Loss of catabolic function in Streptococcus agalactiae strains and its association with neonatal meningitis

The abilities of 151 Streptococcus agalactiae strains to oxidize 95 carbon sources were studied using the Biolog system. Two populations were constituted: one with a high risk of causing meningitis (HR group; 63 strains), and the other with a lower risk of causing meningitis (LR group; 46 strains). Strains belonging to the HR group were significantly less able to use four carbon sources, i.e., alpha-D-glucose-1-phosphate, D-ribose, beta-methyl-D-glucoside, and D,L-alpha-glycerol phosphate, than strains from the LR group (P <= 0.004). Moreover, strains in the HR group significantly more frequently possessed one of several mobile genetic elements or genome deletions previously shown to be associated with strains responsible for neonatal meningitis than strains in the LR group (P < 0.001). These findings suggest that genetic disruption might have occurred in virulent clones of S. agalactiae. Fifteen biotypes (B1 to B15) were identified from the results of oxidation of the four carbon sources, of which six (B1 to B6) included 92% of the isolates belonging to the HR group. Strains of biotypes B1 to B6 are thus 13 times more likely to be able to invade the central nervous system of neonates than strains of biotypes B7 to B15. In addition, 86% of strains recently associated with neonatal meningitis (42 strains studied) were identified as being of biotypes B1 to B6. Identification of particular S. agalactiae biotypes may therefore be one of the criteria to assist clinicians in assessing the level of risk of neonatal meningitis when a mother and/or her neonate is colonized with S. agalactiae.