Antibiogram Surveillance to Determine Appropriate Initial Empiric Antibiotic Therapy for Ventilator Associated Pneumonia

Author(s):
Andy Kerwin; G. Christopher Wood; Saskya Byerly; Dina Filiberto; Julie Farrar; Maegan Rogers; Martin Croce

Background:

Early initiation of empiric antibiotic therapy for ventilator associated pneumonia is essential. Inappropriate empiric antibiotic therapy can lead to increased mortality.  Previous work from our institution defined protocolized empiric antibiotic therapy for early (<7 days; ampicillin/sulbactam) ventilator associated pneumonia (VAP) and late (>7 days; cefepime plus vancomycin) VAP based on our local antibiogram. This longstanding empiric antibiotic therapy protocol has consistently covered the pathogenic organisms causing VAP with inadequate empiric antibiotic therapy (IEAT) occurring approximately 15% of the time. We reviewed our trauma ICU antibiogram to determine if the incidence of IEAT was changing and warranted protocol adjustments.

Hypothesis:

We hypothesized there would be no change in IEAT over time due to vigilant protocol adherence.

Methods:

Quantitative culture results from bronchoalveolar lavage specimens obtained in critically injured trauma patients with a clinical picture suspicious for VAP between 2017 – 2022 were reviewed for identification of pathogens and sensitivity patterns. We reviewed the sensitivity pattern to identify the IEAT percentage and we reviewed changes in the rate per 1000 days present for antimicrobial use for 2018-2022.

Results:

In 2015 the overall percentage of IEAT was 17% and we noted an increase in IEAT beginning in 2017. The percentage of IEAT for early and late VAP are shown in the Table. In early VAP, the increase in IEAT was due to an increase in identification of Gram negative bacteria isolates (7% to 24 %) and increase in Pseudomonas (3% to 10 %), and a decrease in identification of Streptococcus sp (32% to 23%) and Haemophilus influenza (20% to 17%). In late VAP, the increase in IEAT was due to an increase in identification of Stenotrophomonas (3% to 5%), and Acinetobacter (4% to 10%). Antimicrobial use changed as pathogens and sensitivity changed. There were increases in rates per 1,000 days for cefazolin (11.9%), vancomycin (22.8%), cefepime (33.1%), and meropenem (424.7%) while there were decreases in rates per 1,000 days for ampicillin/ sulbactam (-4.5%) and piperacillin/ tazobactam (-9.5%).

Conclusions:

Vigilant monitoring of quantitative culture results of bronchoalveolar lavage specimens has produced a longstanding protocol for initial empiric antibiotic therapy for the management of VAP in critically injured trauma patients. The change in organisms identified and increase in IEAT highlights the importance of continuous antibiogram monitoring and data-driven evaluation of antibiotic adequacy balanced with antibiotic stewardship.