Featured Research

from universities, journals, and other organizations

Novel pathogen epidemic identified in sub-Saharan Africa: Spread of human invasive non-Typhoidal Salmonella tracked

Date:
September 30, 2012
Source:
Wellcome Trust Sanger Institute
Summary:
Researchers have found that the spread of a dangerous bacteria that can be fatal in up to 45% of people infected in sub-Sahara Africa may have been instigated by the emergence and spread of HIV in Africa. The study also found that one of the major contributing factors for the successful spread of the disease – non-Typhoidal Salmonella (iNTS) – was the acquisition of genes that afford resistance to several front line drugs used to treat blood-borne infection such as iNTS.

Geospatial transmission of invasive Salmonella Typhimurium isolates in sub-Saharan Africa. (a,b) Phylogeographic diffusion of lineages I (a) and II (b) across sub-Saharan Africa over time based on a discrete geospatial model with associated geographic coordinates.
Credit: DOI: 10.1038/ng.2423

Researchers have found that the spread of a dangerous bacteria that can be fatal in up to 45% of people infected in sub-Sahara Africa may have been instigated by the emergence and spread of HIV in Africa. The study also found that one of the major contributing factors for the successful spread of the disease -- non-Typhoidal Salmonella (iNTS) -- was the acquisition of genes that afford resistance to several front line drugs used to treat blood-borne infection such as iNTS.

A new study out September 30 reveals that the emergence and spread of a rapidly evolving invasive intestinal disease, that has a significant mortality rate (up to 45%) in infected people in sub-Saharan Africa, seems to have been potentiated by the HIV epidemic in Africa.

The team found that invasive non-Typhoidal Salmonella (iNTS) disease is caused by a new form of the bacteria Salmonella Typhimurium that has spread from two different focal hubs in Southern and Central Africa beginning 52 and 35 years ago, respectively. They also found that one of the major contributing factors for the successful spread of iNTS was the acquisition of genes that afford resistance to several front line drugs used to treat blood-borne infection such as iNTS.

iNTS is a blood-borne infection that kills approximately one of four people in sub-Saharan Africa who catch it. Yet, in the rest of the world, NTS is a leading cause of acute inflammatory diarrhea that is self-limiting and tends to be fatal in less than 1 per cent of people infected. The disease is more severe in sub-Saharan Africa than the rest of the world because of factors such as malnutrition, co-infection with malaria or HIV and potentially the novel genotype of the Salmonella bacteria.

"The immune system susceptibility provided by HIV, malaria and malnutrition at a young age, may provide a population in sub-Saharan Africa that is large enough for this detrimental pathogen to enter, adapt, circulate and thrive," says Chinyere Okoro, joint first author from the Wellcome Trust Sanger Institute. "We used whole genome sequencing to define a novel lineage of Salmonella Typhimurium that is causing a previously unrecognised epidemic across the region. Its genetic makeup is evolving into a more typhoid like bacteria, able to efficiently spread around the human body"

From sequenced samples, the team created a phylogenetic or 'family tree', depicting the pathogen's evolution, dating when each sample first emerged and overlaying this with geographical information about where these samples came from. They found that this invasive disease comprises of two very closely related waves; the first wave originated from a possible south-eastern hub, about 52 years ago and the second originated about 35 years ago, possibly from the Congo Basin.

"The HIV epidemic in sub-Saharan Africa is thought to have begun in a central region and underwent expansion eastwards, a strikingly similar dynamic to that observed for second iNTS wave," says Dr Robert Kingsley, joint first author from the Wellcome Trust Sanger Institute. "Our findings suggest the current epidemic of iNTS and its transmission across sub-Saharan Africa may have been potentiated by an increase in the critical population of susceptible, immune-compromised people."

The team identified that the vast majority of samples from the second wave of iNTS contains a gene that makes them resistant to chloramphenicol, a frontline antibiotic in the treatment of Salmonella. This gene was not present in the samples from the first wave of iNTS. This observation suggests that iNTS acquired this gene early on in the evolution of the second wave, probably around the time of its spread from the Congo basin.

