In a study published in the latest issue of Science (24 November, 2006), an international consortium from the Max-Planck Society, Wellcome Trust Institutes in Britain and Vietnam, and the Institut Pasteur in France have elucidated the evolutionary history of Salmonella Typhi. Typhi is the cause of typhoid fever, a disease that sickens 21 million people and kills 200,000 worldwide every year. The results indicate that asymptomatic carriers played an essential role in the evolution and global transmission of Typhi. The rediscovered importance of the carrier state predicts that treatment of acute disease, including vaccination, will not suffice to eradicate this malady. The results also illuminate patterns leading to antibiotic resistance after the indiscriminate use of antibiotics. Fluoroquinolone treatment in southern Asia over two decades has resulted in the emergence of multiple, independent nalidixic acid-resistant mutants, of which one group, H58, has multiplied dramatically and spread globally. The prevalence of these bacteria hampers medical cure of clinical disease via antibiotics.
Typhoid fever remains a major health problem in the developing world and continues to cause disease in Europe and on the american continent. The evolutionary history and population structure of Typhi were poorly understood, partly because these bacteria show little genetic diversity. Now a team led by Mark Achtman and Philippe Roumagnac from the Max Planck Institute for Infection Biology, Berlin, has applied population genetic experience from prior work with Yersinia pestis, Escherichia coli, Helicobacter pylori and Neisseria meningitidis to provide novel insights into the evolution of this pathogen. The team combined its resources to assemble for the first time a globally representative collection of 105 strains of Typhi and investigated the sequence diversity within 90,000 base pairs per strain. Eighty-eight informative sequence differences were detected, showing that
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Contact: Dr. Mark Achtman
49-302-846-0751
Max-Planck-Gesellschaft
28-Nov-2006