Typhoid is notably called an “ancient” disease — it might be as old as human civilization, dating back to 50,000 years ago. Specifically, Salmonella typhi is the bacterium in question that has traveled through the eons with human beings, laying waste to innumerable lives until the discovery of antibiotics in the 20th century. But we could soon be at dire risk from the organism once again — a new study shows the bacterium is developing dangerous levels of antibiotic resistance. That is, oral medication that emerged as a way to treat the disease is becoming increasingly ineffective.
Published in Lancet Microbe, an alarming study found that an antibiotic-resistant strain of Salmonella typhi is spreading internationally. Researchers conducted genome sequencing using 3,489 samples across four high-burden countries: India, Nepal, Pakistan, and Bangladesh. “Specifically, we found that south Asia continues to be an important hub for the generation of antimicrobial resistance,” the authors wrote.
“The speed at 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, particularly in countries at greatest risk,” said infectious disease specialist Jason Andrews from Stanford University.
There are many types of oral antibiotics administered for typhoid, but many strains of the bacterium have been growing resistant to groups of them and have been spreading — predominantly in South Asia — since 2000. This means that the multi-drug resistant strains are immune to a range of antibiotics administered for typhoid, like ampicillin, chloramphenicol, trimethoprim/ sulfamethoxazole, and even new generations of antibiotics like fluoroquinolones and cephalosporins.
While these strains have declined slightly over the years, researchers have now found one strain — XDR Typhi — that is resistant to almost all antibiotic drugs except azithromycin. But the study found that this line of defense could also be weakening: “Concerningly, azithromycin-resistant S. Typhi have recently been reported in Bangladesh, India, Pakistan, Nepal, and Singapore,” the study reported.
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“Evidence to date suggests that much of the drug-resistance in typhoid has evolved within India, so we certainly need to be concerned about the appearance of drug resistance in the country,” lead author Dr. Jason Andrews of Stanford University told The Indian Express.
A 2021 study published in the Journal of Infectious Diseases found that India continues to carry a heavy typhoid burden, particularly in urban areas. It also highlights the urgency of immunization programs among children. If untreated, the fast spread of the strain could make up to 20% of all typhoid cases — around 11 million annually — fatal.
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“The recent emergence of XDR and azithromycin-resistant S .Typhi creates greater urgency for rapidly expanding prevention measures, including use of typhoid conjugate vaccines in typhoid-endemic countries,” the paper notes.
Yet there is still some hope: vaccines. Typhoid-conjugate vaccines are effective in controlling disease spread, according to the study, and we shouldn’t wait until antibiotic-resistant strains become prevalent before introducing them. “This rapid emergence, spread, and fixation of antimicrobial resistance suggest that making decisions regarding typhoid conjugate vaccine introduction based on current antimicrobial resistance data might miss a crucial window for prevention.”
The study draws attention not only to the spread of dangerous strains of typhoid, but also to the prevalence of antibiotic resistance in India and other South Asian countries. India in particular is a hotspot for antibiotic-resistant superbugs. Newborns are dying from it, and their misuse soared during the pandemic.
