Clean sweep or pathogen paradise? A critical review of cleaning and disinfection practices in broiler barns.

Increased demand for broiler meat, coupled with increased consumer awareness and rising concerns about antimicrobial resistance, makes effective biosecurity more relevant than ever. The goal of this paper was to provide a systematic review of 77 published papers considering the effectiveness of cleaning and disinfection methods and antibacterial compounds applied in broiler barns and to present an overview of the current state of knowledge. To evaluate the completeness of methodological reporting, we developed an "information density" score based on factors described as relevant for the effectiveness of cleaning and disinfection. Aldehydes and quaternary ammonium compounds were the most researched disinfectant compounds, appearing in 57.14% and 48.05% of the papers, respectively. Very few papers presented an adequate amount of data about the cleaning and disinfection procedures, several did not mention the used compounds, and most papers did not describe temperature, detergent use, waiting time, or application technique. The average information density of the papers presenting on-site studies was 44.81%. Based on available numeric data, disinfectants containing aldehydes were overall the most effective disinfectants across all bacteria followed by peroxides, QACs and organic acids, whereas those with potassium peroxymonosulfate or iodine performed the worst. Furthermore, we found a difference in compound effectiveness between relevant pathogens, e.g., QAC-based disinfectants were not as effective against Staphylococcus as against other pathogens. In addition, disinfection effectiveness can be reduced by the presence of organic material, and some risk factors regarding the used water require further investigation to yield conclusive results. The majority of the reviewed studies did not provide enough methodological detail. Critical parameters including water temperature, application technique, detergent use, exposure time, and surface type were often incompletely reported or entirely missing. As a result, the calculated "effectiveness" scores may partly reflect differences in study design and reporting quality rather than the true antimicrobial activity of the disinfectants. Overall, more transparency about the cleaning and disinfection methods is needed to gain knowledge about effective measures against bacterial pathogens.