The bacteria that cause typhoid fever have become more resistant to essential antibiotics like quinolone and have spread widely over the past 30 years, according to a study that was published in the Lancet. The research also found that the percentage of quinolone-resistant strains in India increased to more than 95 percent in the 2000s.
According to the findings of the study, during the early 2000s, quinolone-resistant strains accounted for more than 85 percent of S Typhi (the bacteria that causes typhoid fever) in Bangladesh. By the year 2010, this percentage had increased to more than 95 percent in India, Pakistan, and Nepal.
According to what was found, the mutations that cause resistance to azithromycin, which is a macrolide antibiotic that is frequently used, have also developed at least seven times in the previous 20 years.
According to the largest genome sequencing study of S Typhi, which charted the emergence and spread of antibiotic-resistant strains, an analysis of more than 7,500 S Typhi genomes—mostly from South Asia—showed that resistant strains have spread between countries at least 197 times in the past 30 years. The majority of these resistant strains originated in South Asia.
The authors of the study performed whole-genome sequencing on 3,489 S Typhi isolates that were taken from blood samples collected between 2014 and 2019 from patients in Bangladesh, India, Nepal, and Pakistan who had confirmed cases of typhoid fever.
In addition, the genomes of 4,169 S Typhi samples that were isolated in over 70 different countries between the years 1905 and 2018 were sequenced and included into the analysis.
According to the study, multi-drug resistance to first-line antibiotics has usually decreased in South Asia. However, strains resistant to macrolides and quinolones—two of the most important antibiotics—have significantly increased and have spread often to other countries.
According to the report, “the biggest genome sequencing of Salmonella enterica serovar Typhi (S Typhi) indicates also that resistant strains — almost all of which originated in South Asia — have spread to neighbouring nations over 200 times since 1990.”
Typhoid fever is an issue for public health across the world; each year, there are around 11 million cases of illness and more than 100,000 fatalities. South Asia is the region in which it is most widespread, accounting for 70 percent of the total illness burden worldwide.