Recently, there has been a renaissance of the use of the antibiotic colistin resulting from increasing resistance of bacterial pathogens, particularly in intensive care patients. The study aimed at assessing the impact of colistin consumption on the prevalence of colistin-resistant bacteria in the University Hospital Olomouc (UHO).A laboratory database was retrospectively searched to identify all clinically significant colistin-resistant bacterial strains isolated between 2007 and 2011. These data were compared with colistin consumption over the same period and the results were statistically processed.Over the study period, a total of 6 338 clinically significant colistin-resistant strains were detected in the UHO (Acinetobacter spp., Burkholderia cepacia complex, Citrobacter spp., Enterobacter spp., Escherichia coli, Klebsiella spp., Morganella morganii, Proteus spp., Providencia spp., Pseudomonas spp., Serratia marcesces and Stenotrophomonas maltophilia). Over the same period, the consumption of colistin increased nearly 10-fold. With the increasing colistin consumption, the numbers of colistin-resistant strains of Pseudomonas aeruginosa and Acinetobacter spp. decreased over that period of time. By contrast, there was an increase in the rates of naturally Burkholderia cepacia complex strains naturally resistant to colistin. An alarming finding is that the prevalence of colistin-resistant strains of Klebsiella pneumoniae increased in the last years of the study period, especially in intensive care patients.In the UHO, higher consumption of colistin was accompanied by increased numbers of colistin-resistant strains. There was a marked increase of Burkholderia cepacia complex strains and, recently, a statistically insignificant but alarming increase in colistin-resistant Klebsiella pneumoniae strains.