Chapter 5 - Infection++ Flashcards
What is the most common immune deficiency?
Malnutrition
What is the microflora of the stomach?
Virtually sterile; some GPCs, some yeast
What is the microflora of the proximal small bowel?
10^5 bacteria, mostly GPCs
What is the microflora of the distal small bowel?
10^7 bacteria, GPCs, GPRs, GNRs
What is the microflora of the colon?
10^11 bacteria, almost all anaerobes, some GNRs, GPCs
What is the most common organism in the GI tract?
Anaerobes - Bacteroides
What is the most common aerobic bacteria in the colon?
E. coli
What is the most common bacterial cause of gram-negative sepsis?
E. coli
What type of toxin is released by E. coli, what are its effects?
Endotoxin (lipopolysaccharide lipid A); triggers the release of TNF-alpha from macrophages, activates complement and coagulation cascade
What is the optimal glucose level in a septic patient?
100-120 mg/dL
What is the dx and tx of C. diff colitis?
Dx: fecal leukocytes in stool, C. diff toxin; Tx: oral vanco or flagyl, IV flagyl, lactobacillus
What percentage of abdominal abscesses have anaerobes?
90%
What percentage of abdominal abscesses have both anaerobic and aerobic bacteria?
80%
How many days post-op do abdominal abscesses occur?
7-10d
What are indications (associated diagnosis, exam findings) for antibiotics in patients with abdominal abscesses?
- DM, cellulitis, clinical signs of sepsis
- Fever, elevated WBC
- Bioprosthetic hardware
Wound infections develop in what percentage of clean (hernia) cases?
class I - 1-4%
Wound infections develop in what percentage of clean contaminated cases (elective colon resection w/ prepped bowel)?
class II - 6-9%
Wound infections develop in what percentage of contaminated cases (GSW to colon w/ repair)?
class III - 13-20%
Wound infections develop in what percentage of grossly contaminated cases (stool in peritoneum)?
class IV - 40%
What is the most common organism overall in surgical wound infections?
Staph aureus (coagulase positive)
Central lines and prosthetic grafts have more Staph epi
What is exoslime?
Exopolysaccharide matrix released by staph species
What is the most common GNR in surgical wound infections?
E. coli
What is the most common anaerobe in surgical wound infections?
B. fragilis; presence indicates necrosis or abscess, implies translocation from gut
How many bacteria are needed to create a wound infection?
>10^5, less needed if foreign body present
What are the surgical and patient associated risk factors for perioperative wound infections?
- Surgical: long operations, hematoma/seroma formation
- Patient: advanced age, chronic disease (COPD, renal/liver failure, DM), malnutrition, immunosuppressive drugs
What is the most common nonsurgical infection
UTI (most commonly E. coli), urinary catheters the biggest risk factor
What is the leading cause of infectious death after surgery?
Nosocomial pneumonia
What are the most common organisms in ICU pneumonia?
1 S. aureus, #2 Psuedomonas
What is the most common class of organisms in ICU pneumonia?
GNR - oropharynx gets overgrown by enteric organisms then get aspirated
What are the most common organisms in line infections?
1 S. epidermidis (coag neg staph), #2 S. aureus, #3 yeast
What is the line salvage rate with antibiotics?
50%, less with yeast infections
Which organisms are found in necrotizing soft tissue infectons?
Beta-hemolytic Strep (group A), C. perfringens, mixed organisms
Organisms found in necrotizing fasciitis?
Beta-hemolytic Strep (group A), can be polymicrobial
What are the signs of necrotizing fasciitis?
Overlying skin pale red, progress to purple with blisters; thin, gray, foul-smelling drainage, crepitus
What is the treatment of necrotizing fasciitis?
Early debridement, high-dose penicillins, broad spectrum if thought to be polyorganismal
Clindamycin added for anti-toxin effects
How does necrotic tissue set up an environment for C. perfringens infections?
Decreases oxidation-redux potential
C. perfringens has what type of toxin?
alpha toxin
What will a gram stain show with C. perfringens infection?
GPRs without WBCs
What organisms are found in Fournier’s gangrene?
