A Narrative Review on the Approach to Antimicrobial Use in Ventilated Patients with Multidrug Resistant Organisms in Respiratory Samples-To Treat or Not to Treat? That Is the Question

Abstract

Multidrug resistant organisms (MDRO) are commonly isolated in respiratory specimens taken from mechanically ventilated patients. The purpose of this narrative review is to discuss the approach to antimicrobial prescription in ventilated patients who have grown a new MDRO isolate in their respiratory specimen. A MEDLINE and PubMed literature search using keywords "multidrug resistant organisms", "ventilator-associated pneumonia" and "decision making", "treatment" or "strategy" was used to identify 329 references as background for this review. Lack of universally accepted diagnostic criteria for ventilator-associated pneumonia, or ventilator-associated tracheobronchitis complicates treatment decisions. Consideration of the clinical context including signs of respiratory infection or deterioration in respiratory or other organ function is essential. The higher the quality of respiratory specimens or the presence of bacteremia would suggest the MDRO is a true pathogen, rather than colonization, and warrants antimicrobial therapy. A patient with higher severity of illness has lower safety margins and may require initiation of antimicrobial therapy until an alternative diagnosis is established. A structured approach to the decision to treat with antimicrobial therapy is proposed.

Keywords: ICU; decision; multidrug resistant; treatment; ventilator associated pneumonia; ventilator associated tracheobronchitis.

Figure 1

Risk and benefits of giving and withholding treatment for patients with VAP/VAT or respiratory colonization with MDRO. Red boxes represent consequences when decision to treat or not to treat is incorrect. Green boxes represent best case scenarios even when MDRO is isolated from respiratory samples of ventilated patients. AMR, antimicrobial resistance; MV, mechanical ventilation; VAP, ventilator-associated pneumonia; VAT, ventilator-associated tracheobronchitis.

Figure 2

Outline of key factors to be considered when deciding to treat or not to treat when a ventilated patient has a positive MDRO respiratory specimen. The final decision is based on the final weight of evidence either in favor of likely VAP or not, after systematic consideration of these multiple factors. See text for further explanation. * Does not change the likelihood of VAP diagnosis but does reduce the safety margin of withholding targeted antimicrobial therapy. MDRO, multidrug resistant organism; PEEP, positive end-expiratory pressure; P/F, PaO₂/FiO₂; VAP, ventilator-associated pneumonia; VAT, ventilator-associated tracheobronchitis.