Diphtheria is becoming a global threat again. The bacterium is resistant to antibiotics

The bacterium that causes diphtheria (diphtheria) is becoming resistant to antibiotics, and the COVID-19 pandemic has disrupted the course of vaccines that effectively protect against the disease, according to Nature Communications.

1. Diphtheria (also known as diphtheria, croup or angina) is a contagious disease that is transmitted by droplets – through coughing and sneezing or close contact with an infected person
2. In the patient’s throat, tonsils and larynx, so-called pseudo-membranes, which, in combination with enlarging lymph nodes, can lead to narrowing of the pharynx and larynx and death due to respiratory failure or cardiac arrest
3. In 2018, 16 cases were recorded, more than twice the annual average in 651-1996
4. COVID-19 has severely limited diphtheria vaccination schedules, scientists report
5. More current information can be found on the Onet homepage.

According to a British-Indian team led by scientists from the University of Cambridge, the impact of COVID-19 on diphtheria vaccination schedules, combined with the increase in infections, is making the disease a major global threat once again.

Diphtheria (also known as diphtheria, croup, and angina) is caused by Corynebacterium diphtheriae. A highly contagious infection is spread by airborne droplets – through coughing and sneezing, or through close contact with an infected person. In most cases, bacteria cause acute infections associated with the diphtheria toxin. However, the non-toxin-producing strains of C. diphtheriae can also cause disease, often in the form of systemic infections.

1. Diphtheria (diphtheria) – what is this disease?

Symptoms initially appear at the site of the entry of bacteria – in the throat, on the palatine tonsils, in the larynx, less often in the nose. Bacteria cause tissue necrosis, so-called pseudo-pseudo-membranes, which are gray, translucent or black coatings that bleed when you try to detach.

Membranes, along with enlarging cervical lymph nodes and swelling of the neck, can lead to narrowing of the pharynx and larynx, and death from respiratory failure or cardiac arrest. Mycobacteria of diphtheria secrete a strong toxin that can lead to dysfunction of many organs – myocarditis, renal tubular necrosis. There may also be neurological complications, such as paralysis of the palate and the back of the throat, paralysis of the muscles responsible for eye movements, paralysis of the limbs and facial muscles.

1. Vaccinations – types, compulsory vaccinations, post-vaccination adverse reactions [EXPLAINED]

However, in low- and middle-income countries, the disease may still cause infections or outbreaks of infection in unvaccinated and partially vaccinated communities.

The number of diphtheria cases reported worldwide is gradually increasing. In 2018, 16 cases were recorded, more than twice the annual average in 651-1996, amounting to 2017 cases. More than half of the globally reported cases were in India.

1. The most common bacterial diseases – overview and characteristics

Authors of a study published in Nature Communications used genomics to map infections. By analyzing the genomes of 61 bacteria isolated from patients and combining them with 441 publicly available genomes, scientists were able to build a phylogenetic tree – the genetic ‘family tree’ – to see how infections relate and understand how they spread. They also used this information to assess the presence of antimicrobial resistance (AMR) genes and assess toxin variability.

Clusters of genetically similar bacteria have been isolated from many continents, most often from Asia and Europe. This means that C. diphtheriae has been present in the human population for at least a century, spreading worldwide as the population migrates.

The major pathogen of C. diphtheriae is diphtheria toxin. It is this ingredient that vaccines target. In total, scientists found 18 different variants of the toxin gene, several of which had the potential to alter its structure.

Professor Gordon Dougan of the Cambridge Institute of Therapeutical Immunology and Infectious Disease (CITIID) said: “The diphtheria vaccine is designed to neutralize the toxin, so any genetic variants that alter the structure of the toxin could impact the effectiveness of the vaccine. While our data do not suggest that the vaccine currently in use will be ineffective, the fact that we see an ever-increasing diversity of toxin variants suggests that vaccine and toxin-targeting therapies need to be regularly assessed ».

Diphtheria infections can usually be treated with different classes of antibiotics. While resistance to antibiotics of C. diphtheriae has been reported, the extent of such resistance is largely unknown.

When the team looked for genes that could confer a degree of antimicrobial resistance, they found that the average number of AMR genes per genome increased with each decade. The genomes of bacteria isolated from infections in the last decade (2010-19) showed the highest average number of AMR genes in the genome, almost four times greater than in the 90s.

1. Prof. Hryniewicz: We urgently need new antibiotics with both broad and narrow spectrum of action

“The genome of C. diphtheriae is complex and extremely diverse. He becomes resistant to antibiotics that are not even clinically used to treat diphtheria. Other factors must come into play, such as asymptomatic infection and exposure to a plethora of antibiotics designed to treat other diseases, said Dr. Robert Will, the study’s first author.

The traditionally recommended antibiotics of choice for treating diphtheria are erythromycin and penicillin, although several different classes of antibiotics exist for treating infections. In the 2010 isolates, the team identified variants resistant to six of these classes – more than in any other decade.

Dr. Pankaj Bhatnagar of the World Health Organization national office in India said: “Drug resistance has rarely been considered a major problem in the treatment of diphtheria, but in some parts of the world the bacterial genomes are becoming resistant to many classes of antibiotics. There could be many reasons for this, including exposure of the bacteria to antibiotics in their environment or asymptomatic patients being treated for other infections. ‘

The researchers point out that COVID-19 has had a negative impact on childhood immunization schedules around the world, and is occurring at a time when the number of reported cases of diphtheria is rising, and in 2018 the incidence was at its highest in 22 years.

Dr Ankur Mutreja, who led the study, said: “It is more important than ever that we understand how diphtheria evolves and spreads. Genome sequencing gives us a powerful tool to observe this in real time, enabling public health agencies to act before it’s too late. We must not take our eyes off the diphtheria or we risk it becoming a global threat again, potentially in a modified, better adapted form. ‘

Author: Paweł Wernicki

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