Current standard methods for detecting antibiotic susceptibility are based on the ability of the bacteria to proliferate in the presence of antibiotis, and thus these techniques are time-consuming, costly, and insensitive, particularly for evaluation of slow-growing organisms. To develop a truly rapid susceptibility test, one must circumvent the need for growth. We are developing a microfluidic test that interrogates the response of cells to antibiotics in the presence of mechanical and/or soluble stressors and thereby minimizes the time to results. The core of the hypothesis is that by straining the cell, we induce the cellular repair processes and associated biochemical pathways. These pathways are often targets of antibiotics (e.g., cell wall biosynthesis, protein synthesis, DNA transcription). f the antibiotic hinders those repair processes, the cell will die under the continued application of stress. We posit that monitoring cell death under stress in the presence of antibiotics can provide phenotypic information in an ultra-rapid time frame allowing physicians to make appropriate antibiotic treatment choices sooner. We envisage that this methodology would complement the existing rapid tests based on molecular diagnostics (e.g., PCR) because it would provide a low-cost rapid method that delivers phenotypic information. While genetic tests provide precise information for epidemiological studies, the high reagent costs, relatively high operator skills required, and limited clinical utility continue to limit widespread routine use. Furthermore, the molecular diagnostics suffer from a high number of false positives and unacceptable performance in non-sterile specimens (e.g., polymicrobial samples). As our method could be automated and is based on phenotypic changes, we believe it is superior as a routine clinical diagnostic providing physicians with the information they need to treat their patients, namely what antibiotic to use to kill the infecting pathogen. The method can be multiplexed (multiple antibiotics and multiple organisms) and can be integrated with current bacterial identification methodologies, thus it has the potential to be the basis of a new diagnostics system that rapidly provides clinicians with both identification and antibiotic susceptibility profiles in a timeframe that is much shorter than is currently possible. The method also opens new avenues of research into how stress can potentiate the effects of antibiotics. Once developed, the technique could also be used as a rapid screening technology for new antibiotic drug candidates.

Public Health Relevance

The increasing prevalence of multi-drug resistant bacterial infections is a growing public health problem. To combat this trend, new rapid diagnostic methods for antibiotic susceptibility must be developed. Here, we propose to address this gap by exploiting our technique for rapid detection of antibiotic susceptibility under mechanical stress alone or in combination with soluble Stressors. The work has the potential to revolutionize clinical practice for bacterial infections by enabling physicians to prescribe targetd antibiotic therapy much sooner than is possible with current methods.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Clinical Research and Field Studies of Infectious Diseases Study Section (CRFS)
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Ritchie, Alec
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Fraunhofer Center /Manufacturing Innov
United States
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Campbell, Jennifer; McBeth, Christine; Kalashnikov, Maxim et al. (2016) Microfluidic advances in phenotypic antibiotic susceptibility testing. Biomed Microdevices 18:103
Kalashnikov, Maxim; Campbell, Jennifer; Lee, Jean C et al. (2014) Stress-induced antibiotic susceptibility testing on a chip. J Vis Exp :e50828