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  1. Biological, Chemical, and Physical Contaminants in Animal Food

CVM Issues Field Assignment to Collect and Analyze Commercial Milk Replacer Products for Salmonella

Date: March 19, 2013


FDA’s Center for Veterinary Medicine (CVM) is concerned about animal feeds and feed ingredients serving as vehicles for transmitting Salmonella serotypes that are pathogenic to animals, which can cause illness in animals that consume the feed. Young animals are generally the most susceptible to Salmonella infections. Salmonella infections in young animals are mainly enteric, but may become systemic. Salmonella infections in adult animals, however, are less common and more likely to be enteric and asymptomatic. Host-adapted Salmonella serotypes are much more likely to cause a more severe, systemic disease in animals.

This assignment will provide information on the prevalence of Salmonella and the serotype/genetic fingerprint/antimicrobial susceptibilities of each Salmonella isolate found in the commercial milk replacer products sampled.

CVM’s Approach

Sample Collection

The majority of commercial milk replacer products are manufactured and used by calves although some milk replacer products are also manufactured and used by orphaned or extra piglets, and lambs (young sheep), and other young animals. Therefore, in this assignment, Center for Veterinary Medicine (CVM) will use 80% of its resources on milk replacer products for calves, 10% for piglets, and 10% for lambs.

The 100 official samples of milk replacer products should be collected from unopened bags in dry powder form at commercial feed stores, at commercial feed mills, and at feed mills supporting integrated operations. The number of milk replacer products to collect is divided among the FDA districts based on states where dairy cattle, swine and sheep production are prominent.

Follow the sample collection procedures as described in the FDA Investigators Operations Manual (IOM), Subchapter 4.3, Collection Techniques: aseptic sample collection procedures as described in the IOM, Subchapter 4.3.6, Aseptic Sample; proper controls collected as outlined in IOM 4.3.6. In addition, interstate commerce should be documented; labels and labeling materials should be collected and the address and contact information about the commercial milk replacer products manufacturers should be provided on the sample collection report (C/R).

Sample Size

For this assignment, sample size of each official sample should consist of 10 sub-samples with each sub-sample weighing approximately 200 g (7.1 oz). Each of these 10 sub-samples already includes the 702(b) portions.

Sample Analysis

ORA servicing laboratories will analyze the 100 official samples of commercial milk replacer products for Salmonella. AOAC Official Method 2004.03 [Determination of Salmonella in Foods by VIDAS (SLM) Immunoassay], an enzyme-linked immuno-fluorescent assay, is to be used as the screening method for this assignment. Refer to procedures outlined in the BAM online, Feb. 2011, chapter 5, Salmonella for the confirmatory method to use in this assignment.

Aseptically weigh approximately 37.5 g (~ 1.3 oz) from each of the 10 sub-samples to form a 375 g (13.2 oz) composite sample for Salmonella analysis.

If the sample is positive for Salmonella, the servicing lab will send each Salmonella isolate to ARL or DEN-LAB for serotyping, and retain the duplicate Salmonella isolate in the laboratory. All serotyped Salmonella isolates will be sent to DEN-LAB for antimicrobial-susceptibility testing.

PFGE Image(s)

In addition, each servicing laboratory will conduct a pulsed-field gel electrophoresis (PFGE) for each Salmonella isolate under this assignment.

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