Title : Empirical antibiotic coverage for bacteraemia: A seasonal audit across Hampshire Hospitals NHS Foundation Trust
Abstract:
Background: This audit assesses the coverage of first and second line antibiotic regimens for community and hospital acquired sepsis of unknown origin using blood culture isolates at Hampshire Hospitals NHS Foundation Trust. Coverage was compared across two periods: June and July 2024 (summer) and January and February 2025 (winter). This audit was undertaken in response to concerns regarding rising resistance in Gram-negative organisms, with the aim of ensuring empiric regimens remain both clinically effective, to ensure optimal patient safety, and aligned with antimicrobial stewardship principles.
Methods: Blood culture isolates were identified by specimen date across both periods. Duplicate isolates were removed unless resistance patterns differed, in which case the most resistant result was retained. Isolates were categorised by acquisition (community vs hospital) and assessed against guideline-recommended empiric regimens. Coverage was defined as susceptibility to ≥1 antibiotic within the regimen. Isolates without susceptibility data to any regimen component were classified as “not tested” and excluded from evaluable coverage.
Results: A total of 343 bacterial isolates were included. Gram-negative organisms predominated, with Escherichia coli accounting for ~57% of isolates in both periods. First-line empiric coverage remained high but declined from summer to winter: community 92.7% to 86.0%, and hospital 85.7% to 84.1%. Coverage for E. coli, Staphylococcus aureus, and Proteus mirabilis remained consistently high across both settings. Reduced coverage was observed for Klebsiella pneumoniae in community cases (100% to 57.1%), although numbers were small. A proportion of isolates lack susceptibility data and were excluded from analysis.
Conclusions: Empiric regimens do overall provide high overall coverage across both settings, although a reduction in winter coverage was observed. The explanation for this is likely multifactorial and secondary to changes in isolate distribution, such as increased Klebsiella pneumoniae and Enterococcus faecium, reduced susceptibility in key organisms, and a higher proportion of hospital-acquired infections. Missing susceptibility data remains a key limitation and may impact estimates. Future directions include correlation of coverage data with patient outcomes, and with inpatient pharmacy data.
