Improved Plaque Assay Identifies a Novel Anti-Chlamydia Ceramide Derivative with Altered Intracellular Localization

Abstract

ABSTRACTChlamydia trachomatisis a medically important human pathogen causing different diseases, including trachoma, the leading cause of preventable blindness in developing countries, and sexually transmitted infections that can lead to infertility and ectopic pregnancies. There is no vaccine againstC. trachomatisat present. Broad-spectrum antibiotics are used as standard therapy to treat the infection but have unwanted side effects, such as inducing persistent or recurring infections and affecting the host microbiome, necessitating the development of novel anti-Chlamydiatherapies. Here, we describe the establishment of a robust, fast, and simple plaque assay using liquid overlay medium (LOM) for the identification of anti-Chlamydiacompounds. Using the LOM plaque assay, we identified nitrobenzoxadiazole (NBD)-labeled 1-O-methyl-ceramide-C16as a compound that efficiently inhibitsC. trachomatisreplication without affecting the viability of the host cell. Further detailed analyses indicate that 1-O-methyl-NBD-ceramide-C16acts outside the inclusion. Thereby, 1-O-methyl-NBD-ceramide-C16represents a lead compound for the development of novel anti-Chlamydiadrugs and furthermore constitutes an agent to illuminate sphingolipid trafficking pathways inChlamydiainfections.