The bacteria responsible for causing diphtheria is evolving to resist antibiotics, a new study has found. Its high degree of evolution could eventually make the bacteria resistant to the vaccine as well, researchers add.
Published in Nature Communications, the study examined the genomic variation in Corynebacterium diphtheriae, the diphtheria-causing bacteria, across 16 countries, including India. It found that the bacteria’s “antimicrobial resistance genes, as well as the breadth of antibiotic resistance, is substantially greater in the last decade than ever before.”
In India, for instance, 61 distinct isolates of the bacteria were sequenced to understand whether they had developed resistant genes. The researchers found no antimicrobial resistance in the isolates from Himachal Pradesh, and in some isolates from U.P. and Kerala. But isolates from Haryana were found to be resistant to four classes of antibiotics; isolates from Delhi, Tamil Nadu, and some from Kerala, were resistant to five; and some isolates from U.P. showed resistance to six.
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Given the high rate of change in the bacteria that causes diphtheria, the study expressed significant concerns about the likelihood of its vaccine becoming less effective, which could “potentially lead to an opportunistic return of this communicable disease.” Both the vaccine and antibiotics target a toxin produced by the bacteria; if the genes behind toxin production are evolving, the bacteria could become resistant to its vaccine, as well as antibiotics.
However, their concerns about vaccine efficacy have not come to fruition yet. “While our data does not at present highlight any efficacy concern in the currently used … vaccine, the continually increasing toxin diversity and prevalence of non-toxigenic strains do however forecast a real possibility of vaccine escape and anti-toxin treatment failure in future,” the study notes.
This is especially alarming in the context of diphtheria’s prevalence in India. According to government data, in 2017, India recorded 149 deaths and 5,421 cases of diphtheria. In 2018, the number of deaths had risen to 180, and the number of diphtheria cases had more than doubled to 11,720. In the same year, about half of all the diphtheria cases in the world were in India, The Print reported.
