The role of microbiological results in driving inappropriate antibiotic prescriptions.

Purpose of review: To highlight the unintended consequences of microbiological test results in driving inappropriate antimicrobial prescriptions, and to evaluate strategies - particularly from the perspective of diagnostic stewardship - that may mitigate this issue.

Recent findings: Despite the critical role of microbiological data in guiding appropriate antimicrobial therapy, several studies have demonstrated that misinterpretation of such results frequently leads to unnecessary treatments. Common pitfalls include overinterpretation of positive cultures from poorly collected or clinically unwarranted samples, misclassification of colonization vs. infection, and excessive reliance on test results in the absence of supporting clinical evidence. Emerging diagnostic stewardship interventions - ranging from restricting sample processing and modifying test reporting to implementing decision support tools - have shown promising outcomes in reducing overtreatment without compromising patient safety. Specific examples include urine and wound cultures, respiratory specimens, and the diagnosis of Clostridioides difficile infection. Furthermore, educational and system-level strategies such as the BLADDER score or selective result reporting can improve decision-making at various stages of the diagnostic process.

Summary: Microbiology laboratories play a pivotal role in antimicrobial stewardship and must actively support clinicians in avoiding diagnostic and therapeutic errors. While evidence supports multiple approaches to mitigate inappropriate prescriptions driven by microbiology results, their successful implementation requires interdisciplinary collaboration, tailored interventions, and ongoing evaluation of clinical impact. Diagnostic stewardship, when aligned with clinician education and robust reporting practices, is a crucial component in enhancing the accuracy of infection diagnosis and reducing antimicrobial overuse.