[Pseudomonas aeruginosa: combined treatment vs. monotherapy]

Pseudomonas aeruginosa is a pathogen commonly encountered in clinical practice in critically ill patients. It is a serious cause of infection, associated with a high rate of morbidity and mortality. Inappropriate antimicrobial therapy and delay in starting effective antimicrobial therapy is associated with worse prognostic. This microorganism is clinically indistinguishable from others forms of gram-negative bacterial infection. The rate of multidrug-resistant P. aeruginosa has increased in the last years. For these reasons, patients with Pseudomonas infection might receive empirical antibiotics that are inactive against Pseudomonas, especially before antibiotic susceptibility results become available. It remains controversial whether combination therapy, given empirically or as definitive treatment, for suspected Pseudomonas aeruginosa infections is justifiable. In the present article, we aimed to review recent studies that have evaluated the impact of combination therapy on Pseudomonas infections outcome and we exhibit our point of view in this subject. It seems justifiable to start combination therapy with two antipseudomonal agents in patients with risk for Pseudomonas infection during the first 3-5 days, until having microbiological results. This combination therapy must be changed to monotherapy on the basis on the specific susceptibility pattern of the initial isolate. In cases without microbiological diagnosis and poor outcome, combination therapy will be maintained and other causes of infection will be studied. Multicentre prospective randomized trials in critically ill patients are needed to determine which antimicrobials combinations improve outcome in Pseudomonas infections.