Byoung-Yoon Kim

Prevalence and antimicrobial resistance of Salmonella species isolated from chicken meats produced by different integrated broiler operations in Korea

Prevalence and antimicrobial resistance profiles of Salmonella serotypes isolated from 7 chicken meat brands produced by different integrated broiler operations in Korea were determined. In total, 210 samples were collected from retail supermarkets in Seoul, South Korea, and analyzed for the presence of Salmonella. Of 210 chicken meat samples, overall Salmonella prevalence was 22.4%. Salmonella Enteritidis was the dominant serovar, with an isolation rate of 57.4% from the Salmonella-positive chickens, followed by Salmonella Montevideo. Salmonella isolates frequently were resistant to various antibiotics, including 100% to erythromycin, 87% to cephalothin, 85% to nalidixic acid, and 70% to streptomycin. Of the 47 isolates, 41 (87.2%) isolates were resistant to 3 or more antibiotics. Moreover, the Salmonella profiles of each chicken meat brand were different by broiler operation. Brand A showed the highest prevalence of Salmonella (18 isolates, 60%), whereas brand G showed the lowest prevalence (one isolate, 3.3%). Eight among the 18 isolates of brand A were resistant to 11 antibiotics, whereas 5 of the 6 brand C isolates were resistant to only 2 antibiotics. This study demonstrates that a high proportion of chicken meat in Korea is contaminated with Salmonella and the prevalence and antimicrobial resistance patterns of Salmonella of chicken meat differ significantly according to the integrated broiler operation.

An inactivated oil-emulsion fowl Adenovirus serotype 4 vaccine provides broad cross-protection against various serotypes of fowl Adenovirus.

The number of clinical cases of inclusion body hepatitis (IBH) and hydropericardium-hepatitis syndrome (HHS) has been increasing, resulting in considerable economic losses in many countries. Currently, only fowl Adenovirus (FAdV) serotype 4 (FAdV-4) has been reported as the causative agent of HHS, whereas IBH can be caused by all 12 serotypes of FAdV. For protection against HHS, various live and killed FAdV serotype 4 vaccines have been developed. However, there is a concern whether these vaccines composed of FAdV-4 alone could provide protection against IBH, which is caused by other serotypes of virulent FAdVs. To date, there have been no reports evaluating the protective efficacy of the FAdV-4 vaccine against other serotypes of FAdV. Thus, we investigated the cross-protection efficacy of an inactivated oil-emulsion FAdV-4 vaccine against various serotypes of FAdV field isolates. Our study demonstrated that the inactivated oil-emulsion FAdV-4 vaccine could provide broad cross-protection against various serotypes of FAdV in not only vaccinated birds, but also the progenies of vaccinated breeder. Therefore, we conclude that the inactivated oil-emulsion FAdV-4 vaccine could be effective in preventing the spread of various other serotypes of FAdV as well as FAdV-4 infection in the poultry industry.

Exchange of Newcastle disease viruses in Korea: The relatedness of isolates between wild birds, live bird markets, poultry farms and neighboring countries

Newcastle disease virus (NDV) has a worldwide distribution and is often carried by wild ducks, which may represent one of the natural reservoirs. However, the epidemiological relatedness of NDV between wild ducks and domestic poultry is unclear. A total of 14 isolates were obtained from 8439 samples from live bird markets (LBMs) and wild bird populations in Korea during from 2007 to 2010. These isolates were characterized genetically and phylogenetic analysis was conducted to investigate the relatedness between isolates from wild birds, LBM and poultry farms. In phylogenetic analysis, all 14 isolates belonged to genotype I virus within class II. Of these, nine isolates from wild birds were most closely related to the Aomori-like cluster. The five LBM isolates were most closely related to the V4-like cluster. All isolates in this study were closely related to isolates from domestic duck farms in Korea and Chinese LBM isolates. The results indicate that NDV exchange occurs between wild birds, poultry farms, LBMs and neighboring countries. Enhanced NDV surveillance is required to monitor the introduction of variant NDV in consequence of evolution in LBMs and to investigate NDV epidemiology in various species of putative hosts.

Outbreak of gizzard erosion associated with fowl adenovirus infection in Korea

The pathogenicity of a fowl adenovirus serotype-1 (FAdV-1, K181 strain) isolated from a case of gizzard erosion in layer chickens was investigated in specific-pathogen-free (SPF) chicks. One-week-old SPF chicks were inoculated orally or intramuscularly with the isolate of FAdV-1 and euthanized for necropsy at 7, 14, and 21 d postinoculation. Although there were no clinical signs after inoculation, gizzard erosions were observed grossly and the virus was recovered from the gizzards in the inoculated chickens. Histologically, in the chickens that were infected orally, the lesions found in the gizzard consisted of severe degeneration and necrosis of glandular epitheliums and eosinophilic inclusion bodies. These results indicate that the Korean FAdV-1 isolate could induce gizzard lesions in chickens. Moreover, the present investigation reproduced an outbreak of gizzard erosion caused by FAdV-1 infection and, for the first time, described the isolation of FAdV-1 from chickens in Korea. These findings provide important information on the epidemiology and pathogenesis of FAdV-1 infection in chickens.

