Characterization of virulence-associated traits in Mycoplasma penetrans strains acting as likely etiological agents of idiopathic non-gonococcal urethritis.

Mycoplasma penetrans (Mpe) is an emerging pathogen with a reduced genome. This bacterium has only previously been cultured from individuals with chronic immunodeficiencies. Here we report the characteristics of four Mpe isolates from the urine of immunocompetent males with non-gonococcal urethritis, in comparison with strain HF-2, from an immunocompromised patient. Several features exhibited distinct differences between these isolates and HF-2. Unlike HF-2, all four were resistant to azithromycin. They exhibited greater sialic acid-dependent binding to erythrocytes, gliding motility speed, and H2O2 production than HF-2. All new isolates produced thinner capsules than HF-2. Invasiveness varied, with some isolates being more invasive than HF-2 and some less invasive. Cytotoxicity to HeLa cells was similar to HF-2, and all strains could clear extracellular traps produced by innate immune cells. We conclude that subtle differences among Mpe strains may be critical for this organism to establish an infection in an otherwise healthy individual.