Ancera has adapted CRISPR-SeroSeq technology to conduct ‘deep serotyping’ to identify the prevalence of specific Salmonella serotypes in environmental and product samples. This is critical to mounting an effective program of suppression since efforts should be directed against high-virulence serotypes including S. Enteritidis, S. Infantis and S. Typhimurium1. Knowing which serotypes are present is an essential component of an investigation to determine the source of Salmonella contamination in the production cycle within a complex and to implement corrective action.
Frequently complexes are faced with a high rate of recovery of a specific Salmonella serotype on carcass wash samples but have difficulty in identifying the source. Sampling of replacement pullets, breeder hens, hatcheries and broilers during grow-out may yield different serotypes to those isolated on carcasses after processing. This apparent inconsistency confounds an understanding of the dynamics of Salmonella infection through stages of production extending from the parent generation through to processing.
Failure to identify the predominant serotypes arises from the inherent differences associated with conventional enrichment. Using in vitro culture and conventional bacteriologic procedures, Salmonella serotypes demonstrate variability in growth rate influenced by enrichment media. The lag phase may vary widely extending from four to nine hours especially with a low quantum of organisms in a starting inoculum. The potential for multiplication using conventional microbiology is measured by the doubling time that differs according to serotype and strain. According to Dr. Margaret Kiss, director of R&D at Ancera, differences in lag times influence the rate of multiplication. Examining field strains, Ancera has determined that after nine hours of incubation, an isolate of Salmonella Kentucky would have completed six doubling cycles compared to a field strain of Salmonella Infantis that would have remained in the lag phase over a similar period. Conventional Salmonella culture of a sample containing both serotypes would erroneously reflect Salmonella Kentucky as the only contaminant and would fail to reveal the presence of Salmonella Infantis, an important pathogen. According to Dr. Kiss, “The culture media can influence the Salmonella-growth kinetics depending on the composition of the media and characteristics of the Salmonella strains present in the sample.”
Recognizing the inherent difficulty in determining the identity of Salmonella serotypes in samples when conducting an epidemiologic evaluation, Ancera has commercialized ‘deep serotyping’. This technology, developed at the University of Georgia, applies CRISPR-SeroSeq analysis. The technique refined by Ancera will identify Salmonella serotypes present in a sample based on the ability of PCR to identify conserved regions in the Salmonella genome. The technology effectively eliminates confounding caused by the kinetics of bacterial growth during enrichment. The Ancera approach yields an accurate catalog of Salmonella serotypes present at each stage of the production cycle.
Ancera has developed expertise in designing and implementing epidemiologic evaluation of the Salmonella status of a complex, identifying specific serotypes. This is a necessary precursor to developing an effective and comprehensive program to suppress contamination. Based on training and experience, Ancera can develop a sampling protocol specific for a complex, conduct deep serotyping and identify specific serotypes. Ancera can interpret laboratory findings based on the presence, level of contamination and biochemical characteristics of Salmonella that are present. According to Dr. James Barton, awareness of the specific Salmonella serotypes present at stages in the production cycle through applying deep serotyping is critical to developing an appropriate program to suppress infection and ultimately to reduce contamination of product.
Deep serotyping can be applied to confirm the effectiveness of control measures including chemical rinses such as peracetic acid. Laboratory assay has demonstrated wide differences in the ability of Salmonella serotypes to resume multiplication after exposure to peracetic acid. In a specific study, Salmonella Kentucky was effectively suppressed for 12 hours compared to Salmonella Infantis that resumed growth after 4 hours and Salmonella Enteritidis that was intermediate in recovery after exposure to the antibacterial compound.
Precise knowledge of the identity and prevalence of specific Salmonella serotypes at locations within the production cycle and their susceptibility to antibacterials is essential to an effective program of pathogen suppression. Combining a field presence with a laboratory capability to apply deep serology and quantitative analysis, Ancera provides food safety professionals with comprehensive and accurate data to reduce contamination of carcasses, parts, and in ground chicken and turkey products.
- Kim, M. et al. Risk assessment predicts most of the salmonellosis risk in raw chicken parts is concentrated in those few products with high levels of high-virulence serotypes of Salmonella. J. Food Protection. doi.org/10.1016/j.jfp.2024.100304.