Infection and Immunity, August 1999, p. 4208-4215, Vol. 67, No. 8
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Division of Infectious Diseases,
Received 12 February 1999/Accepted 4 May 1999
Neonatal bacterial meningitis remains a disease with unacceptable
rates of morbidity and mortality despite the availability of effective
antimicrobial therapy. Citrobacter spp. cause neonatal meningitis but are unique in their frequent association with brain abscess formation. The pathogenesis of Citrobacter spp.
causing meningitis and brain abscess is not well characterized;
however, as with other meningitis-causing bacteria (e.g.,
Escherichia coli K1 and group B streptococci), penetration
of the blood-brain barrier must occur. In an effort to understand the
pathogenesis of Citrobacter spp. causing meningitis, we
have used the in vitro blood-brain barrier model of human brain
microvascular endothelial cells (HBMEC) to study the interaction
between C. freundii and HBMEC. In this study, we show that
C. freundii is capable of invading and trancytosing HBMEC
in vitro. Invasion of HBMEC by C. freundii was determined to be dependent on microfilaments, microtubules, endosome
acidification, and de novo protein synthesis. Immunofluorescence
microscopy studies revealed that microtubules aggregated after HBMEC
came in contact with C. freundii; furthermore, the
microtubule aggregation was time dependent and seen with C. freundii but not with noninvasive E. coli HB101 and
meningitic E. coli K1. Also in contrast to other meningitis-causing bacteria, C. freundii is able to
replicate within HBMEC. This is the first demonstration of a
meningitis-causing bacterium capable of intracellular replication
within BMEC. The important determinants of the pathogenesis of C. freundii causing meningitis and brain abscess may relate to
invasion of and intracellular replication in HBMEC.
*
Corresponding author. Mailing address: Division of
Infectious Diseases, MS #51, Childrens Hospital Los Angeles, 4650 Sunset Blvd., Los Angeles, CA 90027. Phone: (323) 669-2509. Fax: (323) 660-2661. Email: kskim{at}chla.usc.edu.
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