Download files
Abstract
Enteric pathogens, such as Salmonella are commonly associated with poultry as a vehicle of transmission to humans. Infection with Salmonella can result in a variety of diseases including gastroenteritis, diarrhea and enteric fever. Studies of the prevalence and diversity of Salmonella species in poultry products is typically critical due to investigate the relationship of pathogenic strains and salmonellosis throughout the entire poultry processing chain. This study deals with quantitative and semi-quantitative methods for ecological investigation of Salmonella species isolated from poultry by cultural and rapid enumeration methods. A centrifugation-plating method, more rapid and sensitive than the conventional direct-plating method was used to determine the diversity of Salmonella species from Australian poultry. APJC (developed by Anprasertporn Pet and Julian Cox), a newly developed APJC medium, formulated as a differential selective medium for enumeration of Salmonella spp. as a differential selective medium was successfully used in this study, providing excellent recovery rate (mean recovery: 101.1%). Moreover, sublethally injured Salmonella are not necessarily detected and enumerated by conventional cultural methods and might be required significant steps for successful isolation. An enhanced enrichment technique that uses a combination of centrifugation-plating and thin agar layer method (TAL) was developed. Using this approach, NaCl injured Salmonella cells recovered significantly higher numbers (P<0.05) than when using selective agars (XLD and APJC), with 99% injured population. Semi-quantitative miniaturized MPN (mMPN) method for enumerating Salmonella from poultry matrices was validated using the Salmonella medium (APJC). Utilization of this medium with the mMPN method correlated strongly with mMPN by using MSRV medium (R2 = 0.92) as well as with traditional MPN (R2 = 0.94). The automated and computerized MPN method using the TEMPO (biomerieux) system was also evaluated in conjunction with the rapid detection method, ICS-Vidas (bioMerieux). Enumeration of Salmonella using the TEMPO system with the new Salmonella medium (APJC) was strongly correlated (R2 = 0.91) with enumeration using the mMPN method, even though there were some incoherent data due to false-positives caused by non-target organisms. The diversity of Salmonella isolates (n = 62) from the centrifugation-plating and mMPN methods were investigated by using DiversiLab, semi-automated rep-PCR system which has been proven to be useful for differentiating Salmonella species at the strain level. Thirteen different Salmonella serotypes, Salmonella serovar Sofia, Agona, Typhimurium, Zanzibar, Infantis, subsp 1 ser rough:k:1.5, Kiambu, subsp 1ser 4,12:d:-, Senftenberg, Tennessee, Singapore, Mbandaka and Montevideo, were identified, indicating broad diversity from Australian poultry.