Cefazolin Plus Ceftazidime versus Cefazolin Monotherapy in the Treatment of Culture-Negative Peritonitis: A Retrospective Cohort Study.

Background: Based on current ISPD guidelines, it is unclear as to whether ceftazidime should be discontinued in subsequent management of culture-negative peritonitis if it is used as empirical gram-negative coverage. Herein, we aim to compare the clinical outcomes of cefazolin plus ceftazidime versus cefazolin alone.

Methods: This was a retrospective cohort study. Adult peritoneal dialysis (PD) patients who were diagnosed with culture-negative peritonitis between 2014 and 2020 were included. Patients were categorized into two groups according to treatment regimen. Primary response rate, peritonitis relapse rate, and time to primary response were compared. Factors that predicted primary response were determined using Cox regression analysis.

Results: A total of 58 patients were included in the study. Of these, 42 received cefazolin plus ceftazidime and 16 received cefazolin monotherapy. Overall, the mean age was 65.7±10.4 years. Most of the patients (81.3%) were prescribed continuous ambulatory peritoneal dialysis. Initial effluent WBC was 4211±10357 in the combination group and 3833±6931 cell/mm³ in the monotherapy group (p=0.89). There was no significant difference in primary response at day 5 between the two groups (95.2% in the combination group vs93.7% in the monotherapy group, p=0.82). However, cumulative probability of primary response by the Kaplan-Meier analysis in the combination group was higher than in the monotherapy group (p=0.02). Adjusted HR of serum potassium level to predict a primary response was 1.83 according to multivariate analysis (p=0.03). There was no difference between the two groups in terms of peritonitis relapse or catheter removal.

Conclusion: This is the first study to compare clinical outcomes between cefazolin plus ceftazidime versus cefazolin monotherapy in culture-negative peritonitis. Our results suggest that if peritonitis is resolving at day 3, discontinuation of ceftazidime could yield favorable treatment outcomes and might be appropriate for subsequent management. However, the risk of not having gram-negative coverage should be considered.