Infection Flashcards
What is the most common immune deficiency that leads to infection?
Malnutrition
What type of microflora inhabit the stomach?
It’s virtually sterile with some GPC and some yeast
What type of microflora inhabit the proximal small bowel?
10^5 bacterial, mostly GPCs
What type of microflora inhabit the distal small bowel?
10^7 bacteria, GPCs, GPRs, GNRs
What type of microflora inhabit the colon?
10^11 bacterial, almost all anaerobes with some GNRs, GPCs
What is the most common organism in the GI tract?
Anaerobes
Why do anaerobes need a low-oxygen environment?
Lack superoxide dismutase and catalase, making them vulnerable to oxygen radicals
What is the most common anaerobe in the colon?
Bacteriodes fragilis
What is the most common aerobic bacteria in the colon?
E. Coli
What is the most common fever source within 48 hours post op?
Atelectasis
What is the most common fever source 48 hours - 5 days post-op?
UTI
What is the most common fever source >5 days post op?
Wound infection
What it’s he most common bacterial to cause gram negative sepsis?
E. Coli
What do gram negative bacteria contain that leads to sepsis?
Endotoxin (lipid A) which triggers release of TNF-a (triggers inflammation), activates complement, and activates coagulation cascade
What is the optimal glucose level in septic patients?
80-120 mg/dL
When does hyperglycemia usually occur in septic patients?
Just before the patient becomes clinically septic
What are the insulin and glucose levels usually in early gram-negative sepsis?
Decreased insulin, increased glucose (impaired utilization)
What are the insulin and glucose levels usually in late gram-negative sepsis?
Increased insulin, increased glucose secondary to insulin resistance
What are the symptoms of Clostridium difficult colitis (pseudomembranous colitis)?
Foul-smelling diarrhea, usually seen in nursing home or ICU patients
How to diagnose C. Diff?
ELISA for toxin A
What lab value is often extremely elevated in patients with C. Diff?
Elevated WBCs often in the 30-40s
What is the treatment for C. Diff?
Oral vancomycin, oral flagyl, or IV flagyl
IVF and stop other antibiotics
Lactobacillus can also help
How to treat C. Diff in pregnant person?
Oral vancomycin because no systemic absorption
What is the treatment of fulminant (severe sepsis, perforation) pseudomembranous colitis?
Total colectomy with ileostomy
How are abscesses treated?
Drainage
After how long post-op do abscesses form?
7-10 days
In what type of patients are antibiotics used for an abscess?
Diabetes, cellulitis, clinical signs of sepsis, fever, or who have bioprosthetic hardware (mechanical valves, hip replacements)
Bacterial component of abdominal abscesses?
90% have anaerobes
80% have anaerobes and aerobes
What surgical wound is considered clean?
Hernia
What are some examples of clean contaminated wounds?
Elective colon resection with prepped bowel
What is a gross contaminated wound?
An abscess
Why are prophylactic antibiotics given pre op?
To prevent surgical site infections
When should prophylactic antibiotics be given pre-op?
Within 1 hour of incision
When should prophylactic antibiotics be stopped post op?
Stop within 24 hours of end operation time
Except cardiac, which is stopped within 48 hours
What is the most common organism overall in surgical site infections?
Staph aureus — coagulase-positive
What is the most common GNR in surgical wound infections?
E. Coli
What is the most common anaerobe in surgical wound infections?
B. Fragilis
What does a surgical wound infection with B fragilis indicate?
Translocation from the gut
How much bacteria is necessary for a wound infection?
10^5
When is less bacteria needed to create a wound infection?
When there is a foreign body present
What are the risk factors for wound infection?
Long operations, hematoma or sermon formation, advanced ago, chronic disease (COPD, renal failure, liver failure, DM), malnutrition, immunosuppressive drugs
What would cause surgical infections within 48 hours of procedure?
Injury to bowel with leak
Invasive soft tissue infection — Clostridium perfringens and beta-hemolytic strep (produce exotoxins)
What is the most common infection in surgery patients?
