Beta-lactam monotherapy or combination therapy for bloodstream infections or pneumonia due to Pseudomonas aeruginosa: a meta-analysis

•Pseudomonas aeruginosa represents a leading cause of healthcare-associated infections, with significant consequences in terms of morbidity and mortality.•No clear evidence is available in the literature on the superiority, in terms of clinical and microbiological outcomes, of combination therapy vs. beta-lactam monotherapy to treat beta-lactam-susceptible strains of P. aeruginosa.•Experimental and observational studies published as full papers up to December 2020 that compared the efficacy of beta-lactams used as monotherapy or in combination with other active agents as empirical or targeted therapy for bloodstream infections or hospital-acquired pneumonia/ventilator-associated pneumonia due to P. aeruginosa were analysed in this meta-analysis.•Six randomized controlled trials, six prospective cohort studies and 21 retrospective cohort studies were included in the analysis, accounting for a total of 3861 subjects.•Considering the 14 studies evaluating empirical therapy, no significant difference in mortality rate was observed between the two groups.•Similar findings were obtained among the 18 studies analysing targeted therapy; however, grouping the studies by design, higher mortality was observed among patients receiving monotherapy in five prospective studies.