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Serotypes Profile of Salmonella Isolates from Meat and Poultry Products January 1998 through December 2011

Tables and figures are available in the PDF version of this document, beginning on page 5. 

The Food Safety and Inspection Service (FSIS) sets Salmonella performance standards for establishments that slaughter or produce selected classes of food animals or raw ground products (4). The Salmonella performance standards provide a measure that industry must meet to show that their Pathogen Reduction/Hazard Analysis and Critical Care Point (PR/HACCP) system controls are effective in addressing pathogens.

Verification testing is a regulatory sampling program that assesses whether meat and poultry establishments have complied with existing, product-specific performance standards (6, 7).  Verification testing includes information on the presence of Salmonella serotypes, providing a profile of the range of serotypes within a sample. The FSIS verification testing results presented in this report provide information on the proportion of Salmonella serotypes among FSIS regulated products.  This report also includes the serotype distributions in a specific product class (i.e., carcass or raw ground product) for the 13-year period following implementation of the PR/HACCP final rule in federally inspected meat and poultry establishments.  These results are not intended to indicate serotype prevalence within a respective product class since the sampling criteria is based on national public health goals.

FSIS uses the Centers for Disease Control and Prevention (CDC) data on serotypes isolated from human cases of salmonellosis and compares these data to Salmonella serotypes isolated from meat and poultry products (2, 3).  Some of the more common serotypes isolated from meat and poultry products are rarely isolated from human patients.  Conversely, some of the serotypes frequently responsible for human cases of salmonellosis occur in various meat and poultry products.  Salmonella serotypes identified from human cases also occur in other food and nonfood sources.  FSIS continues to work with its public health partners to identify the proportion of human salmonellosis attributable to FSIS-regulated products.

Results

Each of the eight tables presented in this report identifies the ten most common Salmonella serotypes isolated annually in a specific product class.  When more than one serotype ranks in tenth place, each serotype in tenth place is listed (Table 1-8).  FSIS reports serotypes by product class and calendar year based on the date of sample collection from 1998 through 2011.  Tables 1-8 include the number of isolates of each serotype and category, the percent of total serotyped isolates, and the percent of total samples collected.  

The 10 most common serotypes identified in 2011, in meat and poultry products were Kentucky (237/1017), Enteriditis (132/1017), Montevideo (103/1017), Typhimurium (including Typhimurium var. 5-) (52/1017), Infantis (41/1017), Dublin (37/1017), Heidelberg (32/1017), Anatum (27/1017), Muenster (23/1017), and Hadar (20/1017).  Five of these serotypes, Enteriditis, Montevideo, Typhimurium (including Typhimurium var. 5-),  Infantis and Heidelberg were the serotypes found in meat and poultry products that were among the top 10 serotypes reported to cause human salmonellosis by the CDC (3).

Figure 1 displays, by year, the most common serotype isolated in young chicken/broilers and the percentage of each serotype isolated in each product class during the previous 12 years.  Comparing 2010 to 2011 data, FSIS verification testing showed an increase in the proportion of Salmonella Kentucky in young chickens (broilers), Meleagridis in cow/bulls, Montevideo in ground beef, Enteriditis in ground chicken, Adelaide in market hogs, Uganda, Agona, and Infantis in steer/heifers, Hadar in young turkey (turkey carcasses), and IIIa18:Z4,Z23:- in ground turkey.

In 2011, the CDC identified Enteritidis, Typhimurium (including Typhimurium var. 5-), Newport, Javiana, I 4,[5],12:i:-, Montevideo, Heidelberg, Muenchen, Infantis, and Branderup as the ten most commonly identified serotypes causing human salmonellosis in the United States (3).  Figures 2-11 identify the proportion of these serotypes out of the total salmonellae isolated through Salmonella verification testing of meat and poultry products.  FSIS found year-to-year variation both within and between product classes of these more commonly isolated human serotypes. 

Background

FSIS used nationwide microbiological baseline studies conducted prior to 1996 to establish the PR/HACCP performance standards for carcasses of cow/bulls, steers/heifers, market hogs, broilers, ground beef, ground chicken, and ground turkey (5).  In June 2006, FSIS began sampling turkey carcasses for Salmonella.  FSIS implemented new performance standards for Salmonella and Campylobacter in chilled carcasses at young chicken and turkey slaughter establishments in 2011. (8).   The performance standards describe the maximum number of positive samples acceptable per sample set.  The number of samples in a sample set varies by product class.   

FSIS initiated the product specific Salmonella performance standards in large establishments on January 26, 1998, small establishments on January 25, 1999, and very small establishments on January 25, 2000.  FSIS inspection personnel randomly collect and submit product samples to one of three FSIS Field Service laboratories in Athens, GA, Alameda, CA, or St. Louis, MO for Salmonella analysis, according to procedures described in Appendix E, Federal Register (1996) to verify that establishments meet standards (4).

