Information, support and advice for the UK meat industries

Salmonella Serotyping Free of Charge

Salmonella isolates from the food production chain are a valuable source of information to food business operators (FBOs) and also to the Food Standards Agency.  Consequently, the Agency strongly encourages plants to send any Salmonella isolated when testing against process and food safety criteria to one of the serotyping reference laboratories listed, so that the strain and type of Salmonella can be determined. The service is offered as a way for FBOs to gather additional information to help make follow-up actions more effective.  Please take specific note that the service cannot be used to confirm positive isolations in the context of the regulations and FBOs should not wait for the results of this testing before instigating corrective actions.  If there is a Salmonella isolated when testing against the food safety microbiological criteria (e.g. Salmonella in minced meat or a meat preparation), then the required action is a removal of the product from the market.  From the 1st December 2011, there are changes to the regulation that require FBOs to serotype Salmonella isolates from fresh poultry meat.  These changes mean the FSA cannot pay for the serotyping of such poultry isolates. Only isolates from pig, cattle, sheep and horse carcasses; together with isolates from minced meat (including poultry) and meat preparations (including poultry) should therefore be submitted .

Detailed instructions for using the free serotyping service can be found here.  A summary flowchart which describes the process is shown below:

A flow diagram describing the serotyping process

Figure 1: A summary flowchart that demonstrates the operation of the free Salmonella serotyping service used for gathering additional information to improve FBO follow up actions.

It is important to stress that:

Sending an isolate for typing is not an obligation and it will not trigger any sort of enforcement from the FSA, Defra, or your OV.

Most of the time, apart from letting you know the results of the typing of your strains, there would be no contact with plants.  The only contact that may be undertaken (and this would be in a very few cases, if at all) would be investigatory (i.e. nothing at all to do with enforcement) in nature.  Generally, contact would only be made for example,if a very rare and or previously unseen type was isolated.  By providing isolates for testing FBOs will be assisting the Agency in the provision of information that is required for risk assessments and foodborne outbreak and attribution studies.  For FBOs, the results are useful for investigating the source(s) of the contamination. In order for the information to be useful, the details requested on species and meat type must be provided. If they are missing the laboratory will be contacted and asked to provide them before the serotyping is undertaken.

During the development of the criteria it was apparent that there was a lack of typing information on Salmonella isolates from the food production chain in comparison with the amount of information available on isolates from humans.

This process will not cost your plant or your testing lab any money because the FSA will pay all of the costs associated with these additional tests -including a small payment to the isolating laboratory to cover their administrative costs.  Instructions for your laboratory which explain how to have an isolate serotyped are available here

Plant operators will be able to see the results of the additional serotyping tests by logging into the meat test results database.  It is hoped that eventually a picture can be built up of commonly-isolated Salmonella from meats and that the primary sources of these isolates can be identified.   An assessment of how dangerous the Salmonella isolates are will also be made available to plant operators through the meat database.

The majority of Salmonella isolated from livestock are not human pathogens.  There is no legal obligation for plants to send their isolates for serotyping, but those that do so will be contributing to gathering national evidence of the salmonellas that are isolated on meat enabling a comparison with those found on farms and in people.

Serotyping of meat is performed according to a slightly modified method to that originally developed by Kauffman and White (1).

The process involves using antibodies (and sometimes bacterial viruses called phages) which selectively recognise specific structures on the outside of the Salmonella cells.  These external structures are called antigens and there are three main types used for Kauffman and White method of Salmonella typing.  The main antigens are the O-types, the H-types and the Vi-types.  Not all Salmonella have all three of these types of antigen.  The combination of O-type, H-type and Vi-type antigens recognised by the antibodies and phages allows the serotype to be identified. 

For example, a Salmonella that is commonly isolated from foods is called Salmonella enterica.  Within Salmonella enterica there are a large number of serotypes.  Some of these are given in the table below

S. enterica serotype Typhimurium               

S. enterica serotype Newport                   

S. enterica serotype Montevideo                 

S. enterica serotype Heidelberg                 

S. enterica serotype Dublin

S. enterica serotype Virchow

S. enterica serotype Bonn

S. enterica serotype Reading

S. enterica serotype Dundee

S. enterica serotype Enteriditis

Table 1:  Commonly-encountered Salmonella enterica serotypes

In time, it is hoped that plant-derived data can, along with other Salmonella isolations be used to generate graphical figures such as the one below.  Such graphical representations allow "hotspots" of Salmonella to be identified and also allow "tracking" of the movements of specific Salmonella serotypes over time. 

Aficticious map showing Salmonella isolations

Figure 2:  (A FICTITIOUS EXAMPLE).  A graphical representation of Salmonella enterica serotype Dublin isolated from Southern Scotland in 2005

In the long term such information may be used to help develop intervention strategies which will help further reduce foodborne illness caused by Salmonella in the UK.  A postcode of the farm that livestock were farmed on, and the plant where the Salmonella were isolated is required for construction of such graphical representations.  This is the only reason the Agency requests the farm or plant postcode is supplied for each isolate that is serotyped.



1. Popoff, Y. Antigenic formulas of the Salmonella serovars, 8th revision. Paris: WHO Collaborating Centre for Reference and Research on Salmonella, Institut Pasteur; 2001.