UTI
What is the biggest risk factor for UTI in surgery patients?
Urinary catheters
What is the MCC of UTI in surgical patients?
E. Coli
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) pseudomonas 3) E. Coli
What class fo organisms is most common in ICU pneumonia?
GNRs
What increases risk of nosocomial pneumonia in surgical patients?
Length of ventilation
Aspiration from duodenum thought to have a role
What are the three most common bacteria in line infections?
- S. Epidermidis
- S. Aureus
- Yeast
What location for central lines has the highest risk of infection? Lowest risk?
Highest risk is femoral line
Lowest risk is subclavian line
What is the salvage rate for lines during infection, when giving antibiotics?
50%
What decreases the line salvage rate when infected?
If the bug is yeast
What are the most common organisms to cause necrotizing soft tissue infections?
Beta-hemolytic Steptococcus, C. Perfringes, or mixed organisms
In what types of patients do necrotizing soft tissue infections usually occur?
Immunocompromised and patients with poor blood supply
How long after injury or post op does it take for necrotizing soft tissue to occur?
Quickly, within hours
What are the signs and symptoms of necrotizing soft tissue infections?
Pain out of proportion to skin findings (infections tarts deep to the skin), mental status change, WBCs>20, thin gray drainage that is foul-smelling, can have skin blistering/necrosis, induration and edema, crepitus or soft tissue gas on x-ray, can be septic
What organism usually causes necrotizing fasciitis?
Beta-hemolytic group A strep or MRSA. Have exotoxin
Why can the overlying skin look normal in the early stages of nec fasc?
Because it spreads deep along fascial planes
Overlying skin progresses from pale red to purple with blister or bullae development
What does thin, foul-smelling gray drainage from would indicate?
A necrotizing fasciitis
What is the treatment for nec fasciitis?
Early debridement, high dose penicillin (broad spectrum if thought to be poly-organisms
What are the common presentations of C. Perfringens infections?
Myonecrosis and gas gangrene
Why is necrotic tissue a perfect environment for C. Perfringens?
Necrotic tissue decreases oxidation-redux potential
What toxin does C. Perfringens have?
Alpha toxin
What does gram stain show in wound with C. Perfringens?
GPRs without WBCs
What is seen on physical exam in a patient with C. Perfringens infection?
Pain out of proportion to exam
What is the treatment for C. Perfringens infected wounds?
Early debridement, high-dose penicillin
What is Fournier’s gangrene?
Severe infection in perineal and scrotal region
What are the risk factors for developing Fournier’s gangrene?
Diabetes and immunocompromised state
What causes Fournier’s gangrene?
Mixed organisms
What is the treatment of Fournier’s gangrene?
Early debridement and try to preserve testicles if possible
Antibiotics
When is fungal coverage warranted?
Positive blood cultures, 2 sites other than blood, 1 site with severe symptoms, endophthalmitis, or patients on prolonged bacterial antibiotics with failure to improve
What symptoms are most common with actinomyces (not a true fungus)?
Pulmonary symptoms
What does Actinomyces usually cause?
Pulmonary symptoms and tortuous abscesses in cervical, thoracic, and abdominal areas
Histologic characteristic of Actinomyces?
Yellow sulfur granules on Gram stain
What is the treatment for Actinomyces?
Drainage and penicillin G
What are the most common symptoms of Nocardia (not a true fungus)?
Pulmonary and CNS symptoms
What is the treatment for Nocardia?
Drainage and sulfonamides (Bactrim)
What organism is the MCC of fungemia?
Candida
Candida is a common inhabitant of what part of the body?
Respiratory tract
What is the treatment of Candida?
Fluconazole or anidulafungin for severe infections
What is the treatment for Candiduria?
Remove urinary catheter only, no anti-fungal is necessary
What is the treatment for Aspergillosis?
Voriconazole for severe infections
What are the most common symptoms of Histoplasmosis?
Pulmonary
Where is Histoplasmosis usually found?
