What are the management strategies for intra-abdominal infections (IAIs)?

From the Guidelines

Management of intra-abdominal infections requires prompt diagnosis and treatment with a combination of source control and appropriate antimicrobial therapy, with the goal of reducing morbidity, mortality, and improving quality of life. The most recent and highest quality study, published in 2017 1, emphasizes the importance of early recognition, adequate source control, and appropriate antimicrobial therapy in the treatment of intra-abdominal infections.

Key Principles of Management

• Initial management should include fluid resuscitation, hemodynamic support, and early surgical consultation for potential source control procedures.
• Source control, which involves drainage of infected fluid collections and repair of anatomic defects, is crucial and should be performed as soon as the patient is hemodynamically stable.
• For empiric antimicrobial therapy, a regimen covering gram-negative aerobic bacilli and anaerobes is recommended, with options including cefazolin plus metronidazole, cefuroxime plus metronidazole, or amoxicillin-clavulanate for mild to moderate community-acquired infections 1.
• For severe community-acquired or healthcare-associated infections, broader coverage is needed with piperacillin-tazobactam, meropenem, imipenem, or ceftriaxone plus metronidazole.

Antimicrobial Therapy

• Therapy should be initiated immediately after diagnosis and continued until resolution of clinical signs of infection, typically 4-7 days, though longer courses may be needed for inadequate source control or immunocompromised patients.
• Antimicrobial therapy should be narrowed based on culture results when available, with susceptibility testing for Pseudomonas, Proteus, Acinetobacter, Staphylococcus aureus, and predominant Enterobacteriaceae, as determined by moderate-to-heavy growth 1.

Rationale

The rationale for this approach is that intra-abdominal infections typically involve polymicrobial flora from the gastrointestinal tract, requiring both surgical intervention to remove the source and antimicrobial therapy to prevent systemic spread and complications. By following these principles, clinicians can provide effective treatment for intra-abdominal infections and improve patient outcomes.

From the FDA Drug Label

1.3 Intra-Abdominal Infections Imipenem and Cilastatin for Injection, USP (I.V.) is indicated for the treatment of intra-abdominal infections caused by susceptible strains of Enterococcus faecalis, Staphylococcus aureus (penicillinase-producing isolates), Staphylococcus epidermidis, Citrobacter species, Enterobacter species, Escherichia coli, Klebsiella species, Morganella morganii, Proteus species, Pseudomonas aeruginosa, Bifidobacterium species, Clostridium species, Eubacterium species, Peptococcus species, Peptostreptococcus species, Propionibacterium species, Bacteroides species including B. fragilis, Fusobacterium species.

The management strategy for intra-abdominal infections (IAIs) includes the use of Imipenem/Cilastatin (IV) as it is indicated for the treatment of IAIs caused by susceptible strains of various bacteria, including Gram-positive and Gram-negative bacteria, as well as anaerobic bacteria 2.

• The key points for management are:
  • Antibiotic therapy: Imipenem/Cilastatin (IV) can be used to treat IAIs.
  • Susceptible bacteria: The drug is effective against a wide range of bacteria, including Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, and Bacteroides species.
  • Usage: The drug should be used only to treat infections that are proven or strongly suspected to be caused by susceptible bacteria.

From the Research

Management Strategies for Intra-Abdominal Infections (IAIs)

The management of IAIs involves several key strategies, including:

• Source control: This is a crucial aspect of IAI management, and involves the removal or drainage of the source of infection 3, 4.
• Antimicrobial therapy: Broad-spectrum antibiotics are typically used to target the most likely pathogens, and should be narrowed and limited in duration when cultures are available 5, 4, 6.
• Fluid resuscitation: Aggressive fluid resuscitation is important to support the patient's overall health and prevent complications 5.
• Supportive care: This may include measures such as pain management, nutritional support, and monitoring for complications.

Antimicrobial Therapy

The choice of antimicrobial therapy for IAIs depends on several factors, including:

• The severity of the infection: More severe infections may require broader-spectrum antibiotics or combination therapy 5, 3.
• The presence of multidrug-resistant organisms: Infections caused by these organisms may require alternative antibiotics or combination therapy 5, 3.
• Patient-specific factors: Such as advanced age, chronic medical conditions, and allergies to certain antibiotics 4.

Duration of Antimicrobial Therapy

The optimal duration of antimicrobial therapy for IAIs is a topic of ongoing debate. Some studies suggest that shorter courses of therapy (e.g. 4-7 days) may be sufficient for uncomplicated IAIs, while others recommend longer courses for more severe or complicated infections 7. The decision on the duration of therapy should be individualized based on the patient's response to treatment and the presence of any complications.

Specific Antimicrobial Agents

Several antimicrobial agents have been studied for the treatment of IAIs, including:

• Beta-lactam/beta-lactamase inhibitor combinations (e.g. piperacillin/tazobactam) 6.
• Carbapenems (e.g. imipenem/cilastatin) 6.
• Newer agents such as ceftolozane/tazobactam, ceftazidime/avibactam, and meropenem/vaborbactam 5.
• Siderophore cephalosporins (e.g. cefiderocol) 5.
• Aminoglycosides (e.g. plazomicin) 5.
• Tetracyclines (e.g. eravacycline) 5.