A study has found the root cause of a “superbug” that has been sweeping across Pakistan. The outbreak of Typhoid fever is thought to have been created due to its extensively drug-resistant nature, a sign that treatment options for the bacterial disease are running out, scientists said on Tuesday.
Researchers from Britain’s Wellcome Sanger Institute who analysed the genetics of the typhoid strain found it had mutated and acquired an extra piece of DNA to become resistant to multiple antibiotics.
The large-scale outbreak of the drug-resistant Typhoid reportedly began in Hyderabad, Pakistan, in November 2016. The disease has spread at an alarming rate and continues to do so, according to experts from Aga Khan University who worked with the Sanger team. Official government data, on the number of cases reported for treatment or fatalities, have not yet been made available; with local Pakistani media reporting, health authorities reportedly detecting more than 800 cases of drug-resistant typhoid in Hyderabad alone in a 10-month period between 2016 and 2017.
The research conducted found the bacterial strain responsible for the outbreak is now resistant to five antibiotics in total, a figure not previously seen before.
Elizabeth Klemm, who co-led the analysis work at the Sanger Institute, spoke candidly about the research being conducted by her team. “This is the first time we have seen an outbreak of extensively drug-resistant typhoid,” said Klemm. “This outbreak was caused by a multidrug-resistant strain that had gone a step further and acquired an extra piece of DNA encoding additional genes for antibiotic resistance.”
Typhoid is a highly contagious infection caused by the Salmonella enterica serovar Typhi bacteria. It is contracted by consuming contaminated foods or drinks and symptoms include nausea, fever, abdominal pain and pink spots on the chest. Untreated, it can be fatal.
Scientists at Aga Khan University in Pakistan are eager to develop new methods to tackle the ongoing outbreak amidst growing pressure. They reportedly contacted the Sanger, in the spring of 2017 and asked scientists there to genetically analyse samples. The team found it was being caused by a strain known as H58, which is already known to be linked to drug-resistant cases. Looking further, they found this H58 strain had gained an extra strand of bacterial DNA – a plasmid – that encoded for additional antibiotic resistance genes. The study’s results were published in the scientific journal mBio.
Charlie Weller, head of vaccines at Britain’s Wellcome Trust global health charity, said the findings were a clear warning that “treatment options for typhoid are running out” and focussing on prevention was now vital.
A new vaccine against typhoid was approved last month by the World Health Organization and the GAVI global vaccine alliance, said last year it had earmarked $85 million to help support the introduction of typhoid vaccines in poor countries.
Previous research by Sanger scientists published in 2015 found that the H58 strain of typhoid first emerged in South Asia an estimated 25-30 years ago. It initially took hold of Asia and Africa before spreading around the world, becoming a prominent strain by 2015.
By Zakaria Abraham