Lethal Salmonella strain targets HIV positive Africans
By Maina Waruru
30 October 2012 - [NAIROBI] - Fears are
growing over an emerging form of intestinal disease in Africa, to which HIV positive people are particularly vulnerable. Medical experts
have expressed concerns that health infrastructures across the
continent lack the capacity to detect or cope with the dangerous bacterium.
The scientists say that invasive non-Typhoidal Salmonella (iNTS) thrives in the blood systems of people in Sub-Saharan Africa
whose body immunity is weakened by HIV/AIDS. This revelation adds yet another dangerous disease to the list of opportunistic infections
plaguing HIV positive people in Africa.
The scientists say that invasive non-Typhoidal Salmonella (iNTS) thrives in the blood systems of people in Sub-Saharan Africa whose
body immunity is weakened by HIV/AIDS . This revelation adds yet
another dangerous disease to the list of opportunistic infections plaguing HIV positive people in Africa.
According to a study by the Wellcome Trust Sanger Institute, a genomics research centre in the United Kingdom, the
relatively new disease causes death in up to 45 per cent of those infected. It has spread from two focal points in Southern and
Central Africa to the rest of the continent, reports the study, published in Nature Genetics last month (30 September).
The study found that iNTS also targets people whose immunity is weakened by other conditions such
as malaria and malnutrition , both
common in Sub-Saharan Africa.
The iNTS-causing bacteria, Salmonella typhimurium, has become resistant to the frontline antibiotics used to treat
related blood-borne intestinal diseases.
"In many places in Africa, the basic microbiological facilities are not available, which makes diagnosis of iNTS difficult,
as blood culture is the only definitive diagnostic for the disease," the Sanger Institute's Robert Kingsley, one of the authors of the study, told SciDev.Net.
Francis Nyamiobo, a research physician at the Kenya Aids Control Project, said that iNTS could be a major cause of death
in HIV positive patients, but could go unrecognised due to "diagnosis challenges".
"Our greatest problem is making the diagnosis," Nyamiobo told SciDev.Net.
Scientists used whole genome sequencing to define a novel lineage of Salmonella typhimurium, which is causing a previously
unidentified epidemic across the region. They discovered that its genetic makeup was evolving into a more typhoid-like bacterium, able
to spread efficiently around the human body.
From sequenced samples, the team created a phylogenetic or 'family tree', depicting the pathogen's evolution. This enabled
them to date when each sample first emerged and overlay this with geographical information about where samples came from.
The scientists found that this invasive disease comprises two very closely related waves: the first wave originating 52
years ago from a possible south-eastern hub; and the second around 35 years ago, possibly from the Congo Basin.
Kingsley recommended further studies to establish whether the pathogen was being transmitted exclusively through humans
or whether a zoonotic (animal) reservoir existed as well.
"We need to understand the transmission routes to address the hypothesis that this pathogen is behaving in a different
mode from that we normally associate with NTS," he explained.
Link to full study
This article has been produced by SciDev.Net's Sub-Saharan Africa desk.
Nature doi:10.1038/ng.2423 (2012)
Source: SciDev Net
SciDev.Net - the Science and Development Network - is a not-for-profit organisation dedicated to providing reliable and authoritative information about science and technology for the developing world.
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