What Is CRE?

Carbapenem-resistant Enterobacteriaceae are superbugs resistant to most antibiotics.

Carbapenem-resistant Enterobacteriaceae, or CRE, are a family of "superbug" bacteria.

They are highly resistant to virtually all antibiotics — including carbapenems — and very difficult to treat.

Carbapenems are a class of antibiotics that includes imipenem, meropenem, ertapenem, and doripenem, which are considered "antibiotics of last resort."

They are typically reserved for treating very serious infections, especially those caused by bacteria that are highly resistant to other antibiotics.

But in recent years, some bacteria have also become resistant to carbapenems.

These bacteria develop certain enzymes — such as Klebsiella pneumoniae carbapenemase (KPC), New Delhi metallo-β-lactamase (NDM), and Verona integron-mediated metallo-β-lactamase (VIM) — that break down carbapenems and render the antibiotics ineffective.

Types and Prevalence of CRE

The two most common types of CRE in the United States are carbapenem-resistant Klebsiella bacteria and carbapenem-resistant Escherichia coli (E. coli), according to the CDC.

Klebsiella bacteria and E. coli normally live in the intestines, where they don't cause illness.

If these microbes get into other areas of the body, however, they can cause various diseases, such as urinary tract infections (UTI), pneumonia, meningitis, and deadly bloodstream infections.

Certain strains of E. coli that normally live in cattle can also cause intestinal infections in people.

Each year in the United States, carbapenem-resistant Klebsiella bacteria cause an estimated 7,900 infections and 520 deaths, while carbapenem-resistant E. coli causes an estimated 1,400 infections and 90 deaths, according to the CDC.

Together, these hardy bacteria cause about 6 percent of the estimated 140,000 Enterobacteriaceae infections that occur each year in healthcare settings in the United States.

'Phantom Menace' CRE

In December 2015, the Centers for Disease Control and Prevention (CDC) reported that an unusually virulent strain of CRE had appeared in 19 U.S. states during the period from June 2010 to August 2015.

This strain of CRE — dubbed "The Phantom Menace" by some researchers — is of particular concern not only because it can break down antibiotics and render them useless against infections, but also because it can transfer this ability to other bacteria (such as E. coli), rendering them antibiotic-resistant.

CRE superbugs that have this ability "are of greatest public health concern because of their potential for rapid global dissemination," according to the CDC.

Who Gets CRE?

Carbapenem-resistant Enterobacteriaceae infections are typically contracted in a healthcare setting, such as a hospital or clinic.

Doctors refer to these healthcare-setting infections as "nosocomial" infections.

During the first half of 2012, about 4 percent of short-stay hospitals and 18 percent of long-term acute care hospitals in the United States had at least one patient with a serious CRE infection, according to the CDC.

The infections usually don't affect healthy people, and primarily affect people with a weakened immune system who are undergoing an invasive procedure or treatment.

The bacteria are spread through contact with wounds or fecal matter, and can find their way into the body via contaminated medical devices, such as:

• Ventilators
• Intravenous (IV) catheters
• Urinary catheters
• Endoscopes (tube-like devices that let doctors view the inside of the body)

Treatment of CRE

Many people may be "colonized" with CRE, meaning that the bacteria live in their bodies, but they don't show signs of infection or require treatment.

When a true CRE infection occurs, a few antibiotics may still help rid the body of the bacteria.

According to a February 2013 report in the journal Diagnostic Microbiology & Infectious Disease, these antibiotics include:

• Aminoglycosides
• Polymyxins
• Tigecycline
• Fosfomycin
• Temocillin

Almost half of all CRE bloodstream infections end in death, according to the CDC.

Research suggests that a combination of antibiotics is the most effective treatment for these infections, according to the 2013 report.