Prof. William Reville
The average British life expectancy at birth in 1900 was 50 years, today it is 81 years. Much of this improvement can be attributed to modern scientific medicine and in particular to the introduction of antibiotics. Many bacterial infections such as septicemia and puerperal fever that killed so many people historically can now be simply treated with antibiotics. Unfortunately this wonder of modern medicine is now threatened by overuse and by inappropriate use. In this article I will describe the crisis arising from the way we have abused antibiotics.
Bacteria are microscopic organisms ubiquitously present in our environment. Many bacteria are useful to us, e.g. the bacteria present in the human gut. Most other bacteria are harmless, but some can cause illness e.g. tuberculosis, some forms of meningitis, salmonella, syphilis, stomach ulcers, gonorrhea, pneumonia, strep throat, ear infections etc.
Although our immune system can normally fight off invading pathogenic bacteria, sometimes the invasion is too strong and we need the help of antibiotics. Antibiotics are chemicals that kill bacteria or stop their growth. Antibiotics are also effective against other micro-organisms that cause illness, e.g. some fungi and parasites, but they are ineffective against viral infections e.g. common cold, influenza, bronchitis, most sore throats, most coughs, some sinus infections, some ear infections and virus stomach flu.
Antibiotics have been seriously overused for a considerable time now both in human and animal medicine (in agricultural production of animals for meat) and also used inappropriately to treat viral infections. This abuse has accelerated the development of antibiotic resistance in bacteria and many antibiotics that used to be standard treatment for bacterial infections are now less effective or don’t work at all.
Bacteria naturally develop resistance to antibiotics as follows. Every population of bacteria contains some bacteria that are naturally more resistant to antibiotics than their fellows. When some of these resistant bacteria survive antibiotic treatments, the overall surviving bacterial population is enriched (selection pressure) in antibiotic-resistant bacteria. Genetic mutations spontaneously arise in bacteria that can confer antibiotic resistance on the bearer of the mutation. All offspring descended from the mutant will bear the resistance mutation (vertical transfer). An antibiotic-resistant bacterium can also genetically transfer (horizontal transfer) its resistance characteristics onto other bacteria that are susceptible to antibiotics. Over time these natural selection/vertical/horizontal transfer pressures will naturally convert antibiotic-susceptible bacteria into antibiotic-resistant bacteria.
Although bacteria naturally develop resistance to antibiotics, the problem now is that overuse and inappropriate use of antibiotics has accelerated this natural process. The greater the usage of antibiotics, the faster antibiotic-resistant bacteria arise. New classes of antibiotics are not being developed rapidly enough to replace the antibiotics that no longer work and the situation has now reached crisis level.
Despite growing awareness of antibiotic resistance the overuse and inappropriate use of antibiotics continues for a number of reasons including: (A) doctors may prescribe antibiotics before receiving test results indicating actual cause of the infection, (B) many doctors succumb to pressure from patients to prescribe antibiotics regardless of the cause of the illness, the patient wrongly believing antibiotics quickly relieve the symptoms of any infection. (C) Some people self-medicate with antibiotics purchased abroad or over the internet.
It is important to only take antibiotics as prescribed by your medical doctor, to take the full course of antibiotics to kill all of the disease causing bacteria and not to stop taking the medication as soon as you feel better. If you ever have leftover antibiotics throw them away and never take them for a later illness – they may neither be the correct antibiotics nor a full course of treatment.
The first real antibiotic, penicillin, was discovered by Alexander Fleming in 1928. For many years discovery of new antibiotics outstripped the development of antibiotic resistance, but this no longer happens. Most of the big pharmaceutical firms have stopped making antibiotics because of high development costs and low return on investment. Payoff on antibiotics is low compared with returns on drugs that treat chronic illness, e.g. drugs to treat high blood pressure, and after a certain age many people use these latter drugs for the rest of their lives. No new class of antibiotics has been introduced since 1987.
Over two million people contract antibiotic-resistant infections annually in the US and 23,000 people die annually from these diseases, 25,000 in the EU. By 2050 as many as 10 million people could die annually worldwide from antibiotic-resistant bacteria if new treatments are not discovered.
About 15,000 people are now infected in India with a TB strain that resists almost every antibiotic available. In November 2015 scientists identified bacteria in patients and livestock in China that are resistant to Colistin, one of the last resort antibiotics used to treat infections that resist all other approaches. It is likely that resistance emerged after Colistin was overused in farm animals. Some scientists have warned that the world is on the cusp of a ‘post-antibiotic era’. If this happens medicine will be put back 100 years.
Urgent action is needed to avert the looming crisis. The pharmaceutical industry must start producing new antibiotics. In 2012 the US Congress passed an act granting an extra five years patent protection for new antibiotics introduced by the industry and also facilitating fast track Food and Drug Administration (FDA) approval of new antibiotics. These measures are helpful but not enough to get the ball rolling strongly. It has been suggested that a $2billion prize be awarded to the first five companies each year who introduce a successful new class of antibiotic. This would be cost effective given that the current annual direct medical cost of antibiotic-resistant disease in the US is $20 billion. We also need to drastically cut back on the overuse of antibiotics in the animal industry. Animal feed accounts for 80% of the antibiotics used in the USA and Irish farmers use four times more antibiotics than the Danes. And of course both doctors and patients must stop abusing antibiotics.
William Reville is an Emeritus Professor of Biochemistry at UCC http://understandingscience.ucc.ie