This study is designed to evaluate the clinical and antibacterial efficacy, safety and pharmacokinetics of the drug Fluorothiazinone compared to placebo to prevent nosocomial gram-negative bacterial infections with participation of patients on mechanical ventilation.

The main objectives of this study are:

• Evaluation of the clinical and antibacterial efficacy of the drug Fluorothiazinone in combination with standard measures for the prevention of nosocomial infections compared to placebo in combination with standard measures for the prevention of nosocomial infections for the prevention of nosocomial infections caused by bacterial gram-negative flora in patients on mechanical ventilation.
• Evaluation of the safety and tolerability of the drug Fluorothiazinone in patients on mechanical ventilation.
• Evaluation of the pharmacokinetics (in whole blood) of the drug Fluorothiazinone with a single daily dose of 2400 mg/day.

Researchers will compare results for the treatment and the placebo arms.

Inclusion Criteria:

1. Patient's written consent to participate in the study in accordance with the current legislation or the decision of the board in case of absence of consciousness of the patient.

2. Patients are at least 18 years old, male and female.

3. Patients who are in the ICU (intensive care unit).

4. Patients with:

   4.1. Laboratory confirmed SARS-CoV-2 (Severe acute respiratory syndrome-related coronavirus-2) on screening (a patient's coronavirus infection can be confirmed either before admission to the hospital (for outpatient treatment) or when admitted to the hospital) by RT-PCR (reverse transcription polymerase chain reaction) AND severe community-acquired pneumonia in ICU with evidence of viral lung injury and symptoms of respiratory failure:

   • SpO2 (peripheral oxygen saturation) ≤ 93%;
   • Lung changes of 3rd- to 4th-degree according to CT (results of computed tomography), consistent with viral involvement; OR 4.2. Acute stroke; OR 4.3. Acute heart failure: Cardiogenic shock of any cause, pulmonary edema, or acute decompensated chronic heart failure.

5. Patients who have been on ALV (artificial lung ventilation) for no more than 12 hours.

6. Patients who are according to the investigator are at high risk to be transferred to ALV within 72 hours of the initiation of the therapy.

7. All women of childbearing age and men with partners of childbearing age should agree to use an effective contraceptive methods (e.g., implants, infections, combination oral contraceptives, intrauterine device, abstinence, vasectomy or vasectomy partner) during the entire study.

Exclusion Criteria:

1. The patient was not switched to ALV within 72 hours (3 days) after receiving the investigational drug.
2. People who have a bloodstream infection, identified during the screening.
3. A patient may terminate his/her participation in the study at any time for any reason and without any explanation.

3. The investigator may also decide to terminate the patient's participation at any time if it is required due to the patient's condition.

4. The sponsor or the regulator may also request the trial to be terminated early, either due to how the trial was conducted, or due to application safety data, or other reasons.

5. The main reasons why the patient may withdraw from the study are:

• Refusal of the patient to participate in the study;
• Development of an AE (adverse event) / SAE (serious adverse event) that prevents further study participation;
• The occurrence of concomitant somatic diseases / symptoms or exacerbation of chronic diseases not related to the investigational drug (at the discretion of the medical investigator).