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Creation of a Combination Antibiogram for Pseudomonas aeruginosa in a Pediatric Intensive Care Unit
Insights
A combination antibiogram improves empiric antimicrobial therapy for Pseudomonas aeruginosa infections. Adding a second agent, like an aminoglycoside or fluoroquinolone, significantly enhances susceptibility rates, especially for resistant strains.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Pseudomonas aeruginosa is a significant opportunistic pathogen, frequently associated with hospital-acquired infections.
- Rising antimicrobial resistance necessitates optimized empiric treatment strategies.
- Standard antibiograms may not fully capture the effectiveness of combination antimicrobial therapy.
Purpose of the Study:
- To develop and evaluate a combination antibiogram for Pseudomonas aeruginosa.
- To identify optimal empiric antimicrobial regimens for P. aeruginosa infections.
- To assess the impact of adding a second antimicrobial agent to common monotherapies.
Main Methods:
- Collection of P. aeruginosa isolates from all sites in PICU patients between 2013-2017.
- Exclusion of cystic fibrosis patients and isolates with identical susceptibility patterns within 30 days.
- Determination of beta-lactam susceptibilities, with and without aminoglycoside or fluoroquinolone addition, summarized in a combination antibiogram.
Main Results:
- Analysis included 199 P. aeruginosa isolates.
- Piperacillin-tazobactam monotherapy showed 70% susceptibility, increasing to over 90% with aminoglycoside or fluoroquinolone addition.
- Combination therapy with cefepime or meropenem achieved over 95% coverage when a second agent was added; higher second-agent susceptibility was needed for decreasing first-line agent effectiveness.
Conclusions:
- Employing a second antimicrobial agent significantly enhances the probability of appropriate empiric coverage for P. aeruginosa.
- Combination antibiograms offer greater benefit than simple antibiograms in high-resistance settings or for specific resistant organisms.
- This approach aids in selecting effective empiric antimicrobial regimens against P. aeruginosa.
Objective:
This study describes the creation of a combination antibiogram directed toward Pseudomonas aeruginosa to determine the most appropriate empiric antimicrobial regimen(s).
Methods:
P aeruginosa isolates were collected from all sites between January 2013 and December 2017 for patients admitted to the PICU. Patients with cystic fibrosis and isolates from the same site and susceptibility pattern obtained within 30 days were excluded. β-Lactam susceptibilities were determined and compared with the addition of an aminoglycoside or fluroquinolone and summarized in a combination antibiogram.
Results:
One hundred ninety-nine P aeruginosa isolates were included for analysis. The addition of a second agent to piperacillin-tazobactam was shown to have the most significant improvement among the β-lactams, with 70% susceptibility as monotherapy and increases to above 90% with the addition of an aminoglycoside or fluroquinolone. The addition of an aminoglycoside or fluroquinolone to cefepime and meropenem increased coverage to above 95%. The addition of a second agent was likely to increase susceptibility of a monotherapy backbone; however, as the susceptibility of the first-line agent decreased, the susceptibility of the second agent needed to be higher to achieve a 95% coverage threshold.
Conclusions:
Our results support use of a second agent to significantly improve the likelihood of appropriate empiric coverage of P aeruginosa. Use of a combination antibiogram may be more beneficial than a simple antibiogram for units with increasing resistance rates, or for coverage of specific resistant organisms.
