Those darn pesky plasmids (commentary)Those darn pesky plasmids (commentary)
January 2, 2016
Plasmid: “n. a genetic element which replicates in the cells independently of the chromosomes….” (Source: World Book Dictionary)
They are a lot more than pesky, they are scary dangerous when talking about antibiotic resistance and they are creating true superbugs that kill.
For clarity and consistency, people do not develop resistance to antibiotics. Germs do.
They can do this in a couple of ways.
The first and probably most common is simple exposure to an antibiotic and going through an evolution of their genome in ways that deactivate antibiotics.
Some bacteria are very efficient at doing this, such as Staph aureus. The right dose for the right germ for the right length of time makes no difference to these bacteria. MRSA did not come about because of overprescribing physicians.
Others, like Streptococcus pneumonia, are not nearly as efficient in developing resistance, but if the wrong dose is given, or the length of therapy is too short, we are helping Strep in its quest to become resistant.
We also expose bacteria to antibiotics when they are not making us sick, such as taking an antibiotic for the common cold.
Many of us carry Staph aureus in our nasal cavities. That penicillin you took for your cold exposed that bacteria to the antibiotic and in turn in may now be a methicillin resistant strain of Staph aureus just waiting for an opportunity to invade your blood stream.
The CDC says 50% of antibiotics prescribed in outpatient settings in the U.S. are done so inappropriately and are unnecessary. That is a lot of unnecessary exposure for any bacteria sitting quietly in our bodies.
The CDC has even mapped out the frequency of prescribing of antibiotics done by primary care physicians by state.
West Virginia has the highest rate of antibiotic prescription writing, with an average of 1.24 prescriptions per person, compared to about half that rate for people living in Alaska.
People in the South, including the states of Louisiana, Mississippi and Arkansas, are almost twice as likely to receive a prescription as a patient living on the West Coast.
The other way bacteria can develop resistance is by sharing, sharing their plasmids. They get infected with a plasmid carrying the resistance gene.
A plasmid can make copies of itself and transfer within a family of bugs or even jump to another family of bacteria.
Bacteria then are resistant to certain antibiotics without having to develop the resistance through exposure and evolution, a so called “short cut.”
This is what appears to be going on in a family of killer bacteria knows as CRE.
CRE stands for carbapenem-resistant Enterobacteriaceae. (See why we call them CREs?)
These are really bad actors.
They are called “Killer Bacteria” for a good reason.
Carbapenem is often the drug of last resort.
You get infected with CRE and you have about a 50-50 chance of living.
“We are holding onto our last antibiotics by a thread”, CDC Director Tom Frieden has said.
I don’t want to be hanging on by a thread if I am infected.
This is not about overprescribing of antibiotics in either the human world or the animal world. This is about plasmid transfers of bacteria that normally reside in our gut and cause no problems.
This is about Klebsiella species and Escherichia coli (E. coli) which are two common examples of Enterobacteriaceae.
CRE infections are not common in healthy individuals, but exceptions do happen.
During calendar year 2013, there were 35 cases of CRE from one Illinois hospital. All cases had an upper GI endoscopy, a procedure done to take a closer look at the stomach lining, pyloric sphincter and upper duodenum among other things.
Generally no incision or cutting, maybe just a little stretching of a tight opening, but all in all not procedure that one links to becoming infected with a superbug.
The most recent occurrence of CRE linked to an upper GI endoscopy that I am aware of occurred in UCLA’s Ronald Reagan Medical Center last summer. Seven were infected, 2 died.
Recently Chinese and British researchers reported finding E. coli with plasmid mediated resistance to Colistin, another drug of last resort.
These superbugs were found in pigs, raw pork and humans.
People, animals and food. Not a good combination when one understands how mobile these plasmids can be.
CRE is truly a top public health threat in the U.S. and the world in general.
We need a frontal, all-out assault to combat these killers and not more rhetoric about how “raised without antibiotics” is going protect you and me from superbugs.
*Dr. Richard Raymond is a former U.S. Department of Agriculture undersecretary for food safety.
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