This is a multicentre, multinational, prospective observational investigation on ICU critically ill patients affected by nosocomial pneumonia, defined as: Out of ICU Hospital-acquired Pneumonia (HAP), Non-ventilator ICU-acquired Pneumonia (NV ICUAP), Ventilator associated pneumonia (VAP) Ventilator associated tracheobronchitis (VAT).

Inclusion Criteria:

• Age ≥ 18 years
• Diagnosis of nosocomial pneumonia
• ICU and HDU admission (patient may be admitted to the ICU with NP or may develop pneumonia during ICU stay)
• Informed consent (if required)

Exclusion Criteria:

• Community Acquired Infection
• Absence of Microbiological Findings

All ICU patients with a documented Nosocomial Lower Respiratory Tract Infection will be eligible for this epidemiological, clinical and microbiological investigation