Susceptibles and Persisters. Phenotypic Differenciation in Photodynamic Inactivation at the Single Bacterium Level.

ANDRES M. DURANTINI

Encuentro; IV Reunión de Fotobiólogos Moleculares Argentinos; 2018

The ability of pathogens to develop resistance and thus survive after different treatments often depends on its phenotypic behaviour. According to their characteristics, bacteria present different resistance to antimicrobial drugs. Nowadays, the statistics reflects a projection for infections death caused by microbes around ten times superior for the year 2050 being the major cause of death worldwide.1Photodynamic inactivation (PDI) of microorganism is an established approach for the targeted destruction of pathogenic cells. It provides a relivable platform for the treatment of drug-resistance microbes. PDI is a multiple stage process, which involves a photosensitizer, light irradiation and molecular oxygen. The photosensitizers can produce free radicals by type I and type II mechanism with diverse efficiencies and different degrees of binding to the bacterial wall. Then, free radicals are capable to attack lipids, proteins and nucleic acids further compromising cell integrity and inducing death.2-4Herein we describe the use of fluorescence microscopy jointly with a handful of photosensitizers to show bacteria phenotypic heterogeneity towards PDI. The photoinactivation efficiency of four different PS was monitored by recording in real-time propidium iodide (PI) emission in three different bacterial genders at the single bacterium level. For the first time, we show a correlation between bacterial susceptibility and photosensitizer efficiency monitoring individual bacterium death. Our results provide insight on how bacterium can overcome a PDI treatment according to phenotypic heterogeneity.