Flashcards in Chapter 5: Infection Deck (97):
MC immune deficiency.
Leads to infection.
Microflora: proximal small bowel
Microflora: distal small bowel
GPCs, GPRs, GNRs.
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
MC aerobic bacteria in the colon
MC source of fever within 48 hours
MC fever source 48 hours - 5 days
Urinary tract infection
MC fever source after 5 days
MCC gram negative sepsis
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
Optimal glucose level in a septic patient
100 - 200 mg/dL
Clostridium difficile colitis
Dx: C difficile toxin
Oral - vancomycin or flagyl
IV - Flagyl; lactobacillus can also help.
- Stop other antibiotics or change them
90% of abdominal abscess have...
80% of abdominal abscess have...
Both anaerobic and aerobic bacteria
- Treated by drainage
- Usually occur 7-10 days after operation
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)
Infection: % Clean contaminated (elective colon resection with prepped bowel)
3 - 5%
Infection: % Contaminated (GSW to colon with repair)
5 - 10%
Infection: % Gross contamination (abscess)
Purpose of prophylactic antibiotics
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
- Coagulase negative organism
Released by staph species in an exopolysaccharide matrix
MC GNR in surgical wound infections
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
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?
- Biggest risk factor - urinary catheters: MC'ly - E coli
Leading cause of infectious death after surgery
What is nosocomial pneumonia related to?
Length of ventilation; aspiration from duodenum thought to have a role.
MC organisms in ICU pneumonia
#1. S aureus
#1 class of organisms in ICU pneumonia
MCC line infections
#1. S epidermidis
#2. S. aureus
What central lines are at highest risk of infection?
% Line salvage rate with infection
50% line salvage rate with antibiotics; much less likely with yeast line infections.
Diagnosis of line infection from central line culture
> 15 colony forming units = line infection -> need new site
- Beta-hemolytic Strep (group A), C perfringens, or mixed organisms
- Usually occur in patients who are immunocompromised (DM) or who have poor blood supply.
- Can present very quickly after surgical procedures (within hours)
Necrotizing soft tissue infections
Pain out of proportion to skin findings, WBCs > 20, thin gray discharge, can have skin blistering / necrosis, induration and edema, crepitus or soft tissue gas on XR, can be septic
Necrotizing soft tissue infections
- Usually beta-hemolytic GAS
- Overlying skin may be pale red and progress to purple with blister or bullae development.
- Overlying skin can look normal in the early stages.
- Thin, gray, foul-smelling drainage; crepitus.
- Beta hemolytic GAS has exotoxin
- Tx: early debridement, high-dose penicillin, may want broad spectrum if thought to be polyorganismal
- Pain out of proportion to exam, may not show signs with deep infection.
- Gram stain shows GPRs without WBCs
- Myonecrosis and gas gangrene (common presentation)
- Can occur with farming injuries
C. perfringens infections
- Tx: early debridement, high dose penicillin
Pathophysiology C. perfringens infection
Necrotic tissue decreases oxidation-redux potential, setting up environment for C. perfringens.
C. perfringens: toxin.
- Severe infection in perineal and scrotal area.
- Risk factors: DM, immunocompromised stat
- Caused by mixed organisms (GPCs, GNRs, anaerobes)
Tx: early debridement, try to preserve testicles if possible; antibiotics.
When do you need fungal coverage in infection?
Need fungal coverage for positive blood cultures, 2 sites other than blood, 1 site with severe symptoms, endopthalmitis, or patients on prolonged bacterial antibiotics with failure to improve.
- Not a true fungus.
- Pulmonary symptoms most common; can cause tortuous abscesses in cervical, thoracic, and abdominal areas
Tx: drainage and penicillin G
- Not a true fungus
- Pulmonary and CNS symptoms most common
Tx: drainage and sulfonamides (Bactrim)
Fungus: common inhabitant of the respiratory tract.
Tx: fluconazole (some Candida resistant), anidulafungin for severe infections
Voriconazole for severe infections
(pulmonary symptoms usual; Mississippi and Ohio River Valleys)
Liposomal amphotericin for severe infections
- CNS symptoms most common; usually in AIDS patients.
Tx: Liposomal amphotericin for severe infections.
