16. Surgical infection within 48 hours of procedure indicates:
    injury to bowel with leak
  17. See pg. 21: Category 1 recommendations form the hospital infection control practices advisory committee for the prevention of surgical site infections
  18. Invasive soft tissue infections:
    1) Clostridium perfringens and beta-hemolytic strep can present within hours postoperative (produce exotoxins)
  19. Whats the most common nonsurgical infection and what are the biggest risk factors?
    • Urinary tract infection (most commonly E. Coli)
    • Biggest risk factor- urinary catheters
  20. Leading cause of infectious death after surgery
    • 1) nosocomial pneumonia
    • 2) related to length of ventilation; aspiration from duodenum thought to have a role
    • 3) Most common organisms in ICU pneumonia-
    • #1 S. aureus
    • #2 pseudomonas
    • 4) GNRs #1 class of organisms in ICU pneumonia
  21. Line infections:
    • 1) #1 S. epidermidis, #2 S. aureus, #3 yeast
    • 2) Femoral lines at higher risk for infection compared with subclavian and intrajugular lines
    • 3) 50% line salvage rate with antibiotics; much less likely with yeast line infections
  22. Central line cultures:
    >15 colony forming units = line infection --> need new site
  23. What should you do if site shows sign of infection?
    • - move to new site
    • - if worried about line infection, best to pull out the central line and place peripheral IVs if central line not needed
  24. See chart on pg 22: Algorithm for catheter infection
  25. Necrotizing soft tissue infections:
    • 1) beta hemolytic strep (group A), C. perfringens, and mixed organism
    • 2) usually occur in patients who are immunocompromised (diabetes mellitus) or who have poor blood supply
    • 3) can present very quickly after surgical procedures (within hours)
  26. Signs & Symptoms of Necrotizing Soft Tissue Infection
    • White blood cell count >20,000mm3
    • Thin, gray drainage
    • Marked induration
    • Edema of entire limb
    • Hyponatremia (Na <135mEq/L)
    • Skin blistering/sloughing
    • Skin necrosis
    • Crepitus/soft tissue gas on xray
    • pain out of proportion to skin findings
    • sepsis (tachycardia, hypotension, high fluid requirements)
  27. Necrotizing fasciitis
    • 1) beta hemolytic group A strep, can be polyorganismal
    • 2) overlying skin may be pale red and progress to purple with blister or bullae development
    • 3) overlying skin can look normal in the early stages
    • 4) Thin, gray, foul-smelling drainage; crepitus
    • 5) Tx:
    • 1- early debridement
    • 2- high-dose penicillin
    • 3- may want broad spectrum if thought to be polyorganismal
  28. C. perfringens infections
    • 1) necrotic tissue decreases oxidation-redux potential, setting up environment for C. perfringens
    • 2) C. perfringens has alpha toxin
    • 3) pain out of proportion to exam
    • 4) may not show skin signs with deep infection
    • 5) gram stains show GPRs without WBCs
    • 6) myonecrosis and gas gangrene- common presentations
    • 7) can occur with farming injuries
    • 8) Tx: early debridement, high dose penicillin
  29. Fournier's gangrene
    • 1) severe infection in perineal and scrotal region
    • 2) Risk factors: daibetes mellitus and immunocompromised states
    • 3) caused by mixed organisms (GPCs, GNRs, anaerobes)
    • 4) Tx: early debridement; try to preserve testicles if possible; antibiotics
  30. Mixed organism infection
    can also cause necrotizing soft tissue infections
  31. Need fungal coverage for:
    • 1) positive blood culture
    • 2) 2 sites other than blood
    • 3) 1 site with severe symptoms
    • 4) endophthalmitis
    • 5) patients on prolonged bacterial antibiotics with failure to improve
  32. Actinomyces
    • 1) not a true fungus
    • 2) pulmonary symptoms most common
    • 3) can cause tortuous abscesses in cervical, thoracic, and abdominal areas
    • 4) Tx: drainage and Penicillin G
  33. Nocardia
    • 1) not a true fungus
    • 2) pulmonary and CNS symptoms most common
    • 3) Tx: drainage and sulfonamides (bactrim)
  34. Histoplasmosis:
    • 1) pulmonary symptoms most common
    • 2) mississippi and Ohio river valleys
    • 3) Tx: amphotericin for severe infections
  35. Cryptococcus:
    • 1) CNS symptoms most common
    • 2) Tx: amphotericin for severe infections
  36. Coccidiomycosis
    • 1) pulmonary symptoms
    • 2) southwest
    • 3) Tx: amphotericin for severe infections
  37. Candida
    • 1) common inhabitant of the respiratory tract
    • 2) Tx: fluconazole (some candida resistant), amphotericin for severe infections
