AUTHOR=Mojica Sergio A. , Eriksson Anna U. , Davis Rohan A. , Bahnan Wael , Elofsson Mikael , Gylfe Åsa 

TITLE=Red Fluorescent Chlamydia trachomatis Applied to Live Cell Imaging and Screening for Antibacterial Agents

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.03151

DOI=10.3389/fmicb.2018.03151

ISSN=1664-302X

ABSTRACT=<p>In this study, we describe the application of a transformed <italic>Chlamydia trachomatis</italic> strain constitutively expressing the red fluorescent protein mCherry, to allow real-time monitoring of the infection cycle and screening for agents that block replication of <italic>C. trachomatis</italic>. The red fluorescent <italic>C. trachomatis</italic> strain was detected autonomously without antibody staining and was equally susceptible to doxycycline as the wild type strain. A high-throughput screening assay was developed using the transformed strain and automated fluorescence microscopy. The assay was used in a pilot screen of a 349 compound library containing natural products from Australian flora and fauna. Compounds with anti-chlamydial activity were tested for dose response and toxicity to host cells and two non-toxic compounds had 50% effective concentration (EC<sub>50</sub>) values in the low micromolar range. Natural products are valuable sources for drug discovery and the identified <italic>Chlamydia</italic> growth inhibition may be starting points for future drug development. Live cell imaging was used to visualize growth of the red fluorescent <italic>C. trachomatis</italic> strain over time. The screening assay reduced workload and reagents compared to an assay requiring immunostaining and could further be used to monitor the development of <italic>Chlamydia</italic> inclusions and anti-chlamydial effect in real time.</p>