Scimex: The bug that causes typhoid, Salmonella typhi, developed resistance to
antibiotics in the last 30 years, and has caused an ongoing, previously
unrecognised, epidemic in Africa, according to an international team
that includes Australian and New Zealand researchers. Analysing the DNA
of 1,832 samples of typhoid bacteria from 63 countries, they found
around half belonged to a single drug resistant strain known as H58.
The antibiotic-resistant strain of Salmonella typhi, the
primary cause of typhoid, emerged within the last 30 years and may
represent an ongoing, previously unrecognized epidemic in Africa,
reports a study published online this week in Nature Genetics.
Typhoid
affects 20-30 million people globally each year. Symptoms include
nausea, fever and abdominal pain. Some people infected with the bacteria
show no symptoms, but they are still able to transmit the disease.
Vaccination and antibiotics can be used to effectively treat many cases
of typhoid, but strains of S. typhi that are resistant to antibiotics have emerged since the 1970s.
Vanessa Wong and colleagues sequenced the genomes of 1,832 samples of S. typhi
that were collected from 63 countries between 1992 and 2013. They found
that 47% belonged to a single strain known as H58, which is resistant
to multiple antibiotics. The geographic pattern of antibiotic resistance
found in this study reflects the usage of antibiotic drugs in those
regions. The researchers found that H58 emerged in South Asia 25-30
years ago and spread to Southeast Asia, Western Asia, East and South
Africa, and Fiji. They also found evidence of a recent and unreported
wave of H58 transmission in multiple countries in Africa, which may
represent an ongoing epidemic.