IDENTIFICATION OF LACTOBACILLUS STRAINS ISOLATED FROM PATIENTS WITH INFECTIVE ENDOCARDITIS AND COMPARISON OF THEIR SURFACE-ASSOCIATED PROPERTIES WITH THOSE OF OTHER STRAINS OF THE SAME SPECIES

Ten strains of lactobacilli isolated from infective endocarditis (IE) cases were speciated using the API 50CHL identification system and the IDENTIFY computer program, and shown to be either Lactobacillus rhamnosus (five strains) or L. paracasei subsp. paracasei strains (five strains). A comparison of their adhesive and surface-associated properties with 14 strains (seven each from the same two species) isolated from other sources indicated that the IE strains showed a significantly greater aggregation by saliva (P=0.005) and a significantly increased binding of fibronectin at pH 5.4. When the two species were compared, the IE L. rhamnosus group of strains had significantly higher values for hydrophobicity, hydroxyapatite adhesion (HA) and salivary aggregation (P<0.05) than the laboratory strains, whereas none of the assays were significantly different for the IE L. paracasei subsp. paracasei strains. Fibronectin binding was significantly increased for both species when the pH was reduced from 7.3 to 5.4. Fibronectin binding at pH 5.4 was correlated with the cell surface charge, while polystyrene adhesion was correlated with both hydrophobicity and HA adhesion. The data indicated that there may be a contributory role for surface-associated properties in the pathogenesis of Lactobacillus endocarditis, and that strains isolated from IE patients, particularly L. rhamnosus, differ in important respects (hydrophobicity, salivary aggregation and HA adhesion) from most other strains of the same species.