The existence of so-called superbugs was predicted, but we are only recently seeing it in horrifying real life. A Nevada woman died from an overwhelming infection caused by bacteria that were resistant to all antibiotics the hospital had, and to all known antibiotics available in the US. When the bacteria circulating in her blood was grown up in the lab and subjected to a series of powerful antibiotics, they it didn’t even make a dent in its growth.
This is at least the third such case in the US in the past year. A gene mutation called mcr1 in the bacterium Klebsiella pneumonia was responsible for two earlier cases of death from superbugs. The mcr1 gene is getting a lot of attention because it is found on a snippet of free DNA on what is called a plasmid. The plasmid can be freely passed to other Klebsiella bacteria but also to bacteria of other (unrelated) species.
But in the Nevada case the bacteria did not have the mcr1 gene – some other unknown mechanism was making the bacteria untouchable by antibiotics. It is a matter of survival of the fittest: bacteria are forced to develop resistance after being repeatedly exposed to an antibiotic. Only the bacteria that have some biochemical quirk or mutant genetic makeup can survive, and then the new, resistant bacteria make more generations like themselves.
These survivor strains can function and persist when other strains are dying off from antibiotic treatment. The more widespread the use of antibiotics, the greater the numbers of individual bacteria that are exposed to threats and compelled to develop survival tactics.
Bacteria have several avenues of developing resistance. Here are some of the more common:
- They can change their DNA to modify the shape of the receptors on their surfaces, sort of like changing out the lock so the key (the drug) no longer fits and cannot gain access.
- Bacteria can modify their internal metabolism so that they skirt around the points disrupted by antibiotics.
- They can develop more effective mechanisms for pumping antibiotics out of themselves, reducing the concentration of poison inside.
- They can also modify the drug molecule to make it inactive.
Bacterial DNA is changed by mutation of existing genes, or by snagging new genes from the environment. New genes can come from the act of “conjugation”—a sort of bacterial sex that allows swapping of gene particles. Viruses that infect the bacteria can also carry new genes in.
Some genetic elements that code for antibiotic resistance are free-floating in the environment. At least one study has shown the presence of antibiotic drugs alone is enough to trigger bacteria to ingest these submicroscopic pieces of genes and incorporate them permanently into their own DNA.
Bacteria, which have been evolving on Earth one thousand times longer than man, produce new generations every 30 minutes on average, while man makes a new generation roughly every 30 years.
Bacteria have the ability to adapt much faster and with more flexibility than the relatively slow and complex human body.
Are you at risk of death from superbugs? It is highly unlikely, because your own baseline health and vitality are much more important than the kinds of bugs you meet. These are called “host factors”, as if your body is the host to the guest bacteria. The main predictors of susceptibility to infection have to do with the host factors of proper nutrition and freedom from underlying severe disease as well as freedom from toxic substances that impair nutrition and the immune system. Topping the list of offending drugs are steroids; medications that inhibit stomach acid; and excessive use of antibiotics.
Action item for the smart consumer: Find out more about antibiotics and their proper use in No-Nonsense Guide to Antibiotics by Moira Dolan, MD.