Top superbugs

An antimicrobial drug is one used against a microorganism – like a bacteria, a virus, a parasite, or a fungus – which causes a disease. Antimicrobial resistance – or AMR - refers to those microorganisms becoming immune to the drugs used to treat them. They are colloquially known as superbugs.

Around 700,000 people die of resistant infections every year, according to estimates from the Review on AMR, chaired by Lord Jim O’Neill and commissioned by the UK government. AMR is predicted to cause 10 million extra deaths by 2050 if no action is taken, according to O’Neill’s report.

Few new antibiotics are being developed to treat infections, and any new drug could take around 10 years to come to market. Last year, the World Health Organisation published a list of 12 families of bacteria that pose the greatest threat to human health.

These are considered the "priority pathogens", with the list designed to encourage research and development into new drugs for these bugs.

Priority 1: CRITICAL

1. Acinetobacter baumannii, carbapenem-resistant

Acinetobacter bugs are found in soil and water, but can survive on people’s skin for several days. They might live on or in a patient without causing symptoms, but can go on to cause serious and deadly lung, blood or wound infections, especially in very ill patients being treated in intensive care. The rise of this bug is worrying as it is very effective at acquiring genes from other resistant bugs which make it resistant to antibiotics.

2. Pseudomonas aeruginosa, carbapenem-resistant

This is a bug that thrives in wet or moist places, and can be deadly as it is has developed resistance to multiple classes of antibiotics. It normally is only seen in people in hospitals or with weakened immune systems – and commonly affects those with cystic fibrosis. However healthy people can develop ear and skin infections, especially if they come into contact with the bug after being exposed to contaminated water. In hospitals it can be spread on the hands of staff or on equipment that isn’t cleaned properly.

3. Enterobacteriaceae, carbapenem-resistant, ESBL-producing

ESBL-producing enterobacteriaceae are bacteria, commonly gut bacteria such as Escherichia coli and Klebsiella pneumoniae which produce an enzyme that can break down two of the main classes of antibiotics. They are increasingly causing urinary tract infections which are more difficult to treat. They can also cause serious lung and bloodstream infections, which can be fatal. Genes giving bacteria the ability to make these ESBL enzymes can be transmitted between some bacteria.

Carbapenem-resistant Enterobacteriaceae are the more dangerous cousins of ESBL-producing enterobacteraciae. They are gut bacteria which have become resistant to carbapenem antibiotics as well as cephalosporins and penicillins. Some, known as CPE, create enzymes which break down these antibiotics, rendering them useless. While many people might carry CRE bacteria harmlessly in their gut, it can become a huge problem if it spreads in hospitals where patients have compromised immune systems. If an infection occurs, doctors have few drugs left to treat it. CRE have been dubbed ‘nightmare bacteria’ by the US Center for Disease Control and Prevention as between 40 and 50 per cent of people with a bloodstream infection die, studies show.

Priority 2: HIGH

1. Enterococcus faecium, vancomycin-resistant

Enterococcus faecium are a type of bacteria that live in the itestins and on the skin, without normally causing problems. Vancomycin-resistant enterococci are a type that have developed resistance to multiple antibiotics, including vancomycin. They can cause infections anywhere in the body, most commonly in the intestines, the urinary tract and in wounds.

2. Staphylococcus aureus, methicillin-resistant, vancomycin-intermediate and resistant

These are skin infections that have become resistant to antibiotics in the penicillin family normally used to treat them. Staphylococcus aureus is found naturally on the skin and in the nose but can become deadly if it gets into the lungs or the bloodstream. Methicillin-resistant resistant Staphylococcus aureus (MRSA) is found widely both in the community and in hospitals. Good infection prevention in hospitals helps stop its spread. 

Vancomycin-intermediate (VISA) and vancomycin-resistant Staphylococcus aureus (VRSA) are forms of the bug that have become resistant to the antibiotic vancomycin, which is given to treat methicillin-resistant forms of the bacteria. It is most commonly seen in patients with underlying health conditions, those who have catheter tubes going into their body, or those with MRSA infection treated with vancomycin.

3. Helicobacter pylori, clarithromycin-resistant

Helicobacter pylori is one of the most prevalent global pathogens. It can lead to gut diseases like ulcers, lymph nodes, tumours in the lymph nodes of the stomach, and small intestine and stomach cancer. Rising resistance to clarithromycin has been documented in many countries. For example the resistance rate is as approximately 30 per cent in Japan and Italy, 50 per cent in China and 40 per cent in Turkey.

