Chapter 5: Infection Flashcards
1
Q
MC immune deficiency. Leads to infection.
A
Malnutrition
2
Q
Microflora: stomach
A
Virtually sterile. Some GPCs. Some yeast.
3
Q
Microflora: proximal small bowel
A
10^5 bacteria. Mostly GPCs.
4
Q
Microflora: distal small bowel
A
10^7 bacteria. GPCs, GPRs, GNRs.
5
Q
Microflora: Colon
A
10^11 bacteria. Almost all anaerobes, some GNRs, GPCs.
6
Q
MC organisms in the GI tract
A
Anaerobic bacteria (more common than aerobic bacteria in the colon 1,000:1)
7
Q
MC anaerobe in the colon
A
Bacteroides fragilis
8
Q
MC aerobic bacteria in the colon
A
Escherichia coli
9
Q
MC source of fever within 48 hours
A
atelectasis
10
Q
MC fever source 48 hours - 5 days
A
Urinary tract infection
11
Q
MC fever source after 5 days
A
Wound infection
12
Q
MCC gram negative sepsis
A
E coli
13
Q
What toxin is release in gram negative sepsis?
A
Endotoxin (lipopolysaccharide lipid A) is released.
14
Q
What does endotoxin release in gram negative sepsis?
A
Endotoxin triggers the release of TNF-alpha (from macrophages), activates complement, and activates coagulation cascade
15
Q
Insulin / glucose: early vs late gram negative sepsis
A
Early: decreased insulin, increased glucose (impaired utilization) Late: increased insulin, increased glucose secondary to insulin resistance
16
Q
Often occurs just before the patient becomes clinically septic
A
Hyperglycemia
17
Q
Optimal glucose level in a septic patient
A
100 - 200 mg/dL
18
Q
Clostridium difficile colitis Dx: ? Tx: ?
A
Dx: C difficile toxin Tx: Oral - vancomycin or flagyl IV - Flagyl; lactobacillus can also help. - Stop other antibiotics or change them
19
Q
90% of abdominal abscess have…
A
Anaerobes
20
Q
80% of abdominal abscess have…
A
Both anaerobic and aerobic bacteria
21
Q
- Treated by drainage - Usually occur 7-10 days after operation
A
Abscesses
22
Q
When do you need antibiotics for abscess?
A
In patients with diabetes, cellulitis, signs of sepsis, fever, elevated WBC, or who have bioprosthetic hardware (e.g. mechanical valves, hip replacements)
23
Q
Infection: % Clean (hernia)
A
2%
24
Q
Infection: % Clean contaminated (elective colon resection with prepped bowel)
A
3 - 5%
25
Infection: % Contaminated (GSW to colon with repair)
5 - 10%
26
Infection: % Gross contamination (abscess)
30%
27
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.
28
- Coagulase positive - MC organism overall in surgical wound infections
Staphylococcus aureus
29
- Coagulase negative organism
Staphylococcus epidermidis
30
Released by staph species in an exopolysaccharide matrix
Exoslime
31
MC GNR in surgical wound infections
E coli
32
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
33
How many bacteria are needed for wound infection?
\> 10^5 bacteria. - Less bacteria is needed if foreign body is present
34
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.
35
Surgical infections within 48 hours of abdominal procedures
- Injury to bowel with leak
- Invasive soft tissue infection
- Clostridium perfringens and beta-hemolytic strep can present within hours postoperatively (produce exotoxins)
36
MC infection in surgery patients - Biggest risk factor?
UTI - Biggest risk factor - urinary catheters: MC'ly - E coli
37
Leading cause of infectious death after surgery
Nosocomial pneumonia
38
What is nosocomial pneumonia related to?
Length of ventilation; aspiration from duodenum thought to have a role.
39
MC organisms in ICU pneumonia
#1. S aureus #2 Pseudomonas
40
#1 class of organisms in ICU pneumonia
GNRs
41
MCC line infections
#1. S epidermidis #2. S. aureus #3. Yeast
42
What central lines are at highest risk of infection?
Femoral lines
43
% Line salvage rate with infection
50% line salvage rate with antibiotics; much less likely with yeast line infections.
44
Diagnosis of line infection from central line culture
\> 15 colony forming units = line infection -\> need new site
45
- 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
46
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
47
- 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?
Necrotizing fasciitis - Tx: early debridement, high-dose penicillin, may want broad spectrum if thought to be polyorganismal
48
- 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?
C. perfringens infections - Tx: early debridement, high dose penicillin
49
Pathophysiology C. perfringens infection
Necrotic tissue decreases oxidation-redux potential, setting up environment for C. perfringens.
50
C. perfringens: toxin.
Alpha toxin
51
- Severe infection in perineal and scrotal area. - Risk factors: DM, immunocompromised stat - Caused by mixed organisms (GPCs, GNRs, anaerobes) Tx?
Fournier's gangrene Tx: early debridement, try to preserve testicles if possible; antibiotics.
52
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.
53
- Not a true fungus. - Pulmonary symptoms most common; can cause tortuous abscesses in cervical, thoracic, and abdominal areas Tx?
Actinomyces Tx: drainage and penicillin G
54
- Not a true fungus
- Pulmonary and CNS symptoms most common
- Tx?
