Healthcare-associated infections could affect the rate of morbidity, mortality and post-discharge hospitalization among patients. They are also dangerous to healthcare professionals and generate significant cost to the healthcare system. The aim of this study was to evaluate the occurrence rate of colonization with various antibiotic-resistant (AR) bacteria among patients admitted to the Department of Immunology, Transplantology and Internal Diseases. The study used retrospective analysis of

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... ients (n = 280) with no clinical signs of infection admitted into the department between November 2015 and May 2017. The observational period lasted until January 2019. Collected data included sex, age at admission, location directly prior to current hospitalization, and medical history. Nasal and rectal swabs were collected, and stool and urine samples were obtained on the day of admission. Specimens were cultured according to standard microbiological procedures. In all cases, the appropriate bioMerieux (Marcy-l'Étoile, France) media were used. Isolates were identified using mass spectrometer (Vitek MS; bioMerieux). One-hundred ninety-one (68.2%) of patients were colonized with AR bacteria. The incidence of colonization was not influenced by age or sex. The risk of colonization was associated with admission from another hospital and history of kidney transplantation (p = 0.0136 and p < 0.001, respectively). The number of hospitalizations during the whole observational period was higher in the group of colonized patients compared to non-colonized (2.76 ±2.4 vs 2.07 ±1.68, p = 0.0099). The number of hospitalizations correlated positively with the number of positive cultures obtained from the same patients (rho = 0.18, p = 0.0274). The rate of colonization at admission to the ward could be high, depending on previous hospitalization and medical history. Colonization significantly increased post-discharge hospitalization rate.