Genomic Characterization of a Nalidixic Acid-Resistant Salmonella Enteritidis Strain Causing Persistent Infections in Broiler Chickens.

Virulent strains of Salmonella enterica subsp. enterica serovar Enteritidis (SE) harbored by poultry can cause disease in poultry flocks and potentially result in human foodborne illness. Two broiler flocks grown a year apart on the same premises experienced mortality throughout the growing period due to septicemic disease caused by SE. Gross lesions predominantly consisted of polyserositis followed by yolk sacculitis, arthritis, osteomyelitis, and spondylitis. Tissues with lesions were cultured yielding 59 SE isolates. These were genotyped by Rep-PCR followed by whole-genome sequencing (WGS) of 15 isolates which were clonal. The strain, SE_TAU19, was further characterized for antimicrobial susceptibility and virulence in a broiler embryo lethality assay. SE_TAU19 was resistant to nalidixic acid and sulfadimethoxine and was virulent to embryos with 100% mortality of all challenged broiler embryos within 3.5 days. Screening the SE_TAU19 whole-genome sequence revealed seven antimicrobial resistance (AMR) genes, 120 virulence genes, and two IncF plasmid replicons corresponding to a single, serovar-specific pSEV virulence plasmid. The pef, spv, and rck virulence genes localized to the plasmid sequence assembly. We report phenotypic and genomic features of a virulent SE strain from persistently infected broiler flocks and present a workflow for SE characterization from isolate collection to genome assembly and sequence analysis. Further SE surveillance and investigation of SE virulence in broiler chickens is warranted.

The role of Enterococcus faecalis during co-infection with avian pathogenic Escherichia coli in avian colibacillosis.

Enterococcus spp. (ENT) are frequently co-isolated with avian pathogenic E. coli (APEC) from poultry with colibacillosis, a leading cause of flock mortality. Although largely overlooked, ENT may play an active role in these infections. To assess the frequency of ENT co-isolation in colibacillosis, cultures were collected from birds with gross lesions of omphalitis, polyserositis, and septicaemia over a 3-year period from three turkey flocks and three broiler flocks. In birds diagnosed with colibacillosis based on gross findings and isolation of E. coli, ENT were co-isolated with APEC in 35.7% (n = 41/115) of colibacillosis mortality and 3.7% of total mortality (n = 41/1122). Co-isolated APEC and ENT pairs (n = 41) were further characterized using antimicrobial resistance phenotyping and in vitro co-culture assays. E. faecalis (EF) was the most commonly co-isolated species (68% n = 28/41) and tetracycline resistance was the resistance phenotype most commonly found among APEC (51% n = 21/41) and ENT (93% n = 38/41). Under iron-restricted conditions, EF enhanced APEC growth in a proximity-dependent manner and APEC grown in mixed culture with EF exhibited a significant growth and survival advantage (P ≤ 0.01). In an embryo lethality assay, APEC co-infection with EF resulted in decreased survival of broiler embryos compared to mono-infections (P ≤ 0.05). These data demonstrate that EF augmented APEC survival and growth under iron limiting conditions, possibly translating to the increased virulence of APEC in broiler embryos. Thus, ENT co-infections may be a previously unrecognized contributor to colibacillosis-related mortality. Further investigations into the mechanism of this interaction are warranted. RESEARCH HIGHLIGHTS Enterococcus is frequently co-isolated with avian pathogenic E. coli (APEC). Enterococcus faecalis (EF) enhances survival of APEC in iron restricted conditions. EF co-infection increases APEC virulence in broiler embryos.

Wooden Breast in Commercial Broilers Associated with Mortality, Dorsal Recumbency, and Pulmonary Disease.

