Enzyme electrophoretic polymorphism differentiates invasive from non-invasive Chlamydia psittaci ruminant isolates

A group of 24 Chlamydia psittaci strains isolated from ruminants, belonging to serotype 1 and previously classified as invasive in a mouse model of virulence, was compared to a group of 10 non-invasive strains belonging to serotype 2 by using determination of glucose-6-phosphate and L-malate dehydrogenase zymotypes resulting of the infection of cells by these strains. The serotype 1 or invasive isolates represent a homogeneous group by sharing a unique zymotype which was not observed in the non-invasive strains. On the contrary, the serotype 2 or non-invasive isolates constitute a heterogeneous group in generating 2 different zymotypes. Zymotyping clearly distinguishes the ruminant strains from an avian C. psittaci and two C. trachomatis isolates studied for comparison. Our results suggest the usefulness of the studied molecular approach for chlamydiae typing. Furthermore, it can be used as marker of virulence within the C. psittaci strains isolated from ruminants.