Mississippi and Ohio River Valleys
What is the treatment of histoplasmosis?
Liposomal amphotericin for severe infections
What symptoms are most common with Cryptococcus?
CNS symptoms
In what patients is Cryptococcus usually found?
AIDS patients
What is the treatment of Cryptococcus?
Liposomal amphotericin
What type of symptoms are often seen with Coccidioidomycosis?
Pulmonary symptoms
What region is Coccidioidomycosis usually found?
Southwest
What is the treatment of Coccidioidomycosis?
Liposomal amphotericin
What are the symptoms of spontaneous bacterial peritonitis (SBP)?
Mental status changes, fever, abdominal pain in cirrhotic patient
What is a risk factor for developing SBP?
Low protein (<1g/dL) in peritoneal fluid
What are the 3 most common causes of SBP?
50% E. coli
20% Streptococcus
10% Klebsiella
What causes SBP?
Secondary to decreased host defenses (intrahepatic shunting, impaired bactericides activity in ascites), NOT transmucosal migration
How do you diagnosis SBP?
Peritoneal tap that shows PMNs >250 or positive cultures
Fluid cultures are often negative
What is the treatment of SBP?
Ceftriaxone or other 3rd-generation cephalosporin
When should you worry about other intra-abdominal causes when treating someone with suspected SBP?
If not getting better on antibiotics or if cultures are polymicrobial
What antibiotic is used for prophylaxis for SBP?
Weekly fluoroquinolones (norfloxacin)
When is SBP prophylaxis indicated?
After an episode of SBP
Can a liver transplant be performed with active SBP?
NO
What is secondary bacterial peritonitis?
Comes from abdominal source
What does secondary bacterial peritonitis imply?
That there is a perforated viscous
What are the common bacterial causes of secondary bacterial peritonitis?
Polymicrobial— B. Fragilis, E. Coli, Enterococcus
What is the treatment for secondary bacterial peritonitis?
Usually laparotomy to find source
What type of virus is HIV?
RNA virus with reverse transcriptase
What are the exposure risks for developing HIV?
HIV blood transfusion — 70%
Infant from positive mother — 30%
Needle stick from positive patient — 0.3%
Mucous membrane exposure — 0.1%
How long does it usually take for seroconversion of HIV Abs?
6-12 weeks
What drugs are used to help decrease seroconversion of HIV after exposure?
AZT (zidovudine, reverse transcriptase inhibitor) and ritonavir (protease inhibitor)
What is the most common indication for laparotomy in HIV patients?
Opportunistic infections
What is the MC infection in HIV patients?
CMV
What is the second MC reason for laparotomy in HIV patients?
Neoplastic disease
What it’s he most common neoplastic disease that requires laparotomy in HIV patients?
Lymphoma
What is the MC intestinal manifestation of AIDS?
CMV colitis— can present with pain, bleeding, or perforation
What is the MC neoplasm in AIDS patients?
Kaposi’s sarcoma —rarely needs surgery
What is the MC and second MC site of lymphoma in HIV patients?
- Stomach
2. Rectum
What type of lymphoma is MC seen in HIV patients?
Non-Hodgkin’s (B cell)
What is the treatment of lymphoma in HIV patients?
Chemotherapy. May need surgery with significant bleeding or perforation
What type of GI bleed is more common in HIV patients? Lower or upper
Lower
What is the MCC of upper GI bleeds in HIV patients?
Kaposi’s sarcoma and lymphoma
What are the MCC of lower GI bleeds in HIV patients?
CMV, bacterial, HSV
What is the normal CD4 count?
800-1200
At what CD4 count wil; HIV be symptomatic?
300-400
At what CD4 count will opportunistic infections occur?
<200
What is the possibility of transmitting hepatitis C through blood transfusion?
0.0001%/unit
What percentage of the population is infected by hepatitis C?
1-2%
In what % of patients with hepatitis C does chronic infection occur?
60%
In what % of patients with hepatitis C dose cirrhosis occur?
15%
In what % of patients with hepatitis C does hepatocellular carcinoma occur?