Prevalence and characterization of Salmonella species in entire steps of a single integrated broiler supply chain in Korea

The purpose of this study was to investigate the distribution of Salmonella species in an integrated broiler supply chain in Korea. A total of 1,214 samples from various steps of an integrated broiler production company including broiler breeder farms, broiler farms, broiler trucks, slaughterhouse, and retail chicken meats were collected and investigated. Salmonella was detected in 195 of the samples. The highest prevalence of Salmonella was observed in broiler transporting trucks (71.43%), followed by the slaughterhouse (63.89%) and broiler farms (16.05%). Salmonella Hadar was the most frequently isolated serotype (83.08%). All Salmonella Hadar isolates investigated in this study with pulsed-field gel electrophoresis showed the same XbaI pulsed-field gel electrophoresis pulsotype.

Cross-Protective Immune Responses Elicited by a Korean Variant of Infectious Bronchitis Virus

SUMMARY Infectious bronchitis virus (IBV) infections cause great economic losses to the poultry industry worldwide. IBVs continuously evolve by developing mutations in antigenic sites; therefore, an IBV vaccine that provides broad cross-protection can be a highly relevant and practical method in IBV control strategies. Although some IBV vaccine strains are known to provide protection against multiple IBV serotypes, in general commercially available IBV vaccine strains provide protection against antigenically related viruses but not distinct heterologous viruses. In the present study we characterized the Korean variant IBV K40/09 strain with regard to its immunogenicity and protective efficacy against seven currently circulating IBV serotypes. Three-week-old specific-pathogen-free chickens were intraocularly immunized with the IBV K40/09 strain at 103.5 50% egg infective dose (EID50). Three weeks after immunization all the birds were challenged with seven different strains at 104.5 EID50. Chickens immunized with the IBV K40/09 strain showed significantly high levels of protection against all challenge viruses at the trachea and kidney levels. Our results suggest that IBV K40/09 could be useful to ensure IBV vaccine effectiveness owing to its cross-protective ability. Therefore, the IBV K40/09 strain merits consideration as a vaccine candidate to prevent infection as well as the spread of new IBV strains and many IBV variants that have been reported worldwide. RESUMEN Nota de Investigación—Respuesta inmune protectora cruzada provocada por una variante coreana del virus de la bronquitis infecciosa. Las infecciones por el virus de bronquitis infecciosa (IBV) causan grandes pérdidas económicas a la industria avícola en todo el mundo. Los virus de la bronquitis infecciosa evolucionan continuamente mediante el desarrollo de mutaciones en sitios antigénicos, por lo tanto, una vacuna contra el virus de bronquitis infecciosa que proporciona una amplia protección cruzada puede ser un método altamente relevante y práctico dentro de las estrategias de control contra este virus. Aunque algunas cepas vacunales del virus de bronquitis proporcionan protección contra múltiples serotipos del virus, en general, las cepas vacunales disponibles comercialmente proporcionan protección contra virus antigénicamente relacionados pero no contra virus heterólogos distintos. En el presente estudio se caracterizó la cepa variante coreana IBV K40/09 con relación a su inmunogenicidad y eficacia protectora contra siete serotipos que circulan actualmente. Aves libres de patógenos específicos de tres semanas de edad, fueron inmunizadas por vía intraocular con la cepa IBV K40/09 con 103.5 dosis infectantes en embrión de pollo 50% (EID50). Tres semanas después de la vacunación, todas las aves fueron desafiadas con siete cepas diferentes, con 104.5 EID50. Los pollos inmunizados con la cepa K40/09 mostraron niveles significativamente altos de protección contra todos los virus de desafío en la tráquea y en riñón. Nuestros resultados sugieren que la cepa IBV K40/09 podría ser útil y eficaz como vacuna contra el virus de bronquitis infecciosa debido a su capacidad de protección cruzada. Por lo tanto, la cepa K40/09 merece consideración como un candidato a vacuna para prevenir la infección y la propagación de nuevas cepas del virus de la bronquitis infecciosa y variantes que han sido reportadas en todo el mundo.

Supplementation of oil-based inactivated H9N2 vaccine with M2e antigen enhances resistance against heterologous H9N2 avian influenza virus infection

Avian influenza virus (AIV) subtype H9N2 has been evolving rapidly and vaccine escape variants have been reported to cause circulation of infections and economic losses. In the present study, we developed and evaluated ectodomain of the AIV matrix 2 (M2e) protein as a supplementing antigen for oil-based inactivated H9N2 vaccine to increase resistance against vaccine escape variants. AIV H9N2 M2e antigen was expressed in Escherichia coli and supplemented to inactivated H9N2 oil emulsion vaccine. Specific pathogen-free chickens received a single injection of inactivated H9N2 oil emulsion vaccines with or without M2e supplementation. At three weeks post vaccination, hemagglutination inhibition tests and enzyme-linked immunosorbent assays were performed to determine serological immune responses. Challenge study using a vaccine escape H9N2 variant was performed to evaluate the efficacy of M2e supplementation. M2e antigen supplemented in oil emulsion vaccine was highly immunogenic, and a single M2e-supplemented vaccination reduced challenge virus replication and shedding more effectively than non-supplemented vaccination.

