MDR (multidrug resistant) gram-negative bacteria have emerged as an important cause of bloodstream infection in hospitalized patients, especially in immunocompromised hosts. It was previously shown, that intestinal colonization with extended-spectrum β-lactamases (ESBL)-producing or carbapenem-resistant Enterobacteriaceae, carbapenem-resistant A. baumannii and P. aeruginosa) is a clinical predictor of bloodstream infections in patients with haematological malignancies and/or haematopoietic stem cell transplantation [Stoma I. et al., 2016].

To the investigators knowledge no randomized, placebo-controlled clinical trial has been performed to study the efficacy and safety of selective intestinal decolonization strategies in high-risk patients with haematological malignancies. Possible decolonization of MDR gram-negative bacteria in haematological patients could be important for the patient by reducing the risk of infection and for the community by reducing the risk of transmission.

The purpose of the proposed study is to assess the efficacy and safety of selective intestinal decolonization of MDR gram-negative bacteria with oral administration of Colistimethate sodium in high risk patients with haematological malignancies.

Inclusion Criteria:

1. Microbiologically proven rectal carriage of ESBL-producing Enterobacteriaceae or carbapenem-resistant Enterobacteriaceae, A. baumannii, P. aeruginosa without signs and symptoms of active infection.
2. Patient must give written informed consent to participate in the study. The informed consent can be given by the legal representative if necessary.

Exclusion Criteria:

1. Active bacterial, viral, fungal or protozoal infection
2. Women who are pregnant or nursing
3. Antibacterial therapy in previous 10 days
4. Contraindication to the use of one of the study drugs (including known hypersensitivity)
5. Patient already enrolled in another study, or in the present study for a previous episode
6. Psychiatric disorder or unable to understand or to follow the protocol directions
7. Resistance of the primarily isolated colonizing microorganism to polymyxin antibiotics proven by methods of polymerase chain reaction