What You Should Know About the CRE Superbug

Patient sitting on hospital bed
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CRE is Carbapenem-Resistant Enterobacteriaceae. These are bacteria that fight back and win against antibiotics. The bacteria resist and overcome the antibiotics meant to protect us. These bacteria bring us closer to the time before antibiotics.- or as we say, the post-antibiotic era that we hope will never happen.

Let's Break It Down

Carbapenems are a class of antibiotics.

This class of antibiotics is often are the last line of good defense against resistant bacteria. Doctors often reach for these antibiotics when other antibiotics don't work, frequently because of antibiotic resistance. These antibiotics are often what we call second line antibiotics. This class includes meropenem, ertapenem, imipenem, and doripenem.These antibiotics treat a lot of different types of bacteria (gram positive and negative, aerobic and anaerobic) in a lot of different parts of the body from the skin to blood to heart to genitourinary tract. As such, these antibiotics are often reserved for very serious infections when other antibiotics won't work.

Resistant bacteria are those that do not respond to antibiotics anymore. We choose antibiotics specifically for the type of infection or the specific identified cause of the infection. Sometimes the antibiotics stop working, Oftentimes because they have acquired genes that let them bypass how the bacteria interact with the antibiotic. This means the antibiotic can't harm the bacteria - or can't do so sufficiently to be effective.

Enterobacteroacae are a family of gram negative bacteria in the shape of rods. Bacteria from this family are normally found in our intestinal tracts. They are part of our normal gut flora - the microbiome. Sometimes though they can make us sick. They can cause anything from urinary tract infections to newborn meningitis to pneumonia to diarrhea to blood infections to bones.

The common bacteria from this family are Enterobacter, Escherichia, Klebsiella, Proteus, Providencia, Salmonella, Shigella, and Serratia. 

Who Gets These Infections?

CRE usually infects someone who is already in the hospital, a nursing home, or has a procedure in an outpatient clinic. Those who have any sort of foreign device or medical equipment inserted are more at risk. This means those who have a catheter for urinating, an IV line, or on a ventilator to help them breathe are at more risk. Those who take a lot of antibiotics are also at more risk.

Transmission usually occurs from the hands of healthcare workers or from medical equipment that hasn't been thoroughly disinfected between use. There was an outbreak among those who had a gastrointestinal scope that harbored the bacteria, despite the device having been cleaned and disinfected.

Normally, healthy people do not get CRE.

This means that those who get CRE are often already sick. This may help contribute to the high mortality seen, possibly as high as 50% of those infected. These infections may be resistant to almost all antibiotics.

Do Many People Get This?

Not yet in the US. The concern is that if it did begin to spread that we would not have the antibiotics to easily stop it spreading in hospitals.

Where Is It?

These Superbugs are found worldwide from India to Greece to Puerto Rico and New York City. They are less common where these drugs are very rare, such as low resource countries. There are certain hotspots around the world where infection rates have been rising.

Does Everyone Who Gets the Bug Become Sick?

No, some people are colonized. This means the bacteria lives somewhere in their body without causing infection. These bacteria can sit in the gut without causing any health problems. However, they could pass the resistance on to other bacteria in the gut and they could, in the future, cause infection, such as a urinary tract infection.

How Do the Bacteria Become Resistant?​

Sometimes mutations develop. Oftentimes, plasmids, which contain bits of genetic material, pass the resistance from one bacteria to another.

Are There Different Types?​

There are multiple types. Doctors know of Klebsiella pneumoniae carbapenemase (KPC), New Delhi metallo-β-lactamase (NDM), Verona integron encoded metallo-β-lactamase (VIM), imipenemase metallo-β-lactamase (IMP), and oxacillinase-48 (OXA-48).

In the US, KPC is most common. It makes the cell wall not as easily passed through.

More worrisome have been the carbapenemase producing strains (KPC, NDM, VIM, IMP, andOXA- 48). These have begun to spread more worldwide.

How Is This Different From Other Superbugs?​

These bacteria are a specific type of bacteria called gram negative bacteria. This makes CRE different from many other Superbugs like MRSA and VRE, which are gram positive bacteria. Gram positive bacteria respond to different antibiotics that might not treat gram negative infections. There are some antibiotics that can treat both.

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