Deadly, Drug-Resistant ‘Superbugs’ Pose Huge Threat, W.H.O. Says

Acinetobacter baumannii, a group of drug-resistant bacteria commonly found in soil and water. The W.H.O. rated research on this and two other pathogens as “critical priority.” Credit Todd Parker/Center for Disease Control

The World Health Organization warned on Monday that a dozen antibiotic-resistant “superbugs” pose an enormous threat to human health, and urged hospital infection-control experts and pharmaceutical researchers to focus on fighting the most dangerous pathogens first.

The rate at which new strains of drug-resistant bacteria have emerged in recent years — prompted by overuse of antibiotics in humans and livestock — terrifies public health experts. Many consider the new strains just as dangerous as emerging viruses like Zika or Ebola.

“We are fast running out of treatment options,” said Dr. Marie-Paule Kieny, the W.H.O. assistant director general who released the list. “If we leave it to market forces alone, the new antibiotics we most urgently need are not going to be developed in time.”

Britain’s chief medical officer, Sally C. Davies, has described drug-resistant pathogens as a national security threat equivalent to terrorism, and Dr. Thomas R. Frieden, the recently retired director of the Centers for Disease Control and Prevention, called them “one of our most serious health threats.”

Last week, the European Food Safety Authority and European Center for Disease Prevention and Control estimated that superbugs kill 25,000 Europeans each year; the C.D.C. has estimated that they kill at least 23,000 Americans a year. (For comparison, about 38,000 Americans die in car crashes yearly.)

The W.H.O. report rated research on three pathogens as “critical priority.” They are carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa, along with all members of the Enterobacteriaceae family resistant to both carbapenems and third-generation cephalosporins.

(The Enterobacteriaceae family includes familiar names like E. coli and salmonella, which live in human and animal guts and can cause food poisoning, and Yersinia pestis, which causes bubonic plague. Carbapenems and cephalosporins are each “families” of related antibiotics; both break down bacterial cell walls.)

The W.H.O.’s third category was “medium priority,” which included drug-resistant versions of Streptococcus pneumoniae, Haemophilus influenzae and shigella, all three of which cause common childhood infections. For now, most of those infections are curable, but doctors fear that resistant strains will push out weaker ones.

The C.D.C. released a similar report in 2013, ranking 18 drug-resistant bacteria and fungi in three categories: urgent, serious and concerning.

W.H.O.’s Priority Pathogens List

Bacteria listed by the World Health Organization, and the antibiotics to which they are resistant.

  • Priority 1: Critical

  • Acinetobacter baumannii; carbapenem
  • Pseudomonas aeruginosa; carbapenem
  • Enterobacteriaceae; carbapenem
  • Priority 2: High

  • Enterococcus faecium; vancomycin
  • Staphylococcus aureus; methicillin and vancomycin
  • Helicobacter pylori; clarithromycin
  • Campylobacter spp.; fluoroquinolone
  • Salmonellae; fluoroquinolone
  • Neisseria gonorrhoeae; cephalosporin and fluoroquinolone
  • Priority 3: Medium

  • Streptococcus pneumoniae; penicillin-non-susceptible
  • Haemophilus influenzae; ampicillin
  • Shigella spp.; fluoroquinolone

The two lists have some differences, noted Jean B. Patel, a C.D.C. specialist in drug-resistant bacteria who consulted with the W.H.O. For example, N. gonorrhoeae was a higher priority on the C.D.C. list because it is hard to treat, even though it rarely kills; the W.H.O. list focused more on fatal infections.

It’s useful for the W.H.O. to set global research priorities because drug-resistant strains are not evenly spread around the world. Some strains are more common on some continents, although jet travel and medical tourism are making most spread worldwide.

Strains can even vary within hospitals.

For example, the antibiotics used in a transplant unit often differ from those used in neonatal intensive care, so different resistant bacteria may circulate, said Dr. William Schaffner, head of preventive medicine at Vanderbilt University Medical Center.

Resistance to carbapenems, which had been reliable “last line of defense” drugs, has developed recently among pathogens, as a gene first found in India in 2008 — and named NDM for “New Delhi metallo-beta-lactamase” — spread around the world.

The latest last-ditch antibiotic to start failing is colistin, which was invented in 1959 but shelved because it caused kidney damage. Chinese pig farmers adopted it and feed nearly 12,000 tons to their pigs each year to speed their growth.

Drug-resistant strains were first found in China in 2015, with a disturbing aspect: the resistance-conferring gene was not in the bacteria’s own DNA but on a plasmid, a small DNA ring that can jump from one bacterial species to another. The Chinese study found it in 21 percent of pigs sampled, and 1 percent of hospitalized humans. The first American patient with it was found last year.

The W.H.O. list, Dr. Patel said, will also help a project the W.H.O. began in 2015, the Global Antimicrobial Resistance Surveillance System, which seeks to standardize all countries’ efforts to detect resistance and keep records to see how they spread.

“We’re at a tipping point,” Dr. Patel said. “We can take action and turn the tide — or lose the drugs we have.”

Source: NYTimes