Serotypes Profile of Salmonella Isolates from Meat and Poultry Products January 1998 through December 2013
Tables and figures are available in the PDF version of this document, beginning on page 5.
The Food Safety and Inspection Service (FSIS) conducts Salmonella serotype testing on sample isolates collected from raw meat and poultry products at all slaughter facilities under the Pathogen Reduction Hazard Analysis and Critical Control Point (PR/HACCP) program . The serotype results are presented here and provide an estimate of relative serotype distributions in raw products for each product class during the 16-year period following implementation of the PR/HACCP program (1998-2013). The information in this report supports food safety national strategic goals to better understand Salmonella as a foodborne pathogen.
In the early- to mid-1990s, FSIS conducted nationwide microbiological baseline studies that estimated the prevalence and levels of bacteria of public health concern in specific food commodities (10). FSIS used this information to develop performance standards for carcasses of cow/bulls, steers/heifers, market hogs , broilers, ground beef, ground chicken, and ground turkey (5,10). In July 1996, FSIS published the (PR/HACCP) Systems, Final Rule, which established 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 measurable standard by which industry can calibrate their HACCP systems and FSIS inspection personnel can monitor the effectiveness of an establishment’s HACCP controls. The performance standards include a description of the maximum number of positive samples allowed in a sample set. The number of samples and allowable positives in a sample set vary by product class and pathogen. In June 2006, FSIS implemented Salmonella performance standards for turkey carcasses (10). In 2011, FSIS implemented more stringent standards for Salmonella and Campylobacter in poultry carcasses (chicken/turkey) (8).
Prior to 2006, there were two phases of the PR/HACCP for Salmonella in raw products: non-targeted and targeted testing. FSIS collected non-targeted or "A" set samples at establishments randomly selected from the population of eligible establishments with a goal of scheduling every eligible establishment at least once a year. Other codes (such as "B", "C", and "D") represented sample sets collected from establishments targeted for follow-up testing following a failed set.
In June 2006, FSIS began to schedule establishments based on new criteria that are risk-based, rather than random (6,7). The new scheduling criteria focused FSIS resources on establishments with the most Salmonella-positive samples, including serotypes most frequently associated with human salmonellosis (3). As a result of this change in sampling, results from establishments prior to June 2006 cannot be compared to those reported following the new schedule. 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 comparison over time (10).
In 2013, FSIS identified and serotyped 878 Salmonella-positive meat or poultry samples. The “top ten” most common serotypes identified include:
- Kentucky 28% (248/878)
- Montevideo 10% (89/878)
- Enteritidis 9.4% (83/878)
- Typhimurium 8.7% (77/878)
- Infantis 4.8% (43/878)
- Heidelberg 4.1% (36/878)
- I 4,,12:i:- 3.6% (32/878)
- Schwarzengrund 2.6% (23/878)
- Muenchen 2.5% (22/878)
- Dublin 2.1% (19/878) and Newport 2.1% (19/878)
FSIS compares the CDC data on serotypes isolated from human salmonellosis cases to Salmonella serotype data isolated from meat and poultry products (1,2,3). In 2012, the CDC identified Enteritidis, Typhimurium (including Typhimurium var. 5-), Newport, Javiana, I 4,,12:i:-, Montevideo, Infantis, Muenchen, Heidelberg, and Bareilly as the ten most commonly identified serotypes causing human salmonellosis in the United States (3).
The top 10 serotypes found in meat and poultry products in 2013 that were among CDC’s top 10 list for 2012 were Enteritidis, Typhimurium, Newport, Heidelberg, Infantis, I 4,,12:i:-, Montevideo, and Muenchen (3). Because human salmonellosis cases are attributable to non-FSIS regulated foods and non-food sources, FSIS works closely with its public health partners to identify the proportion of human salmonellosis attributable to FSIS regulated products.
Summary of PR/HACCP Data (1998-2013)
Since 1998, Salmonella Kentucky has ranked as the most common serotype identified among young chicken (broilers) samples during the last 16 years. Prior to 2005, Salmonella Heidelberg has ranked as the second most common serotype in broilers. Since then Salmonella Enteriditis has ranked in the second position among broilers.
For ground chicken samples, Salmonella Enteritidis and Salmonella Kentucky alternate between the first and second most common serotypes. For ground turkey samples, Salmonella Heidelberg ranked as the most common serotype identified followed by Salmonella Hadar. For young turkey (turkey carcasses) sample sets, that began in 2006, Salmonella Hadar has ranked as the most common serotype identified followed by Salmonella Heidelberg.
Because of the low number of positive samples recovered from the cow/bull and steer/heifer product classes, sample set scheduling was suspended for cow/bulls in 2011 and steer/heifers in 2012.
From 1998-2010, Salmonella Derby was ranked as the most common serotype in market hogs. In 2011, Salmonella Adelaide ranked as the most common serotype and S. Derby moved to the number three position. In 2012, Salmonella St. Paul was the only identified serotype in market hogs. Market hog sampling was suspended in 2012 due to the low number of positive samples.
Tables and Figures
Each table presented in this report identifies the ten most common Salmonella serotypes isolated annually per specific product class (1998-2013). When more than one serotype ranks in tenth place, each serotype in tenth place is listed (Table 1-8). 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 FSIS could not identify a specific serotype or identified a sample as monophasic  or nonmotile , the sample was entered as “Unidentified” in the tables. Samples that FSIS was unable to serotype are listed in the tables as “Not typed." Each table includes the number of isolates of each serotype and category, the percent of total serotyped isolates, and the percent of total samples collected.
Figure 1 displays, by year, the three most common serotypes isolated from ground beef, young chicken, ground chicken and young, turkey from 1998-2013. Five serotypes are listed in the number one position for ground turkey.
Figure 2 identifies the proportion of CDC’s top 20 serotypes that cause human salmonellosis in the United States out of the total Salmonellae isolated through PR/HACCP testing of meat and poultry products. The more commonly isolated serotypes in human salmonellosis cases vary from year-to-year both within and between product classes.
Recurring critical review and analysis of Salmonella serotype data support both Healthy People 2020 goals and FSIS’ strategic goals to reduce salmonellosis illnesses attributable to FSIS regulated products. The serotype data along with other sampling data collected through the PR/HACCP program is used to inform FSIS regulatory decisions and Agency policy development, inform in-plant best practices and outbreak investigations, and advance our understanding of Salmonella as a foodborne pathogen.
To more closely estimate the prevalence of Salmonella in FSIS products and monitor trends, FSIS is changing its current sampling scheme from a set-based model to a continuous sampling model using moving windows to assess process control (9). The moving window approach provides FSIS with more flexibility for scheduling sample collection at different establishments.