Now, the WHO has come up with a list of antibiotic-resistant "priority pathogens" - 12 families of bacteria that pose the greatest threat to human health.
Medical research charity the Wellcome Trust said that the list was important to steer research into new antibiotics.
The bacteria on this list can cause severe and often deadly infections such as bloodstream infections and pneumonia and the most critical group includes multi-drug-resistant bacteria that pose a particular threat in hospitals and nursing homes.
Other increasingly drug-resistant bacteria, which are deemed "high" and "medium" priority, cause more common diseases such as gonorrhoea and food poisoning - caused by salmonella.
"Antibiotic resistance is growing and we are fast running out of treatment options," said Dr Marie-Paule Kieny, WHO's assistant director-general for health systems and innovation.
If we leave it to market forces alone, the new antibiotics we most urgently need are not going to be developed in time.
The WHO said that it hoped the list would spur governments to put in place policies to incentivise the development of new drugs.
Experts came up with the list by examining a number of criteria, including how deadly the infections the bacteria cause are and whether new antibiotics to treat them are already in the pipeline.
Commenting on the publication of the list, Tim Jinks, head of drug resistant infections at Wellcome Trust, said: "This priority pathogens list, developed with input from across our community, is important to steer research in the race against drug-resistant infection - one of the greatest threats to modern health.
"Without effective drugs, doctors cannot treat patients.
"Within a generation, without new antibiotics, deaths from drug-resistant infection could reach 10 million a year.
"Without new medicines to treat deadly infection, life-saving treatments like chemotherapy and organ transplant, and routine operations like caesareans and hip replacements will be potentially fatal.
"Wellcome is committed to helping tackle this growing problem, guided by WHO priorities."
The WHO bacteria list
Broken down according to the urgency of need for new antibiotics
Priority 1: Critical
1: Acinetobacter baumannii, carbapenem-resistant
2: Pseudomonas aeruginosa, carbapenem-resistant
3: Enterobacteriaceae, carbapenem-resistant, ESBL-producing
Priority 2: High
4: Enterococcus faecium, vancomycin-resistant
5: Staphylococcus aureus, methicillin-resistant, vancomycin-intermediate and resistant
6: Helicobacter pylori, clarithromycin-resistant
7: Campylobacter spp, fluoroquinolone-resistant
8: Salmonellae, fluoroquinolone-resistant
9: Neisseria gonorrhoeae, cephalosporin-resistant, fluoroquinolone-resistant
Priority 3: Medium
10: Streptococcus pneumoniae, penicillin-non-susceptible
11: Haemophilus influenzae, ampicillin-resistant
12: Shigella spp, fluoroquinolone-resistant