The bugs include strains of bacteria that can trigger life-threatening illnesses, including sepsis, meningitis and cellulitis, and are "extremely" drug resistant.
An increase in deaths
Certain strains of Klebsiella pneumoniae are resistant to a type of antibiotic known as carbapenems. These drugs represent the last line of defence in treating infections.
Once the bug develops a resistance and antibiotics stop working against the bacteria, there are few options left for doctors, with the elderly and people with weak immune systems at greatest risk.
Deaths from carbapenem-resistant K. pneumoniae have increased six-fold from 341 in Europe in 2007, to 2,094 by 2015.
Scientists from the Wellcome Sanger Institute and the University of Freiburg analysed more than 2,000 samples of K. pneumoniae from patients in 244 hospitals across 32 countries.
The study, published in the scientific journal Nature Microbiology, found that a small number of genes can cause resistance to carbapenem antibiotics. These genes produce enzymes which effectively 'chew up' the antibiotics, rendering them useless, scientists discovered.
Scientists warned the heavy use of antibiotics in hospitals encourages these highly-resistant bacteria to spread.
Dr Sophia David, first author of the study, said, "The 'One Health' approach to antibiotic resistance focuses on the spread of pathogens through humans, animals and the environment, including hospitals.
"But in the case of carbapenem-resistant Klebsiella pneumoniae, our findings imply hospitals are the key facilitator of transmission.
"Over half of the samples carrying a carbapenemase gene were closely related to others collected from the same hospital, suggesting that the bacteria are spreading from person-to-person primarily within hospitals."
Scientists also found the antibiotic-resistant bacteria samples were also much more likely to be closely related to samples from a different hospital in the same country, rather than across countries.
This suggests that national healthcare systems play an important role in the spread of the potentially life-threatening bugs. The study argues that more effective infection control in hospitals could help to prevent the spread of the bug.
The scientists recommended reviewing how patients move between hospitals and hygiene interventions could make a big difference.
Professor Hajo Grundmann, co-lead author of the study, said, "We are optimistic that with good hospital hygiene, which includes early identification and isolation of patients carrying these bacteria, we can not only delay the spread of these pathogens, but also successfully control them.
"This research emphasises the importance of infection control and ongoing genomic surveillance of antibiotic-resistant bacteria to ensure we detect new resistant strains early and act to combat the spread of antibiotic resistance.”