Deadly salmonella epidemic in Africa has arisen because of HIV

Atypical strain of salmonella poisoning is fatal in half of patients, appeared in Africa thanks to the smooth evolution of this pathogen in the blood of people infected with the human immunodeficiency virus, according to a paper published in the journal Nature Genetics.
"The vulnerability of the immune system, courtesy of the HIV virus, and malaria and the lack of food in his youth, has allowed bacteria to penetrate, to adapt, to spread and thrive in the intestines of people in tropical Africa. Complete sequencing of the genome of Salmonella has allowed us to identify a new strain of Salmonella serovar Typhimurium, causing epidemic in this region, "- said one of the authors Chinery DROP (Chinyere Okoro) of the Sanger Institute in Hinxton (UK).
Team of biologists led by Gordon Dugan (Gordon Dougan) from Sanger Institute tried to find the source of a highly unusual epidemic of salmonellosis (iNTS) in Africa, studying the genome of Salmonella (Salmonella enterica), extracted from the intestines of the dead people of Kenya, Malawi and other African countries.
Dugan and his colleagues sequenced the genomes of more than 120 strains of Salmonella, compared them and prepared a "family tree" that describes the relationship between the different cultures of bacteria. To do this, scientists have identified thousands of SNPs 10.6 - differences in a single "letter" in the DNA nucleotide - and compared their sets in the genomes of Salmonella.
It was found that all strains of atypical Salmonella are divided into two groups, the scientists identified as "Line 1" and "Line 2". The genome of the bacteria is markedly different from the unit of DNA "normal" strains of Salmonella serovar Typhimurium, in which they are incorporated. For example, the genomes of normal and atypical Salmonella different mutations on 700, while the maximum number of differences between different strains of the bacteria does not exceed 450.
Scientists have imposed the resulting family tree on a map of Africa and determined the origin of the time and location of the source of the "parent" strains iNTS. It turned out that the "Line 1" appeared about 50 years ago in Malawi, in areas that are associated with the beginning of the AIDS epidemic in Africa. Then this group iNTS infiltrated into Kenya, the Democratic Republic of the Congo, Uganda and Mozambique.
The second line came much later - in 1977 in the Democratic Republic of Congo. It spread to the same sub-Saharan Africa about the same routes as the "Line 1", but managed to get on - in Niger, Mali and other northern countries. Starting in 2003, the line begins to rapidly displace bacteria from the first group, as the bacillus of "line 1" were resistant to chloramphenicol - an antibiotic with which doctors tried to save the victims of salmonella.
Place of origin of the bacteria, and the trajectory of their distribution largely coincides with how increased the scale of the HIV epidemic in Africa. This allowed the scientists to suggest that this subspecies of Salmonella developed in the population with HIV in central and eastern Africa.
"It is estimated that the HIV epidemic in sub-Saharan Africa began in the central regions of the continent and spread to the east, about the same as the iNTS. Our results indicate that the development of this form of salmonella and its spread could be exacerbated by a large population of people with undermined immunity "- said one of the authors, Robert Kinsley (Robert Kinsley) of the Sanger Institute.
It is still not clear how the bacteria spread and how they infect healthy people. Scientists plan to find answers to these questions, please continue to study the genome of Salmonella.