After one of the FSIS laboratories reports the analysis results, isolates of Salmonella-positive samples become eligible for serotyping at the USDA Animal and Plant Health Inspection Service’s (APHIS) National Veterinary Services Laboratories (NVSL) in Ames, Iowa.  Salmonella testing and serotype data, along with complementary data from molecular and phenotypic analyses, provide an opportunity to compare strains isolated on-farm, from meat and poultry products, and from human cases of salmonellosis.

Prior to 2006, the FSIS regulatory program for identifying Salmonella in raw products consisted of two phases: non-targeted and targeted testing.  Non-targeted or "A" set sample collection occurred randomly at selected establishments with a goal of scheduling every eligible establishment at least once a year.  Other codes (e.g., "B," "C," and "D") represented sample sets collected from establishments targeted for additional testing following an "A" set failure. 

In June 2006, FSIS developed new criteria for scheduling establishments for sampling, replacing the targeted/non-targeted approach with sampling based on public health goals (e.g., Healthy People food safety goals) (8).  The new scheduling criteria focused FSIS resources on establishments with the most Salmonella-positive samples, including serotypes most frequently associated with human salmonellosis as defined by the CDC.  Of note, FSIS suspended scheduling market hogs, cows/bulls, and steer/heifers for sampling in 2011 because of the low number of positive samples.

The restructuring of Salmonella set scheduling prevents the comparison of results from 2006 onwards to previous years.  For such comparisons, nationwide baseline study results provide valid estimates of the prevalence of certain pathogens of public health concern and allow for valid statistical comparisons over time.

Notes on Tables and Graphs

  • The 10 most common serotypes isolated from a specified product class during a given year are identified by name while less commonly identified serotypes are included in the "other serotypes" category.  When there is more than one serotype in tenth place, FSIS lists all serotypes in tenth place.  

  • FSIS includes entries classified as "not typed" and "unidentified" in the serotype profile.  "Not typed" Salmonella entries were not serotyped.  Unidentified entries include isolates in which a single specific serotype could not be determined, those partially serotyped, and those identified as monophasic or nonmotile.  Prior to 2004, FSIS classified serotypes identified solely by antigenic formulas as monophasic, such as 4,[5],12:i:-, and included them in the unidentified isolates category.  

  • From 1998-2005, only "A" set samples were included in the report because they were randomly collected and most reflective of incidence.  Beginning with the second 2006 quarterly report, FSIS summarized data from all samples in the reports.  

In this report, variants of Salmonella Typhimurium are reported separately (Table 1).  Tables 2, 3, 6, 7, and 8 include one variant per serotype.  Reporting combined variants may facilitate comparisons of the proportion of Salmonella Typhimurium in product classes with human health surveillance data.  Figures 2-10 report data with variants combined.  

  • The figures display the percent of isolates identified out of total isolates serotyped for each product class.  The y-axis, the serotype percentage, varies from graph to graph because the percent of different serotypes varies by commodity and year.

References

1CDC.2006. PHLIS Surveillance Data, Salmonella Annual Summary.  Available at: http://www.cdc.gov/ncidod/dbmd/phlisdata/salmonella.htm.  Accessed 1 June 2013.

2CDC. 2013.  Vital Signs:  Incidence and Trends of Infection with Pathogens Transmitted Commonly Through Food – Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 1996 – 2012. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6215a2.htm?s_cid=mm6215a2_w  Accessed on 1 June 2013.

3CDC. 2012.  National Enteric Disease Surveillance: Salmonella Annual Report, 2011.  http://www.cdc.gov/ncezid/dfwed/PDFs/salmonella-annual-report-2011-508c.pdf  Accessed June 28, 2013.

4Federal Register.  1996. Pathogen Reduction; Hazard Analysis and Critical Control Point (HACCP) Systems, Final Rule. Accessed on 8 January 2013.

5Federal Register. 2005. Generic E. Coli and Salmonella Baseline Results.  Available at: http://www.fsis.usda.gov/OPPDE/rdad/FRPubs/02-046N.pdf. Accessed on 1 June 2013.

6Federal Register. 2006. Salmonella Verification Sample Results Reporting: Agency Policy and Use in Public Health Protection. Accessed on 8 January 2013.  

7Federal Register. 2008. Salmonella Verification Sampling Program: Response to Comments and New Agency Policies. Accessed on 8 January 2013.

8FSIS. 2011. New Performance Standards for Salmonella and Campylobacter in Chilled Carcasses at young chicken and Turkey Slaughter Establishments. http://www.fsis.usda.gov/OPPDE/rdad/FSISNotices/31-11.pdf  Accessed on 1 June, 2013.

Last Modified Aug 22, 2013