A report published online in the journal PLOS ONE says that researchers from Baylor College of Medicine (BCM) collaborating with Dr. Michelle Swick at The University of Texas Medical School established a technique of pooling drug-resistant bacteria with similar antibiotic resistance and sequencing the DNA of those pools. In the study, researchers sequenced the DNA of E.coli SMS-3-5, which has a strong resistance against fluoroquinolone (for example, ciprofloxacin or Cipro®), and found four mutations on the gene of gyrA, mutM, ligB and recG in all the isolates banked in the laboratory since 1999.
This approach could be used to uncover conserved mutations in bacteria that are resistant to other drugs and to other problematic bacteria as well.
“We decided to ignore all the other information about the bacterium, for example, which body site the bacteria came from, how virulent it was, which ward or hospital it came from, which patient and what age or gender the patient was. We put only the antibiotic resistance information into the computer for every strain we had and let a computer algorithm determine how the bacteria clustered considering only resistance status to 21 different antibiotics,” said Dr. Lynn Zechiedrich, professor of molecular virology and microbiology at BCM and corresponding author of the report. “We saw that the computer grouped the microbes by antibiotic resistance beautifully. For example, in one pool, all the bacteria were resistant to 12 drugs and no others. The mutations in the genome that we see that are the same across all microbes in the pool are associated with the antibiotic resistance of that pool. The ones that are not consistent could have to do with the myriad other differences among the different bacteria.”
The next study will be to design a rapid detection test for the mutations that correlate with antibiotic resistance so that physicians can quickly determine, not only the presence of bacteria causing the infection, but also the antibiotic resistance status of those bacteria.