Intra-Abdominal Infections Management

Pathogens and Epidemiology

The major pathogens involved in community-acquired intra-abdominal infections include Enterobacteriaceae, Viridans group streptococci, Anaerobes, and Enterococcus spp. (in 7.7-16.5% of cases) 1

Piperacillin-tazobactam 3.375g IV every 6-8 hours, Ertapenem 1g IV every 24 hours, Imipenem-cilastatin 1g IV every 6-8 hours, or Meropenem 1g IV every 8 hours are first-line options for the treatment of intra-abdominal infections 2
For suspected MRSA or resistant gram-positive organisms, Vancomycin should be added to the treatment regimen 2
For ESBL-producing Enterobacteriaceae, consider carbapenems if the patient has risk factors (recent antibiotic exposure within 90 days or known colonization) 1
Third-generation cephalosporins, such as cefotaxime 2g IV every 6-8 hours or ceftriaxone 1g every 12-24 hours, are recommended as first-line treatment for 5-7 days in uncomplicated cases without contraindications 3, 4, 5, 6
Oral ofloxacin has shown similar results to IV cefotaxime in uncomplicated SBP, and five-day therapy with third-generation cephalosporins is as effective as 10-day treatment for SBP 6
Combinations of cephalosporins with metronidazole or aminoglycosides with metronidazole/clindamycin may be used for severe infections 7, 2

Source control is critical, and surgical intervention remains the cornerstone of management for secondary peritonitis and must not be delayed 1
Culture-guided therapy is recommended, with peritoneal fluid obtained for culture before starting antibiotics, and therapy adjusted based on culture results 1
Regional epidemiological data and resistance patterns should guide the choice of empiric therapy 1
Diagnostic paracentesis is recommended in all patients with new-onset ascites, cirrhotic patients with ascites on hospital admission, and patients with GI bleeding, shock, fever, signs of systemic inflammation, gastrointestinal symptoms, hepatic encephalopathy, or worsening liver/renal function, with follow-up paracentesis after 48 hours of antibiotic therapy 3, 4, 5
The European Association for the Study of the Liver recommends diagnosing Spontaneous Bacterial Peritonitis (SBP) when ascitic fluid polymorphonuclear leukocyte (PMN) count is >250/mm³, regardless of culture results, with blood cultures performed before starting antibiotics in patients with suspected SBP 6, 3, 4, 5
IV albumin is recommended in addition to antibiotics, with a dosage of 1.5 g/kg on day 1 and 1 g/kg on day 3, particularly beneficial for patients with acute kidney injury, jaundice, or serum creatinine ≥1 mg/dL, reducing the incidence of hepatorenal syndrome and decreasing mortality from 29% to 10% 5, 8

Secondary bacterial peritonitis should be suspected if multiple organisms are present on culture, ascitic PMN count is high (>1000/mm³), or there is an inadequate response to therapy, and requires surgical intervention and anaerobic antibiotic coverage, with a high mortality rate (50-80%) 4, 9
Bacterascites (PMN <250/mm³ with positive culture) without signs of infection does not require antibiotics as it often self-resolves, but repeat diagnostic paracentesis should be performed to monitor for progression to SBP 5
If no improvement is seen after 48 hours of antibiotic therapy, treatment failure, resistant organisms, or secondary bacterial peritonitis should be considered, with management involving ruling out secondary bacterial peritonitis, adjusting antibiotics based on culture results, and considering broader spectrum antibiotics for resistant organisms 4, 8, 7, 10
The European Association for the Study of the Liver and the American Association for the Study of Liver Diseases recommend avoiding nephrotoxic antibiotics, such as aminoglycosides, as empirical therapy in SBP patients, as they may accelerate loss of residual renal function, and non-selective beta-blockers (NSBBs) should be temporarily held in patients who develop hypotension or acute kidney injury 3, 4, 5, 11

Follow-up imaging (CT scan) should be obtained after 5-7 days to exclude residual peritonitis or abscess formation, and the treatment regimen should be continued for 7-14 days, depending on clinical response and culture results, with clinical assessment being crucial 7, 12, 11
The American Association for the Study of Liver Diseases recommends offering prophylaxis to high-risk patients with ascitic protein count <1.5 g/dL or gastrointestinal bleeding, with norfloxacin being the most widely used option, and patients who have recovered from SBP should receive norfloxacin, ciprofloxacin, or co-trimoxazole as prophylaxis 3, 9
The treatment of bacterial peritonitis requires immediate administration of antibiotics, with a duration of 7-10 days, adjusting according to clinical response 7