PURPOSE: To identify the risk factors of ventilator-associated pneumonia (VAP) due to difficult-to-treat (DTT) bacteria (i.e., Pseudomonas aeruginosa, Acinetobacter baumannii and oxacillin-resistant Staphylococcus aureus), and to assess the rate and the causes of inappropriateness of empirical antimicrobial therapy.

METHODS: In an intensive care unit of a university hospital, patients bacteria if the patients had no prior hospitalization or prior administration of antibiotics, according to local guidelines.

RESULTS: Overall, the empirical antimicrobial therapy was appropriate in 190 (87%) out of 218 patients with VAP. Fifty (23%) patients developed problems due to DTT bacteria. The risk factors for VAP due to DTT bacteria were shock state, prior antimicrobial therapy, prior stay in long-term care facilities and late-onset VAP. Empirical antimicrobial therapy was inappropriate in 20 (40%) patients with VAP due to DTT bacteria and 8 (5%) patients with VAP due to non-DTT (P = 0.001). Guidelines violations (nine patients), bacteria not included in antibiotic spectrum (eight patients) and bacterial resistance (three patients) were the causes of inappropriateness in case of DTT bacteria.

CONCLUSION: Despite the abundant information for the treatment of VAP and the establishment of guidelines, too many patients with DTT bacteria received inappropriate antimicrobial therapy. Since 45% of the cases are related to non-adherence to the local protocol, there is room for improvement by implementing educational programs. Also, since DTT bacteria are found in 23% of late-nset VAP, empirical antibiotic treatment should be directed against these pathogens.