Chapter 5: Infection Flashcards
MC immune deficiency.
Leads to infection.
Malnutrition
Microflora: stomach
Virtually sterile.
Some GPCs.
Some yeast.
Microflora: proximal small bowel
10^5 bacteria.
Mostly GPCs.
Microflora: distal small bowel
10^7 bacteria.
GPCs, GPRs, GNRs.
Microflora: Colon
10^11 bacteria.
Almost all anaerobes, some GNRs, GPCs.
MC organisms in the GI tract
Anaerobic bacteria (more common than aerobic bacteria in the colon 1,000:1)
MC anaerobe in the colon
Bacteroides fragilis
MC aerobic bacteria in the colon
Escherichia coli
MC source of fever within 48 hours
atelectasis
MC fever source 48 hours - 5 days
Urinary tract infection
MC fever source after 5 days
Wound infection
MCC gram negative sepsis
E coli
What toxin is release in gram negative sepsis?
Endotoxin (lipopolysaccharide lipid A) is released.
What does endotoxin release in gram negative sepsis?
Endotoxin triggers the release of TNF-alpha (from macrophages), activates complement, and activates coagulation cascade
Insulin / glucose: early vs late gram negative sepsis
Early: decreased insulin, increased glucose (impaired utilization)
Late: increased insulin, increased glucose secondary to insulin resistance
Often occurs just before the patient becomes clinically septic
Hyperglycemia
Optimal glucose level in a septic patient
100 - 200 mg/dL
Clostridium difficile colitis
Dx: ?
Tx: ?
Dx: C difficile toxin Tx: Oral - vancomycin or flagyl IV - Flagyl; lactobacillus can also help. - Stop other antibiotics or change them
90% of abdominal abscess have…
Anaerobes
80% of abdominal abscess have…
Both anaerobic and aerobic bacteria
- Treated by drainage
- Usually occur 7-10 days after operation
Abscesses
When do you need antibiotics for abscess?
In patients with diabetes, cellulitis, signs of sepsis, fever, elevated WBC, or who have bioprasthetic hardware (e.g. mechanical valves, hip replacements)
Infection: % Clean (hernia)
2%
Infection: % Clean contaminated (elective colon resection with prepped bowel)
3 - 5%
Infection: % Contaminated (GSW to colon with repair)
5 - 10%
Infection: % Gross contamination (abscess)
30%
Purpose of prophylactic antibiotics
- Dosing?
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.
- Coagulase positive
- MC organism overall in surgical wound infections
Staphylococcus aureus
- Coagulase negative organism
Staphylococcus epidermidis
Released by staph species in an exopolysaccharide matrix
Exoslime
MC GNR in surgical wound infections
E coli
MC anaerobe in surgical wound infections
- Recovery from tissue indicates necrosis or abscess (only grows in low redox state)
- Also implies translocation from the gut
B. fragilis
How many bacteria are needed for wound infection?
> 10^5 bacteria.
- Less bacteria is needed if foreign body is present
Risk factors for wound infection
Long operations. Hematoma or serum formation. Advanced age. Chronic disease (e.g., COPD, renal failure, liver failure, DM), 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)
MC infection in surgery patients
- Biggest risk factor?
UTI
- Biggest risk factor - urinary catheters: MC’ly - E coli
Leading cause of infectious death after surgery
Nosocomial pneumonia
What is nosocomial pneumonia related to?
Length of ventilation; aspiration from duodenum thought to have a role.