1044. Aztreonam (AZT) vs. Cephalosporin (CEP) Therapy for the Treatment of Gram-Negative Bacteremia

Background The IDSA recommends use of AZT in patients with a confirmed beta-lactam allergy for nosocomial Gram-negative infections. Despite this recommendation, there is limited data to suggest AZT is inferior to cephalosporins (CEP) for the treatment of Gram-negative infections. This study aims to evaluate clinical outcomes in bacteremic patients treated with either AZT or CEP therapy. Methods A single-center, retrospective chart review of adult patients with positive blood cultures for Escherichia coli, Klebsiella pneumoniae or Pseudomonas aeruginosa was conducted to compare clinical outcomes between those who received ≥ 48 hours of AZT or CEP therapy (cefepime or ceftriaxone). The following clinical outcomes were assessed: clinical cure, in-hospital mortality, post-infection length of stay (LOS), post-infection intensive care unit LOS, microbiologic cure and leukocytosis resolution. Results One-hundred and twenty-nine patients met criteria for evaluation: 41 received AZT and 88 received CEP therapy. At baseline, patients who received AZT were more likely to have renal dysfunction (34.1% vs. 18.2%, P = 0.046), receive synergistic antimicrobials (61% vs. 28.4%, P < 0.001) and had a longer pre-infection LOS (1 day [0–2] vs. 0 [0–1], P = 0.032) compared with those who received CEP. Although in-hospital mortality rates were similar between both groups (2.4% vs. 3.4%, P = 1.000), there was a statistically significant difference in clinical cure rates (70.7% vs. 90.9%, P = 0.003), post-infection length of stay (7 days [5–10] vs. 5 [4–8], P = 0.007), and time to clinical cure (2.8 days (1.6–5.8) vs. 2.0 (1.2–2.9), P = 0.018) in the AZT and CEP groups respectively. In a multivariate logistic regression model, patients who received AZT were significantly less likely to achieve clinical cure (OR=0.187, 95% CI (0.058–0.597). In a pre-determined subgroup analysis, clinical cure rates varied in E. coli (72% vs. 94.4%, P = 0.009), K. pneumoniae (70% vs. 90.5%, P = 0.296) and P. aeruginosa (66.7% vs. 76.9%, P = 1.000) in the AZT and CEP group respectively. Conclusion Patients who receive aztreonam for Gram-negative bacteremia may be more likely to experience clinical failure. Larger, prospective studies are warranted to confirm these findings. Disclosures All authors: No reported disclosures.