Nocardia
Tx: drainage and sulfonamides (Bactrim)
55
Fungus: common inhabitant of the respiratory tract.
Tx?
Candida Tx: fluconazole (some Candida resistant), anidulafungin for severe infections
56
Tx: aspergillosis
Voriconazole for severe infections
57
Tx: histoplasmosis (pulmonary symptoms usual; Mississippi and Ohio River Valleys)
Liposomal amphotericin for severe infections
58
- CNS symptoms most common; usually in AIDS patients. Tx?
Cryptococcus Tx: Liposomal amphotericin for severe infections.
59
- Pulmonary symptoms - Southwest Tx?
Coccidioidomycosis Tx: liposomal amphotericin for severe infections
60
Risk factor for spontaneous bacterial peritonitis (SBP; primary)
Low protein (
61
Organisms in primary SBP
Monobacterial
- 50% E. coli
- 30% Streptococcus
- 10% Klebsiella
62
Pathophysiology of primary spontaneous bacterial peritonitis
Secondary to decreased host defenses (intrahepatic shunting, impaired bactericidal activity in ascites); not due to transmucosal migration
63
Cultures in primary spontaneous bacterial peritonitis
Fluid cultures are negative in many cases
64
Dx: primary spontaneous bacterial peritonitis
Ascites fluid: PMNs \> 500 cells/cc diagnostic
65
Primary spontaneous bacterial peritonitis: Tx? Prophylaxis?
Tx: Ceftriaxone or other 3rd generative cephalosporin Prophylaxis: fluoroquinolonges good (norfloxacin)
66
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
67
- Intra-abdominal source (implies perforated viscus) - Polymicrobial (B fragilis, E coli Enterococcus MC organisms) Tx?
Secondary bacterial peritonitis Tx: Usually need laparotomy to find source
68
HIV Exposure risk: HIV+ blood transfusion
70%
69
Exposure risk: infant from positive mother with HIV
30%
70
Exposure risk: Needle stick form HIV positive patient
0.3%
71
Exposure risk: HIV positive Mucous membrane exposure
0.1 %
72
HIV: helps decrease seroconversion after exposure
AZT (zidovudine, reverse transcriptase inhibitor) and ritonavir (protease inhibitor)
73
When do you dose antivirals after HIV exposure?
Within 1-2 hours of exposure
74
MCC for laparotomy in HIV+ patients
Opportunistic infections.
MC: CMV
2nd MC: Neoplastic disease
75
MC intestinal manifestation of AIDS (can present with pain, bleeding or perforation)
CMV colitis
76
MC neoplasm in AIDS patients (although surgery rarely needed)
Kaposi's sarcoma
77
MC site of lymphoma in HIV patients
Stomach most common followed by rectum.
78
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
79
GIB in HIV: lower or upper more common?
Lower more common than upper
80
HIV: cause upper GIB
Kaposi's sarcoma, lymphoma
81
HIV: cause lower GIB
CMV, bacterial, HSV
82
CD4 counts in Normal - Symptomatic disease - Opportunistic infections
Normal: 800 - 1200
Symptomatic: 300- 400
Opportunistic: 200
83
- Now rarely transmitted with blood transfusion (0.0001%/unit)
- 1% - 2% of the population infected
- Fulminant hepatic failure rare.
- Interferon may help prevent the development of cirrhosis
Hepatitis C
84
Hepatitis C Percentages: Chronic infection - Cirrhosis - Hepatocellular carcinoma
- Chronic infection: 60%
- Cirrhosis: 15%
- HCCa: 1-5%
85
Tx: brown recluse spider bites
Tx: dapsone initially, may need resection of area and skin graft for large ulcers later
86
Acute septic arthritis: - Bugs? - Tx?
- Bugs: Gonococcus, staph, H. influenza, strep
- Tx: Drainage, **3rd generation cephalosporin** and **vancomycin** until cultures show organisms
87
Diabetic foot infections - Bugs? - Tx?
Bugs: Mixed staph, strep, GNRs, anaerobes Tx: broad-spectrum antibiotics (Unasyn)
88
Bug: found only in human bites, can cause permanent joint injury. Tx?
Human bite: Eikenella --\> can cause permanent joint injury
Tx: Broad-spectrum antibiotics (Augmentin)
89
Bugs: found in cat and dog bites Tx?
Pasteurella multocida
Tx: broad-spectrum antibiotics (Augmentin)
90
MCC impetigo, erysipelas, cellulitis, folliculitis
Staph and strep most common
91
- Boil - Usually S. epidermidis or S. aureus Tx?
Furuncle Tx: drainage +/- antibiotics
92
Multiloculated furuncle
Carbuncle
93
MCC peritoneal dialysis catheter infection
S. aureus and S. epidermidis
94
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.
- Focal peritonitis: requires laparotomy to find the perforation
95
Risk factors: sinusitis
Nasoenteric tubes, intubation, patients with severe facial fractures. Usually polymicrobial.
96
Sinusitis: CT? Tx?
CT head: shows air-fluid levels in the sinus
Tx: broad-spectrum antibiotics; rare to have to tip sinus percutaneously for systemic illness
97
Clippers vs razors?
Use clippers preoperatively instead of razors to decrease chance of wound infection
