Ceftolozane–tazobactam for resistant P. aeruginosa infections linked to high clinical success

In the treatment of invasive infections due to multidrug-resistant P. aeruginosa, the use of ceftolozane–tazobactam combination appears to yield higher rates of clinical success than the ceftazidime–avibactam combination, according to an observational study.

The study included 420 adult patients with microbiologically confirmed multidrug-resistant P. aeruginosa pneumonia or bacteraemia. Of these, 210 were treated with ceftolozane–tazobactam and 210 with ceftazidime–avibactam for more than 48 hours. The two groups were matched according to study site, severity of illness, time to treatment initiation (≤72 h or >72 h), and infection type.

Clinical success at day 30 was the primary outcome. Clinical success was defined as survival, resolution of signs and symptoms of infection with the intended treatment course, and the absence of recurrent infection due to P. aeruginosa. All-cause mortality and development of resistance to study drug were also assessed.

At baseline, 350 patients (83 percent) had pneumonia and 70 (17 percent) had bacteraemia. Baseline patient characteristics were similar between the treatment groups. In the entire cohort, clinical success was documented in 61 percent of patients treated with ceftolozane–tazobactam and in 52 percent of those treated with ceftazidime–avibactam (adjusted odds ratio [aOR], 2.07, 95 percent confidence interval [CI], 1.16–3.70).

Among patients with pneumonia, clinical success occurred in 63 percent of patients with ceftolozane–tazobactam group and in 51 percent with ceftazidime–avibactam (aOR, 2.34, 95 percent CI, 1.22–4.47). Among patients with bacteraemia, clinical success rates were 51 percent and 57 percent, respectively (aOR, 0.76, 95 percent CI, 0.23–2.57).

No significant between-group differences were seen in 30-day or 90-day mortality. Among patients whose baseline isolates were tested for susceptibility, resistance occurred in 22 percent of ceftolozane–tazobactam-treated patients and in 23 percent of those treated with ceftazidime–avibactam.