Chapter 5: Infection Flashcards
MC cause of immune deficiency.
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 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
mechanism of gram negative sepsis
Endotoxin (lipopolysaccharide lipid A) is released and 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.
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
MC anaerobe in surgical wound infections
B. fragilis
- 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
UTI
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.
MC organisms in ICU pneumonia
#1 S aureus #2 Pseudomonas
1 class of organisms in ICU pneumonia
GNRs
MCC line infections
#1. S epidermidis #2. S. aureus #3. Yeast
% Line salvage rate with infection
50% line salvage rate with antibiotics; much less likely with yeast line infections.
Necrotizing soft tissue infections
- 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 fasciitis
- 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.
- Tx: early debridement, high-dose penicillin, may want broad spectrum if thought to be polyorganismal
C. perfringens infections
- 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
- 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.
Alpha toxin
Actinomyces
- Pulmonary symptoms most common; can cause tortuous abscesses in cervical, thoracic, and abdominal areas
Tx: drainage and penicillin G
Nocardia
- Not a true fungus
- Pulmonary and CNS symptoms most common
Tx: drainage and sulfonamides (Bactrim)
Candida
Fungus: common inhabitant of the respiratory tract.
Tx: fluconazole (some Candida resistant), anidulafungin for severe infections
Aspergillosis
Voriconazole for severe infections
Histoplasmosis
Pulmonary symptoms usual
Mississippi and Ohio River Valleys
Tx: Liposomal amphotericin for severe infections
Cryptococcus
CNS symptoms most common; usually in AIDS patients.
Tx: Liposomal amphotericin for severe infections.
Coccidioidomycosis
Pulmonary symptoms
Southwest
Tx: liposomal amphotericin for severe infections
Risk factor for spontaneous bacterial peritonitis
Low protein
Organisms in primary SBP
Monobacterial
- 50% E. coli
- 30% Streptococcus
- 10% Klebsiella
Pathophysiology of spontaneous bacterial peritonitis
Secondary to decreased host defenses (intrahepatic shunting, impaired bactericidal activity in ascites); not due to transmucosal migration
Cultures in spontaneous bacterial peritonitis
Fluid cultures are negative in many cases
Dx: spontaneous bacterial peritonitis
PMNs > 500 cells/cc diagnostic
spontaneous bacterial peritonitis: treatment, prophylaxis
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
Secondary bacterial peritonitis
- Intra-abdominal source (implies perforated viscus)
- Polymicrobial (B fragilis, E coli Enterococcus MC organisms)
Tx: Usually need laparotomy to find source
Exposure risk: HIV blood transfusion
70%
Exposure risk: infant from positive mother with HIV
30%
Exposure risk: Needle stick form HIV positive patient
0.3%
Exposure risk: HIV positive Mucous membrane exposure
0.1 %
HIV: helps decrease seroconversion after exposure
AZT (zidovudine, reverse transcriptase inhibitor) and ritonavir (protease inhibitor) within 1-2 hours of exposure
MCC for laparotomy in HIV patients
Opportunistic infections.
MC: CMV
2nd MC: Neoplastic disease
MC intestinal manifestation of AIDS (can present with pain, bleeding or perforation)
CMV colitis
MC neoplasm in AIDS patients (although surgery rarely needed)
Kaposi’s sarcoma
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
CD4 counts
- Normal
- Symptomatic disease
- Opportunistic infections
Normal: 800 - 1200
Symptomatic: 300-400
Opportunistic: <200
Hepatitis C Percentages
- Chronic infection
- Cirrhosis
- 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?
- Tx?
- Bugs: Gonococcus, staph, H, influenza, strep
- Tx: Drainage, 3rd generation cephalosporin and vancomycin until cultures show organisms
Diabetic foot infections
- Bugs?
- Tx?
Bugs: Mixed staph, strep, GNRs, anaerobes
Tx: broad-spectrum antibiotics (Unasyn)
Bugs: found in cat and dog bites
Tx?
Pasteurella multocida
Tx: broad-spectrum antibiotics (Augmentin)
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
