Clinical characteristics, causative organisms, and antimicrobial resistance profiles of hospital-acquired invasive gram-negative bacterial infections at a tertiary-care center in Saudi Arabia: a five-year retrospective cohort study (2020-2024).

BACKGROUND

Hospital-acquired gram-negative bacterial (HA-GNB) infections are a leading cause of nosocomial morbidity and mortality, yet local epidemiological data to guide empirical therapy remain limited.

METHODS

We conducted a retrospective cohort study of 377 adult patients with culture-confirmed invasive gram-negative infection acquired ≥ 48 h after admission to King Abdulaziz Medical City (KAMC), Jeddah, Saudi Arabia (2020-2024). Demographics, comorbidities, infection type, microbiology, susceptibility, complications, and outcomes were analyzed using chi-square/Fisher's exact tests and t-tests/Mann-Whitney U tests; multivariable logistic regression was used to identify independent predictors of multidrug-resistant (MDR) infection and in-hospital mortality. Infection types were classified according to U.S. Centers for Disease Control and Prevention / National Healthcare Safety Network (CDC/NHSN) surveillance definitions.

RESULTS

Mean age was 64.6 ± 17.7 years (59.4% male). Hypertension (61.0%), diabetes (54.6%), and cardiovascular disease (40.8%) were the commonest comorbidities. Pneumonia predominated (47.1%), followed by bloodstream infection (33.0%), surgical-site infection (15.7%), and ventilator-associated pneumonia (9.6%). Klebsiella pneumoniae (41.9%), Pseudomonas aeruginosa (34.0%), and Escherichia coli (15.4%) were the predominant pathogens. Resistance was highest for ciprofloxacin (44.4%), ceftazidime (40.2%), and cefepime (39.9%), and 34.3% for meropenem. Overall morbidity was 68.6% and mortality 39.9%. Mortality was significantly higher in patients with cardiovascular disease (48.8% vs. 34.3%, p = 0.011), hypertension (45.4% vs. 31.5%, p = 0.015), and COPD (100.0% vs. 39.2%, p = 0.025). Diabetes was strongly associated with multidrug-resistant infection (OR 3.60, 95% CI 1.44-9.04; p = 0.004) and remained an independent predictor in multivariable logistic regression adjusting for age, sex, cardiovascular disease, and pneumonia (adjusted OR 2.82, 95% CI 1.11-7.17).

CONCLUSIONS

HA-GNB infections at this Saudi tertiary center are dominated by K. pneumoniae and P. aeruginosa, carry a roughly two-in-five case fatality, and show worrying resistance to commonly used empirical agents. Within the constraints of a single-center, retrospective design, these findings support local antibiogram-informed review of empirical protocols, continued antimicrobial stewardship, and heightened infection-control attention to high-risk subgroups, particularly patients with diabetes and cardiopulmonary comorbidities; confirmation in prospective, multi-center studies is warranted.