Isolation and Characterization of Avian Chlamydia psittaci from Symptomatic Pet Birds in Southern Hunan, China.

is a zoonotic pathogen with multiple hosts, especially avian, and can be transmitted to humans, causing psittacosis or ornithosis. No effective vaccines have been developed. We therefore isolate and genotype avian strains and investigate the pathogenicity of isolates in the southern Hunan area of China. Among 200 suspicious avian specimens, eight were positive for the outer membrane protein A () gene (4%), and seven were successfully cultured in human epithelial type 2 and Vero cells (87.5%). Genotyping of the gene of the eight PCR-positive samples revealed that all of the cultured strains, except for the E9 strain, belonged to genotype A. Pathologic changes in the mice infected with via intranasal inoculation showed severe pneumonia and intense infiltration of inflammatory cells in the lung in a dose-dependent manner, and immunohistochemical staining displayed different levels of infiltration of inclusions in the heart, liver, spleen, kidney, and, especially, lung. Our findings demonstrate that genotype A dominates all genotypes in the southern Hunan area and that the avian isolates in this region possess dose-dependent pathogenicity.