Sunday, January 29, 2006

Can antibiotic resistance in soil bacteria jump to human pathogens?

An article in the Jan 20th Science (Sampling the Antibiotic Resistome by Vanessa M. D'Costa, Katherine M. McGrann, Donald W. Hughes, and Gerard D. Wright, Science 20 January 2006: 374-377 requires subscription) explores the many antibiotic resistant strains of microbes found in soil. These microbes are constantly producing both antibiotic agents and developing mechanisms to disable antibiotics in chemical warfare competition with each other. Pharmaceutical researchers have used these soil microbes as sources for new antimicrobial agents. In some cases that means there is resistance to the antibiotic to be found in other soil microbes.

The authors isolated 480 microbes from the soil and found that the isolated microbes were resistant to at least 6 to 8 different antibiotics and some to as many as 20. Further investigation showed that the different strains also had multiple mechanisms of resistance. Since several studies show that antibiotics used for both humans and livestock are excreted and appear in groundwater (and here), these soil bacteria may be exposed to antibiotics currently in use to treat humans and could evolve further resistance.

Probably the most concerning aspect of the article was the suggestion that this resistance could move from the soil bacteria to bacteria known to cause pathology in humans. All that has to happen is for the genes encoding the resistance to be packaged in a plasmid or phage for potential transfer to a new bacterial strain. These sources of potential antibiotic resistance bear continued monitoring for that very reason.

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