Fever temperature enhances mechanisms of survival of Streptococcus agalactiae within human endothelial cells

Abstract

Group B streptococci (GBS) are the most common cause of pneumonia and sepsis during the neonatal period. However, the pathogenesis of invasive infection is poorly understood. We investigated the ability of GBS grown at 37 degrees C and 40 degrees C to adhere and invade human umbilical vein endothelial cells (HUVECs) at different periods of incubation (0, 0.5, 1, 2, 18 and 24 h). All strains tested, except strain 88641-vagina survived for 24 h in the intracellular environment at 40 degrees C. For serotype III grown at 40 degrees C, both strains (80340-vagina and 90356-liquor) showed increased adherence and intracellular survival when compared to bacteria grown at 37 degrees C (P<0.01). GBS serotype V strains (88641-vagina and 90186-blood) showed ability to survive inside HUVECs until 2 and 24 h post-infection at 40 degrees C and 37 degrees C, respectively (P<0.01). Influence of growth temperature in bacterial interaction with endothelial cells was partially dependent of serotypes and the clinical origin of strains. Serotypes III and V strains grown at both temperatures remained viable within acidic endothelial vacuoles which acquired Rab7 and LAMP-1 endosomal markers. The data emphasize the influence of temperature on cellular events of phagocytosis and pathogenesis of GBS diseases.