Rate of bacterial positivity following antibiotic initiation: a systematic review and meta-analysis

Bacterial culture remains a critical tool for pathogen identification and antimicrobial susceptibility testing. However, its diagnostic accuracy is often compromised by prior antibiotic administration, which can reduce the recovery of viable organisms and lead to false-negative results. Given the variability and limitations in the existing studies, a systematic review is needed to better understand the influence of antibiotics on culture yield.

We conducted an electronic search in PubMed, Embase, Scopus and Web of Science from their inception through March 2025. The Newcastle-Ottawa Scale was used to assess the methodological quality of the included articles. Random effects models were used to estimate the proportions and 95% Confidence Intervals (CIs). The protocol for this review was registered in PROSPERO: CRD42025648397.

Of the 1226 articles obtained from the search, 11 were eligible. The eligible articles comprised 67,330 samples with culture results after antibiotic administration. The pooled proportion for bacterial growth was 37% (95% CI 20-56%) and 18% (95% CI 10-29%) before and after antibiotic administration, respectively. Significant heterogeneity (I² = 99.8%, p-value < 0.001) was observed across the included studies.

Bacterial growth decreased by more than half following antibiotic administration, indicating a strong suppressive effect. This highlights the importance of considering the timing of sample collection in relation to antibiotic initiation. Where necessary, particularly in cases of uncertain clinical progress, sampling after antibiotic administration can be useful for monitoring prognosis and guiding further treatment decisions.

PROSPERO: CRD42025648397.