4. Campylobacter spp., fluoroquinolone-resistant

Campylobacter is the main cause of food poisoning in the UK, responsible for half a million infections, 100 deaths and 80,000 GP consultations every year. Fluoroquinolones are the antibiotics used to treat the infection. Campylobacter is caught through eating contaminated milk, water or meat, especially chicken. In the UK, three quarters of supermarket chickens are known to carry campylobacter. After the last audit, the Food Standards Agency found 5 per cent of samples of the bacteria – taken from chickens sold across the country – were resistant to many antibiotics, including fluoroquinolones.

5. Salmonellae, fluoroquinolone-resistant

Non-typhoidal salmonella is a bacteria that commonly causes food poisoning. It becomes more dangerous when it is resistant to antibiotics like fluoroquinolones.

Salmonella typhi/paratyphi is another type of salmonella bug. There is now an epidemic of drug resistant typhoid fever is the Indian subcontinent, Asia and Africa, with an estimated 10 to 30 million cases a year. It is spread through contaminated food and water.

6. Neisseria gonorrhoeae, cephalosporin-resistant, fluoroquinolone-resistant

Gonorrhea is a sexually transmitted infection which is normally treated with the antibiotic azithromycin. Now the bacteria are becoming resistant to this drug, meaning there is only one other drug, ceftriaxone (a type of cephalosporin antibiotic) which can be used to treat it. This raises the prospect of it becoming untreatable if the bacteria becomes resistant to ceftriaxone. There is an outbreak of this resistant strain in the UK, with 48 confirmed cases between November 2014 and August 2016.

Priority 3: MEDIUM

1. Streptococcus pneumoniae, penicillin-non-susceptible

Streptococcus pneumoniae causes different types of infection, including ear infections and pneumonia. It spreads through the in droplets from coughing and sneezing. Pneumoccoccal infections caused by this bacteria can be serious and potentially fatal.

Penicillin is normally used to treat such infections, but if the bug is no longer susceptible to it they can be more challenging to treat and the risk of complication is higher. However, babies, elderly people and those with impaired immune systems are given pneumococcal vaccines to protect them against this bacteria. This has led to fewer cases of infection.

2. Haemophilus influenzae, ampicillin-resistant

Haemophilus influenza is a bacteria which cause a range of infections, from mild ear infections to severe diseases, like bloodstream infections. They can invade parts of the body which are normally germ-free, like spinal fluid or blood. This can be fatal. Some of these bacteria are now resistant to ampicillin antibiotics.

3. Shigella spp., fluoroquinolone-resistant

Shigella is a highly contagious bacteria that can cause diarrhoea with blood or mucus, which is becoming resistant to antibiotics. Fluoroquinolones are bacteria normally used to treat it, but some strains have acquired resistance to these drugs. It is spread by contact with infected food or water, while travelling or between people in hospitals or care homes for long periods. It causes more than a million deaths worldwide a year, mainly in children in developing countries. In the UK, most cases are acquired in people who have travelled but it can also spread from child to child at home or in nurseries. Some species are more common among gay and bisexual men.

This is by no means an exhaustive list of superbugs. For example there are other groups which cause high numbers of infections or deaths. Two notable ones are:

Clostridium difficile

This is a superbug which occurs as a result of patients being given many courses of antibiotics or drugs over long periods of time. The drugs kill off all other bacteria in the gut, allowing the C difficile bugs to multiply and take over, causing an infection which can be lethal. Symptoms include severe diarrhoea and as the bug is resistant to antibiotics, it can be difficult to treat. Hospitals are required to report C difficile cases to the government.

Drug resistant tuberculosis

Tuberculosis is a disease caused by bacteria spread from person to person through the air. It usually affects the lungs but can also affect the brain, kidneys or spine. It is curable if treated, but the emergence of drug resistant TB is worrying as it is much harder, and more expensive, to treat. There are multi-drug-resistant TB (MD TB) which is resistant to the two most potent TB drugs. Extensively drug-resistant TB (XDR TB) describes bacteria which has become resistant to a wider range of antibiotics, meaning patients are left with less effective treatment options. Patients with XDR TB are much more likely to develop disease and have a higher risk of death.