Comorbidities and mortality in colistin-resistant gram-negative infections among hospitalized patients in Qassim, Saudi Arabia.

Colistin has served as a last-resort agent against multidrug-resistant Gram-negative bacilli (MDR-GNB). However, the emergence of resistance has substantially eroded its therapeutic value, particularly among hospitalized patients. Evidence regarding the clinical outcomes of colistin-resistant infections in Saudi Arabia, however, remains scarce. This study aimed at assessing the clinical characteristics and outcomes of colistin-resistant bacterial infections among hospitalized patients in the Qassim region. We conducted a single-center retrospective observational study at King Fahad Specialist Hospital, Qassim, Saudi Arabia, reviewing the records of hospitalized patients with colistin-resistant infections between 2019 to 2023. Demographic, clinical, microbiological, therapeutic, and outcome data were retrieved from both electronic and paper health records. Eighty-five patients (mean age, 65.8 years; 60% male) with eighty-five colistin-resistant isolates were identified. Enterobacterales predominated (85.9%), followed by Pseudomonas aeruginosa (9.4%) and Acinetobacter baumannii (4.7%). All isolates showed extensive colistin resistance (100% in Acinetobacter and Pseudomonas, 82.8% in Enterobacterales), acknowledging the small number of non-Enterobacterales isolates. Limited sensitivity to cephalosporins and carbapenems, underscoring the therapeutic challenge of MDR-GNB. Meropenem (39.7%) and tigecycline (15.1%) were the most frequently prescribed agents, whereas combination therapy was employed in 16.6% of cases. The overall in-hospital mortality was 54.1% (95% CI: 43.0-65.0), with substantially higher mortality among patients admitted to the ICU (70.8%, 95% CI: 55.9-83.0) compared with those managed in non-ICU settings (32.4%, 95% CI: 18.0-49.8). After adjustment for clinical indicators, ICU admission was independently associated with increased mortality. Colistin-resistant Gram-negative infections hospitalized patients were characterized by severely limited therapeutic options, substantial reliance on carbapenems and tigecycline, and high observed mortality. These observations underscore the need for strengthened antimicrobial stewardship, improved availability of rapid diagnostic tools, and expanded access to newer therapeutic agents. In the absence of such measures, the burden of colistin resistance is likely to persist in hospital settings, including patients requiring intensive care.