Stomach – virtually sterile; some GPCs, some yeast

  Proximal small bowel – 10⁵ bacteria, mostly GPCs

  Distal small bowel – 10⁷ bacteria, GPCs, GPRs, GNRs

  Colon – 10¹¹ bacteria, almost all anaerobes, some GNRs, GPCs

  Anaerobes (anaerobic bacteria)

•  Most common organisms in the GI tract

•  More common than aerobic bacteria in the colon (1,000:1)

•  Bacteroides fragilis – most common anaerobe in the colon

  Escherichia coli – most common aerobic bacteria in the colon

FEVER

GRAM-NEGATIVE SEPSIS

  E. coli most common

  Endotoxin (lipopolysaccharide lipid A) is released

  Endotoxin triggers the release of TNF-α (from macrophages), activates complement, and activates coagulation cascade

  Early gram-negative sepsis – ↓ insulin, ↑ glucose (impaired utilization)

  Late gram-negative sepsis – ↑ insulin, ↑ glucose secondary to insulin resistance

  Hyperglycemia – often occurs just before the patient becomes clinically septic

  Optimal glucose level in a septic patient – 100–120 mg/dL

CLOSTRIDIUM DIFFICILE COLITIS

  Dx: C. difficile toxin

  Tx: oral – vancomycin or Flagyl; IV – Flagyl; lactobacillus can also help

  Stop other antibiotics or change them

ABSCESSES

  90% of abdominal abscesses have anaerobes

  80% of abdominal abscesses have both anaerobic and aerobic bacteria

  Abscesses are treated by drainage

  Usually occur 7–10 days after operation

  Antibiotics for an abscess are needed in patients with diabetes, cellulitis, clinical signs of sepsis, fever, elevated WBC, or who have bioprosthetic hardware (eg mechanical valves, hip replacements)

WOUND INFECTION (SURGICAL SITE INFECTION)

  Clean (hernia): 2%

  Clean contaminated (elective colon resection with prepped bowel): 3%–5%

  Contaminated (gunshot wound to colon with repair): 5%–10%

  Gross contamination (abscess): 30%

  Prophylactic antibiotics are given to prevent surgical site infections (stop within 24 hours of end operation time, except cardiac, which is stopped within 48 hours of end operation time)

  Staphylococcus aureus – coagulase-positive

•  Most common organism overall in surgical wound infections

  Staphylococcus epidermidis – coagulase-negative

  Exoslime released by staph species is an exopolysaccharide matrix

  E. coli – most common GNR in surgical wound infections

  B. fragilis – most common anaerobe in surgical wound infections

•  Recovery from tissue indicates necrosis or abscess (only grows in low redox state)

•  Also implies translocation from the gut

  ≥ 10⁵ bacteria needed for wound infection; less bacteria is needed if foreign body present

  Risk factors for wound infection: long operations, hematoma or seroma formation, advanced age, chronic disease (eg COPD, renal failure, liver failure, diabetes mellitus), malnutrition, immunosuppressive drugs

  Surgical infections within 48 hours of procedure

•  Injury to bowel with leak

•  Invasive soft tissue infection – Clostridium perfringens and beta-hemolytic strep can present within hours postoperatively (produce exotoxins)

Stay updated, free articles. Join our Telegram channel

Join