Conventional vs antibiotic-free farming and antimicrobial resistance in food: a meta-analysis
Abstract
Background: Conventional farming may increase antimicrobial resistance (AMR) in food before processing, yet the magnitude of this association remains poorly characterised. This systematic review and meta-analysis compared phenotypic AMR in unprocessed food matrices between conventional production systems and antibiotic-free, organic, or wildlife comparators.
Methods: Databases were searched from inception to Feb 28, 2025 (protocol: osf.io/pf7b4). Quality was assessed using validated tools. For each antibiotic, summary odds ratios (ORs) with 95% confidence intervals (CIs) were estimated using restricted maximum-likelihood random-effects models, with prespecified subgroup analyses by matrix and bacterial genus.
Findings: Eleven studies, mostly cross-sectional and of moderate-to-high quality, met inclusion criteria, covering dairy cattle (n = 6;raw milk), swine (n = 2;carcasses), and poultry (n = 3;eggs and carcasses). Conventional farming was associated with significantly higher ORs to ampicillin (OR 2·89, 95% CI 1·64–5·09; I²=34%), penicillin (OR 1·57, 95% CI 1·12–2·19; I²=7%), tetracycline (OR 3·37, 95% CI 1·83–6·18; I²=52%), erythromycin (OR 3·00, 95% CI 1·36–6·62; I²=72%), spiramycin (OR 5·24, 95% CI 1·04–26·41; I²=0%), tylosin (OR 4·54, 95% CI 1·02–20·11; I²=0%), and pirlimycin (OR 4·42, 95% CI 1·42–13·83; I²=33%). Teicoplanin showed a significant association (OR 4·04, 95% CI 1·10–14·88), and rifampicin a significant inverse association (OR 0·15, 95% CI 0·03–0·70). Subgroup analyses showed the strongest associations in raw milk and for Staphylococcus spp.
Interpretation: Conventional production was associated with higher phenotypic AMR in pre-processing food, indicating a measurable resistance footprint entering the human supply chain. These findings support WHO stewardship priorities targeting agricultural use of critically important antimicrobials and highlight the need for production-level surveillance to safeguard food system sustainability and planetary health.
Key messages: • Conventional farming is associated with higher antimicrobial resistance in unprocessed food matrices compared to antibiotic-free, organic, or wildlife comparators, across dairy, swine, and poultry.
• A measurable resistance footprint enters the food supply chain at production level, supporting WHO priorities on agricultural antimicrobial stewardship and the need for production-level surveillance.
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BibTeX
@article{bonanno2026conventional,
title = {{Conventional vs antibiotic-free farming and antimicrobial resistance in food: a meta-analysis}},
author = {G Bonanno and A Sciurti and V Baccolini and L M Siena and B Goletti and V Turroni Casadei and R Pausilli and C Tommasino and P Villari and G Migliara},
journal = {The European Journal of Public Health},
year = {2026},
month = oct,
doi = {10.1093/eurpub/ckag169.424},
url = {https://doi.org/10.1093/eurpub/ckag169.424},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Conventional vs antibiotic-free farming and antimicrobial resistance in food: a meta-analysis
AU - G Bonanno
AU - A Sciurti
AU - V Baccolini
AU - L M Siena
AU - B Goletti
AU - V Turroni Casadei
AU - R Pausilli
AU - C Tommasino
AU - P Villari
AU - G Migliara
PY - 2026
DA - 2026/10/01
JO - The European Journal of Public Health
DO - 10.1093/eurpub/ckag169.424
UR - https://doi.org/10.1093/eurpub/ckag169.424
AB - Background: Conventional farming may increase antimicrobial resistance (AMR) in food before processing, yet the magnitude of this association remains poorly characterised. This systematic review and meta-analysis compared phenotypic AMR in unprocessed food matrices between conventional production systems and antibiotic-free, organic, or wildlife comparators. Methods: Databases were searched from inception to Feb 28, 2025 (protocol: osf.io/pf7b4). Quality was assessed using validated tools. For each antibiotic, summary odds ratios (ORs) with 95% confidence intervals (CIs) were estimated using restricted maximum-likelihood random-effects models, with prespecified subgroup analyses by matrix and bacterial genus. Findings: Eleven studies, mostly cross-sectional and of moderate-to-high quality, met inclusion criteria, covering dairy cattle (n = 6;raw milk), swine (n = 2;carcasses), and poultry (n = 3;eggs and carcasses). Conventional farming was associated with significantly higher ORs to ampicillin (OR 2·89, 95% CI 1·64–5·09; I²=34%), penicillin (OR 1·57, 95% CI 1·12–2·19; I²=7%), tetracycline (OR 3·37, 95% CI 1·83–6·18; I²=52%), erythromycin (OR 3·00, 95% CI 1·36–6·62; I²=72%), spiramycin (OR 5·24, 95% CI 1·04–26·41; I²=0%), tylosin (OR 4·54, 95% CI 1·02–20·11; I²=0%), and pirlimycin (OR 4·42, 95% CI 1·42–13·83; I²=33%). Teicoplanin showed a significant association (OR 4·04, 95% CI 1·10–14·88), and rifampicin a significant inverse association (OR 0·15, 95% CI 0·03–0·70). Subgroup analyses showed the strongest associations in raw milk and for Staphylococcus spp. Interpretation: Conventional production was associated with higher phenotypic AMR in pre-processing food, indicating a measurable resistance footprint entering the human supply chain. These findings support WHO stewardship priorities targeting agricultural use of critically important antimicrobials and highlight the need for production-level surveillance to safeguard food system sustainability and planetary health. Key messages: • Conventional farming is associated with higher antimicrobial resistance in unprocessed food matrices compared to antibiotic-free, organic, or wildlife comparators, across dairy, swine, and poultry. • A measurable resistance footprint enters the food supply chain at production level, supporting WHO priorities on agricultural antimicrobial stewardship and the need for production-level surveillance.
SN - 1101-1262
SN - 1464-360X
ER -