Mixed organisms (GPCs, GNRs, anaerobes)
When do you cover for fungal infection?
Positive blood cultures, 2 sites other than blood, 1 site with severe symptoms, endophthalmitis, pts on prolonged bacterial abx without improvement
Description of abscess caused by Actinomyces (not a true fungus)? Locations? Most common organ system with symptoms?
Tortuous abscesses in cervical, thoracic, abdominal areas; most commonly with pulmonary symptoms
Treatment for Actinomyces?
Drainage and penicillin G
Organ systems affected by Nocardia (not a true fungus)?
Pulmonary and CNS
Treatment for Nocardia?
Drainage and sulfonamides (bactrim)
Organ system affected by Histoplasmosis? What geographical regions are associated with infection?
Pulmonary most common; Mississippi and Ohio River valleys
Treatment for Histoplasmosis?
Can watch if no symptoms. Amphotericin for severe infections
Organ system affected most with Cryptococcus?
CNS most common
Treatment for Cryptococcus?
Amphotericin for severe infections
Symptoms with Coccidioidomycosis?
Pulmonary; Southwest
Treatment for Coccidioidomycosis?
Amphotericin for severe infections
Spontaneous (primary) bacterial peritonitis is secondary to what?
Decreased host defenses (intrahepatic shunting, impaired bactericidal activity in ascities); NOT due to transmucosal migration
SBP is caused by which organisms?
Monobacterial: 50% E. coli, 30% Strep, 10% Klebsiella
What is diagnostic of SBP on paracentesis?
PMNs > 250 cells/cc, cultures positive, no other causes
Treatment for SBP?
Ceftriaxone or other 3rd generation cephalosporin
What is used for short term prophylaxis against SBP?
Fluoroquinolones (cipro)
What causes secondary bacterial peritonitis?
Intra-abdominal source (transmucosal migration, perforated viscus); polymicrobial, B. fragilis, E. coli, Enterococcus
Treatment for secondary bacterial peritonitis?
Broad spec abx and often laparotomy
Chance of contracting HIV with HIV+ blood transfusion?
70%
Chance of infant contracting HIV from positive mother?
30%
Chance of contracting HIV from needle stick?
0.3%
Chance of contracting HIV from mucous membrane exposure?
1%
What is the most common cause for laparotomy in HIV patients?
Opportunistic infections (CMV most common)
What is the most common intestinal manifestation of AIDS?
CMV colitis (pain, bleeding or perforation)
Most common organ affected by lymphoma in HIV patients?
Stomach, followed by rectum (mostly Non-Hodgkin’s, 70% B cell)
What causes GI bleeds in HIV patients?
Upper: Kaposi’s sarcoma; Lower: CMV, bacterial, HSV (lower more common)
What are the CD4 counts in normal, symptomatic disease, and opportunistic infections?
Normal: 800-1200; Symptomatic disease: 300-400; Opportunistic infections: 200
*Keep cutting in half: 800 to 400 to 200
Chronic infection occurs in what % of Hep C patients?
60%
Cirrhosis occurs in what % of Hep C patients?
15% over 20y
HCC occurs in what % of Hep C patients?
1-5%
Treatment of brown recluse spider bites?
Dapsone; may need resection of area/skin graft for large ulcers
What organisms cause acute septic arthritis?
staph A, strep, N gonorrhea
Treatment of acute septic arthritis?
Drainage, 3rd-gen cephalosporins and vanco
What organisms cause diabetic foot infections?
Mixed staph, strep, GNRs, anaerobes
Treatment of diabetic foot infections?
Broad spectrum abx: Unasyn, Zosyn
What organism is found in human bites?
Eikenella, can cause pernament joint inujury
What organism is found in dog/cat bites?
Pasturella multocida
Treatment for human/dog/cat bites?
Broad-spectrum abx: Augmentin
Most common organisms for impetigo, erysipelas, cellulitis, folliculitis?
Staph and strep
Most common organisms in PD cath infections?
S. aureus, S. epidermidis
Treatment of PD cath infections?
Intraperitoneal vanco/gent; removal of catheter for peritonitis that lasts for 4-5d
Risk factors for sinusitis?
