What are the principles for selecting antimicrobial (antibiotic) therapy for bacterial infections?

From the Guidelines

Selecting appropriate antimicrobial therapy for bacterial infections requires consideration of several key principles, including identifying the likely pathogen, using empiric therapy, and narrowing the therapy to the most effective and specific agent (de-escalation) once culture results are available, as recommended by the most recent guidelines 1.

Key Principles for Selecting Antimicrobial Therapy

• Identify the likely pathogen based on clinical presentation, infection site, and patient factors before obtaining culture results
• Use empiric therapy that targets the most probable organisms while awaiting definitive identification
• Narrow the therapy to the most effective and specific agent (de-escalation) once culture results are available
• Consider patient-specific factors, including allergies, kidney and liver function, pregnancy status, and age, when selecting antibiotics
• Choose antibiotics that can adequately penetrate the infection site and minimize collateral damage to normal flora

Factors to Consider When Selecting Antimicrobial Therapy

• Local resistance patterns, as regional variations can significantly impact efficacy
• Duration of therapy, which should be tailored to the specific infection type
• Potential adverse effects and the need for regular reassessment of therapy based on clinical response, culture results, and potential adverse effects

Recommendations for Antimicrobial Therapy

• The choice of an antibiotic regimen should be based on the likely or proven causative pathogen(s) and their antibiotic susceptibilities, as well as other factors such as availability, published evidence of efficacy, and clinical severity of the infection 1
• Consider consulting infectious diseases/microbiology experts about antibiotic therapy for difficult cases, such as those caused by unusual or highly resistant pathogens 1
• Regularly reassess therapy based on clinical response, culture results, and potential adverse effects to optimize treatment outcomes while minimizing resistance development and toxicity 1

From the FDA Drug Label

To reduce the development of drug-resistant bacteria and maintain the effectiveness of meropenem for injection and other antibacterial drugs, meropenem for injection should only be used to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy To reduce the development of drug-resistant bacteria and maintain the effectiveness of amoxicillin and clavulanate potassium tablets USP, and other antibacterial drugs, amoxicillin and clavulanate potassium should be used only to treat infections that are proven or strongly suspected to be caused by susceptible bacteria When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy

The principles for selecting antimicrobial therapy for bacterial infections include:

• Using the drug only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria
• Considering culture and susceptibility information when available
• Using local epidemiology and susceptibility patterns to contribute to the empiric selection of therapy when culture and susceptibility information are not available
• The goal is to reduce the development of drug-resistant bacteria and maintain the effectiveness of the antibacterial drugs 2 3

From the Research

Principles for Selecting Antimicrobial Therapy

The selection of antimicrobial therapy for bacterial infections is guided by several key principles, including:

• The seriousness of the infection 4
• The patient's drug allergies 4
• Drug efficacy, toxicity, and cost 4
• The use of rapid stains, cultures, and sensitivity studies to guide therapy 4
• Consideration of other forms of management, such as control of the source of infection, prophylaxis, and physiologic management 4

Essential Characteristics of Antibiotics

Antimicrobial agents must possess certain essential characteristics to be effective in treating seriously ill patients, including:

• In vivo and in vitro effectiveness 5
• Lack of toxicity 5
• Reasonable cost 5
• Ability to penetrate to the site of infection and retain significant activity at that location 5

Pharmacokinetic and Pharmacodynamic Criteria

Pharmacokinetic (PK) and pharmacodynamic (PD) criteria can be used to predict bacteriologic efficacy, including:

• Serum concentration profiles 6
• Penetration to the site of infection 6
• Susceptibility 6
• Concentration- versus time-dependent killing 6
• Post-antimicrobial effects 6

Goals of Antimicrobial Therapy

The primary goal of antimicrobial therapy is to eradicate bacteria at the site of infection, which can be achieved by:

• Selecting an antimicrobial agent with appropriate PK/PD parameters 6
• Using the shortest duration of treatment and dose that will reliably eradicate the pathogen(s) 6
• Considering the potential for resistance and the need for ongoing monitoring and adjustment of therapy 6, 7