Virus-Like Particle Vaccine Confers Protection against a Lethal Newcastle Disease Virus Challenge in Chickens and Allows a Strategy of Differentiating Infected from Vaccinated Animals

ABSTRACT In this study, we developed Newcastle disease virus (NDV) virus-like particles (VLPs) expressing NDV fusion (F) protein along with influenza virus matrix 1 (M1) protein using the insect cell expression system. Specific-pathogen-free chickens were immunized with oil emulsion NDV VLP vaccines containing increasing dosages of VLPs (0.4, 2, 10, or 50 μg of VLPs/0.5-ml dose). Three weeks after immunization, the immunogenicity of the NDV VLP vaccines was determined using a commercial enzyme-linked immunosorbent assay (ELISA) kit, and a lethal challenge using a highly virulent NDV strain was performed to evaluate the protective efficacy of the NDV VLP vaccines. NDV VLP vaccines elicited anti-NDV antibodies and provided protection against a lethal challenge in a dose-dependent manner. Although the VLP vaccines containing 0.4 and 2 μg of VLPs failed to achieve high levels of protection, a single immunization with NDV VLP vaccine containing 10 or 50 μg could fully protect chickens from a lethal challenge and greatly reduced challenge virus shedding. Furthermore, we could easily differentiate infected from vaccinated animals (DIVA) using the hemagglutination inhibition (HI) test. These results strongly suggest that utilization of NDV VLP vaccine in poultry species may be a promising strategy for the better control of NDV.

Immunization with a Thermostable Newcastle Disease Virus K148/08 Strain Originated from Wild Mallard Duck Confers Protection against Lethal Viscerotropic Velogenic Newcastle Disease Virus Infection in Chickens

Newcastle disease (ND) is one of the most devastating poultry infections because of its worldwide distribution and accompanying economical threat. In the present study, we characterized the ND virus (NDV) K148/08 strain from wild mallard duck, with regard to safety, thermostability, immunogenicity, and protective efficacy against velogenic ND viral infection. The NDV K148/08 strain offered enhanced immunogenicity and safety relative to commercially available vaccine strains. The NDV K148/08 strain was safe in 1-day-old SPF chicks after vaccination using a coarse or cabinet-type fine sprayer. We demonstrated that the NDV K148/08 strain elicited high levels of antibody responses and provided protective efficacy against lethal NDV challenge. In addition, the thermostability of the NDV K148/08 strain was as high as that of the thermostable V4 strain. Therefore, the NDV K148/08 strain may be useful to ensure NDV vaccine performance and effectiveness in developing countries, especially in remote areas without cold chains.

Diagnosis of Leucocytozoon caulleryi infection in commercial broiler breeders in South Korea.

SUMMARY This report confirms a recent outbreak of a Leucocytozoon caulleryi infection in a commercial broiler breeder flock in South Korea. Seven, 18-day-old broiler breeders (Gallus gallus) were necropsied following a history of depression, sudden death, and subcutaneous hemorrhages. On necropsy, subcutaneous hemorrhages were identified in the wings and legs, pectoral and thigh muscles, thymus, epicardium, pancreas, and kidneys. On histopathology, there were numerous schizonts and merozoits of a Leucocytozoon sp. noted in the heart, spleen, liver, kidneys, thymus, and bursa of Fabricius. Molecular analysis of the mitochondrial cytochrome oxidase b confirmed that the causative agent was Leucocytozoon caulleryi. Although L. caulleryi was diagnosed previously in South Korea, there had been no reports of L. caulleryi over the past several decades. RESUMEN Reporte de Caso—Diagnóstico de la infección en Leucocytozoon caulleryi en rereproductores pesados comerciales en Corea del Sur. Este informe confirma un brote reciente de la infección con Leucocytozoon caulleryi en un lote comercial de reproductoras pesadas en Corea del Sur. Se realizó la necropsia de siete reproductores de 18 días de edad (Gallus gallus) que tenían una historia de depresión, muerte repentina y hemorragias subcutáneas. A la necropsia, se identificaron hemorragias subcutáneas en las alas y las piernas, los músculos pectorales y del muslo, el timo, epicardio, páncreas y los riñones. A la histopatología, se observaron numerosos esquizontes y merozoitos de Leucocytozoon sp. especialmente en el corazón, bazo, hígado, riñones, timo y en la bolsa de Fabricio. El análisis molecular del gene mitocondrial citocromo b oxidasa confirmó que el agente causal era Leucocytozoon caulleryi. Aunque L. caulleryi fue diagnosticado previamente en Corea del Sur, no había reportes de L. caulleryi durante las últimas décadas.