.Millions of people die every year from bacterial infections, even after using antibiotics. This is because the drugs are often no longer effective as the bacteria have become more resistant. According to estimates by the World Health Organization (WHO), antibiotic resistance in bacteria caused approximately 1.27 million deaths worldwide in 2019.

The difference between antibiotic resistance and antimicrobial resistance

Today we are focusing on the resistance of bacteria to antibiotics, on the occasion of the awareness week on the subject that has been declared by the World Health Organization since Monday, November 18. In contrast, the term antimicrobial resistance (AMR) refers to all types of microorganisms – bacteria, parasites, viruses and fungi – that have adapted to become resistant to conventional treatments.

The problem is that the existing drugs are less effective if not at all. Alternative solutions often do not exist, making even some conditions that are basically treatable, such as urinary tract infections, fatal.

How are bacteria rated as ‘dangerous’?

The WHO classifies bacteria based on various criteria:

Mortality rates
Incidence (number of infections)
Health burden
Evolution of resilience
Contagiousness
Possibility of prevention
Treatment options
Development course of new drugs

The bacteria are scored based on the above criteria and then ranked in an order of danger. The WHO 2024 list includes 24 bacteria, with 8 of them standing out.

1. Klebsiella pneumoniae (Klebsiella pneumoniae)
Klebsiella species are found in the intestine and human feces. Klebsiella pneumoniae causes pneumonia, sepsis and infections after injuries. If it gets into the nervous system, it can cause meningitis. In hospitals, it can develop into a superbug that is multiresistant, rendering antibiotic treatments ineffective. It is also resistant to the carbapenem “family” of antibiotics, which are used when all other treatments fail.

2. Enterohemorrhagic colibacter (Escherichia coli – E. coli)
Like Klebsiella bacteria, E. coli is commonly found in the gut of humans and animals as well as in the environment, food and water. Although most species of E. coli are harmless, some cause diarrhea, urinary tract infections, pneumonia, and sepsis. E. coli is resistant to third-generation cephalosporins and carbapenems.

3. The bacterium Acinetobacter baumannii
Acinetobacter baumannii is probably the most important Acinetobacter species and is associated with hospital-acquired infections, especially in immunocompromised patients. It is also resistant to carbapenems.

4. Mycobacterium tuberculosis (Mycobacterium tuberculosis)
Mycobacterium tuberculosis causes tuberculosis (TB), a potentially fatal bacterial infection of the lungs. Some strains are multiresistant. In 2023, tuberculosis caused 1.25 million deaths, making it one of the leading causes of death from infections.

5. Salmonella serotype Typhi (Salmonella Typhi)
Salmonella Typhi causes typhus, a serious disease that affects areas with poor sanitary conditions. It is resistant to fluoroquinolone antibiotic drugs.

6. Shigella
Shigella bacteria cause diarrhea, abdominal pain, and fever. They are transmitted through contaminated food, water or sexually and are also resistant to fluoroquinolone antibiotics.

7. Enterococcus faecium
It lives in the microbial flora of the gut but can cause serious infections, such as urinary tract infections or kidney failure – especially in diabetics. The bacterium is resistant to vancomycin.

8. Pseudomonas aeruginosa
It causes blood, lung and urinary tract infections, often after surgery. It is multiresistant, even to carbapenems.

Edited by: Chrysa Vachtsevanu