  38. Spontaneous (primary) Bacterial Peritonitis:
    • 1) Protein <1g/dL in peritoneal fluid- risk factor
    • 2) monobacterial (50% E. coli, 30% streptococcus, 10% klebsiella)
    • 3) secondary to decreased host defenses (intrahepatic shunting, impaired bactericidal activity in ascites); NOT due to transmucosal migration
    • 4) fluid cultures negative in many cases
    • 5) PMNs>500cellcs/cc diagnostic
    • 6) Tx: ceftriaxone or other 3rd generation cephalosporin
    • 7) need to rule out intra-abdominal source (diverticular abscess, perforation) if not getting better on antibiotics or if cultures are polymicrobial
    • 8) liver transplantation not an option with active infection
    • 9) fluoroquinolones good for short-term prophylaxis
  39. Secondary bacterial peritonitis:
    • 1) Intra-abdominal source (transmucosal migration, perforated viscus)
    • 2) Polymicrobial:
    • 1- B fragilis
    • 2- E. Coli
    • 3- Enterococcus
    • 3) Tx: usually need laparotomy to find source
  40. HIV
    • 1) Exposure risk:
    • 1- HIV blood transfusion- 70%
    • 2- Infant from positive mother- 30%
    • 3- Needle stick from positive patient- 0.3%
    • 4- Mucous membrane exposure- 1%
    • 2) Seroconversion occurs in 6-12 weeks
    • 3) AZT and lamivudine can help decrease seroconversion after exposure
    • 4) should be given within 1-2 hours of exposure
  41. Opportunistic infections
    • 1) most common cause for laparotomy in HIV patients (CMV infection most common)
    • 2) neoplastic disease- 2nd most common reason for laparotomy
  42. CMV colitis:
    1) most common intestinal manifestation of AIDS (can present with pain, bleeding, or perforation)
  43. Lymphoma in HIV patients
    • 1) stomach most common followed by rectum
    • 2) Mostly non-hodgkin's, 70% B cell
    • 3) Tx: chemotherapy
  44. Which GI bleeds are more common in HIV patients? Lower or upper?
    lower GI bleeds are more common than upper GI bleeds in HIV patients

    • Upper GI bleeds: Kaposi's sarcoma, lymphoma
    • Lower GI bleeds: CMV, bacterial, HSV
  45. CD4 counts:
    • Normal: 800-1200
    • Symptomatic Disease: 300-400
    • Opportunistic infections: 200
  46. Hepatitis C:
    • 1) now rarely transmitted with blood transfusion (0.0001%/unit)
    • 2) 1-2% of population infected
    • 3) fulminant hepatic failure rare
    • 4) Chronic infection occurs in 60%
    • 5) Cirrhosis in 15% over 20 years
    • 6) Hepatocellular carcinoma in 1-5%
    • 7) interferon may help prevent development of cirrhosis
  47. Brown recluse spider bites:
    • 1) Tx: dapsone initially
    • 2) may need resection of area and skin graft for large ulcers later
  48. Acute septic arthritis:
    • 1) Bugs:
    • 1- gonoccocus
    • 2- staph
    • 3- H. influenza
    • 4- strep
    • 2) Tx:
    • 1- drainage
    • 2- 3rd generation cephalosporin and vancomycin until cultures show organism
  49. Diabetic foot infections:
    • 1) Bugs:
    • 1) mixed staph, strep, GNRs, and anaerobes
    • 2) Tx: broad spectrum antibiotics (unasyn, zosyn)
  50. cat/dog/human bites:
    • (polymicrobial)
    • 1) Eikenella- found only in human bites; can cause permanent joint injury
    • 2) Pasteurella multicocida- found in cat and dog bites
    • 3) Tx: broad-spectrum antibiotics (augmentin)
  51. Impetigo, erysipelas, cellulitis, and folliculitis- what are the most common organisms?
    staph and strep most common organisms
  52. Furuncle:
    • 1) boil
    • 2) usually S. epidermidis or S. aureus
    • 3) Tx: drainage +/- antibiotics
  53. Carbuncle-
    a multiloculated furuncle
  54. Peritoneal dialysis catheter infections:
    • 1) S. aureus and S. epidermidis most common
    • 2) fungal infections hard to treat
    • 3) Tx: intraperitoneal vancomycin and gentamicin; increased dwell time and intraperitoneal heparin may help
    • 4) removal of catheter for peritonitis that lasts for 4-5 days
    • 5) fecal peritonitis requires laparotomy to find perforation
    • 6) some say need removal of peritoneal dialysis catheter for all fungal, tuberculous, and pseudomonas infections
  55. Sinusitis
    • 1) Risk factors:
    • 1- nasoenteric tubes
    • 2- intubation
    • 3- patients with severe facial fractures
    • 2) usually polymicrobial
    • 3) CT head shows air-fluid levels in the sinus
    • 4) Tx: broad spectrum antibiotics; rare to have to tap sinus percutaneously for systemic illness
  56. Preoperative use of clippers vs razors:
    use clippers preoperatively instead of razors to decrease chance of wound infections

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