Diphtheria’s threat is increasing as the easily-preventable infection, usually treated with antibiotics and vaccines, is evolving with antimicrobial-resistant (AMR) strains, posing a risk that the disease may once again become a major global challenge.
This is according to an international team of researchers from the UK and India. They conducted the study using genomics to map infections. When researchers analysed the genomes of bacteria isolated from patients, and publicly available genomes, they found that the average number of AMR genes per genome was increasing each decade providing an indication as to why there has been an increase in resistance.
Overall, there was an identification of a trend suggesting that isolated genomes from the most recent decade (2010-19) showed the highest average number of AMR genes per genome – almost four times as many on average than in the next highest decade, the 1990s. Notably, isolated genomes including those from India showed a disproportionately high number of AMR genes, and that the sulfonamide S (=O)2-NH2 resistance gene was the most common, being consistently found in Indian isolated genomes.
Robert Will, first author on the study led by researchers at the University of Cambridge, said “the C. diphtheriae genome is complex and incredibly diverse. It’s acquiring resistance to antibiotics that are not even clinically used in the treatment of diphtheria. There must be other factors at play, such as asymptomatic infection and exposure to a plethora of antibiotics meant for treating other diseases.”
Diphtheria challenge for India
The data from the study published in Nature Communications included a subset from India where over half of the globally reported cases occurred in 2018. The findings pose potential problems for a which is already a prime battleground for AMR. India already has one of the highest incidences of bacterial infections in the world, including in the form of typhoid, cholera, pneumonia, and tuberculosis.
When considering India already has issues tackling bacterial infections, and the threat of AMR, reports of damning statistics around diphtheria immunity in children are unlikely to help. According to the New Indian Express, the majority of children aged 5-17 years in India are either only partially or non-immune to diphtheria with a survey of over 8,000 children showing that 10.5 percent were non-immune and 59.8 percent were partially immune.
The results of the survey which were published in The Lancet also showed that there were varying degrees of immunity across India’s regions. Six percent of children living in the south of the country were non-immune to diphtheria, whilst in the northeast this rose to 16.8 percent. Variation was also found between children living in urban and rural areas with 9.9 percent of children in rural areas and 13.1 percent in urban areas displaying a lack of immunity to diphtheria.
Research into India’s history tackling the disease outlines challenges it would hope to stave off once more with a survey carried out by the Indian Council of Medical Research’s National Institute of Epidemiology revealing how diphtheria was once a leading cause of childhood morbidity and mortality, prior to a DTP vaccine being included in the country’s National Immunisation Programme in 1978.
As Health Issues India previously reported, drug resistance is developing in a host of diseases and the longer it is left to fester, the more difficult the situation will be to address in the future. But to curtail the rise of AMR in diseases such as diphtheria, there is a fundamental need to tackle AMR at large, which in India has seen an increased focus on stewardship due to poor availability and utilisation of diagnostics.
