Non-typhoidal (NTS) usually cause gastroenteritis in humans, but in recent years NTS have begun to cause epidemics of bloodstream infections in Africa. Enteritidis is the second most common serovar associated with this invasive form of NTS disease (iNTS) in Africa. To establish a systemic infection, must survive and replicate within host cells, with macrophages being a primary target. Genomic characterisation of Enteritidis isolates from human bloodstream has identified two new clades that are unique to Africa and distinct from the Global Epidemic clade. The African S. Enteritidis clades exhibit genomic degradation, and possess a distinct prophage repertoire and are multi-drug resistant. However, little is known about the virulence factors that allow African S. Enteritidis to cause systemic infection in susceptible hosts. We screened libraries of random insertion mutants of African and Global S. Enteritidis by transposon insertion sequencing (TIS), and identified about 280 genes belonging to each clade that contribute to bacterial survival and replication in murine macrophages. The genes were associated with 5 pathogenicity-islands, or encoded the global regulators PhoPQ and OmpR-EnvZ. Experiments are ongoing to investigate the role in intra-macrophage replication of genes that are uniquely identified in African Salmonella. It is hoped that our findings will contribute to a greater understanding of African infection biology, and that some of the virulence-associated genes could be potential targets for novel therapeutics.

  • This is an open-access article distributed under the terms of the Creative Commons Attribution License.

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