Serological and molecular characterization of Chlamydophila psittaci strains using serovar-specific monoclonal...

In the present study, 21 avian Chlamydophila psittaci field isolates from 4 different European countries (Belgium, Germany, Italy and The Netherlands) were characterized using serovar-specific monoclonal antibodies as well as ompA sequence analysis, enabling the comparison between the two characterization methods for future epidemiological studies. The 21 European isolates included 6 isolates from the order Psittaciformes, 6 isolates from the Anseriformes, 5 isolates from the order Columbiformes and 4 Galliformes respectively. Only 19 on 21 isolates could be serotyped while all isolates were successfully genotyped. In addition, genotyping revealed the presence of mixed infections in 5 on 21 isolates while serotyping could only detect one of these 5 mixed infections. Interestingly, genotyping indicated the existence of a new genotype designated E/B. The E/B genotype is closely related to the genotypes A, B and E but the ompA gene of E/B strains shows a guanosine on position 1006 and 1021 in combination with a cytidine on position 1022 to be unique. Genotype E/B isolates reacted with both the serovar E- and B-specific monoclonal antibody leading to the conclusion of a mixed infection while only one specific ompA sequence was present in the sample. For epidemiological studies genotyping by use of ompA sequence analysis is to be preferred as it is more sensitive than serotyping and can distinguish genotype B, E and E/B strains.