Escherichia coli infections known as colibacillosis constitute a considerable challenge to poultry farmers worldwide, in terms of decreased animal welfare and production economy. Colibacillosis is caused by avian pathogenic E. coli (APEC). APEC strains are extraintestinal pathogenic E. coli and have in general been characterized as being a genetically diverse population. In the Nordic countries, poultry farmers depend on import of Swedish broiler breeders which are part of a breeding pyramid. During 2014 to 2016, an increased occurrence of colibacillosis on Nordic broiler chicken farms was reported. The aim of this study was to investigate the genetic diversity among E. coli isolates collected on poultry farms with colibacillosis issues, using whole genome sequencing. Hundred and fourteen bacterial isolates from both broilers and broiler breeders were whole genome sequenced. The majority of isolates were collected from poultry with colibacillosis on Nordic farms. Subsequently, comparative genomic analyses were carried out. This included in silico typing (sero- and multi-locus sequence typing), identification of virulence and resistance genes and phylogenetic analyses based on single nucleotide polymorphisms. In general, the characterized poultry isolates constituted a genetically diverse population. However, the phylogenetic analyses revealed a major clade of 47 closely related ST117 O78:H4 isolates. The isolates in this clade were collected from broiler chickens and breeders with colibacillosis in multiple Nordic countries. They clustered together with a human ST117 isolate and all carried virulence genes that previously have been associated with human uropathogenic E. coli. The investigation revealed a lineage of ST117 O78:H4 isolates collected in different Nordic countries from diseased broilers and breeders. The data indicate that the closely related ST117 O78:H4 strains have been transferred vertically through the broiler breeding pyramid into distantly located farms across the Nordic countries.

Disinfection of hatching eggs is essential to ensure high quality production of broilers. Different protocols are followed in different hatcheries; h

Sertraline, an antidepressive drug, has been reported to inhibit general bacterial efflux pumps. In the present study, we report for the first time a synergistic effect of sertraline and tetracycline in a TetA-encoded tetracycline-resistant strain of Escherichia coli. Synergy between sertraline and tetracycline in an E. coli strain with TetA-mediated tetracycline resistance (E. coli APEC_O2) was assessed by the MIC and checkerboard assays. The global transcriptome of E. coli APEC_O2 exposed to ½ MIC concentrations of sertraline and/or tetracycline was analyzed to elucidate the interaction mechanism between sertraline and tetracycline. The fractional inhibitory concentration index for tetracycline and sertraline in E. coli APEC_O2 was 0.5. In addition, in the presence of ½ MIC of sertraline, the sensitivity of E. coli APEC_O2 to tetracycline could be restored according to clinical standards (from 64 to 4 mg l-1). RNA data suggest changes in respiration that is likely to decrease intracellular pH and thereby the proton-motive force, which provides the energy for the tetracycline efflux pump. Furthermore, sertraline and tetracycline may induce a change from oxidation to fermentation in the E.coli, which further decreases pH, resulting in cell death. This study shows that sertraline interacts with tetracycline in a synergistic and AcrAB-TolC pump-independent manner. The combinational treatment was further shown to induce many changes in the global transcriptome, including altered tetA and tetR expression. The results indicate that sertraline may be used as a helper compound with the aim to reverse tetracycline resistance encoded by tetA.

Pododermatitis has been observed in several layer flocks in Denmark during 2015. The aetiology is complex, including litter quality, nutrition and management. Bacterial pathogens associated with pododermatitis, however, have not received much attention. The aim of the present study was, therefore, to identify 106 bacterial isolates obtained from pododermatitis in table egg layers in addition to five isolates from spleen/bursa presternalis. Isolates were obtained from layers from six affected flocks. All isolates were identified by standard bacterial methods, species-specific PCRs, 16S rRNA sequencing or matrix-assisted laser desorption-ionization identification. Staphylococcus aureus and Enterococcus faecalis made up 75/111 (68%) and 15/111 (14%) of the isolates from pododermatitis, respectively; the remaining isolates represented Escherichia coli (10), Staphylococcus hyicus (5), Gallibacterium anatis (3), Trueperella pyogenes (2) and Aerococcus urinaeequi (1). All isolates of S. aureus were spa-typed. Spa-type t8646 and t002 made up 72% and 26% of the S. aureus isolates, respectively. The same types were also demonstrated from spleen/bursa presternalis. The same or closely related spa-types were found among 6/11 sepsis-affected day-old chicks included for comparison, indicating that these types of S. aureus are ubiquitous pathogens in poultry. In contrast, isolates of E. faecalis and E. coli showed major population diversity. In conclusion, the results suggest that S. aureus is a major pathogen associated with pododermatitis abscesses, which could be from a common source, whereas the diversity among the E. faecalis and E. coli populations suggests that these bacteria might originate from multiple sources.

Footpad lesions are an important factor in evaluation of animal welfare in broilers regulated by law; however, no legal requirements have been set for the parent birds. Nevertheless, the present study confirms that foot health in broiler breeders declines significantly with increasing age, thus potentially impairing the animal welfare due to pain and discomfort from footpad dermatitis. Furthermore, this is the first report demonstrating a correlation between the presence of footpad lesions and systemic bacterial infections with Gram-positive cocci in broiler breeder birds.