Food Safety News sat down with McGill University Associate Professor Lawrence Goodridge, Ph.D., at IAFP 2015 in Portland, OR, in late July to discuss Salmonella and his team’s new $10-million research project aimed at significantly enhancing our understanding of the bacterium.

Watch the interview here, or skip below for highlights from the conversation:

Highlights from the conversation are slightly edited or condensed.

On the initial inspiration for his team’s $10-million research project to map the genomes of all known Salmonella varieties:

We had previously conducted environmental sampling in agriculture environments where fresh produce was being prepared, and we saw that we routinely isolated Salmonella serotypes, and when we sampled those serotypes, they seemed to be different than those types that cause human disease. So, we were wondering about that. We typically see 20-25 serotypes of Salmonella that cause human disease, and yet there are more than 2,500 different types identified.

We were wondering why is it only 25 types that cause the majority of human disease, and what are the nature of these other 2,500 types that are in the environment, but don’t seem to make people sick?

On the importance of studying Salmonella:

Salmonella causes approximately 93 million cases of foodborne illness worldwide each year. In North America, it’s one of the leading causes of illnesses, hospitalizations and deaths. And we still have so many questions to ask and answer about Salmonella.

For example, Salmonella can cause outbreaks in a plethora of foods, including dry foods. That raises questions about its ability to survive in places where we don’t normally see other foodborne pathogens surviving.

With respect to fresh produce, fresh fruits and vegetables, Salmonella now accounts for almost half of the outbreaks caused by those commodities. There are many questions regarding why that is.

On how the Salmonella study will operate:

Like I said, there are 2,500-plus types of Salmonella. Our goal will be to sequence 4,500 isolates from those [2,500] different types, to obtain information regarding the DNA sequence of the whole genome of each bacterium. Those bacteria will come from the types of Salmonella that we commonly see causing illness in humans, as well as Salmonella that are rare or have perhaps never caused illness in humans.

We hope to compare the genomes of those different types and, when combined with other methods, obtain information that will tell us more precisely why there are certain types of Salmonella that seem to commonly cause illness and other types that do not.

Some of that work has already been accomplished in other studies, but certainly not in as comprehensive a manner as what we hope to do with this work.

We’ll be sequencing the entire genomes of the bacteria we’re testing, which has been done previously but on a small scale. In our case, we’ll be sequencing 4,500 isolates of Salmonella obtained from around the world. And while most studies seem to focus on the few isolates that cause human illness, we will expand that and focus not only on those types, but types that are rare, in order to really understand why there’s such a small number of Salmonella that seem to cause the majority of human illness.

On how the study will help prevent Salmonella contamination:

The objective of the study is to ultimately reduce the number of Salmonella cases that occur through consumption of contaminated food. The information from this study will help us to do that in three ways:

First, we’ll make use of the information to develop novel strategies to control Salmonella on fresh produce as it’s growing on the field — pre-harvest.

Second, the information will be used to develop better and more accurate diagnostic tests. For example, if we can show that there are some Salmonella that are more virulent than other types of Salmonella, and we can identify the markers in the bacteria that cause one serotype of Salmonella to be more virulent than another, then we can actually build that into the new test so that when we actually detect Salmonella, we’ll not only know that the Salmonella is present, but we’ll know about its ability to cause human disease.

Finally, we hope to develop new methods that could be used to track the sources of contaminated food during an outbreak so that those foods can be removed from retail circulation faster.

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  • Carl Custer

    First, preharvest control of clinical strains of salmonellae in food animal production will reduce the environmental burden including irrigation water, feral animals, and fields. Second, Yea! improve the current tests for virulence markers so those strains can be targeted. Finally, retail yeah but also the sources of those virulent clinical strains.