Antibiotics, drugs used to treat bacterial infections, have been pivotal in curing many bacterial diseases since its discovery in 1928. However, an emerging threat to using them is the rise of bacterial strains that are resistant to antibiotics. In recent years, antibiotic-resistant bacteria have started to cause havoc on human health—they take longer to heal, and increase medical costs and mortality. Globally, antibiotic resistance is estimated to result in 10 million deaths annually by 2050. Ironically, it’s the reckless overuse of antibiotics that has resulted in the evolution of these resistant superbugs! Today, there are drug-resistant infections of pneumonia, tuberculosis, blood poisoning and gonorrhoea, among others.
In a recent study, a team of researchers from the USA’s Johns Hopkins School of Medicine, Johns Hopkins Bloomberg School of Public Health and the Center for Disease Dynamics, Economics & Policy, have used Drug Resistance Index (DRI) to measure the effectiveness of antibiotics against specific bacteria. They have also explored the use of different types of antibiotics across 41 countries. The study was published in the journal BMJ Global Health and was funded by the Bill and Melinda Gates Foundation and the US Centers for Disease Control and Prevention.
The Drug Resistance Index is a single value calculated mathematically by combining the measurements of antibiotic use and antibiotic resistance for a particular antibiotic-pathogen combination. It ranges from 0 to 100, with 0 indicating 100% susceptibility and 100 indicating 100% resistance. This score makes it easy to measure the effectiveness of an antibiotic against a specific bacteria, and therefore, look for potential solutions to reduce antibiotic resistance.
“The introduction of the DRI was a first step in evaluating the relative problems of resistance and communicating the findings to a broad audience,” say the researchers on this study. They have used DRI to demonstrate how the problems of resistance vary widely by geography and reflect the trends in antibiotic use among countries.
The researchers calculated the DRI of certain antibiotics and high priority pathogen combinations across 41 countries. The pathogens include Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecium and Enterococcus faecalis. The antibiotic classes include broad-spectrum penicillins, which act on many types of bacteria, and narrow-spectrum penicillins that kill specific bacterial species.
The study found that antibiotic use and antibiotic resistance varied across countries. Acinetobacter baumannii and Enterococcus faecium showed the highest rate of resistance across all classes of antibiotics, but especially to broad-spectrum penicillins. Broad-spectrum penicillins had a high DRI score because they were the most widely used antibiotics across all countries. Narrow spectrum penicillins, which are expensive and have limited access in developing countries, were the least used class of antibiotics. Hence, they had a low DRI score. These observations confirm that excessive use of antibiotics leads to increased antibiotic resistance.
The study also found that high-income countries like Sweden, Canada, Norway, Finland and Denmark had the lowest DRI scores. The researchers attribute this to the fact that these countries had a high usage of narrow-spectrum penicillins along with access to more effective and expensive antibiotics. Low and middle-income countries like India, Thailand, Ecuador and Venezuela had high DRI scores, with India topping the list. The researchers point out that in these countries, the use of broad-spectrum penicillins is high, and access to newer and more effective antibiotics are lacking.
India leads the world in the antibiotic consumption per person as there is rampant use of broad-spectrum penicillins, which are cheap and easily accessible. Hence, the country also carries the most considerable burden of drug-resistant pathogens. This trend is a warning bell for the healthcare industry of our country to take stringent measures against the aggressive and unnecessary use of antibiotics.
The DRI, developed in this study, can thus effectively track antibiotic use and resistance for multiple pathogens across countries, revealing where drug resistance poses a health risk. This information can be used by health care facilities to make informed decisions about the antibiotics being used for treatment, to curb drug resistance. As a next step, the researchers suggest investigating country-specific data, use of different drug–pathogen combinations and comparing them across countries.