[Persistent non-inflammatory carriage of group B Streptococcus in organs of newborn mice].
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.
Kobayashi
M
M
Department of Pediatrics, Tokyo Women's Medical College Daini Hospital.
D000818:Animals; D000831:Animals, Newborn / Q000382:microbiology*; D002353:Carrier State; D051379:Mice; D013290:Streptococcal Infections / Q000635:transmission; D013292:Streptococcus agalactiae / Q000302:isolation & purification*