World's most threatening superbugs ranked in new list

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Shown here are two mustard-colored, rod-shaped carbapenem-resistant Klebsiella pneumonias bacteria, part of the family of germs known as Enterobacteriaceae.

The World Health Organization has issued a list of the top dozen bacteria most unsafe to humans, warning that doctors are fast running out of treatment options. "With this list we are also asking governments to commit funds to R&D to address antibiotic resistance now in order to reduce the amount of resources that they will need to spend later when resistance to antibiotics develops into an even bigger crisis". The WHO hopes the specificity of the new list can help drug makers and medical researchers home in on the most dire threats.

The top three are all gram-negative bacteria that are resistant to multiple drugs. "If we leave it to market forces alone, the new antibiotics we most urgently need are not going to be developed in time", said Dr. Marie-Paule Kieny, the WHO's assistant director-general for health systems and innovation. "It's meant to signal research and development priorities to address urgent public health threats". While these pathogens are not widespread, "the burden for society is now alarming", she said. In September 2013, the US Centers for Disease Control and Prevention (CDC) named carbapenem-resistant Enterobacteriaceae (CRE) and other multidrug-resistant bacteria "urgent" public-health threats. In some instances, it kills up to 50 percent of patients who become infected.

"Improved diagnostics - ones that are fast, easy to use in field settings, and that can determine what infections are bacterial, identify what bacteria they are, and assess whether they are resistant to certain drugs - are crucial to reducing inappropriate antibiotic use in the first place", according to the MSF statement. This group includes Streptococcus pneumoniae that is not susceptible to penicillin. Also listed is Pseudomonas aeruginosa, which can be spread on the hands of health-care workers or by equipment that gets contaminated and is not properly cleaned.

The second and third tiers contain drug-resistant bacteria that cause "more common" diseases such as gonorrhoea and salmonella-induced food poisoning, said the WHO.

The "priority pathogens" list has three rankings - critical, high and medium - according to how urgently new antibiotics are needed.

Drug companies have also tended to focus more on gram-positive bacteria that tend to colonize the skin of healthy individuals and generate less resistance, said Evelina Tacconelli, who heads the infectious diseases division at the University of Tübingen in Germany, which helped develop the World Health Organization list.

Antibiotics are one of the most important discoveries in human history. And there aren't enough drugs in the pipeline to meet future needs, Allan Coukell, senior director of health programs at Pew, said Monday.

Governments should put in place policies to boost public and private funding for drug research and development against the listed microbes, the World Health Organization said in a statement.

Those under the high priority category include less hardy but still risky bacteria like Staphylococcus aureus strains that are resistant to common antibiotics as well as vancomycin, a last-resort drug for staph; Salmonella strains that are resistant to fluoroquinolones and cause food poisoning; and Helicobacter pylori strains that are resistant to the first line drug clarithromycin and often cause chronic ulcers.