INTRODUCTION
The number of people aged 65 years and older is increasing globally. With aging, the incidence of chronic disease and malignancy rises, and decline in physiologic and immune functions increases susceptibility to infections (1). Healthcare-associated bacterial infections in old age are particularly alarming because patients over 65 are more frequently hospitalized and subjected to invasive procedures.
There has been a significant increase in infections caused by resistant gram-negative microorganisms. The lack of new drugs effective in the treatment of resistant infections has led to the reintroduction of colistin (COL), which was largely abandoned in clinical practice due to its nephrotoxic and neurotoxic adverse effects (2-4). Being treated in intensive care units (ICUs) and older age are factors that increase the frequency of infections caused by resistant microorganisms and complicate the management of the antimicrobial agents used. Some studies have shown that COL nephrotoxicity increases with age, while no relationship between age and COL-related renal toxicity was detected in others (5-9). The present study aimed to identify risk factors associated with COL nephrotoxicity in the general population and geriatric patients hospitalized in the ICUs of our hospital.