Rapid Identification and Strain Typing of Salmonella in Food Using Genome Sequence Scanning Technology

PathoGenetix, Inc., a commercial-stage developer of an automated system for rapid bacterial identification, has announced new research demonstrating the use of Genome Sequence Scanning™ (GSS™) technology to confirm and identify pathogenic Salmonella strains in enriched spinach samples in less than five hours. The study findings were detailed in a poster presented last week at the General Meeting of the American Society for Microbiology in Denver.

The results demonstrate the ability of GSS to shorten the time for pathogen subtyping and serotype determination from an enriched food sample, and to quickly derive additional strain and serotype information from the numerous pathogen screening tests commonly used in the food industry. Because GSS isolates and scans microbial DNA directly from a mixed culture and does not require a pure culture isolate, it greatly reduces the time, complexity, skill and cost required by other molecular and whole genome identification approaches. As a result, GSS can enable quicker decisions affecting food safety and public health. The GSS technology will be commercially available in 2014 in the RESOLUTION™ Microbial Genotyping System.

The research spiked ten common Salmonella strains in leafy spinach greens including multiple serotypes of Typhimurium and Enteritidis, as well as the Javiana, Newport, Montevideo and Heidelberg serotypes. The test samples modeled “presumptive-positive” enriched food samples like those that would result from a pathogen screening test indicating the presence of Salmonella. Additional non-Salmonella bacteria were added to half of the test samples to evaluate the technology’s ability to identify and strain type Salmonella in the presence of competing background microorganisms.

Of the 120 samples spiked with Salmonella, GSS positively identified the correct Salmonella serotype in 116 of the samples. (Salmonella was not detected in four samples, due to poor growth of Salmonella in the enrichment of the initial sample, not related to the GSS technology.) The strain type information provided by GSS was comparable to pulsed field gel electrophoresis (PFGE), the current standard for pathogen typing in foodborne outbreak investigation and response. No false positives were recorded from the 12 control samples that had not been spiked with Salmonella.

According to the 2011 Estimates for Foodborne Illness from the Centers for Disease Control and Prevention (CDC), Salmonella is the second most common pathogen contributing to domestically acquired foodborne illnesses, causing well over one million illnesses (1,027,561) each year. It tops the list in number of hospitalizations and deaths, and is responsible for an estimated 19,336 hospitalizations (35%) and 378 deaths (28%) each year.

Other research presented by PathoGenetix at ASM showed that GSS also can be used to reliably differentiate and strain type pathogenic E. coli, including the most frequently isolated STEC (Shiga toxin-producing E. coli) serotypes from both sporadic cases and multiple foodborne illness outbreaks.