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Updated: Aug 10, 2026
A Murine Model of Group B Streptococcus Vaginal Colonization
Published on: November 16, 2016
[Persistent non-inflammatory carriage of group B Streptococcus in organs of newborn mice]
1Department of Pediatrics, Tokyo Women's Medical College Daini Hospital.
Insights
Group B Streptococcus (GBS) type III can persist in newborn mice after vertical transmission. This continuous carriage may explain late-onset GBS infections, potentially leading to disease when host defenses are compromised.
Area of Science:
- Microbiology
- Neonatal Infections
- Bacterial Pathogenesis
Context:
- Group B Streptococcus (GBS) is a significant neonatal pathogen with increasing incidence in Japan.
- Early-onset GBS infections are linked to vertical transmission, while late-onset forms are attributed to horizontal or nosocomial spread.
- This study investigates an alternative hypothesis for late-onset GBS: continuous carriage following vertical transmission.
Purpose:
- To investigate the potential for continuous carriage of Group B Streptococcus (GBS) in neonates following vertical transmission.
- To compare the persistence of GBS type Ia and type III in mouse models after neonatal intraperitoneal injection.
Summary:
- Neonatal mice were inoculated with type Ia or type III GBS.
- Bacterial counts were assessed in liver, spleen, lung, and brain tissues on days 2, 5, 8, and 10 post-injection.
- Type III GBS was recovered from multiple organs, indicating prolonged carriage, whereas type Ia GBS showed limited persistence.
Impact:
- Suggests that type III GBS may establish long-term, non-inflammatory carriage after vertical transmission in neonates.
- Provides a potential mechanism for late-onset GBS disease, where symptoms manifest upon disruption of the host-parasite balance.
- Highlights the importance of understanding GBS carriage dynamics in neonatal infection epidemiology.
Abstract:
Group B Streptococcus (GBS) is an important pathogen in newborn infants and has shown a remarkable increase in Japan since 1970. It has been reported that the early-onset type of GBS infection may be caused by vertical transmission whereas the late-onset type may be caused by horizontal or nosocomial transmission. However we think that the late-onset type may be caused by continuous carriage of GBS after vertical transmission. Therefore, we studied the continuous carriage of GBS using mice. Mice were separated into two groups, and one was given 10(3) colony-forming units of type Ia and the other type III GBS (isolated from the affected human neonates) by intraperitoneal injection on the first day of life. Then, on the 2nd, the 5th, the 8th and the 10th day after injection, viable counts were obtained per 10 mg of liver, spleen, lung and brain tissues. Each organ was homogenized and dissolved in 1 ml physiological saline per 10 mg of tissue, and 0.1 ml of each was infused into brain-heart infusion agar and incubated for 36 hours at 37 degrees C. The type III GBS isolated from many organs on these days, but type Ia was isolated in only two among 72 mice. These results suggested the possibility that type III GBS acquired by vertical transmission at birth may be carried over in a non-inflammatory state for a long time, and that the symptoms will become manifest only when the host-parasite relationship is disturbed later.
