An article published on June 21 in the scientific journal The Lancet Microbe shows that the bacteria that cause typhoid fever are increasingly resistant to antibiotics, in addition to having spread sharply and frequently in some countries in the last 30 years.
Typhoid fever is a systemic disease caused by bacteria salmonella typhi (S. typhi).
You main symptoms are fever, prostration, abdominal pain and pink rash (reddened skin irritation).
This was the largest genetic sequencing study of S. typhi and analyzed more than 7,500 genomes.
“The analysis shows that resistant strains of S. typhi have spread between countries at least 197 times since 1990. Although these strains have occurred most frequently in South Asia and South Asia to Southeast Asia, East and South Africa, they have also been reported in the UK, US and Canada “, say the authors of the work in a statement.
Treatment of typhoid fever involves the use of antibiotics such as chloramphenicol and trimethoprim/sulfamethoxazole.
Macrolide antibiotics (the main example is azithromycin) and quinolones (eg ciprofloxacin) can also be used.
In the work, the researchers classified as multidrug-resistant strains those that had genetic characteristics that matched resistance to first-line antibiotics – ampicillin, chloramphenicol and trimethoprim/sulfamethoxazole.
They also tracked the presence of genes that confer resistance to macrolides and quinolones, “which are among the most important antibiotics for human health.”
The results were worrying. The genetic mutations that make the S. typhi resistant to quinellones, for example, have spread at least 94 times since 1990, with 97% originating in South Asia.
Azithromycin-resistant mutations appeared at least seven times in a 20-year interval.
“In Bangladesh, strains containing these mutations emerged around 2013, and since then their population size has steadily increased,” the authors say.
The study’s lead author, Jason Andrews, from Stanford University (USA), warns of the need to see the control of typhoid fever and antibiotic resistance in general as a global health problem.
“The speed with which highly resistant strains of S. typhi have emerged and spread in recent years is a real cause for concern and highlights the need to urgently expand prevention measures, especially in countries most at risk.”
The researchers point out that the study would need to be more comprehensive in samples collected in regions such as sub-Saharan Africa and Oceania, where typhoid fever is endemic.
“How do the genomes of S. typhi cover only a fraction of all typhoid cases, estimates of mutations causing resistance and international spread are likely to be underestimates,” they say.
The WHO (World Health Organization) estimates that between 11 million and 21 million people get sick from typhoid worldwide annually. Of this total, between 128,000 and 161,000 die.
The disease is more common in communities without access to clean water and sanitation.
“Even when symptoms disappear, people can still be carrying the typhoid bacteria, which means they can spread it to other people through their faeces,” the WHO notes.