Spring 2015

Serotype-specific Salmonella surveillance data is essential to monitor the burden of disease, follow trends in antibiotic resistance, detect outbreaks and evaluate national policies aimed at reducing the incidence of salmonellosis. Additionally, Salmonella results from public health laboratories are used to conduct attribution and other special studies.

However, budget cuts limit the ability of state and local public health laboratories to fully characterize all enteric pathogens they receive, including Salmonella. And with the advent of culture independent diagnostic tests, public health laboratories now receive stool specimens and other clinical materials instead of pure isolates, making the work even more costly, complex and time consuming.

To address these issues, APHL’s Salmonella Work Group has released a white paper, “Salmonella Serotyping in US Public Health Laboratories,” examining currently acceptable methods for Salmonella serotyping, including advantages, disadvantages and cost considerations for each. It describes the considerations for implementing new molecular methods versus maintaining traditional serologic techniques. It also discusses ways to incorporate Pulsed Field Gel Electrophoreses into the Salmonella serotyping workflow. Both traditional and molecular Salmonella serotyping methods will continue to sustain public health surveillance systems until whole genome sequencing (WGS) methods are well established.

A Model to Sustain National Salmonella Surveillance

Given resource limitations, CDC along with state and local public health laboratories and clinical partners must explore ways to sustain a national Salmonella surveillance system that does not depend on CDC as the primary reference laboratory for routine testing. In collaboration with CDC’s Enteric Diseases Laboratory Branch, APHL’s Salmonella Work Group proposed a model intended to maintain Salmonella serotyping in public health laboratories. APHL’s Salmonella Serotyping Sustainability Model outlines roles for CDC’s National Salmonella Reference Laboratory, state and local public health laboratories and a small number of new Salmonella serotyping reference laboratories should funding become available. The model has three main goals:

  1. To encourage state and local public health laboratories to serotype all clinical Salmonella isolates whether in-house or referred
  2. To reserve use of CDC’s National Salmonella Reference Laboratory for atypical or difficult isolates
  3. To set up a small number of Salmonella Serotyping Reference Laboratories to conduct serotyping (serovar determination) using WGS

The model is intended to maintain current Salmonella surveillance practices using accepted methods until WGS has been widely implemented and traditional and molecular serotyping are no longer routinely required.

APHL will continue to work closely with CDC to develop a three to five year plan to transition Salmonella serotyping to WGS technologies.

Contact  Contact

​Shari Shea, MHS, MT(ASCP)
Director of Food Safety