A Combination Antibiogram Evaluation for Pseudomonas aeruginosa in Respiratory and Blood Sources from ICU and Non-ICU Settings in US Hospitals [Susceptibility]

Background: Pseudomonas aeruginosa (PsA) is an important pathogen associated with significant morbidity and mortality. US guidelines for hospital-acquired and ventilator-associated pneumonia recommend the use of two antipseudomonal drugs for high-risk patients to ensure ≥95% of patients receive active empiric therapy. We evaluated the utility of combination antibiograms in identifying optimal PsA drug regimens.

Methods: We conducted a retrospective cross-sectional analysis of antimicrobial susceptibility of all non-duplicate PsA blood and respiratory isolates collected between October 1, 2016 and September 30, 2017 from 304 US hospitals in the BD Insights Research Database. Combination antibiograms were used to determine in vitro antimicrobial susceptibility rates for potential PsA combination regimens consisting of a backbone antibiotic (extended-spectrum cephalosporin, carbapenem, or piperacillin/tazobactam) plus an aminoglycoside or fluoroquinolone.

Results: Single agent susceptibility rates for the 11,701 non-duplicate PsA isolates ranged from 72.7% for fluoroquinolones to 85.0% for piperacillin/tazobactam. Susceptibility rates were higher for blood versus respiratory isolates (P < 0.05). Antibiotic combinations resulted in increased susceptibility rates, but did not achieve the goal of 95% antibiotic coverage. Adding an aminoglycoside resulted in higher susceptibility rates than adding a fluoroquinolone; piperacillin/tazobactam plus an aminoglycoside had the highest susceptibility rate (93.3%). Intensive care unit (ICU) isolates generally had lower susceptibility rates than non-ICU isolates.

Conclusions: Commonly-used antipseudomonal drugs, either alone or in combination, do not achieve 95% coverage against US hospital PsA isolates, suggesting that new drugs are needed to attain this goal. Local institutional use of combination antibiograms has the potential to optimize empiric therapy of difficult-to-treat pathogens.

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