Identification of a putative IS element in Streptococcus equi subspecies equi

Abstract: The gram-positive, catalase negative bacteria Streptococcus equi subspecies equi is the causative agent for a disease in horses called strangles. The disease is spread worldwide and apart from the suffering of horses, it causes severe economical losses. The classic description of strangles includes swelling and infection of the throat region, although the symptoms can vary from case to case. The bacteria enter the horse via the mouth or nose and are then transported to the lymphoid glands. To investigate the infection process the bacterial virulence factors have to be identified and analysed. When studying the bacteria/ host interaction various methods are used, one method called phage display has previously been successfully used to identify bacterial proteins interacting with host components. In this work different studies have been performed. A shotgun phage display library of S. equi subsp. equi strain 62 was affinity selected against both horse serum and horse blood respectively. The aim was to investigate if any new potential virulence factors involved in the adhesion process between the bacteria and the horse could be discovered. The clones found in two types of experiments had inserts homologous to previously described proteins. The panning against horse serum resulted in phagemid clones which harboured inserts which were homologous to the genes encoding the fibronecting-binding protein FNZ (Lindmark et al, 1996) and the a2-macroglobulin, albumin and IgG-bindning protein ZAG (Jonsson et al, 1995). Where as in the panning against erythrocytes the inserts of the phagemid clones were homologous to an IS element 861 found in Streptococcus agalactiae (Rubens et al, 1989) as well as an IS element associated protein found in S. pyogenes (Feretti et al, 2001).