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Serotypes Profile of Salmonella Isolates from Meat and Poultry Products
January 1998 through December 2006
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Tables and figures are available
in the PDF version of this document (3MB).
Links to CDC and other sites outside USDA open in a second window.
Background
The Food Safety and Inspection Service (FSIS) issued the Pathogen Reduction; Hazard Analysis and Critical
Control Point (PR/HACCP) Systems, Final Rule on July 25, 1996: Federal Register, Vol. 61, No. 144,
pp. 38805-38989 (http://www.fsis.usda.gov/OPPDE/rdad/
FRPubs/93-016F.pdf).
The PR/HACCP rule sets Salmonella performance standards for establishments slaughtering selected
classes of food animals or producing selected classes of raw ground products to verify that industry systems
are effective in controlling the contamination of raw meat and poultry products with disease-causing bacteria.
Raw products with established performance standards include: carcasses of cows/bulls, steers/heifers, market hogs,
and broilers. Processed products measured by performance standards include: ground beef, ground chicken, and
ground turkey. The performance standards for these product classes are based on the prevalence of Salmonella
as determined from the Agency's nationwide microbiological baseline studies conducted before PR/HACCP was
implemented. In addition, turkey carcass sampling for Salmonella was initiated June 2006. Guidance
using young turkey carcass baseline levels can be found in the Federal Register, Vol.70, No. 32, pp.8058-8060
(http://www.fsis.usda.gov/OPPDE/rdad/
FRPubs/02-046N.pdf).
The product-specific FSIS Salmonella limits became effective in large establishments on January 26, 1998,
in small establishments on January 25, 1999, and in very small establishments on January 25, 2000. FSIS inspection
personnel verify that establishments are meeting the standards by collecting randomly selected product samples
and submitting them to one of three FSIS laboratories for Salmonella analysis, according to procedures
described in Appendix E of the PR/HACCP Final Rule: Federal Register, Vol. 61, No. 144, pp. 38917-38928
(http://www.fsis.usda.gov/OPPDE/rdad/
FRPubs/93-016F.pdf).
After one of the FSIS Field Service laboratories in Athens, GA; Alameda, CA; or St. Louis, MO, reports the
analysis results, isolates of Salmonella-positive samples become eligible for serotyping at the
USDA Animal and Plant Health Inspection Service's National Veterinary Services Laboratories in Ames, IA.
Salmonella testing and serotype data, along with complementary data from molecular and phenotypic
analyses, provide an opportunity to examine the association among serotypes isolated on-farm, from meat and
poultry products, and from human cases of salmonellosis.
Prior to 2006, there were two phases of the FSIS regulatory program for Salmonella in raw products:
non-targeted and targeted testing. FSIS collected non-targeted or "A" set samples at establishments
randomly elected 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.
Beginning June 2006, establishments were scheduled based on new criteria
(http://www.fsis.usda.gov/pdf/
scheduling_criteria_salmonella_sets.pdf)
that are risk-based, not random, and are designed to focus FSIS resources on establishments with the most samples
positive for Salmonella and the greatest number of samples with serotypes most frequently associated with
human salmonellosis, as identified by the Centers for Disease Control and Prevention (CDC)
(http://www.cdc.gov/ncidod/dbmd/phlisdata/salmonella.htm).
Beginning with the second 2006 quarterly report, serotype data are summarized from all sample sets.
Note: Restructuring how Salmonella sets are scheduled means that comparison of results
from 2006 onwards to previous years would not be appropriate. For such comparisons, the results of upcoming
nationwide baseline studies can provide valid estimates of the prevalence of certain pathogens of public
health concern and will permit valid statistical comparisons to be made over time.
From January 1998 through December 2006, Salmonella isolates were serotyped for four carcass and three
raw ground product classes. Starting in June 2006, Salmonella isolates were also serotyped for turkey
carcasses. Each of the eight tables
presented in this report (PDF Only) identifies the ten most commonly isolated Salmonella serotypes by
calendar year in a specific carcass or raw ground product class. When more than one serotype ranks in tenth place,
each serotype in tenth place is listed. The Agency believes that researchers can use this product-specific
serotype information to support foodborne pathogen surveillance. Future updates of serotype distribution results
will be provided. Figure 1
displays, by year, the most common serotype isolated in combined chicken classes (Kentucky), the ground turkey
class (Hadar), combined cattle classes (Montevideo), and the market hog class (Derby) in 2006.
FSIS is providing links to the CDC data on the serotypes isolated from human cases of salmonellosis so that
the reader has easy access to data on both the serotypes found in meat and poultry products and those causing human illness:
Some of the more common serotypes isolated from meat and poultry products are rarely isolated from human patients.
Conversely, some of the serotypes frequently found in human cases of salmonellosis are found in various meat and
poultry products. Serotypes identified from human cases of salmonellosis can also be found in other food and non-food
sources.
CDC identifies Typhimurium, Enteritidis, Newport, Javiana, Montevideo, Heidelberg and I 4,[5],12:i:- as the seven
most commonly identified serotypes causing human infection in the United States. Combined, these serotypes
accounted for a majority (64%) of human infections in the Foodborne Diseases Active Surveillance Network (FoodNet)
sites in 2006 (http://www.cdc.gov/mmwr/preview/mmwrhtml/
mm5614a4.htm?s_cid=mm5614a4_e).
The percentages at which the top seven human serotypes are identified in meat and poultry product classes are
presented in Figures 2-9.
