The objective of this study is to assess the diagnostic performance of multiplex respiratory PCR (PCR-RM) compared to standard microbiological tests and its potential impact on the early adaptation of antibiotic treatment in intensive care patients with severe pneumonia.

This is a prospective, observational, multicenter ICU study. Adult patients with severe pneumonia requiring invasive mechanical ventilation will be included. Severe pneumonia consists of 3 categories of pneumonia: community-acquired pneumonia (CAP), hospital-acquired pneumonia (HAP), and ventilator-acquired pneumonia (VAP). The microbiological testing will be performed before antibiotic initiation on tracheobronchial aspirations, protected distal sampling, or mini-bronchoalveolar lavage as part of routine care. No additional samples will becollected for this study. Respiratory samples will be simultaneously tested by conventional microbiological techniques and multiplex respiratory PCR [PCR-RM] (BIOFIRE® FILMARRAY® Pneumonia Panel Plus). Classical microbiological culture (CMC) will be considered the gold standard for microbiological pneumonia diagnosis. The agreement between the results of the Pneumonia Plus® panel and the results of conventional microbial culture (CMC) will be assessed.

An empiric antibiotic therapy will be prescribed according to the local ecology and the protocols of each ICU unit. Two senior experts in each participating center will have to approve the antibiotic prescription. The antibiotic therapy could be modified after the reception of the Mutilpex PCR results by the two senior experts. After the reception of the results of the classic microbiological culture, the previous antibiotic changes will be judged as appropriate or inappropriate by a multidisciplinary team including intensivists, infectious disease specialists, and microbiologists. Appropriate changes include adequacy, de-escalation, and optimization of antibiotic therapy, and inappropriate changes include inadequacy, escalation, and de-optimization.

Inclusion Criteria:

• critically ill adult patients
• clinical, biological, and radiological signs of severe pneumonia.
• community-acquired pneumonia, hospital-acquired pneumonia, or ventilator-associated pneumonia
• invasive mechanical ventilation.

Exclusion Criteria:

- Non-invasive mechanical ventilation.

Critically ill patients with ventilator-associated pneumonia (VAP), community-acquired pneumonia (CAP), or hospital-acquired pneumonia (HAP). For CAP and HAP, only patients under invasive mechanical ventilation will be included.

The datasets of the study will be available from the principal investigator on reasonable request.

until 5 years after study completion

Healthcare workers.