Some bacteria in the environment may already have a natural resistance to certain antibiotics, due only to genetic variation and not to antibiotic exposure. These bacteria could provide a key to the rational design of new antibiotics, say researchers in the December 1997 issue of Antimicrobial Agents and Chemotherapy.
The researchers, from TerraGen Diversity, Inc., Vancouver, Canada, studied random samples of bacteria cultured from the soil, looking at their resistance to fluoroquinolone antibiotics and the genetic basis for that natural resistance. They found that the quinolone resistance-determining region of the bacterial gene known as gyrA was highly variable and that fluoro-quinolone resistance was due, in part, to natural DNA sequence variation.
Sequence analysis of microbes that are naturally resistant to potential antimicrobials would be valuable in predicting mechanisms of resistance likely to be encountered in subsequent clinical use, say the researchers. Such early warning would permit rational design of agents active against resistant strains.