Antibiotic-resistant typhoid strains rising, shows new research

The emergence of increasingly antibiotic-resistant Typhoid strains has threatened the effective treatment and control of the disease, as per a new study, published in Lancet Microbe.

The study conducted, involved the genomic sequencing of 3489 S Typhi strains isolated from Nepal, Bangladesh, and India (between 2014 and 2019) and was later combined with a global collection of 4169 S Typhi genome sequences isolated between 1905 and 2018.

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The findings of the study showed a declining trend of multidrug-resistant typhoid in South Asian countries but the presence of fluoroquinolone-resistant mutants and the displacement of the older strains have become a cause of worry for the scientists who worry that typhoid strains have become resistant to almost all kinds of antibiotics available till date.

Typhoid fever is a disease caused by Salmonella enterica serovar Typhi (S Typhi). The disease causes 11 million cases and more than 1,00,000 deaths worldwide annually.

As per the report, since 2000, the multi-drug resistant (MDR) S Typhi has declined steadily in Bangladesh and India, remained low in Nepal, and increased slightly in Pakistan. The recent emergence of extensively drug-resistant (XDR) typhoid suggests that the current antibiotics may soon seem ineffective against the bacteria.

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Multidrug-resistant (MDR) typhoid is resistant to three first-line antibiotics used to treat typhoid that include – chloramphenicol, ampicillin, and cotrimoxazole. These strains first appeared in the 1970s and then spread globally. H58 strain is considered the globally dominant strain of MDR typhoid.

In response to MDR typhoid, another set of drugs called fluoroquinolones was introduced in the 1990s. With its frequent usage worldwide, it led to the emergence of a fluoroquinolones-resistant strain, widespread in South Asia. This has led to azithromycin and third-generation cephalosporins as the only available treatment. However, the new report suggests the emergence of XDR typhoid has left only one oral antibiotic, azithromycin as effective in the treatment of the disease.

WHO has time and again explained the need for vaccines against typhoid fever.

Typbar TCV, a typhoid conjugate vaccine was prequalified by the World Health Organization (WHO) in January 2018. Typbar TCV is manufactured by Bharat Biotech International Limited and is indicated for use in individuals aged 6 months to 45 years. WHO has recommended that the introduction of TCV must be prioritized in countries with the highest burden of antibiotic-resistant bacteria.

For the above-cited study, the genome sequencing was performed at the Wellcome Trust Sanger Institute (UK) and at the Wellcome Trust Research Laboratory in the Christian Medical College (Vellore, India).

As per a media report, a professor of CMC Vellore has said that surveillance at 18 Indian sites has shown that typhoid is as common today as it was two decades ago and if the resistance against the antibiotic increases then this may affect the severity of the disease as well.

Typhoid fever includes symptoms of persistent high fever, weakness, stomach pain, headache, diarrhoea or constipation and loss of appetite.