Antibiotic Management Following Urine and Blood Culture Results: A Retrospective Single-Centre Observational Study at University Hospital Hairmyres, United Kingdom.

Background Timely review and actioning of microbiological culture results are essential for effective antimicrobial stewardship. Delays in modifying therapy when cultures demonstrate resistance may result in prolonged exposure to ineffective antimicrobials and suboptimal management. This study aimed to evaluate the timeliness and appropriateness of antibiotic initiation and modification following positive urine and blood culture results in a district general hospital and to compare management between these two specimen types. Methods A retrospective observational study was conducted at University Hospital Hairmyres, United Kingdom, analysing 100 positive urine cultures and 25 positive blood cultures collected between the 4th and 17th December 2023. Patients with repeat samples or Candida infections were excluded. Data were extracted from the NHS clinical portal and the Hospital Electronic Prescribing and Medicines Administration (HEPMA) system. Variables included empirical antibiotic use, antimicrobial sensitivities, and time to initiation or modification of therapy following availability of culture and sensitivity results. Thirteen predefined study questions were used to assess antimicrobial management. "Appropriate modification" was defined as changing to an agent to which the organism was reported susceptible, taking into account route and documented allergies where available; clinical factors, such as renal function, infection site, and local guidance, were not systematically captured. Results A total of 125 patients were included (mean age: 71.9 years, SD: 16.8; 64% female). Among urine culture patients, 76/100 (76.0%) received antibiotics, including 59/100 (59.0%) prescribed empirical therapy. Of those receiving empirical treatment with susceptibility data available for the prescribed drug (n = 36), 15/36 (41.7%) received an antibiotic to which the organism was resistant. In this resistant group, 6/15 (40.0%) were not switched to a susceptible agent despite available results. Where therapy was modified appropriately, the mean delay between availability of sensitivity results and modification was 2.22 days. Among 41 patients not initially prescribed empirical antibiotics, 17 were commenced on treatment following culture positivity, with a mean delay of 2.24 days. All 25 blood culture patients received antibiotics, including 24/25 (96.0%) prescribed empirical therapy. Resistant empirical therapy was identified in 2/24 (8.3%) cases; both were appropriately changed to a susceptible agent prior to formal sensitivity reporting. Resistant empirical therapy was more frequent in urine than blood culture episodes when analysis was restricted to cases with interpretable susceptibility data (15/36 (41.7%) vs 2/24 (8.3%), Fisher's exact test, p = 0.0075). Empirical therapy was significantly more common in blood than urine cultures (24/25 (96.0%) vs 59/100 (59.0%), p=0.001). Conclusions This study identified delays in modifying antibiotic therapy following positive urine culture results, with a substantial proportion of patients remaining on resistant empirical regimens despite available sensitivity data. Findings suggest gaps in the timely review and optimisation of therapy, particularly for urine cultures. Implementation of enhanced notification systems and structured review processes may support more timely antimicrobial decision‑making and strengthen stewardship.