"Because it acquired resistance to chloramphenicol, this pathogen has much greater opportunity to survive and spread across the region," says Professor Gordon Dougan, lead author from the Wellcome Trust Sanger Institute. "This is the first time that the power of whole-genome sequencing has been used to track the spread of iNTS. Our research highlights the power this approach has to monitor the emergence and spread of dangerous pathogens both locally and globally over time."

"There has been some evidence that this disease can be passed from human to human. Now the race is on to discover how NTS is actually transmitted in sub-Saharan Africa so that effective intervention strategies can be implemented."


Story Source:

The above story is based on materials provided by Wellcome Trust Sanger Institute. Note: Materials may be edited for content and length.


Journal Reference:

  1. Chinyere K Okoro, Robert A Kingsley, Thomas R Connor, Simon R Harris, Christopher M Parry, Manar N Al-Mashhadani, Samuel Kariuki, Chisomo L Msefula, Melita A Gordon, Elizabeth de Pinna, John Wain, Robert S Heyderman, Stephen Obaro, Pedro L Alonso, Inacio Mandomando, Calman A MacLennan, Milagritos D Tapia, Myron M Levine, Sharon M Tennant, Julian Parkhill, Gordon Dougan. Intracontinental spread of human invasive Salmonella Typhimurium pathovariants in sub-Saharan Africa. Nature Genetics, 2012; DOI: 10.1038/ng.2423

Cite This Page:

Wellcome Trust Sanger Institute. "Novel pathogen epidemic identified in sub-Saharan Africa: Spread of human invasive non-Typhoidal Salmonella tracked." ScienceDaily. ScienceDaily, 30 September 2012. <www.sciencedaily.com/releases/2012/09/120930141545.htm>.
Wellcome Trust Sanger Institute. (2012, September 30). Novel pathogen epidemic identified in sub-Saharan Africa: Spread of human invasive non-Typhoidal Salmonella tracked. ScienceDaily. Retrieved October 22, 2014 from www.sciencedaily.com/releases/2012/09/120930141545.htm
Wellcome Trust Sanger Institute. "Novel pathogen epidemic identified in sub-Saharan Africa: Spread of human invasive non-Typhoidal Salmonella tracked." ScienceDaily. www.sciencedaily.com/releases/2012/09/120930141545.htm (accessed October 22, 2014).

Share This



More Health & Medicine News

Wednesday, October 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

CDC Revamps Ebola Guidelines After Criticism

CDC Revamps Ebola Guidelines After Criticism

Newsy (Oct. 21, 2014) The Centers for Disease Control and Prevention have issued new protocols for healthcare workers interacting with Ebola patients. Video provided by Newsy
Powered by NewsLook.com
WHO: Ebola Vaccine Trials to Start a in January

WHO: Ebola Vaccine Trials to Start a in January

AP (Oct. 21, 2014) Tens of thousands of doses of experimental Ebola vaccines could be available for "real-world" testing in West Africa as soon as January as long as they are deemed safe in soon to start trials, the World Health Organization said Tuesday. (Oct. 21) Video provided by AP
Powered by NewsLook.com
First-Of-Its-Kind Treatment Gives Man Ability To Walk Again

First-Of-Its-Kind Treatment Gives Man Ability To Walk Again

Newsy (Oct. 21, 2014) A medical team has for the first time given a man the ability to walk again after transplanting cells from his brain onto his severed spinal cord. Video provided by Newsy
Powered by NewsLook.com
CDC Issues New Ebola Guidelines for Health Workers

CDC Issues New Ebola Guidelines for Health Workers

Reuters - US Online Video (Oct. 21, 2014) The U.S. Centers for Disease Control and Prevention has set up new guidelines for health workers taking care of patients infected with Ebola. Linda So reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins