Inclusion Criteria:  Patients admitted to the ICU, COVID-19 positive by RT-PCR, who require assisted mechanical ventilation. Adult patients over 18 years of age. Patients who agree to participate in the study and sign the informed consent form (family members or legal representative). Patients in whom the identification of the causative agent of coinfection is attempted within the first 48 hours of hospitalization.  Exclusion Criteria:  Patient on mechanical ventilation for more than 24 hours without being evaluated for study entry. Patient who was treated with antibiotics 7 days prior to hospitalization or time of assessment for the study. Pregnant or breastfeeding patients. People who belong to population groups with increased vulnerability such as, for example, prison population, minors detained in orphanages or people in street situations.  No research procedure, clinical or paraclinical, or taking of clinical information or biological samples will be performed before the patient or his/her legal representative agrees to participate in the study and signs the informed consent form.