Evaluating First Positive Cultures in Burns: Rethinking Broad-Spectrum Antibiotic Choices

Infection is a nearly universal complication among patients with major burns, yet guidance on early empiric antibiotic therapy remains limited. Broad-spectrum antibiotics are commonly initiated in the early phase of care but carry risks of antimicrobial resistance and drug toxicities. This single-centre, retrospective study evaluated the microbiological profiles and antibiotic prescribing patterns associated with first positive cultures (FPCs) in major burn patients admitted to Canada's highest-volume adult burn centre between January 1, 2018 and May 1, 2023. A total of 114 patients with ≥20% total body surface area burns were included. Among 145 FPCs, the most commonly cultured sites were respiratory (55%) and wound (30%). The most frequently identified organisms were methicillin-sensitive Staphylococcus aureus (19%), Haemophilus influenzae (15%), Enterobacter cloacae complex (8%), Escherichia coli (7%), MRSA (7%), and Pseudomonas aeruginosa (6%). Notably, only 3% of patients who screened negative for MRSA on admission developed MRSA-positive cultures. Antibiotic therapy was initiated in 99% of patients with FPCs, most commonly with piperacillin-tazobactam (41%), vancomycin (16%), and cefazolin (14%). Dual therapy, typically piperacillin-tazobactam plus vancomycin, was used in 13% of cases. Sensitivity data demonstrated that meropenem (90%) and the combination of ciprofloxacin with cefazolin (83%) covered the highest proportion of isolates. While piperacillin-tazobactam remains effective for early empiric use, our findings indicate that targeted alternatives-such as reserving meropenem for select cases or using ciprofloxacin plus cefazolin in appropriate patients-could provide comparable coverage while adhering to antimicrobial stewardship principles. A negative MRSA screening swab on admission demonstrated a high negative predictive value (~97%), supporting the withholding of vancomycin in screen-negative patients. This study supports evidence-based antibiotic use in burn patients and underscores the need for local, data-driven stewardship.