Diphtheria is a highly contagious infection that targets the nose, throat and skin. In high-income countries babies are vaccinated against it, however, low-income countries struggle to keep their populations vaccinated. This preventable infection has concerned University of Cambridge scientists as it continues to evolve resistance against a number of antibiotics. Additionally, the researchers warn that resistant diphtheria can escape vaccine efforts in the future.
Steadily increasing, the number of diphtheria cases in 2018 was 16,651, more than double the yearly average for 1996-2017 (8,105 cases). Primarily caused by the bacterium Corynebacterium diphtheriae. In a study published in Nature Communications, an international team of researchers from the UK and India used genomics to map infections.
By analyzing the genomes of 61 bacteria isolated from patients and combining these with 441 publicly available genomes, the researchers developed a phylogenetic tree to better understand how the infections are related and understand how they spread.
Professor Gordon Dougan from the Cambridge Institute of Therapeutic Immunology and Infectious Disease (CITIID) explained, "The diphtheria vaccine is designed to neutralize the toxin, so any genetic variants that change the toxin's structure could have an impact on how effective the vaccine is. While our data doesn't suggest the currently used vaccine will be ineffective, the fact that we are seeing an ever-increasing diversity of tox variants suggests that the vaccine, and treatments that target the toxin, need to be appraised on a regular basis."