Molecular Identification of an Avian Strain of Chlamydia psittaci Causing Severe Keratoconjunctivitis in a Bird Fancier

A healthy female bird fancier developed progressive follicular keratoconjunctivitis despite topical treatment with antibiotics and steroids. Although bacterial, viral, and chlamydial cultures were negative, direct fluorescent antibody staining of conjunctival scrapings revealed chlamydial lipopolysaccharide; however, this procedure failed to detect the major outer membrane protein (MOMP) of Chlamydia trachomatis. The polymerase chain reaction (PCR) used with species-specific primers to the MOMP gene detected DNA of Chlamydia psittaci. Genotype analysis of the infecting strain revealed a nucleotide homology of 96% with C. psittaci avian strain 6-BC. Serum IgG titers were measured at 1:512 by microimmunofluorescence at 6 weeks, and they remained elevated for 3 months. A 10-week course of treatment with doxycycline was required for eradication of the infection. This case illustrates the importance of PCR/genotyping for direct detection and typing of Chlamydia species when chlamydial infections are suspected. To our knowledge, this is the first report of a naturally occurring ocular infection due to an avian strain of C. psittaci.