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article imageDirty dozen: The 12 most dangerous bacteria

By Tim Sandle     Mar 1, 2017 in Health
The World Health Organization (WHO) has named the top dozen of bacteria that pose the greatest risk to humanity. The United Nations health agency also warns that medics are running out of options to treat the diseases.
This week WHO held a press conference where the world’s most dangerous bacteria were presented. Given there are twelve in all the term ‘dirty dozen’, Medical Express reports, was adopted by some of the science journalists who were present.
Placed at the number one position is Acinetobacter baumannii. These organisms can cause a diseases ranging from pneumonia to blood or wound infections. A. baumanii an opportunistic pathogen in humans, affecting people with compromised immune systems, and is becoming increasingly important as a hospital-derived infection. The main risk is with the production of a toxin. When Acinetobacter infections occur, they typically involve organ systems that have a high fluid content (such as the respiratory tract, peritoneal fluid, or the urinary tract).
The other organisms are:
Critical risk
Pseudomonas aeruginosa, carbapenem-resistant
Enterobacteriaceae, carbapenem-resistant, 3rd generation cephalosporin-resistant
High risk
Enterococcus faecium, vancomycin-resistant
Staphylococcus aureus, methicillin-resistant, vancomycin intermediate and resistant
Helicobacter pylori, clarithromycin-resistant
Campylobacter, fluoroquinolone-resistant
Salmonella spp., fluoroquinolone-resistant
Neisseria gonorrhoeae, 3 rd generation cephalosporin-resistant, fluoroquinolone-resistant
Medium risk
Streptococcus pneumoniae, penicillin-non-susceptible
Haemophilus influenzae, ampicillin-resistant
Shigella spp., fluoroquinolone-resistant
Commenting on the list, Professor Evelina Tacconelli, executive committee member of the European Society of Clinical Microbiology and Infectious Diseases said: “This report marks a major step forward in identifying which bacteria pose the greatest risk for patient care because of a lack of effective treatments. We hope that it will drive governments and research groups working in antibiotic development to set the right research priorities that will reduce the burden of antibiotic-resistant infections globally.”
Interestingly the bacterium responsible for causing tuberculosis is not on the list. This is despite a global rise in incidences. For instance, in 2016 the number of tuberculosis cases in the U.S. rose last year for the first time in nearly a quarter-century, the Centers for Disease Control and Prevention has reported.
The reason why some of the bacteria are troubling is not so much with the inherent pathogenicity but because they have developed antibacterial resistance. This pose concerns for the elderly, the very young and for those with weakened immune systems. As the website Pharmaceutical Microbiology reported, without effective antibiotics, human society will no longer be able to conduct the types of medical procedures that can lead to immunosuppression. Such therapies include those for cancer treatments or to address autoimmune disorders. Those at greatest risk are in hospitals, nursing homes and with patients who need ventilators or catheters.
While some microorganisms are naturally resistant to certain antimicrobials, many develop resistance as a result of changes in microbial genes (a spontaneous or induced genetic mutation). In some cases, the genes causing resistance can be also be transferred between different strains of microorganism (what is termed either horizontal gene transfer via conjugation, transduction, or transformation).
In a telling rebuke to the pharmaceutical industry, WHO senior scientist Marie-Paule Kieny stated that of the development of new antibiotics and antimicrobial was left simply to market forces then "the new antibiotics we most urgently need are not going to be developed in time." This is because of the relatively low return on investment and the amount of profit that drugs companies can extract. Instead, investment and support from academia and governments is required. The typical timeline for the development of a new antimicrobial is around ten years.
As an example of a successful collaboration, WHO is working with the University of Tubingen in Germany to develop new candidate antimicrobials. Some of these organisms have developed resistance to the so-termed antimicrobials of last resort, such as colistin. These drugs in themselves carry side-effects that are unpleasant to many patients.
In discussing the issues of antimicrobial resistance further, WHO has issued a new report laying out the challenges for the fight against drug-resistant bacteria.
More about Bacteria, Pathogens, Infection, Patient, Hospital