These serotypes are among the more commonly identified serotypes in meat and poultry products with the exception of
Javiana, which is uncommon in meat and poultry products. Year-to-year variation both within and between product
classes, with respect to these more common human serotypes, can be observed. Kentucky, Hadar, and Derby, the
predominant serotypes identified in 2006 from meat and poultry products (Figure 1)
were not found among the top seven serotypes identified in human surveillance data. As reported by the CDC, the
estimated incidence of Montevideo (Figure 8),
a common serotype in cattle classes, did not change significantly compared with the baseline
(http://www.cdc.gov/mmwr/preview/mmwrhtml/
mm5614a4.htm?s_cid=mm5614a4_e#fig2).
FSIS keeps abreast of serotypes emerging as human health concerns. Human illnesses attributable to Salmonella
Newport began to rise in the late 1990's (http://www.cdc.gov/mmwr/preview/mmwrhtml/
mm5614a4.htm?s_cid=mm5614a4_e).
Recent FoodNet data show that the incidence of infection from Newport has increased 42% when compared with the
baseline period of 1996-1998 (http://www.cdc.gov/mmwr/preview/mmwrhtml/
mm5614a4.htm?s_cid=mm5614a4_e#fig2).
Newport is detected in all FSIS commodities; most frequently, the cattle classes (Figure 5).
After peaking in 2003 as the most commonly isolated serotype in ground beef, the cattle class for which the most isolates
were recovered, Newport has occupied a steady position as the fourth most commonly identified serotype. Though Newport
isolations appear to have risen in frequency in 2006 in the other cattle classes (Figure 5),
only one cow/bull (Table 3) and
two steer/heifer (Table 4) Newport isolates were recovered.
CDC now estimates that the incidence of infection from Enteritidis has increased by 28 percent. In recent years,
FSIS verification testing has found an increase in the proportion of Salmonella isolates that are
Enteritidis in broilers and ground chicken (Figure 4),
while at the same time, the proportion that are Heidelberg appears to have decreased in broilers and ground
turkey and increased in ground chicken (Figure 7).
CDC reported that a Salmonella serotype having the antigenic formula, I 4,[5],12:i:- has been
increasingly recognized since the mid 1990's in human illness cases. In 2006, the serotype was the 7th most
commonly identified serotype in U.S. human surveillance data
(http://www.cdc.gov/mmwr/preview/mmwrhtml/
mm5614a4.htm?s_cid=mm5614a4_e).
FSIS laboratories did not report antigenic formulas until 2004. Prior to 2004, serotypes identified solely by
antigenic formulas that would classify them as "monophasic" were included in the "unidentified"
isolates category. I 4,[5],12:i:- was the sixth most commonly identified serotype in broiler isolates in 2004 and
2005 and the fifth most commonly identified serotype in broiler isolates in 2006 (Table 1).
Javiana is reported by CDC to have increased by 92 percent since 1996-1998
(http://www.cdc.gov/mmwr/preview/mmwrhtml/
mm5614a4.htm?s_cid=mm5614a4_e#fig2).
The serotype is not commonly isolated from FSIS-regulated products (Figure 6).
Inasmuch as verification testing is a regulatory sampling program intended to assess the ability of meat and
poultry establishments to comply with existing, product-specific performance standards, serotype profile results
are not intended to indicate a national prevalence for a specific serotype within a respective product class.
Despite limitations to interpretation, FSIS believes that verification testing results presented in this report
provide a good indication of relative serotype distributions in raw products for each product class for the nine years
following the implementation of the PR/HACCP final rule in federally inspected meat and poultry establishments.
FSIS continues to work with public health partners to better identify the proportion of human salmonellosis
attributable to FSIS-regulated products.
Results
- Serotypes are reported by product class and by calendar year based on the date of sample collection from
1998 through 2006. The number of isolates of each serotype and category, the percent of total serotyped
isolates, and the percent of total samples collected are displayed in Tables 1-8.
- The ten most commonly isolated serotypes for a specified product class during a listed 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, all serotypes in tenth place are listed.
- Included in the serotype profile are entries classified as "not typed" and "unidentified."
Entries identified as not typed are those in which Salmonella serotyping was not performed.
Unidentified entries include isolates in which a single specific serotype could not be determined. Prior to
2004, serotypes identified solely by antigenic formulas that would classify them as monophasic, such as
I 4,[5]12:i:-, were included in the unidentified isolates category.
- From 1998-2005, only "A" set samples were included in the report. Beginning with the second
2006 quarterly report, data from all samples collected are summarized in the reports.
- Six months of serotype data for turkey carcasses are reported in Table 8.
- Variants of serotypes have been reported separately. Tables 1, 2, and 5-8 display data for each product
class when variants are combined for 2006. Tables 3 (Cows/Bulls) and 4 (Steers/Heifers) do not require
merging of variants as only one variant per serotype was observed. Merging variants is most useful in
facilitating comparisons of the proportion of Salmonella Typhimurium in product classes with U.S.
human health surveillance data: Typhimurium and Typhimurium variant Copenhagen (an O:5-negative variant of
Salmonella Typhimurium) are combined and reported as Typhimurium in U.S. human health surveillance
data (http://www.cdc.gov/ncidod/dbmd/phlisdata/salmtab/
2005/SalmonellaTable1_2005.pdf).
- The figures display the percent of isolates identified out of total isolates serotyped for each product
class. The y-axis, representing the serotype percentage, varies from graph to graph because the level of
different serotypes by commodity varies greatly and year-to-year variations in percentages are difficult to
discern on one scale of high value.
Tables and Figures
All tables and figures are available in this 72-page PDF document.
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Last Modified:
August 10, 2007 |
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