Patients in hospital intensive care units have a higher risk of developing pneumonia when they are treated with topical antibiotics.

The findings contradict previously published research that topical antibiotics—medication applied to the patient’s airway—would decrease pneumonia rates.

Ventilator-associated pneumonia develops in approximately 20 percent of patients in intensive care units (ICUs) who are receiving prolonged medical ventilation.

However, in the control groups of these published clinical trials of topical antibiotics in this patient group, the pneumonia rates were as high as 40 percent.

For a new study published in the journal CHEST, researchers analyzed 206 international publications evaluating pneumonia prevention methods in ICU’s from the last 30 years.

Use of topical antibiotics increases the pneumonia risk in ICU patients by disrupting the balance of bacteria, not only in patients that received these antibiotics but also in control group patients also staying in the ICU.

The new findings will help improve understanding of how to evaluate pneumonia prevention methods in the ICU, says associate professor James Hurley from the University of Melbourne.