1-5%
What is the most common indication for liver transplant?
Hepatitis C
What drugs are used to cure hepatitis C?
Sovaldi (sofosbuvir) with ribavirin
Is fulminant hepatic failure common in patients with hepatitis C?
NO
How is CMV transmitted?
Via leukocytes
What is the most common infection in transplant patients?
CMV
What is the MC manifestation of CMV?
Febrile mononucleosis (sore throat, adenopathy)
What is the most deadly form of CMV?
CMV pneumonitis
How do you diagnose CMV infection?
Biopsy and CMV serology
What would you see on the biopsy in someone infected with CMV?
Characteristic cellular inclusion bodies
What is the treatment for CMV?
Ganciclovir, CMV immune globulin (Cytogram)
In what cases is CMV immune globulin (Cytogram) given?
For severe infections or a CMV-negative patient receiving a CMV-positive organ
Where in the lungs is aspiration pneumonia MC seen?
Superior segment of the right lower lobe
What is the MC organism causing aspiration pneumonia? What other class of organism must you also treat against?
Strep pneumonia. Must also cover anaerobes
What is the highest sensitivity test for osteomyelitis?
MRI (avoid bone biopsy)
What is the treatment for Brown recluse spider bites?
Oral Dawson initially, avoid early surgery, but may need resection of area and skin graft for large ulcers later
What are the most common causes of diabetic foot infections?
Usually polymicrobial. Staph, strep, GNRs, and anaerobes
What is the treatment for diabetic foot infections?
Broad-spectrum antibiotics (Unasyn, Zosyn)
What are the MC causes of acute septic arthritis?
Gonococcus, staph, H. Influenzae, strep
What is the treatment for acute septic arthritis?
Drainage, 3rd generation cephalosporin and vancomycin until results of cultures
What organism is only found in human bites and cause permanent joint injury?
Eikenella
What organism is found in cat and dog bites?
Pasteurella multocida
What is the antibiotic of choice for cat/dog/human bites?
Augmentin
What is the MC infection resulting from cat/dog/human bites?
Strep pyogenes
What are the 2 MC organisms to causes impetigo, erysipelas, cellulitis, and folliculitis?
Staph (MC) and strep
What is a furuncle and what organisms usually cause it?
A boil. S. Epidermidis or S. Aureus
What is the treatment of a furuncle?
Drainage +/- antibiotics
What is a carbuncle?
A multiloculated furuncle
What are the symptoms of a peritoneal dialysis catheter infection?
Cloudy fluid, abdominal pain, fever, usually mono bacterial
What are the MC organisms to cause peritoneal dialysis catheter infections?
S. Epidermidis (MC), S. Aureus, and pseudomonas
What is the treatment for peritoneal dialysis catheter infections?
Intraperitoneal vancomycin and gentamicin (IV not as effective) and increased dwell time and intraperitoneal heparin
When should you remove the catheter in a patient with a peritoneal dialysis catheter infection?
For peritonitis that lasts 4-5 days
Peritoneal dialysis catheter should be removed if infected with what organisms?
Fungal, tuberculosis, and pseudomonas infections
What are the risk factors for developing sinusitis?
Nasoenteric tubes, intubation, patients with severe facial fractures
What organisms usually cause sinusitis?
Polymicrobial
What would the CT head of a patient with sinusitis show?
Air-fluid levels in the sinus
What is the treatment of sinusitis?
Broad-spectrum antibiotics
It is rare to have to tap sinus percutaneously for systemic illness
What is the best prevention strategy to prevent nosocomial infections?
Hand washing
What patients have the highest risk of developing a nosocomial infection?
Burn patients
What are the prevention strategies used to prevent surgical site infections?
- Use clippers preoperativey instead of razors
- Keep glucose 80-120
- Keep PO2 elevated (give 100% oxygen)
- Keep patient warm (keep OR 70F, and use Bair Hugger (warm air conduction)
- Chlorhexidine prep with iodine-impregnated drapes