Fluorescence Microscopy Technique Rapidly Determines Antibiotic Susceptibility

A recently developed diagnostic method that does not rely on culture growth or knowledge of the genes that convey resistance is based on quantitative fluorescence microscopy and enables the rapid determination of the antibiotic susceptibility of Staphylococcus aureus isolates.

The method called bacterial cytological profiling (BCP), which measures antibiotic induced changes in cellular architecture, was developed by investigators at the University of California, San Diego (USA). This technique employs quantitative cell biology methods to study how different conditions or drugs affect the overall cytological characteristics of microbial cells. BCP detects disturbances in all essential cellular pathways in a single, rapid test, making it a powerful antibiotic discovery platform. Furthermore, the technology is capable of detecting cytological changes that do not impair growth, making it highly sensitive and allowing the discovery of molecules previously missed by other whole cell based screens. BCP works with all types of potential antimicrobial compounds, including small synthetic chemicals, crude natural product extracts, fractionated natural products, peptides, or synthetic molecules that mimic peptides.

BCP was shown to discriminate between methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) clinical isolates of S. aureus within one to two hours with 100% accuracy. Similarly, BCP correctly distinguished daptomycin susceptible (DS) from daptomycin non-susceptible (DNS) S. aureus strains within 30 minutes. Among MRSA isolates, BCP further identified two classes of strains that differed in their susceptibility to specific combinations of beta-lactam antibiotics.

“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 senior author Dr. Kit Pogliano, professor of biology at the University of California, San Diego. “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.”

A description of the BCP technique, which is being commercialized by Linnaeus Bioscience Inc. (San Diego, CA, USA), was published in the January 28, 2016, online edition of the journal EBioMedicine.

Related Links:
University of California, San Diego
Linnaeus Bioscience Inc.