The 12 Deadliest Drug-Resistant Bacteria Have Officially Been Ranked

Know your enemy.

In the face of rising antibiotic resistance, the World Health Organisation (WHO) has published its first ever list of the deadliest superbugs that threaten human health.

This so-called dirty dozen encompasses 12 families of dangerous bacteria that have developed resistance to the drugs used to treat common infections. Antibiotic-resistance costs some 700,000 lives each year, and if the phenomenon can't be halted, experts predict that the number could grow to 10 million deaths annually by 2050.

"Antibiotic resistance is growing, and we are fast running out of treatment options," says the WHO's assistant director-general for health systems and innovation, Marie-Paule Kieny.

"If we leave it to market forces alone, the new antibiotics we most urgently need are not going to be developed in time."

The list is divided into three urgency categories – critical, high, and medium – representing how badly we need new antibiotics to treat their respective superbugs.

The "critical" section includes three bacteria – Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacteriaceae – which are all resistant to multiple drugs, and can cause a range of serious infections, including pneumonia and blood infections.

These species are all examples of what's called gram-negative bacteria – bugs that usually live in the gut that have developed two cellular membranes, making it harder for drug molecules to penetrate them.

"So if you can't get the molecule in, it can't act and kill the bacteria," antibiotics researcher Carolyn Shore from Pew Charitable Trusts explained to Kelly Crowe at CBC News.

The nine other pathogens making up the high and medium urgency categories are bacteria that cause more common diseases – such as gonorrhoea and food poisoning – but which can also be deadly, and are increasingly resistant to drugs.

These include methicillin-resistant Staphylococcus aureus (MRSA), Salmonellae, and Haemophilus influenzae.

The list is a grave acknowledgement by the WHO that current pharmaceutical research efforts to curb antibiotic resistance aren't doing enough to curb the risks posed by these superbugs.

The list "is not meant to scare people about new superbugs, but to signal to researchers and pharmaceutical companies what their priorities should be", Kieny told media at a press conference in Geneva, Switzerland on Monday.

According to Kieny, one of the problems with producing new antibiotics is they don't make a lot of profit for pharmaceutical companies,which lowers the incentive to make them.

While antibiotics require a huge amount in terms of research and development costs, they are only taken by patients for a short time, meaning only a small volume is sold.

One solution could be to alter how companies and research institutions are financially rewarded for developing new antibiotics, rather than just generating their profits through products sales.

But for such a system to work, it will take a lot of cooperation from governments around the world.

"This is not a problem that we can solve at a national level, and it is one in which low- and middle-income countries are linked to high-income ones," antimicrobial specialist Petra Gastmeier from Charité University in Germany told Science.

Here's hoping the new list provided by the WHO can help nations focus on the right ways to combat these deadly pathogens.

With Kieny estimating new drugs could still be a decade away, the earlier we address this, the better.

The WHO list appears below:

WHO priority pathogens list for R&D of new antibiotics

Priority 1: CRITICAL

1. Acinetobacter baumannii, carbapenem-resistant

2. Pseudomonas aeruginosa, carbapenem-resistant

3. Enterobacteriaceae, carbapenem-resistant, ESBL-producing

Priority 2: HIGH

1. Enterococcus faecium, vancomycin-resistant

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

3. Helicobacter pylori, clarithromycin-resistant

4. Campylobacter spp., fluoroquinolone-resistant

5. Salmonellae, fluoroquinolone-resistant

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

Priority 3: MEDIUM

1. Streptococcus pneumoniae, penicillin-non-susceptible

2. Haemophilus influenzae, ampicillin-resistant

3. Shigella spp., fluoroquinolone-resistant

The full report is available on the WHO's website.



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