This is the first study to quantify the dependence on wind velocity of airborne bacterial emission fluxes from soil. It demonstrates that manure bacteria get aerosolized from fertilized soil more easily than soil bacteria, and it applies bacterial genomic sequencing for the first time to trace environmental faecal contamination back to its source in the chicken barn. We report quantitative, airborne emission fluxes of bacteria during and following the fertilization of agricultural soil with manure from broiler chickens. During the fertilization process, the concentration of airborne bacteria culturable on blood agar medium increased more than 600 000-fold, and 1 m 3 of air carried 2.9 × 10 5 viable enterococci, i.e. indicators of faecal contamination which had been undetectable in background air samples. Trajectory modelling suggested that atmospheric residence times and dispersion pathways were dependent on the time of day at which fertilization was performed. Measurements in a wind tunnel indicated that airborne bacterial emission fluxes from freshly fertilized soil under local climatic conditions on average were 100-fold higher than a previous estimate of average emissions from land. Faecal bacteria collected from soil and dust up to seven weeks after fertilization could be traced to their origins in the poultry barn by genomic sequencing. Comparative analyses of 16S rRNA gene sequences from manure, soil and dust showed that manure bacteria got aerosolized preferably, likely due to their attachment to low-density manure particles. Our data show that fertilization with manure may cause substantial increases of bacterial emissions from agricultural land. After mechanical incorporation of manure into soil, however, the associated risk of airborne infection is low.

Applying broiler litter containing extended-spectrum beta-lactamase ( ESBL )–producing Escherichia coli ( E. coli ) to arable land poses a potential risk for humans to get colonized by contact with contaminated soil or vegetables. Therefore, an inactivation of these bacteria before land application of litter is crucial. We performed 2 short-term litter storage trials (one in summer and winter, respectively), each covering a time span of 5 D to investigate the effectiveness of this method for inactivation of ESBL-producing E. coli in chicken litter. Surface and deep litter samples were taken from a stacked, ESBL-positive chicken litter heap in triplicates in close sampling intervals at the beginning and daily for the last 3 D of the experiments. Samples were analyzed quantitatively and qualitatively for ESBL-producing E. coli , total E. coli , and enterococci. Selected isolates were further characterized by whole-genome sequencing ( WGS ). In the depth of the heap ESBL-producing E. coli were detected quantitatively until 72 h and qualitatively until the end of the trial in winter. In summer detection was possible quantitatively up to 36 h and qualitatively until 72 h. For surface litter samples a qualitative detection of ESBL-producing E. coli was possible in all samples taken in both trials. In the deep samples a significant decrease in the bacterial counts of over 2 Log 10 was observed for total E. coli in the winter and for total E. coli and enterococci in the summer. Genetic differences of the isolates analyzed by WGS did not correlate with survival advantage. In conclusion, short-term storage of chicken litter stacked in heaps is a useful tool for the reduction of bacterial counts including ESBL-producing E. coli . However, incomplete inactivation was observed at the surface of the heap and at low ambient temperatures. Therefore, an extension of the storage period in winter as well as turning of the heap to provide aerobic composting conditions should be considered if working and storage capacities are available on the farms.

During a field experiment applying broiler manure for fertilization of agricultural land, we detected viable Clostridioides (also known as Clostridium) difficile in broiler faeces, manure, dust and fertilized soil. A large diversity of toxigenic C. difficile isolates was recovered, including PCR ribotypes common from human disease. Genomic relatedness of C. difficile isolates from dust and from soil, recovered more than 2 years after fertilization, traced their origins to the specific chicken farm that had delivered the manure. We present evidence of long-term contamination of agricultural soil with manure-derived C. difficile and demonstrate the potential for airborne dispersal of C. difficile through dust emissions during manure application. Clostridioides genome sequences virtually identical to those from manure had been recovered from chicken meat and from human infections in previous studies, suggesting broiler-associated C. difficile are capable of zoonotic transmission.

No abstract

No abstract