Intra-abdominal Infections Flashcards
By definition an IAI is:
A diverse set of diseases
Peritoneal inflammation in response to microorganisms with associated purulence in the peritoneal cavity
IAI classifications
Primary organ infected
Uncomplicated vs. complicated
Uncomplicated-infection contained in single organ (e.g., stomach) without anatomical disruption
Setting of acquisition
(CA-IAI) Community-acquired intra-abdominal infection
(HA-IAI) Healthcare- or hospital acquired-intra-abdominal infection
Severity of illness and risk
What makes an IAI complicated?
Extends beyond source organ into the peritoneal space
Peritoneal inflammation with:
Localized peritonitis –> abscess
Diffuse peritonitis
Intra-abdominal abscess
Purulent collection of fluid
Contains:
- Necrotic debris
- Bacteria
- Inflammatory cells
- Fibrous capsule
Walled off by inflammatory cells and adjacent organs
Hard for antibiotics to penetrate
Ideal environment for anaerobes
Tertiary peritonitis
Persistent or recurrent at least 48 hours after appropriate management of primary or secondary peritonitis
Associated with low virulence organisms in critically ill or immunosuppressed
Secondary peritonitis
Spread from another organ resulting in focal disease in the abdomen
Polymicrobial
Primary peritonitis
Infection of peritoneal cavity without an evident source in the abdomen
Spontaneous bacterial peritonitis
Monomicrobial
Primary peritonitis
Occurs in children and adults
10-30% of alcoholic cirrhotic patients (SBP)
Peritoneal dialysis patients average 1 episode
Secondary peritonitis
Account for 80-90% of intra-abdominal infections
Appendicitis is most common
Primary peritonitis
Bacteria enter via:
Bloodstream or the lymphatic system via gut transmigration
Indwelling peritoneal dialysis catheter
Fallopian tubes in females
Secondary peritonitis
Bacteria enter via:
Perforation of GI or female genital tracts after
Disease process
Trauma
Introduction during surgery
Contamination
Anastomotic leak
Which of the following DOES NOT represent a common etiology of primary peritonitis?
A.) Cirrhosis with ascites B.) Trauma C.) Peritoneal dialysis D.) Nephrotic syndrome E.) Spontaneous bacterial peritonitis
B.) Trauma
Microbiology of primary peritonitis
Normally monomicrobial
Cirrhotic ascites
E. coli (most common)
Other: Klebsiella spp., S. pneumoniae, and enterococci
Peritoneal dialysis
Staphylococci
Streptococci
E. coli
Klebsiella spp.
Pseudomonas spp.
Microbiology of cIAI
Most common pathogens (Greater than 10%)
Facultative and aerobic gram-negative:
Gram-positive aerobic cocci:
Anaerobic:
Facultative and aerobic gram-negative:
Escherichia coli
Klebsiella species
Pseudomonas aeruginosa
Gram-positive aerobic cocci:
Streptococcus species
Enterococcus faecalis
Anaerobic: Bacteroides fragilis Other Bacteroides species Clostridium species Prevotella species Peptostreptococcus species Eubacterium species
Which of the following DOES NOT represent a common pathogen (>10%) isolated from complicated IAIs?
A.) Escherichia coli B.) Streptococcus species C.) Bacteroides fragilis D.) Staphylococcus aureus E.) Klebsiella species
D.) Staphylococcus aureus
Clinical presentation of primary and secondary peritonitis
Voluntary to involuntary abdominal guarding, abdominal tenderness and distension, faint bowel sounds.
