Introduction: In health care institutions, microorganisms that can originate from patients, healthcare workers or health care environment are present. The bacteria of the genus Pseudomanas that are already intrinsically resistant to numerous antibiotics and disinfectants can frequently be found in health care environment, mostly in water, liquids and damp surfaces. The resistance of these bacteria to beta-lactam antibiotics carbapenems is a challenge that healthcare workers are facing, as it limits the treatment options of infections. In the period from 2015 to 2017, the Department of Internistic Oncology encountered the carbapenem resistant Pseudomonas putida strains, which were found in the stool samples of 88 hospitalized patients. Purpose: The research was carried out in order to find out the origin and route of transmission of the bacterium Pseudomonas putida at the Department of Internistic Oncology and to prove that the patients were not colonised with the bacterium Pseudomonas putida but the contamination arose during the collection the stool sample as a surveillance culture. Working methods: The research was carried out in two steps. In the first step, we described the characteristics of patients, whose stool surveillance cultures showed the presence of bacterium Pseudomonas putida, and the results of microbiological sampling of surfaces, water and liquids in the Department of Internistic Oncology. In the second step, we collected the surveillance cultures of the same patients again and tested their colonization with the bacterium Pseudomonas putida. Based on the results of microbiological surface sampling in the first step of research, we focused on the sampling of the inside surfaces of toilet bowls in order to prove the source of the bacterium Pseudomonas putida. Results: The research showed that the presence of the bacterium Pseudomonas putida in the stool surveillance cultures could be the consequence of the inappropriate collection directly from the inside surfaces of the toilet bowls where its presence was proven by the microbiological sampling. The primary source of the bacterium, found on the toilet bowl surfaces, was not discovered. Discussion and conclusion: The prevention and control measures related to healthcare impose numerous measures form cleaning the health care environment to prescribing antibiotics to patients. One of the important measures is to look for the carriers of the multi-drug resistant bacteria that we identify by collecting surveillance cultures, which has to be collected in accordance with the internal instructions of health care institution and instructions of microbiology laboratory. Healthcare workers have to be familiar with the correct procedure of collecting stool samples for microbiological investigstions and the possibility for mistekes. When patients take a stool samples themselves, they need to be carefully taught about all the stages of the procedure. Healthcare workers have to follow the instructions and measures related to the prevention and control of infections in healthcare settings.