Dynamics of extended-spectrum cephalosporin-resistant Escherichia coli in pig farms: A longitudinal study.

OBJECTIVES: Point prevalence estimates of extended-spectrum cephalosporin-resistant Escherichia coli (ESC-R-Ec) are important surveillance measures but may not uncover the ESC-R-Ec dynamics within pig farms. A longitudinal study was therefore performed by sampling individual pigs, pig farmers and the environment. METHODS: On average, 30 (range 10-46) piglets of 31 Swiss farms were sampled during the suckling, weaning and fattening stages (n= 2437 samples). In addition, stool from pig farmers and environmental samples were obtained and metadata collected by questionnaires. ESC-R-Ec was identified by routine culture, and clonal relationships and resistance genes were derived from whole genome sequencing data. RESULTS: Working on pig farms was not associated with an increased prevalence of ESC-R-Ec in humans. ESC-R-Ec prevalence significantly decreased from 6.2% to 3.9% and 1.8% for the suckling, weaned and fattening pigs, respectively (P < 0.001). Within the 57 ESC-R-positive suckling piglets, persisting carriage was detected in 25 animals at two consecutive time points and one animal at three consecutive time points. Clonal spread (n=7 farms, 22.6%) and horizontal gene transfer (n=1 farm, 3%) within pigs but not between humans and animals was detected. Liquid manure (n=10 samples, 16.7%) was identified as the major environmental reservoir of ESC-R-Ec in the pig farm environment. CONCLUSIONS: Pig farming practices like all-in-all-out systems, but not antimicrobial usage, were associated with reduced risk of ESC-R-Ec at the farm level. As carriage duration is normally short within the individual pigs, the risk of recolonisation and clonal spread of ESC-R-Ec might be reduced by applying appropriate decontamination strategies.

Influence of pig farming on human Gut Microbiota: role of airborne microbial communities.

It has been hypothesized that both genetics and diet influence the composition of the human cecal microbiota. However, it remains unclear whether and how occupational exposure to microbes impacts the microbial communities in human guts. Using a One Health approach, we visited pig farms (n = 26) and collected stool specimens from pig workers (n = 59), pig barn air samples (n = 19), and rectal swabs from pigs at three different growth stages (n = 144). Stool samples from cattle workers were included as a control group (n = 22). Each sample's microbiota was characterized using 16S rRNA gene sequencing and the DADA2 pipeline.We obtained a significantly different clustering of the microbial compositions of pig and cattle workers by permutational multivariate analysis of variance (PERMANOVA; P < .001). Workers primarily exposed to pigs had higher relative abundances of Prevotellaceae and less Bacteroidaceae than workers exposed to cattle. We also found that the microbial compositions of pig workers' stool samples shared extensive fractions with the samples from their pigs. We also identified amplicon sequencing variants (ASVs) in the airborne microbiota which were likely involved in zoonotic transmission events.We hypothesize that ASVs originating from pig feces are aerosolized and, through breathing, get trapped in the pig farm workers' upper respiratory tract from where they can get swallowed. Consequently, some of the animal associated ASVs are transferred into the gastrointestinal tracts (GITs) which leads to changes in the composition of the human gut microbiota. The importance of this finding for human health must be investigated further.