Pyocyanin Inhibits Chlamydia Infection by Disabling Infectivity of the Elementary Body and Disrupting Intracellular Growth [PublishAheadOfPrint]

The obligate intracellular bacterium Chlamydia is a widespread human pathogen that causes serious problems including (but not limited to) infertility and blindness. Our search for novel antichlamydial metabolites from marine-derived microorganisms led to isolation of pyocyanin, a small compound from Pseudomonas aeruginosa. Pyocyanin is an effective antichlamydial for all three Chlamydia spp. tested. It has an IC₅₀ of 0.019 ~ 0.028 μM, which is comparable to the IC₅₀ of tetracycline. At concentrations as low as 0.0039 μM, pyocyanin disables infectivity of the chlamydial elementary body (EB). At 0.5 μM or higher concentrations, continuous presence of pyocyanin also inhibits chlamydial growth in the inclusion during later stages of the developmental cycle. Oxidative stress, a major known antimicrobial mechanism of pyocyanin, appears to be responsible for only the inhibition of bacterial growth but not the disinfection of EBs. Pyocyanin is well-tolerated by probiotic vaginal Lactobacillus spp. Our findings suggest that pyocyanin is of therapeutic value for chlamydial infections, and can serve as a valuable chemical probe for studying chlamydial biology.

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