A study of Salmonella Typhi, the bacteria that causes typhoid fever, has confirmed a concern that doctors in India had been raising for long — the typhoid-causing bacteria have become resistant to essential antibiotics.
The study, published in The Lancet Microbe, is based on the whole genome sequencing on 3,489 S. Typhi isolates obtained from blood samples collected between 2014 and 2019 from people with typhoid fever in India, Bangladesh, Nepal and Pakistan.
A collection of 4,169 S. Typhi samples from more than 70 countries isolated between 1905 and 2018 was also sequenced and included in the analysis. The analysis shows resistant S. Typhi strains have spread between countries at least 197 times since 1990. While these strains most often occurred within south Asia and from south Asia to southeast Asia, east and southern Africa, they have also been reported in the UK, US and Canada.
Lead author Dr Jason Andrews of Stanford University, US, said, “The speed at which highly-resistant strains of S. Typhi have emerged and spread in recent years highlights the need to urgently expand prevention measures, particularly in countries at greatest risk. At the same time, the fact resistant strains of S. Typhi have spread internationally so many times, underscoring the need to view typhoid control and antibiotic resistance more generally as a global rather than local problem.”
Typhoid is a major public health infection with symptoms such as persistent high fever, nausea, headache and abdominal pain, among others. Antibiotics can be used to treat typhoid fever infections, but their effectiveness is threatened by the emergence of resistant S. Typhi strains.
“While most typhoid cases could earlier be managed with oral antibiotics called quinolones, we now have to use injectable drugs, that too for a longer duration. Otherwise, there is relapse,” said Dr Suranjit Chatterjee, senior consultant, internal medicine, Indraprastha Apollo Hospitals. He said the administration of injectable antibiotics often necessitates hospitalisation.
Dr Atul Kakar, vice-chairperson of the medicine department, Sir Ganga Ram Hospital, said that multi-drug resistance was a major public health crisis. “When I was a student, we used to give chloramphenicol — a type of antibiotic — to treat typhoid. Its use was discontinued due to high toxicity,” recalled Kakar. “Recently, we observed that the same drug was sensitive to typhoid-causing bacteria when the newer drugs were failing. This means we may have to go back in time and use the older drugs with known side effects if drug resistance continues to increase. Also, the majority of the patients admitted require two drug regimens for fever reduction.”
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