| − | Paired serum samples showing a positive rise in antibody titre can be used in some cases for confirmation of infection. The organism can be isolated by culture in a special medium, of it can be viewed under dark field microscopy. | + | Paired serum samples showing a positive rise in antibody titre can be used in some cases for confirmation of infection. The organism can be isolated by culture in a special medium, or it can be viewed under dark field microscopy. |