Title: Measuring antibiotic permeation in single bacteria with absorption spectroscopy
Funder: The Academy of Medical Sciences

Abstract: The aim of this project is to develop a generic label free spectroscopic method for quantifying antibiotic intake in bacteriaâ€“ a key bottleneck in designing antibiotics that penetrate through bacterial porins and avoid efflux pumps. Antibiotics are an essential drug for modern medicine, however the future of antibiotic use may become compromised as pathogens increasingly develop resistance. The ability of an antibiotic to kill bacteria is limited by its ability to enter and remain inside bacteria. Gram negative bacteria are a particular concern for antibiotic resistance, as they possess two cellular membranes. The outer membrane of gram negatives is embedded with pores that allow nutrients uptake, but limit antibiotic intake. This molecular sieve coupled with efflux pumps efficiently act across bacterial membranes to reduce the antibiotic concentration in bacteria. To date we lack generic methods to quantify antibiotic intake in bacteria. Here I propose to develop a novel technology which relies on the property of antibiotics of absorbing light to detect the amount of antibiotic present in a bacterium. A novel ultrasensitive absorption spectroscopy method will be developed, to detect changes in the absorption spectrum induced by the antibiotic intake in single bacteria. Using semi-transparent mirror cavities, light will be circulated several times through the bacteria before reaching the light detector. This will ensure that enough photons are absorbed by the bacterium and the absorption light spectrum will provide a signature of antibiotic presence.

Lay abstract: The widespread misuse of antibiotics has caused a real and imminent threat to public health due to the ability of bacteria to develop into superbugs resistant to antibiotic treatment. A simple to ask but not easy to answer question, important for understanding and fighting antimicrobial resistance, is: How many antibiotic molecules have entered a bacteria? Answering this question is essential since the number of antibiotics inside a bacteria can determine if a bacteria dies or survives an antibiotic treatment, possibly developing antibiotic resistance. Here I am proposing to develop an optical platform which uses the property of matter to absorb light to quantify the uptake of antibiotics in bacteria. The absorption spectrum of light interacting with matter provides a â€œmolecular fingerprintâ€ that enables analysis of the molecular type and its amount. Hence the light absorption spectrum of a bacteria with antibiotic entrapped differs from the absorption spectrum in the absence of the antibiotic, allowing for the measurement of antibiotic concentration. To achieve this quantification an ultrasensitive light spectrometer will be developed here. This novel spectrometer uses mirrors to circulate the light hundreds of times through the bacteria so that very fine spectroscopic details can be determined. This new optical platform will allow scientists to evolve better antibiotics, designed to accumulate in bacterium, but also will provide the medical doctors important information on the antibiotic dosage required to kill a bacteria in, for example, a hospital setting.

Research activity codes: 2.1 BIOLOGICAL AND ENDOGENOUS FACTORS
Health categories: GENERIC HEALTH RELEVANCE;INFECTION