Clinical presentation of primary peritonitis laboratory tests
Mildly elevated WBC, elevated fluid WBC (e.g., >250 leukocytes/mm3 in ascitic fluid)
Clinical presentation of secondary peritonitis laboratory tests
Leukocytosis, elevated hematocrit and BUN d/t dehydration, progresses to acidosis from vomiting
Diagnosing peritonitis
Ultrasound and CT
CT more difinitive
Fluid workup in primary peritonitis
>250 PMN/mm3 (ascitic) in SBP
>100/µL white cell count (dialysis effluent) in peritoneal dialysis catheter infection
Treatment of primary peritonitis
Cirrhotic ascites-SBP
Primary treatment:
Cefotaxime or ceftriaxone (preferred)
Duration of therapy: 5 days
Secondary prophylaxis
Ciprofloxacin, trimethoprim-sulfamethoxazole
Peritoneal dialysis
Primary treatment:
vancomycin + 3rd generation cephalosporin or aminoglycoside
Overall approach to IAI
NON-PHARM
SOURCE CONTROL
Evaluate microbial agents
Source control for IAI
“Considered fundamental to the treatment of most patients with IAI”
Undertake within 24 hours of diagnosis
Use least invasive procedure
Percutaneous drainage
Antimicrobial approach
Patient risk category
Setting of acquisition
Previous resistance documented
Local resistance patterns
In general should cover:
Typical Gram-negative enterics
Gram-positive cocci
Obligate anaerobes
Healthcare- or Hospital-Acquired-IAI definition
Infection developing greater than 48 hours after initial source control
Hospitalized for greater than 48 hours during current admission or within the previous 90 days
Residence in a skilled nursing or other long-term care facility within the previous 30 days
Home infusion therapy, home wound care, or dialysis within the preceding 30 days
Use of broad-spectrum antimicrobial therapy for 5 d or more during the preceding 90 days
Which of the following patients would be classified as HA-IAI?
A.) 73 y/o who developed IAI 36 hours after initial source control
B.) 55 y/o who was hospitalized 30 days ago for surgical procedure
C.) 66 y/o who received home wound care 90 days ago
D.) 45 y/o that received 2d of vancomycin and piperacillin/tazobactam during a previous admission 75 days ago.
E.) 22 y/o with no PMH presenting with perforated appendicitis
B.) 55 y/o who was hospitalized 30 days ago for surgical procedure
**Do NOT use first line**
Ampicillin/sulbactam (Unasyn)
Cefazolin + metronidazole
Cefoxitin/cefotetan
Tigecycline
Clindamycin (unless under 1 MONTH of age)
Community-Acquired IAI
Treatment for LOW-RISK Patients
cefotaxime OR ceftriaxone + metronidazole
ertapenem
moxifloxacin OR ciprofloxacin + metronidazole
(if severe β-lactam allergy or local susceptibility demonstrated per antibiogram)
Community-Acquired IAI
Treatment for HIGH-RISK Patients
piperacillin/tazobactam
cefepime OR ceftazidime + metronidazole
doripenem OR imipenem/cilastatin OR meropenem
aztreonam + vancomycin + metronidazole
(if severe β-lactam allergy)
Which of the following would represent the most appropriate treatment for a lower-risk community-acquired IAI?
A.) Ciprofloxacin B.) Ciprofloxacin + metronidazole C.) Ceftriaxone + metronidazole D.) Ertapenem E.) Cefepime + metronidazole
C.) Ceftriaxone + metronidazole
HA-IAI: microbiology
Decreased incidence of:
E. coli
Aerobic streptococci
***Increased incidence of: Enterobacter spp. Pseudomonas aeruginosa and Acinetobacter spp. Enterococcus spp. S. aureus Candida spp. Multi-drug resistant organisms (MDROs)
HA-IAI: microbiology Treatment:
piperacillin/tazobactam
Or
cefepime + metronidazole
OR
imipenem/cilastatin
OR
ceftazidime + metronidazole
HA-IAI: microbiology Treatment for E. faecalis
piperacillin/tazobactam OR imipenem/cilastatin w/wo Addition of ampicillin or vancomycin
HA-IAI: microbiology Treatment for E. faecium
vancomycin
HA-IAI: microbiology Treatment for Vancomycin resistant Enterococcus spp.
daptomycin
linezolid
Which of the following regimens would NOT provide adequate anti-Enterococcal coverage?
