CDC: Deadly superbugs pose greater threat than previously estimated

Drug-resistant germs and related infections sicken about 3 million people and kill about 48,000 every year in the United States, according to a new report from the Centers for Disease Control and Prevention. The new estimates show that previous figures missed about half of the illnesses and deaths.

That means, on average, someone in the United States gets an antibiotic-resistant infection about every 10 seconds and someone dies about every 11 minutes.

The long-awaited report, released Wednesday, establishes a new national baseline of infections and deaths from bacteria and fungi that have developed the ability to defeat drugs designed to kill them. Scientists, doctors and public health officials have increasingly warned that antibiotic resistance is one of the gravest public health threats of our time.

The new numbers, though still conservative, underscore the magnitude of the problem and will help prioritize resources to address the most pressing threats, infectious disease experts said. These germs spread through people, animals and the environment.

The report details the toll that 18 pathogens are taking on humans, ranking the threat of each as "urgent," "serious," or "concerning."

Five germs account for the most urgent threats. Three are long-recognized dangers: Clostridioides difficile (C. diff.), drug-resistant gonorrhea, and Carbapenem-resistant Enterobacteriaceae (CRE), also known as "nightmare bacteria" because they pose a triple threat. They are resistant to all or nearly all antibiotics; they kill up to half of patients who get bloodstream infections from them; and the bacteria can transfer their antibiotic resistance to other related bacteria, potentially making the other bacteria untreatable.

Two new ones were added to the urgent category since the CDC's first report in 2013: a deadly superbug yeast that has alarmed health officials around the world and a family of bacteria that has developed resistance to nearly all antibiotics.

For the first time, the CDC also added a new category to the ones used to classify the 18 pathogens: a watch list of three germs that officials are monitoring because they have the potential to spread resistance widely or are not well-understood in the United States.

Prevention efforts in recent years have reduced the number of infections and deaths in some health-care settings, CDC officials said. Superbug deaths in hospitals decreased by nearly 30% from 2012 to 2017.

But the report cites two worrisome trends: the increasing numbers of resistant infections in the community, including highly drug-resistant gonorrhea, and the growing ability of drug-resistant microbes to share their dangerous resistance genes with other kinds of bacteria, making those other germs untreatable as well.

Antibiotic resistance is particularly deadly for patients in hospitals and nursing homes, and for those with weak immune systems. But these hard-to-treat infections now threaten people undergoing common modern surgeries and therapies, such as knee replacements, organ transplants and cancer treatments.

Helen Boucher, chief of infectious diseases at Tufts University Medical Center, cares for many transplant patients who are vulnerable to these infections.

"But we also see people from everyday life, who are young and otherwise healthy, who get a MRSA infection on their skin," she said, referring to methicillin-resistant Staphylococcus aureus, which the CDC lists as a serious threat.

If a young and otherwise healthy woman gets a urinary tract infection from another type of bacteria listed as a serious threat, ESBL-enterobacteriaceae, "all we can offer is an intravenous antibiotic for 10 to 14 days" because clinicians no longer have other effective treatments, Boucher said. The intravenous antibiotic can be administered at home. But it requires a catheter to be inserted into a vein, a procedure that also poses an infection risk, she said.

"We want to have diagnostic tools and medical treatments for problems we know we're going to have," she said. "But we also need to prepare for the kind of resistance that we could never predict. We know from history that bacteria and mother nature are smarter than we are."

The CDC report estimates that bacterial and fungal infections that are directly resistant to the drugs that once controlled them cause more than 2.8 million infections and 35,000 deaths each year. Another bacterium closely linked to antibiotic use is C. diff., which can thrive when antibiotics kill beneficial bacteria in the digestive system that normally keep it under control, and then can cause deadly diarrhea. When the C. diff illnesses and deaths are added, the annual U.S. toll of all these pathogens is more than 3 million infections and 48,000 deaths.

The CDC had previously estimated about 2 million infections and 23,000 deaths in a 2013 report. The new report used previously unavailable data, including electronic health databases from more than 700 acute-care hospitals. By using the new methods, the CDC calculated that the 2013 data undercounted the problem by about half.

It's difficult to estimate the number of drug-resistant infections because no comprehensive surveillance system or database exists. Antibiotic resistance also isn't a single disease.

Other estimates place the true burden of these infections as much higher. Researchers at the Washington University school of medicine have estimated the death toll at about 153,000 annually.

Jason Burnham, an infectious-disease expert at Washington University who led the research, said he and colleagues included more pathogens and a broader definition of drug resistance in their analysis than the CDC.

Bacteria are constantly evolving to fend off the drugs used to kill them. As they mutate, some develop the ability to fight off antibiotics and survive to multiply and spread resistance. The more antibiotics are used, in health-care and agriculture, the less effective they become.

Overuse of antibiotics is a likely reason for the dramatic rise in resistant infections, the report said. Nearly a third of antibiotics prescribed in doctors' offices, emergency rooms and hospital-based clinics in the United States are not needed, according to a 2016 study. Most of them were prescribed for conditions that don't respond to antibiotics, such as colds, sore throats, flu and other viral illnesses.

Among the report's other findings:

- Drug-resistant gonorrhea infections have surged. More than half a million such infections occur each year, twice as many as reported in 2013. Their increase could be an unintended consequence of the success of PrEP, the once-a-day pill that protects users against HIV infection, which may make people less vigilant about using condoms.

"People may feel very confident that they're not going to get HIV using PrEP, but that is not going to protect you from bacterial illnesses," said Michael Craig, CDC's senior adviser on antibiotic resistance.

Gonorrhea has quickly developed resistance to all but one class of antibiotics; half of all infections are resistant to at least one antibiotic. Untreated gonorrhea can cause serious and permanent health problems, including ectopic pregnancy and infertility.

- ESBL-producing Enterobacteriaceae are one of the leading causes of death from resistant germs. They often cause infections in otherwise healthy people. The CDC estimates that there were 197,400 cases in hospitalized patients in 2017, including 9,100 deaths.

- Erythromycin-resistant group A Streptococcus infections have quadrupled since the 2013 report. Currently, strep throat is not resistant to common first-line antibiotics such as penicillin or amoxicillin. But doctors often use erythromycin and azithromycin to treat the condition, especially for people allergic to penicillin. More than 1 in 5 invasive strep infections are caused by resistant strains, limiting treatment options for patients.

- One of the two new urgent threats is carbapenem-resistant Acinetobacter. The bacteria, which can cause pneumonia and/or bloodstream- and urinary-tract infections, are already resistant to many antibiotics, and frequently contaminate health-care facility surfaces and medical equipment. But the CDC moved these germs from serious to urgent threats because they have developed resistance to the most powerful antibiotics. They also carry mobile genetic elements that can spread resistance to other germs.

- The other new urgent threat is Candida auris, a fungus that can cause life-threatening infections if it gets into the bloodstream. It spreads easily between hospitalized patients and nursing home residents. It is often resistant to all the major antifungal drugs.

When the CDC issued its first report on drug-resistant infections, there was no mention of C. auris because the newly discovered germ only began spreading in the United States in 2015.

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