Drug-resistant typhoid tracked worldwide, public health threat ‘critical’

A medical technician takes a blood sample from a patient to check for dengue and typhoid at a government health center in Jakarta (AFP Photo)

A medical technician takes a blood sample from a patient to check for dengue and typhoid at a government health center in Jakarta (AFP Photo)

A deadly typhoid ‘superbug’ is spreading across Africa and Asia, creating a “previously under-appreciated and ongoing epidemic,” a groundbreaking international study warns. H58, driven by a single family of the bacteria, is resistant to most antibiotics.

Researchers from the Wellcome Trust Sanger Institute, who have
been studying the far-reaching infection, say typhoid affects
around 30 million people each year. According to researchers, H58
has emerged and spread throughout Asia and Africa over the last
30 years.

Evidence of a recent unreported wave of H58 transmission in many
countries in Africa has also been found.

The scientists say the study results add to the message that
“bacteria do not obey international borders.”

What sounds even worse is that H58 is currently “displacing
other typhoid strains that have been established over decades and
centuries throughout the typhoid endemic world, completely
transforming the genetic architecture of the disease,”
researchers, whose work has been published in the journal Nature Genetic, have
pointed out in a statement. The large-scale research involved
some 74 scientists in almost two dozen countries.

The research team sequenced the genomes of 1,832 samples of
Salmonella typhi bacteria collected from 63 countries between
1992 and 2013. As much as 47 percent were from the H58 strain,
the scientists say.

Image from sanger.ac.uk

Dr. Vanessa Wong, lead author from the institute, added in a
that global surveillance to address public health
threat in many developing countries around the world “at this
scale is critical.”

Typhoid, also called typhoid fever, is highly contagious and is
caused by a bacterium called Salmonella typhi (related to the
bacteria which cause salmonella food poisoning.) Symptoms include
nausea, fever, abdominal pain accompanied by pink spots on the
chest. Typhoid is contracted by drinking or eating contaminated
matter. Children and younger adults are most at risk of
developing typhoid fever because their immune systems are more
vulnerable. Untreated, the disease can lead to complications
which may turn fatal for up to 20 percent of patients.

Vaccines are available, but due to limited cost-effectiveness
they are not widely used in poorer countries. Therefore the
disease is mostly controlled through antibiotic drugs. However,
over 70 scientists involved in the latest study have come to the
conclusion that the H58 “superbug” version, which is resistant to
multiple types of antibiotics, is now becoming dominant,
continuing to evolve.”

According to Dr. Kathryn Holt, a scientist at the University of
Melbourne in Australia who also worked on the landmark study,
multidrug resistant typhoid has been “coming and going”
since the 1970s. She says it’s caused by the bacteria picking up
new antimicrobial resistance genes, which are usually lost when
people switch to a new drug.

“In H58, these genes are becoming a stable part of the
genome, which means multiply antibiotic resistant typhoid is here
to stay,
” Holt said.

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