Biochemical and immunological characterization of the extracellular nucleases of group B streptococci.

Abstract

The emergence of the group B Streptococcus as a leading agent of neonatal sepsis and meningitis (1) has stimulated interest in furthering understanding of the biology and immunochemistry of this organism. Various antigens of the five major human group B streptococcal serotypes have been under recent investigation, including type-specific antigens (2-4) as well as an intracellular enzyme, hippuricase (5), and also the extracellular enzyme, neuraminidase (6), and CAMP protein (7). Advances in our knowledge of the group B Streptococcus have been the subject of recent reviews (8-10).Our studies were undertaken to explore the possibility that group B streptococci may elaborate extracellular nucleases different from those of group A streptococci, and that these nucleases may be valuable antigenic markers that could be used to follow the immune response to group B streptococcal colonization or infection.The frequency of production of extracellular DNase had been reported to be 38% in group B streptococci in contrast to 100% in group A streptococci (11). The possibility that these differences might be a result of the production of lower levels of enzyme by group B streptococci led to the examination of methods that are more sensitive for screening group B streptococcal strains for nuclease activity. Because of the high prevalence of nuclease activity detected in the initial screening of many group B streptococcal strains (vide infra), studies were continued to isolate the nucleases and to characterize them biochemically and immunologically. Materials and MethodsBacteria. The group B streptococci were recent human isolates from the maternal genital tract, and from the mucosal sites, blood, and cerebrospinal fluid of infants. Identification of their serological group was by the hot-acid extraction and capillary precipitin method of Lancefield (12), and typing was done by immunodiffusion in agar (13) and also by capillary precipitin technique using rabbit antisera prepared in our laboratory. (grouping) and antisera provided by the Center for Disease Control, Atlanta, Ga. (typing). Streptococcal strains were grown up to log phase and frozen in small aliquots at -20°C.

Investigation of a Novel DNase of Streptococcus suis Serotype 2

“…Among the reasons for such an association was the observation that nuclease activity is directed against DNA, which is essential for the functioning of the target cell. Furthermore, production of anti-DNase antibodies was noted as a common feature during GAS (3), S. agalactiae (group B Streptococcus [GBS]) (15), and staphylococcal (10) infections, which correlates with the observations in this study. If there is an association between nucleases and virulence, it may be indirect, in that the enzyme would provide oligonucleotides to serve as a nutrient source (47).…”

“…By way of comparison, essentially all strains of GAS produce nuclease(s) (13). Furthermore, nearly all GBS strains were found to produce nuclease(s) (15), despite previous observations that the majority of strains did not; the difference in prevalence was due to the sensitivities of the nuclease detection assays. The possession of a functional nuclease enzyme(s) would appear to be important in other streptococci, and it would be surprising if the same was not also true of S. suis.…”

Influence of capsular neuraminic acid on properties of streptococci of serological group B

“…In an attempt to define virulence factors of group B streptococci various extracellular products have been isolated and studied. These included enzymes (Kjems et al, 1980;Milligan et al, 1978;Ferrieri et al, 1980;Straus et al, 1980) and haemolytically active substances (Marchlewicz & Duncan, 1981 ;Bernheimer et al, 1979;Jurgens e? al., 1987).…”

Group B Streptococcal Infections

“…Another group of enzymes elaborated by nearly all GBS are the extracellular nucleases [83]. Three distinct nucleases have been physically and immunologically characterized.…”