Another source for antibiotic resistant microbes
Here at BIO230, I’ve put up news articles relating the medical certainty of antibiotic resistance in bacteria. Diseases that were easily resolved less than a generation ago are now becoming increasingly difficult for health care workers to treat, and consequently prevention (particularly in health care settings) has become a more and more critical endeavor. Furthermore, the genetic elements for resistance to many common antibiotics appear to be present in bacteria, before they ever come into contact with these antibiotics, as detailed from this report examining 30,000 year old bacteria isolated from Siberian permafrost. A new report in the medical journal PLoSONE, and summarized at io9.com pushes back this boundary even further.
Researchers at McMaster University in Ontario, and the University of Akron examined the microbiome of an isolated section of Leguchilla Cave in New Mexico. The section of the cave that was examined have been geologically and environmentally isolated for 4 million years, with extremely minimal human incursion into these regions. Cave samples were prepared for plating in situ, spread onto a variety of culture media designed to mimic the cave environment, and then incubated in the dark for 2 to 6 weeks at 21°C, which is the temperature of Leguchilla Cave. Isolated colonies were then subcultured on rich media for subsequent analysis.
A screen of antibiotic resistance of these microorganisms is shown in the figure to the left. Significant percentages of the culturable organisms demonstrate resistance at clinical levels to many common antibiotics, with resistance to folate pathway and cell wall synthesis inhibiting antibiotics being very common. This reservoir of antibiotic resistance points to a mechanism for acquisition of resistance in clinically relevant species; they are able to acquire resistance in many cases through genetic exchange with environmental species, which helps to explain the rapidity of resistance emergence in many cases. The authors state:
This work demonstrates that antibiotic resistance is widespread in the environment even in the absence of anthropogenic antibiotic use. Lechuguilla Cave represents a remarkable ecosystem that has been isolated for millions of years, well before the clinical and agricultural use of antibiotics. The presence of multidrug resistant organisms even in this pristine environment reinforces the notion that the antibiotic resistome is an ancient and pervasive component of the microbial pangenome.
All is not gloomy, as several bright points can be brought forward with this report. First, none of the isolated organisms from Leguchilla Cave represent even remotely pathogenic microorganisms, so the health risk directly due to these organisms is negligible. Second, genes found in these microorganisms that can confer antibiotic resistance might be used as molecular “tags” that health care workers might watch for in the emergence of antibiotic resistance in clinical settings. Third, the widespread presence of antibiotic resistance to known antibiotics in a presumably pristine environment infers the existence infers the existence of novel antibiotics in the environment that might, for at least a period of time, help us to remain temporarily ahead of the curve in treating infectious disease.
Posted on April 20, 2012, in Danger danger danger!, Strange but True and tagged Antibiotic resistance, Carlsbad Cavern National Park, McMaster University, University of Akron. Bookmark the permalink. 9 Comments.