News ID: 135495
Published: 0801 GMT January 23, 2016

Biologists develop method for antibiotic susceptibility testing

Biologists develop method for antibiotic susceptibility testing

A team of biologists and biomedical researchers at UC San Diego has developed a new method to determine if bacteria are susceptible to antibiotics within a few hours, an advance that could slow the appearance of drug resistance and allow doctors to more rapidly identify the appropriate treatment for patients with life threatening bacterial infections.

The scientists showed the development of a rapid susceptibility test for Staphylococcus aureus, a bacterium that causes some 60 percent of hospital-acquired infections and which has spread in communities, causing pneumonia and a variety of skin and tissue infections in both healthy and immune-compromised individuals, Medical Xpress said.

Rapid antimicrobial susceptibility testing allows doctors to discriminate between infections caused by drug sensitive bacteria, which can be treated with safe and effective antibiotics developed in what scientists call the golden age of drug discovery (the mid-20th century) such as penicillin, and those caused by drug resistant bacteria, which might require newer antibiotics, such as daptomycin or cubicin. This approach will decrease the emergence of resistance by reserving the newest drugs for those infections where they are most needed.

"Previously we developed a microscopy-based method that performs an autopsy on bacterial cells that allows us to determine how each cell died, and we have shown that this method can identify new antibiotics and help understand how these antibiotics work," said Kit Pogliano, a professor of biology at UC San Diego who headed the research team.

 "We tested to see if this method could be applied to antibiotic susceptibility testing. Surprisingly, we not only found that our method was able to accurately differentiate sensitive S. aureus strains from resistant MRSA strains, but that we were able to identify two subgroups of MRSA strains, one of which is susceptible to combinations of antibiotics that could be used in the hospital. We are excited by the accuracy and speed of this test, as well as by its unanticipated ability to identify these two types of MRSA infections, which would have been missed by other tests."

Examining single cells has two key advantages over other testing methods, say the researchers. First, it is rapid, cutting days off the time for typical culture-based assays. It often takes days for a doctor to receive information on resistance, and this means that patients with life-threatening infections are often treated with the assumption that the infection is drug-resistant. Second, this method does not rely on having any detailed understanding of the bacterium causing the infection, or of the genes that convey resistance. This is particularly important in this case, since resistance to the drugs used to treat MRSA infections arise by several evolutionary pathways via different combinations of mutations, and it could also provide rapid treatment information for newly emerging bacterial pathogens, such as that which caused the infections transmitted by endoscopes.

The UC San Diego biologists say their new method has the potential to be applied to many different types of bacteria.

 

   
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