Vol. 173 July 1, 2017 Bugs and Drugs

July 1, 2017

 

“Eat dirt, and thrive”

 

Since Fleming discovered a mold that produced penicillin which killed Streptococcus bacteria, scientists for decades have been mining soil as a source of new antibiotics. There are so many bacteria competing for nutrients in the dirt that some bacteria will produce toxins to kill their neighbors. The current belief is that soil extraction for new antibiotics has been going on for so long that soil is about tapped out as a source for novel ones.

Antibiotics kill bacteria by attacking their cell walls. Bacteria develop “resistance” to antibiotics with changes in their cell walls that resist the medicinal attack. Individual bacteria cells can’t change their cell walls, but the population of pathogen bacteria as a whole, the “microbiome”, can become “resistant” as the bacteria cells replicate again and again. When only the bacteria which have mutated to ones with a different “resistant” wall remain, the bacteria has become “resistant” to the antibiotic. Your body does not become “resistant”, the bacteria community does..

Viruses have no cell walls, and that is why antibiotics don’t work on viruses, like the ones causing the common cold. Anti-viral medicines against the flu and HIV work by attacking the internal functions of the virus. Some anti-viral medicines attack the virus DNA, others attack the virus RNA, and others attack intracellular proteins or enzymes necessary for virus replication.

Scientists at Rutgers have recently described a whole new class of antibiotics extracted from soil (Italian soil to be exact, if you think that’s important) that don’t work by attacking the cell wall. The new compound inhibits an internal protein, a polymerase, in the bacteria which is necessary for the bacteria to survive. The compound is 10 times less likely to trigger a mutation that leads to drug resistance than current antibiotics. Also it can kill dormant, non-replicating bacteria much better than current antibiotics. Similar compounds that attack polymerases has been successful in treating viruses like Hepatitis C and HIV, but this is the first example of a successful antibacterial effect. It will send many scienticists looking for new antibiotics back to the dirt.

Could this just be another reason to eat dirt? Eating dirt, or geophagia, is a recognized way for animals, and some humans in special situations, to obtain minerals. Pica , eating non-food substances, in a child can indicate that the child is iron deficient or anemic. Pregnant women in Africa are known to eat dirt to enrich their stores of calcium for the fetus. Parrots, bats, and some pregnant women have been observed eating soil with a high clay content to help with gastrointestinal distress. Since dirt can contain lead and other toxins, most people are advised to just take a swig of Kaopectate.

Why not just skip the dirt and go right for the pure mixture of bacteria, a probiotic? In fact, the evidence for the benefits of the use of probiotics is mixed. The use of probiotics has not been dramatically positive in treating diarrhea, eczema, and preventing the side effects of antibiotics. True that probiotics have no significant side effects (the FDA has labeled them as “safe”), but some researchers are concerned that overuse may have deleterious effects on our normal gut bacterial flora.

There are approximately 100 Trillion (that is a “T”) bacteria in our gut. They have been officially awarded recognition as the “gut microbiome”. It is a hot research topic focussing on its roles in digestion, metabolism, immunity, dementia, and even autism. Fecal transplant therapy  (infusion of a solution of healthy donor feces through a nasogastric tube) repopulates the intestine with “good” bacteria as treatment for certain diseases caused by “bad” bacteria (Clostridium difficle) (1) More recently, the dscription of a “breast microbiome” in association with some breast cancers is spurring research into using bacteria as biomarkers in screening for breast cancer.

” The Hidden Half of Nature”, published in 2008, tells a positive story of a couple changing their lives by enriching their garden soil with bacteria-heavy materials while enriching the bacteria of their own intestines by “eating healthy”. One of the authors summed up their approach as: “Mulch your soil, inside and out”.

  1. N Engl J Med 2013; 368:407-415, January 31, 2013
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