Production of bacteremia and meningitis in infant rats with group B streptococcal serotypes

Abstract

Group B streptococcal strains, representing the five major serotypes, were inoculated into infant rats by intranasal, oral, and intraperitoneal routes. Bacteremia regularly followed injection by the intraperitoneal route. Four strains (three of type III) isolated from human cerebrospinal fluid appeared more virulent for 5-day-old rats. Injection of fewer than 10 colony-forming units of one strain, a type III, led to bacteremia and death in 27% of animals. The cumulative bacteremia and mortality rate with this strain was 66% in animals given inocula of less than 10 to 10(3) colony-forming units. Bacteremia developed by 24 to 48 h with concentrations of greater than 10(5) colony-forming units per ml of blood, and death occurred soon afterward. Among bacteremic animals, positive cerebrospinal fluid cultures were found in 97%, and cerebrospinal fluid bacterial concentrations were equal to or exceeded bacterial counts in blood. The susceptibility of infant rats to infection with type Ia, Ic, or III strains was age dependent. Histopathological studies of the brain and meninges in 34 bacteremic animals with culture-positive cerebrospinal fluid revealed that 5- to 10-day-old animals had numerous bacteria distributed in a perivascular pattern but, with one exception, no leukocytic infiltration. In contrast, three of the 11- to 12-day-old and two 15-day-old animals had very thickened meninges infiltrated with polymorphonuclear leukocytes, macrophages, and bacteria.

Attenuated virulence of Streptococcus agalactiae deficient in D‐alanyl‐lipoteichoic acid is due to an increased susceptibility to defensins and phagocytic cells

“…Group B streptococci is the leading cause of meningitis in human newborns. In the neonatal rat model, development of GBS meningitis is correlated with the magnitude and duration of bacteraemia (Ferrieri et al, 1980), an observation which is also true for other bacterial pathogens responsible for childhood meningitis (Bortolussi et al, 1978;Salit and Tomalty, 1986;Berche, 1995). We observed that in a mouse i.v.…”

Srr2, a multifaceted adhesin expressed by ST‐17 hypervirulent Group B Streptococcus involved in binding to both fibrinogen and plasminogen

“…Previous studies in human and animals have demonstrated that high level of GBS bacteremia is a prerequisite to trigger central nervous system inflammation (Ferrieri et al, 1980). This implies that, following the traversal of the mucosal barriers to reach the bloodstream, bacteria should overcome the killing activity of host phagocytic cells, mainly neutrophils and macrophages, to massively multiply.…”

Age-dependent presence of antibodies in rat dams, capable of conferring protection against group B Streptococcus infection in neonates

“…Studies designed to develop vaccines against this disease require an e¤cient model system. Models which have been developed include mouse [2], primate [3] and rat [4]. While the mouse model has been used for active vaccination studies, the neonatal rat model lends itself to passive vaccination studies.…”