Typing of Chlamydia psittaci to monitor epidemiology of psittacosis and aid disease control in the Netherlands, 2008 to 2013

A simple genotyping method was developed and validated for all known Chlamydia psittaci reference genotypes. C. psittaci is currently divided into nine genotypes (A-F, E/B, M-5(6) and WC), all more or less associated with the preferred avian host. This method targeting variable domain 4 of the ompA gene has a lowest detection limit of 1 to 10 copies per PCR and was applied to 69 human samples collected in nine hospitals in the Netherlands from September 2008 until the end of October 2013. Genotype A was the most prevalent genotype. In addition, genotypes B, C, a new genotype, and C. abortus were found. A C. caviae infection was detected as a result of extension of this surveillance study to the national level. The sensitivity of this method compared with our real-time diagnostic PCR was 0.98 (66/67 typable samples). Specificity was 1.0 based on 33 commonly encountered bacterial and yeast species and 20 human respiratory samples. This typing method could help monitor C. psittaci infections in humans and provides insight into the relationships between notified human 'psittacosis' cases and the probable avian and other animal sources. When needed, a result can be obtained within 24 hours.