Abstract
Antimicrobial resistance (AMR) is rising alarmingly in Saudi Arabia, as evidenced by surveillance data. This retrospective cohort study evaluated the association between parenteral antimicrobial use and bacterial resistance at King Khaled Hospital, Al-Kharj, using electronic health records. Linear regression analyzed antibiotic exposure-resistance relationships over 36 months (January 2022-December 2024). Eligible participants were hospitalized ≥ 48 h and received ≥ 1 parenteral antimicrobial. The required sample size was 384 (calculated via Cochran's formula). Inclusion mandated laboratory-confirmed bacterial infections (positive cultures with susceptibility testing). Investigated pathogens included Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus. Among 4,007 participants, 59.02% were female, and 73.07% were Saudis. Findings revealed severe AMR, particularly in Escherichia coli and Klebsiella pneumoniae, with high resistance to multiple antibiotic classes. Acinetobacter baumannii exhibited near-pan-drug resistance (> 90% resistance to most antibiotics). Imipenem use strongly correlated with Escherichia coli resistance (R(2) = 1.000, p-value = 0.009), indicating significant carbapenem-driven selection pressure. Meropenem exposure also closely linked to Klebsiella pneumoniae resistance (R(2) = 0.994, p-value = 0.050). Widespread resistance to β-lactams, fluoroquinolones, and aminoglycosides-combined with near-pan-resistant Acinetobacter baumannii-highlights escalating treatment challenges. Crucially, carbapenem usage (imipenem/meropenem) strongly predicted resistance in Escherichia coli and Klebsiella pneumoniae, reinforcing antimicrobial pressure's role in resistance development. These results emphasize the urgent need for antimicrobial stewardship at King Khaled Hospital to curb carbapenem overuse and combat resistant infections.