- Pulmonary symptoms
Tx: liposomal amphotericin for severe infections
Risk factor for spontaneous bacterial peritonitis (SBP; primary)
Low protein (
Organisms in primary SBP
- 50% E. coli
- 30% Streptococcus
- 10% Klebsiella
Pathophysiology of primary spontaneous bacterial peritonitis
Secondary to decreased host defenses (intrahepatic shunting, impaired bactericidal activity in ascites); not due to transmucosal migration
Cultures in primary spontaneous bacterial peritonitis
Fluid cultures are negative in many cases
Dx: primary spontaneous bacterial peritonitis
PMNs > 500 cells/cc diagnostic
Primary spontaneous bacterial peritonitis:
Tx: Ceftriaxone or other 3rd generative cephalosporin
Prophylaxis: fluoroquinolonges good (norfloxacin)
What do you need to r/o in primary spontaneous bacterial peritonitis?
Intra-abdominal source (eg, bowel perforation) if not getting better on antibiotics or if cultures are polymicrobial
- Liver transplant not an option with active infection
- Intra-abdominal source (implies perforated viscus)
- Polymicrobial (B fragilis, E coli Enterococcus MC organisms)
Secondary bacterial peritonitis
Tx: Usually need laparotomy to find source
Exposure risk: HIV blood transfusion
Exposure risk: infant from positive mother with HIV
Exposure risk: Needle stick form HIV positive patient
Exposure risk: HIV positive Mucous membrane exposure
HIV: helps decrease seroconversion after exposure
AZT (zidovudine, reverse transcriptase inhibitor) and ritonavir (protease inhibitor)
When do you dose antivirals after HIV exposure?
Within 1-2 hours of exposure
MCC for laparotomy in HIV patients
2nd MC: Neoplastic disease
MC intestinal manifestation of AIDS (can present with pain, bleeding or perforation)
MC neoplasm in AIDS patients (although surgery rarely needed)
MC site of lymphoma in HIV patients
Stomach most common followed by rectum.
Lymphoma in HIV patients is mostly due to .... and treatment is....
Mostly due to non-Hodgkin's (B cell)
Tx: chemotherapy usual, may need surgery with significant bleeding or perforation
GIB in HIV: lower or upper more common?
Lower more common than upper
HIV: cause upper GIB
Kaposi's sarcoma, lymphoma
HIV: cause lower GIB
CMV, bacterial, HSV
- Symptomatic disease
- Opportunistic infections
Normal: 800 - 1200
Symptomatic: 300- 400
- Now rarely transmitted with blood transfusion (0.0001%/unit)
- 1% - 2% of population infected
- Fulminant hepatic failure rare.
- Interferon may help prevent development of cirrhosis
Hepatitis C Percentages
- Chronic infection
- Hepatocellular carcinoma
- Chronic infection: 60%
- Cirrhosis: 15%
- HCCa: 1-5%
Tx: brown recluse spider bites
Tx: dapsone initially, may need resection of area and skin graft for large ulcers later
Acute septic arthritis:
- Bugs: Gonococcus, staph, H, influenza, strep
- Tx: Drainage, 3rd generation cephalosporin and vancomycin until cultures show organisms
Diabetic foot infections
Bugs: Mixed staph, strep, GNRs, anaerobes
Tx: broad-spectrum antibiotics (Unasyn)
Bug: found only in human bites, can cause permanent joint injury.
Tx: Broad-spectrum antibiotics (Augmentin)
Bugs: found in cat and dog bites
Tx: broad-spectrum antibiotics (Augmentin)
MCC impetigo, erysipelas, cellulitis, folliculitis
Staph and strep most common
- Usually S. epidermidis or S. aureus
Tx: drainage +/- antibiotics
MCC peritoneal dialysis catheter infection
S. aureus and S. epidermidis
Tx: peritoneal dialysis catheter infections
Tx: intraperitoneal vancomycin and gentamicin; increased dwell time and intraperitoneal heparin may help.
- Remove catheter: peritonitis that lasts for 4-5 days.
- Fecal peritonitis: requires laparotomy to find perforation
Risk factors: sinusitis
Nasoenteric tubes, intubation, patients with severe facial fractures. Usually polymicrobial.
CT head: shows air-fluid levels in the sinus
Tx: broad-spectrum antibiotics; rare to have to tip sinus percutaneously for systemic illness