A new piece of the typhoid ‘puzzle’

In October 2016, researchers at the Aga Khan University’s microbiology laboratory spotted a number of unusual organisms in blood samples from Hyderabad. Blood culture tests from the city contained a novel strain of typhoid that had developed resistance to an unprecedented range of antibiotics.
Over the next few months, several similar cases were detected from the city pointing to an outbreak of a form of the disease that would be especially difficult to treat. 
The research team, led by Pofessor Rumina Hasan, acted quickly to alert local government, the National Institutes of Health and the World Health Organization to this development. They also contacted the UK-based Wellcome Sanger Institute to explore the genetic cause behind the emergence of this extensively drug-resistant (XDR) typhoid strain.
“This was the world’s first outbreak of XDR typhoid,” said Professor Zahra Hasan of the department of pathology and laboratory medicine. “Understanding this new threat required high-level genome sequencing which would enable us to analyse the molecular blueprint of this new form of typhoid.”
Over the next six months, the research team collaborated with experts at the Wellcome Sanger Institute to jointly analyse over 100 DNA samples which resulted in a striking finding. The typhoid bacteria had acquired a DNA molecule through a plasmid from a bacterium commonly found in contaminated water and food, making it resistant to the majority of available medications .  
“We used to think that we had a complete picture of the typhoid ‘puzzle’,” said Dr Sadia Shakoor, assistant professor in pathology and laboratory medicine at AKU. “Together with our partners, we’ve found a missing piece that affects how we diagnose and treat the most complex strains of the disease.”   
Since patients with XDR typhoid do not respond to commonly prescribed antibiotics, blood culture tests have become an even more important tool for physicians, according to Dr Shakoor. Not only do these tests enable early detection but they also highlight the type of typhoid being tackled that affects the choice of antibiotic.
“There are currently three antibiotics available to treat XDR typhoid,” Dr Shakoor stated. “These drugs are expensive and we must only prescribe them when needed. Otherwise, bacteria could develop resistance to the only medications we have left.”
Beyond resistance, researchers also warn of the risk of the disease spreading since every patient is a potential ‘disease carrier’. The likelihood of the proliferation of the disease is especially high in developing countries where poor sanitation facilities result in the contamination of drinking water with sewage containing the typhoid bacteria.
Aga Khan Universitywww.aku.edu/news/Pages/News_Details.aspx?nid=NEWS-001521