Table 1 Inclusion and exclusion criteria

Age ≥18 years.

Renal insufficiency in substitute treatment.

≥96 hours of mechanical ventilation.

Corporal weight <40 kg or >150 kg.

<96 hours of mechanical ventilation +7 days in-hospital +5 days of antibiotic treatment.

Refractory shock or another disease that, according to the researcher, presents a life expectancy inferior to 48 hours after recruitment.

Clinical criteria of VAP (at least one required)

Patients with:

Documented fever

Known or suspected CABP or viral pneumonia

An elevated total peripheral white blood cell (WBC) count (WBC greater than 10,000/mm); or greater than 15% immature neutrophils (bands), regardless of total peripheral WBC count; or leukopenia with total WBC less than 4,500/mm.

Acute exacerbation of chronic bronchitis without evidence of pneumonia

New onset of expectorated or suctioned respiratory secretions characterized by purulent appearance indicative of bacterial pneumonia.

Tracheobronchitis

Primary lung cancer or another malignancy metastatic to the lungs

Cystic fibrosis, bronchiectasis, HIV/AIDS, known or suspected Pneumocystis jiroveci pneumonia, or known or suspected active tuberculosis

Immunocompromised patients; hematologic neoplasia, solid organ transplant or congenital or acquired diseases that cause significant immunodeficiency (examples: common variable immunodeficiency), patients with neutropenia <500PMN/mm3.

Radiological criteria of VAP: new or progressive pulmonary infiltrate in the thorax radiography which suggests pneumonia and with no other probable cause.

The isolation in respiratory samples from surveillance cultures of GNB colistin or meropenem resistant in the 7 days previous to inclusion.

Modified Clinical Pulmonary Infection Score (CPIS) >4

Respiratory secretion sample BAL or endotracheal aspirates obtained in the 24 hours previous to the beginning of antimicrobial treatment of the study.

Previous use of meropenem: the current use of meropenem at the time of diagnosis is not permitted (unless this was a unique dose of 1,000 mg as initiation of empiric treatment).

A negative pregnancy test in women of childbearing potential.

A duly signed informed consent form.