Salmonella, gene swapping and antibiotic resistance: Five questions with Sid Thakur

November 29, 2018 by Tracey Peake, North Carolina State University
Credit: CC0 Public Domain

Sid Thakur is a professor of population health and pathobiology and the director of NC State's and the College of Veterinary Medicine's Global Health programs. He studies antibiotic resistance in Salmonella and how antibiotic resistant Salmonella affect food animal and human populations. In his latest work, Thakur compared the genomes of over 200 different strains of Salmonella, looking for genetic similarities across strains. He spoke with the Abstract about what this work can tell us, and how it may help to keep us and our food supply safe.

The Abstract (TA): In this paper you compared the genomes of 200 different Salmonella strains taken from humans, pigs, chickens and farm environments. Are there more varieties of Salmonella out there?

Thakur: Salmonella has more than 2,500 different serotypes. The common ones we typically encounter during outbreaks include Typhimurum, Heidelberg, Enteritidis, Newport, 4[5], 12:i:- and Muenchen, to name a few. Many of these serotypes are adapted, meaning they predominantly appear in one host – for example, Enteritidis is usually found in eggs. Many others exist in multiple hosts – Typhimurium occurs in humans, animals and the environment.

TA: Why did you choose the strains you chose?

Thakur: The main reason is because these strains were isolated from multiple sources including humans, animals and the environment. These strains are responsible for many of the recent outbreaks in humans, and we wanted to determine if these Salmonella serotypes from multiple sources had similar or diverse characteristics. Finally, many of these strains are resistant to multiple antimicrobials, and it is important to compare their genomic profiles so we can understand what makes them resistant.

TA: What can comparing the DNA of different Salmonella strains tell us?

Thakur: Genome comparison can reveal a lot of information that other molecular-based approaches like PCR lack. We can identify genomic regions that are similar or different. We can get insights into the and virulence profiles across multiple genomes and understand how the strains are evolving under different selective pressures. Genome comparison can help us understand whether different strains are exchanging genomic material, identify new emerging pathogenic and compare the profiles at the global level.

TA: Different Salmonella strains can swap genes. Why do they do this? Is there a way to prevent it?

Thakur: Pathogens are continuously evolving trying to counteract the harmful environment they encounter. The Darwinian principle "survival of the fittest" holds true here. If pathogens don't evolve then they will not survive. Salmonella is a good example and specific serotypes of this pathogen are more diverse at the genomic level. One good example is Salmonella Typhimurium, which is a diverse serotype and hence has the ability to survive in multiple hosts. Flexibility in the genomes allows pathogens to make changes in their DNA and, in many cases, exchange genes with other pathogens. As such, Typhimurium is responsible for many outbreaks in humans that get exposed to it through different hosts, including food products and the environment. The swapping of genes and genomic material is a continuous process and difficult to control or prevent. That is what makes this field so challenging and exciting to work in at the same time.

TA: What was the most interesting result of the work? Were there any surprises?

Thakur: We detected close relationships between different Salmonella serotypes across multiple hosts, potentially indicating zoonotic transmission, where the infection is transmitted from an animal to a human. We also compared different approaches to improve the resolution of Salmonella phylogenetic trees that we create using the genomic data. We identified the same drug resistance genes, plasmid types and virulence genes distributed across multiple hosts – and the number of hosts and extent of the switching was surprising and interesting to study.

Explore further: Do people and pigs share salmonella strains?

Related Stories

Do people and pigs share salmonella strains?

April 3, 2014
If antimicrobial-resistant Salmonella is showing up in pigs, then are bacon-loving people also at risk? In his latest research, NC State population health and pathobiology professor Sid Thakur looks at serotypes, or groups, ...

Salmonella found to be resistant to different classes of antibiotics

November 12, 2018
Brazil's Ministry of Health received reports of 11,524 outbreaks of foodborne diseases between 2000 and 2015, with 219,909 individuals falling sick and 167 dying from such diseases. Bacteria caused most outbreaks of such ...

A new machine learning tool could flag dangerous bacteria before they cause an outbreak

May 8, 2018
A new machine learning tool that can detect whether emerging strains of the bacterium, Salmonella are more likely to cause dangerous bloodstream infections rather than food poisoning has been developed. The tool, created ...

Covert tactics used by bacteria to trick human immune system

October 23, 2018
McMaster University researchers have found a new way bacteria evade the human immune system and promote infection.

Researchers track antibiotic-resistant strains of Salmonella from farm to fork

August 29, 2013
Continuing research on Salmonella may enable researchers to identify and track strains of antibiotic resistant bacteria as they evolve and spread, according to researchers in Penn State's College of Agricultural Sciences.

Recommended for you

RNA processing and antiviral immunity

December 14, 2018
The RIG-I like receptors (RLRs) are intracellular enzyme sentries that detect viral infection and initiate a first line of antiviral defense. The cellular molecules that activate RLRs in vivo are not clear.

Faster test for Ebola shows promising results in field trials

December 13, 2018
A team of researchers with members from the U.S., Senegal and Guinea, in cooperation with Becton, Dickinson and Company (BD), has developed a faster test for the Ebola virus than those currently in use. In their paper published ...

Drug targets for Ebola, Dengue, and Zika viruses found in lab study

December 13, 2018
No drugs are currently available to treat Ebola, Dengue, or Zika viruses, which infect millions of people every year and result in severe illness, birth defects, and even death. New research from the Gladstone Institutes ...

Urbanisation and air travel leading to growing risk of pandemic

December 13, 2018
Increased arrivals by air and urbanisation are the two main factors leading to a growing vulnerability to pandemics in our cities, a University of Sydney research team has found.

Researchers discover new interactions between Ebola virus and human proteins

December 13, 2018
Several new connections have been discovered between the proteins of the Ebola virus and human host cells, a finding that provides insight on ways to prevent the deadly Ebola virus from reproducing and could lead to novel ...

Faecal transplants, 'robotic guts' and the fight against deadly gut bugs

December 13, 2018
A simple compound found in our gut could help to stop dangerous bacteria behind severe, and sometimes fatal, hospital infections.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.