The evolution of drug-resistant microorganisms in patients with prolonged mechanical ventilation

Abstract

Patients requiring prolonged mechanical ventilation (PMV) tend to become reservoirs of antimicrobial resistance. We assessed antimicrobial-resistant microorganisms in the respiratory tracts of patients receiving PMV. Over a 6-month period, the microorganisms from tracheal aspirates of PMV patients with lower airway infection were analyzed. Antimicrobial use was greatest during the acute critical stage of respiratory failure. Antimicrobial resistance in Pseudomonas aeruginosa and Klebsiella pneumoniae peaked during the fourth to 15th weeks of PMV. Methicillin-resistant Staphylococcus aureus (MRSA) developed rapidly during the first 3 weeks of PMV. The acquisition of multidrug-resistant P aeruginosa and MRSA were significantly correlated with previous exposure to ceftazidime (odds ratio [OR] = 121.3 and 72.5; P = .01 and .01, respectively). The rise of multidrug-resistant Acinetobacter baumannii was significantly correlated with previous exposure to piperacillin/tazobactam (OR = 26.81; P = .02) and imipenem (OR = 16.91; P = .03). Using univariate and multivariate logistic regression models, the lower respiratory tract infections with multidrug-resistant microorganisms were independently associated with increased 6-month mortality (OR = 3.41; P < .01). In patients receiving PMV, lower respiratory tract infection with multidrug-resistant microorganisms is common and is associated with higher mortality.