BIOCHEMICAL PREDICTORS OF ANTIMICROBIAL RESISTANCE IN HOSPITALIZED PATIENTS WITH GRAM NEGATIVE BACTERIAL INFECTIONS

Abstract

Background: Antimicrobial resistance in Gram-negative pathogens is an escalating problem in hospital practice, particularly when multidrug-resistant (MDR) infection is not recognized before empirical antimicrobial therapy is selected. A readily available biochemical profile that identifies patients with a higher probability of MDR infection could strengthen early clinical risk assessment while definitive susceptibility testing is pending. Objective: To determine whether routinely measured biochemical and inflammatory markers are independently associated with MDR Gram-negative bacterial infection in hospitalized adults and to assess their discriminatory performance for early risk stratification. Methods: In this prospective cohort study, 150 hospitalized adults with culture-confirmed Gram-negative bacterial infection were evaluated between January 2025 and January 2026. C-reactive protein (CRP), procalcitonin (PCT), serum albumin, lactate, creatinine, total bilirubin, and the CRP-to-albumin ratio (CAR) were assessed in relation to resistance status. MDR was defined as acquired non-susceptibility to at least one agent in three or more antimicrobial categories. Independent associations were examined with multivariable logistic regression, and discriminatory performance was quantified using receiver operating characteristic (ROC) analysis. Results: MDR organisms were recovered from 88 of 150 patients (58.7%). Escherichia coli was the most frequently isolated pathogen, whereas Acinetobacter baumannii showed the greatest organism-specific proportion of MDR. Relative to the non-MDR group, patients with MDR infection had higher median CRP (128 vs. 74 mg/L), PCT (3.4 vs. 1.0 ng/mL), lactate (2.8 vs. 1.9 mmol/L), and CAR (46.1 vs. 22.0), together with lower serum albumin (2.8 vs. 3.4 g/dL). After multivariable adjustment, PCT ≥2.0 ng/mL (aOR 2.71), CAR ≥35 (aOR 2.54), and albumin <3.0 g/dL (aOR 2.19) remained independently associated with MDR infection. The combined biochemical model yielded an AUC of 0.86, which increased to 0.89 when major clinical risk factors were incorporated. Conclusion: A biochemical pattern characterized by elevated PCT, increased CAR, and hypoalbuminemia was independently associated with MDR Gram-negative infection. These routinely available measures may add clinically useful information to exposure history and microbiological assessment, but they should be interpreted as components of an integrated risk model rather than as substitutes for definitive susceptibility testing.