Occurrence of mortality, wooden breast, and pulmonary disease in broiler chickens during the last 16 days of production in a teaching flock of 4000 commercial broilers was determined. A new syndrome was identified, in which broilers fell over for an unknown reason and were unable to right themselves (dorsal recumbency). Birds affected by dorsal recumbency were alert and responsive and showed no clinical signs except for occasional mild to moderate dyspnea. When turned over, they resumed normal behavior. Mortality (14 culls; 49 dead) during the last 16 days of production accounted for 1.6% of the flock and 36% of total mortality. Among these, 71% were heavy males, 70% had wooden breast, and 71% had pulmonary congestion and edema. Gross lesions of concurrent wooden breast and pulmonary disease occurred in 68% of the mortality, including 21 of 22 dead birds found on their backs. These findings indicate that wooden breast is associated with mortality prior to processing as a result of pulmonary disease in heavy male broilers. When birds with wooden breast fall onto their backs for unknown reason(s), they are unable to right themselves. If not found and turned over, they may not survive. Based on these findings, wooden breast is likely greater than just a problem with meat quality and should be considered an animal well-being issue.

Reporte de caso- Presencia de "pechuga de madera" en pollos de engorde comerciales asociada con mortalidad, recumbencia dorsal y enfermedad pulmonar. Se determinó la presentación de mortalidad, "pechuga de madera" y enfermedad pulmonar en pollos de engorde durante los últimos 16 días de producción en una parvada de 4000 pollos de engorde comerciales. Se identificó un nuevo síndrome en el que los pollos se postraban por una razón desconocida y no podían enderezarse (recumbencia dorsal). Las aves afectadas por la recumbencia dorsal estaban alertas y respondían, y no mostraban signos clínicos, excepto casos de disnea ocasional de leve a moderada. Cuando las aves se colocaban en posición normal, retomaban su comportamiento normal. La mortalidad (14 aves eliminadas; 49 muertas) durante los últimos 16 días de producción representó el 1.6% de la parvada y 36% de la mortalidad total. Entre estos, el 71% eran machos pesados, 70% tenían "pechuga de madera" y 71% tenían congestión pulmonar y edema. Lesiones macroscópicas concurrentes de enfermedad pulmonar y de "pechuga de madera" ocurrieron en el 68% de la mortalidad, incluyendo 21 de las 22 aves muertas que fueron encontradas postradas sobre sus dorsos. Estos hallazgos indican que la "pechuga de madera" se asocia con la mortalidad antes del procesamiento como resultado de enfermedad pulmonar en pollos de engorde machos pesados. Cuando las aves con "pechuga de madera" se caen de espaldas por razones desconocidas, no pueden enderezarse. Si no se encuentran y se colocan en posición normal, pueden no sobrevivir. Según estos hallazgos, la "pechuga de madera" es probablemente más que solo un problema con la calidad de la carne y también debe considerarse un problema de bienestar animal.

Use of real-time PCR to rule out Marek's disease in the diagnosis of peripheral neuropathy.

This article reports nine cases of neurological disease in brown layer pullets that occured in various European countries between 2015 and 2018. In all cases, the onset of neurological clinical signs was at 4-8 weeks of age and they lasted up to 22 weeks of age. Enlargement of peripheral nerves was the main lesion observed in all cases. Histopathological evaluation of nerves revealed oedema with moderate to severe infiltration of plasma cells. Marek's disease (MD) was ruled out by real-time PCR as none of the evaluated tissues had a high load of oncogenic MD virus (MDV) DNA, characteristics of MD. Based on the epidemiological data (layers with clinical signs starting at 5-8 weeks of age), gross lesions (peripheral nerve enlargement with a lack of tumours in other organs), histopathological lesions (oedema and infiltration of plasma cells), and no evidence of high load of MDV DNA, we concluded that those cases were due to peripheral neuropathy (PN). PN is an autoimmune disease easily misdiagnosed as MD, leading to a costly enforcement of the vaccination protocol. Additional vaccination against MD does not protect against PN and could worsen the clinical signs by over-stimulating the immune system. Differential diagnosis between PN and MD should always be considered in cases of neurological disease with enlargement of peripheral nerves as the only gross lesion. This case report shows for the first time how real-time PCR to detect oncogenic MDV is a very valuable tool in the differential diagnosis of PN and MD.