It is hypothesized that microorganisms reach the ETT either as a consequence of a contaminated oropharynx or reflux of gastric secretions29, selective digestive tract decontamination (SDD) and selective oropharyngeal decontamination (SoD) are measures in which antibiotic therapy is used to eradicate potentially pathogenic microorganisms in oral, gastric, and intestinal flora 17, 18.