Oral Cavity Colonization with Multidrug-Resistant Gram-Negative Bacteria after Preoperative Prophylactic Use of Antibiotics as a Risk Factor for Ventilator-Associated Pneumonia.

BACKGROUND: Although it was previously shown that prolonged prophylactic antibiotic exposure and multiple inadequate antibiotic therapies are independent risk factors for multidrug-resistant ventilator associated pneumonia there were no studies investigating whether pre-operative prophylactic dose of antibiotics changes oral microbiome and increases the risk of ventilator associated pneumonia. The aim of the study was to determine if pre-operative prophylactic dose of antibiotics affects the oral microbiome, increases the colonization with Gram-negative bacteria and subsequent risk of ventilator associated pneumonia.

SUBJECTS AND METHODS: Mechanically ventilated adult patients receiving surgical antibiotic prophylaxis were included in the study. The presence of Gram negative microorganisms in the pre-prophylactic and post-prophylactic oral swabs and tracheal aspirates, as well as the occurrence of ventilator associated pneumonia, were analyzed.

RESULTS: Number of patients colonized with Gram negative bacteria in post- prophylactic oral swab was significantly higher compared to oral swab taken before prophylactic antibiotic. On the other hand, the number of patients with Gram- negative bacteria in tracheal aspirates remained similar as in post- prophylactic oral swabs. Moreover, we found that presence of Gram- negative bacteria in both pre- and post- prophylactic oral swabs was in the positive correlation with the presence of Gram- negative bacteria in tracheal aspirates.

CONCLUSIONS: This study showed increased colonization of oral cavity with Gram- negative bacteria after preoperative prophylactic antibiotics. Furthermore, receiving two prophylactic antibiotics from WHO Watch list increased the incidence of Gram- negative bacteria in oral swabs and tracheal aspirates, and the risk of ventilator associated pneumonia development.