A.) Piperacillin/tazobactam B.) Cefepime + metronidazole C.) Imipenem/cilastatin D.) Vancomycin + cefepime + metronidazole E.) Vancomycin + ceftazidime/avibactam
B.) Cefepime + metronidazole
Treatment of HA-IAI: anti-staphylococcal therapy:
Considered at risk for MRSA in HA-IAI:
Known colonization
Patient has several risk factors
Advanced age
Co-morbid medical conditions
Previous hospitalization or surgery
Significant recent exposure to antibiotics
Treatment options
Vancomycin
Daptomycin
Linezolid
Treatment options for MDR GNRs
ESBL-producing or AmpC-B-lactamase producing Enterobacteriaceae
Use of a broad-spectrum carbapenem
Treatment options for MDR GNRs
Klebsiella pneumoniae carbapenemas (KPC)-producing Enterobacteriaceae
Combination therapy with a broad-spectrum carbapenem plus and aminoglycoside, polymyxin, or tigecycline
OR
ceftazidime/avibactam
Treatment options for MDR GNRs
MDR strains of Pseudomonas aeruginosa
Combination therapy with an aminoglycoside plus colistin
OR
ceftolozane/tazobactam
OR
ceftazidime/avibactam
Treatment options for MDR GNRs
MDR strains of Acinetobacter baumannii
Combination therapy with a broad-spectrum carbapenem plus(+) an aminoglycoside, polymyxin, or tigecycline
When in an IAI do you add antifungal therapy?
Patients at risk
Upper gastrointestinal perforations
Recurrent bowel perforations
Surgically treated pancreatitis
Received prolonged courses of broad-spectrum antimicrobial therapy
Known to be heavily colonized with Candida
Antifungal therapy for IAI Candida albicans
Echinocandin for critically ill patients
and
Fluconazole for less critically ill patients
Antifungal therapy for IAI Non-Candida albicans
Echinocandin
Which of the following regimens would be considered the most appropriate treatment of non-Candida spp. isolates in a critically ill patient?
A.) Micafungin B.) Liposomal-amphotericin B C.) Fluconazole D.) Voriconazole E.) Isavuconazole
A.) Micafungin
Echinocandin drugs
Cancidas - Generic name: caspofungin
Eraxis - Generic name: anidulafungin
Mycamine - Generic name: micafungin
Timing and dosing of IAI treatment
Initiation within one hour or as soon as possible after the time of diagnosis is made in septic or septic shock patients
Re-administer an antimicrobial agent within one hour before start of source control procedure
What is treatment failure?
Progressive organ dysfunction within 24-48 hours after source control
No clinical improvement in organ dysfunction 48+ hours after source control
Persistent signs of inflammation 5-7 days after source control
Management of treatment failure?
Repeat imaging
Pursue additional source control
Obtain peritoneal cultures
Adjust antimicrobials
Duration of antimicrobial therapyof IAI
Generally 24 hours
Adequate source control - 4 days
Inadequate source control - 5-7 days
A 45 y/o with a complicated intra-abdominal infection and associated intra-abdominal abscess resulting from gun shot wound received adequate source control today following surgical intervention. Based on culture results the patient is on adequate antimicrobial therapy. How many more days of therapy does the patient require?
A.) 4 days B.) 6 days C.) 7 days D.) Stop therapy today E.) 14 days
A.) 4 days
Oral completion of therapy?
Amoxicillin/clavulanate
Moxifloxacin
Ciprofloxacin + metronidazole
Key points Good bioavailability Return of gastrointestinal function Complete short course DO NOT PROLONG THERAPY!
Biliary Infections: Cholecystis
RUQ pain, Murphy’s sign, tachycardia, fever, leukocytosis
Biliary Infections: Charcot’s triad:
jaundice, RUQ pain, fever, Reynold’s pentad (Charcot’s plus); hypotension, confusion; leukocytosis; elevated bilirubin; elevated GTT
