Direct Disk Diffusion Testing and Antimicrobial Stewardship for Gram-Negative Bacteremia in the Context of High Multidrug Resistance

<b>Background:</b> Combining direct disk diffusion (DD) testing with antimicrobial stewardship (AMS) may optimize antibiotic use and improve outcomes in patients with Gram-negative bloodstream infections (GNBSIs). <b>Methods:</b> This quasi-experimental study was conducted at Srinagarind Hospital, Khon Kaen University, between 13 September 2022 and 11 April 2023. Patients with GNBSIs were enrolled during two phases: a standard care phase (13 September 2022-2 January 2023) and an intervention phase (16 January 2023-11 April 2023), during which therapy adjustments were guided by DD results interpreted by infectious disease specialists. <b>Results:</b> Among the 141 patients included (68 in the standard care group and 73 in the intervention group), the mean age was 61.7 years, and 60.2% were male. <i>Escherichia coli</i> (36.5%) and <i>Klebsiella pneumoniae</i> (27.6%) were the most frequently isolated pathogens, with intra-abdominal and urinary tract infections being the most common sources. Multidrug-resistant (MDR) organisms were identified in 48.9% of cases. Compared to standard care, the intervention group had a significantly shorter median time to optimal therapy (40.0 vs. 59.1 h, <i>p</i> = 0.037) and a higher proportion of patients receiving optimal therapy within 72 h (86.2% vs. 62.3%, <i>p</i> = 0.002). While 30-day mortality did not differ significantly between groups (17.2% vs. 16.7%, <i>p</i> = 0.98), MDR bacteremia and ICU admission were associated with increased mortality. In contrast, receiving optimal therapy within 72 h was associated with reduced mortality. <b>Conclusion:</b> Direct DD testing combined with AMS significantly reduced the time to optimal antibiotic therapy and decreased inappropriate antibiotic use in GNBSI patients. Achieving optimal therapy within 72 h was associated with a trend toward reduced mortality.