Electron microscopy of the pathology and chemotherapy of Legionella pneumophila infection in the chick embryo.

The ultrastructural pathology induced in organs of chick embryos previously infected with 100 times the yolk sac LD50 of Legionella pneumophila was examined by electron microscopy. Subtle pathological changes were observed three days post-inoculation while more extensive cellular and sub-cellular necrosis occurred at four days post-inoculation. Selected antimicrobial agents were administered three days after infection and evaluated for their ability to reduce or reverse ultrastructural lesions. In this study, ciprofloxacin was the only antibiotic that reversed tissue damage induced in response to infection with L. pneumophila while doxycycline, erythromycin, and rifampicin were also effective, but to a lesser degree. These results demonstrated the superior antimicrobial activity of ciprofloxacin and further illustrated the efficacy of the fertile hen's egg as a useful in vivo assay system for the evaluation at the ultrastructural level of putative chemotherapeutic agents for the treatment of Legionnaires' disease.