Resistance to all β-lactams is emerging among Pseudomonas aeruginosa (PA) clinical isolates. Aztreonam and cefepime act synergistically in vitro against AmpC overproducing PA isolates. The objective of this study was to evaluate the clinical efficacy of this treatment in ICU patients infected with multidrug-resistant PA.

Retrospective study (2 years, 2 ICUs) in a tertiary university hospital. Inclusion criteria were proven infection with evidence of a bacterial strain of PA resistant to all β-lactams and treated with the association of at least aztreonam plus cefepime. Treatment was considered effective for pneumonia using CPIS scores at the end of treatment and for other infections, using the SOFA score and signs of infection improvement at the end of treatment. Infectious episodes were classified as cure or failure.

Thirteen patients were included (10 nosocomial pneumonia, 3 nosocomial intra-abdominal infections). The median [25th–75th percentiles] admission SAPS2 score was 54 [51–69] and the median SOFA score at the beginning of infection was 7 [4–8]. The median CPIS scores for pneumonia at the beginning and end of treatment were 9 [7–10.5] and 2 [0.75–5.5]. The duration of treatment with the combination of aztreonam plus cefepime was 14 days [9.5–16]. Nine episodes were classified as cures and 4 as failures, indicating a clinical efficacy of 69.2%. Overall mortality was 38.5%.

These data suggest that the association of cefepime plus aztreonam could be an attractive alternative in the treatment of infections with multidrug-resistant PA to all β-lactams with a clinical efficacy rate of 69%.