Nasoenteric tubes, intubations, facial fractures
If a high fever (102) occurs within 48 hrs postop, what are three diagnostic considerations?
- atelectasis - dec breath sounds, dec O2; CXR
- viscous injury/leak - review op note, peritonitis; OR
- invasive wound infection - B-hemolytic strep, clostridia; OR
What is included in the ventilator bundle to prevent VAP?
- HOB elevation
- sedation vacation
- assess readiness for extubation
- PUD ppx
- DVT ppx
- daily chlorhexidine care
What modifications were added to the ventilator bundle for non-intubated postop patients to prevent HAP?
- IS
- mobilization
- chlorhexidine mouth care
In febrile ICU patients with nasogastric or nasotracheal tubes, especially with facial fractures, what diagnosis needs to be considered?
- paranasal sinusitis
- if suspicious, get CT - air-fluid levels, mucosa thick
- dx: sinus aspirate - WBC, bacteria
- of note, can have concurrent otitis media
- tx: irrigation, decongestion, abx (like HAP)
What are four controllable perioperative factors that can prevent SSI?
- sterile technique
- appropriate ppx abx
- temperature
- glucose
In surgical wounds away from the perineum and without bowel entry, what are the likely pathogens?
- S aureus
- streptococci
- tx with ancef 1g q8h
- risk of MRSA: vancomycin
In surgical wounds near the perineum or with associated bowel entry, what is characteristic of a culture?
- mixed aerobic and anaerobic bacteria
- tx with cefoxitin 1g q6h
- if infection severe, broaden coverage - imipenem, meropenem, zosyn
In a patient who is systemically with a pleural effusion and no other source of infection, what test should be done?
thoracentesis - gram stain and culture
In a patient s/p esophagectomy who presents with empyema, what pathology should be ruled out?
- leak
- get swallow study, CT, endoscopy
- consider stent
In a patient who has undergone a pneumonectomy who presents with a fistula, what pathology must be ruled out?
- bronchopleural fistula
- imaging can be nonspecific, often need bronchoscopy
- often need reoperation with closure including a pedicle tissue flap buttress
In an immunocompromised patient, what further antibiotic should be considered in a patient w/ empyema s/p esophageal or pulmonary surgery?
antifungal
Retained hemothorax in trauma can cause empyema, what imaging study is superior?
CT
If a patient with hemothorax s/p tube has persistent collection or output greater than 10 ml/kg, what is the next step in management?
second tube
early VATS can prevent empyema
How is superficial sternal wound infection diagnosed?
- clinically
- purulent drainage, redness, fever, tenderness
What is the hallmark of deep sternal wound infection?
- instability or palpable clicking
- suspect mediastinitis with systemic signs
- CT used to determine if mediastinitis is present
How are sternal infections treated?
OR with debridement and flap
In a patient s/p cranial trauma or intracranial instrumentation who has neck stiffness, AMS, and systemic illness, what diagnostic study should be performed?
dx: suspect meningitis
workup: diagnostic lumbar puncture, start abx, await cx results
All open fractures should receive what to prevent OM?
- abx ppx
- cover gram positives (S aureus)
- some need gram negative ppx (P aeruginosa)
What are the requirements to diagnose CLABSI?
- one of the following:
- non-contaminant pathogen isolated in 1/2 cx not related to other sites of infection
- >1 positive cx of skin contaminant on separate occasions with signs of systemic illness
What is the decision-making point in workup of long-term catheter infections?
- determine if exit-site vs tunnel - abx vs removal
- exit site - signs within 2 cm around the exit site
For locally infected central line catheters (w/o changes in vitals or labs), what can be considered adequate treatment?
removal of the catheter; monitor for improvement - if afebrile without leukocytosis in 24 hrs, no abx needed
In a patient who needs central access with an infected catheter, what should be done to get access?
place a line at a separate site, don’t just exchange the line
When can a line exchange be done?
In a patient with systemic signs of illness without a source and without local signs of line infection, the line can be exchanged for a new one and sent for semiquantitative culture.
Most common pathogens in intra-abdominal infections.
- E. coli, Bacteroides, and Streptococcus
- gram-positive, gram-negative and anaerobes
