Friday, August 31, 2012

Wash your hands, there are resistomes in that dirt!

A remarkable paper by Forsberg et al. was just published in Science1.  Using sophisticated “high-throughput” (fast and automatic) gene analysis techniques the authors demonstrated that soil contains antibiotic resistant bacteria and that resistance signals (messages, resistomes) are transmitted to other bacteria including types that make humans sick (pathogens). 
Now, I am not going to pretend to understand all the technical details of this elegant paper. However, I can understand that some may take this paper’s findings as “alarming”.  “The soil is awash with resistance, and it is due to antibiotic use in animals,” they may say.
However, as with all science, one paper’s findings must be compared and viewed in the greater body of knowledge.2  Also, when considering causation, timing is key. If we are creating this resistance pool, then there should be a time when little or no resistance existed. However, a few recent and also elegant papers show that antibiotics, as well as antibiotic resistance, have been around for a long, long time, way before people were using antibiotics, and maybe even before people walked the earth.  For example, Bhullar et al. found antibiotic multiple resistance in soil in a cave untouched for 4,000,000 years by mammalian life.3 Also, a study from D’Costa et al. found antibiotic resistance in 30,000 year old permafrost.4 Furthermore, another study states that a class of antibiotics called β-lactamases (which includes antibiotics such as penicillin), have been around for over 2 billion years, and even after decades of being used clinically, bacteria are still susceptible.5
I guess that is one more reason Mom made us wash our hands. However, it will be hard to explain to kids as they come screeching inside for dinner, “Wash your hands! That soil contains AB95 resistomes, DUDE!”

1Forsberg, K.J. et al. 2012. The Shared Antibiotic Resistance of Soil Bacteria and Human Pathogens. Science 337:1107-1111

2Crombie, I.K, Davies, H.T. 2009. What is meta-analysis? Evidence-Based Medicine, 2nd edition. pp. 1-8.

3Bhullar, K. et al. 2012. Antibiotic Resistance is Prevalent in an Isolated Cave Microbiome. PLoS One 7(4): 1-11.

4D’Costa, V. et al. 2011. Antibiotic Resistance is ancient. Nature 477:457-461

5Wright, G.D. 2007. The antibiotic resistome: the nexus of chemical and genetic diversity. Nature Reviews Microbiology 5:175-186.

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