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Interaction of Citrobacter diversus strains with HEp-2 epithelial and human umbilical vein endothelial cells
C R Woods1, E O Mason, S L Kaplan
1Department of Pediatrics, Baylor College of Medicine, Houston.
Abstract:
More than 75% of neonates with Citrobacter diversus meningitis develop brain abscesses. Interaction of C. diversus strains with HEp-2 and human umbilical vein endothelial cells (HUVEC) was studied to examine mechanisms related to brain abscess formation. Two of 9 strains invaded HEp-2 cells and 0 of 6 invaded HUVEC better than the others. C. diversus survived at least 20 h within HEp-2 cells (in decreasing numbers). Adhesion to HEp-2 cells was increased in 3 of 4 strains expressing type 1 fimbriae, but this did not correlate with increased invasion. Inhibition of RNA or protein synthesis blocked invasion but not adhesion. Thus, invasion requires ongoing protein synthesis, and adhesion to and invasion of HEp-2 cells by type-1-fimbriated strains are independent steps. Invasion was inhibited by cytochalasin D. A 32-kDa protein found in cerebrospinal fluid isolates of C. diversus was not related to invasion of either cell line. Ability to invade HEp-2 cells was not increased among strains isolated from central nervous system sources.
Insights
Citrobacter diversus meningitis in neonates often leads to brain abscesses. This study found that bacterial invasion of host cells, requiring protein synthesis, is key to abscess formation, independent of fimbriae presence.
Area of Science:
- Microbiology
- Infectious Diseases
- Neonatal Health
Background:
- Neonatal meningitis caused by Citrobacter diversus frequently results in brain abscesses, affecting over 75% of affected infants.
- Understanding the pathogenic mechanisms of C. diversus is crucial for developing effective treatments and preventing severe neurological complications.
Purpose of the Study:
- To investigate the interaction mechanisms between Citrobacter diversus and host cells (HEp-2 and human umbilical vein endothelial cells) relevant to brain abscess formation.
- To determine the role of bacterial adhesion, invasion, and intracellular survival in the pathogenesis of C. diversus meningitis.
Main Methods:
- Assessing the invasion and intracellular survival of C. diversus strains in HEp-2 and HUVEC cell lines.
- Investigating the role of type 1 fimbriae in adhesion and invasion using fimbriated and non-fimbriated strains.
- Examining the requirement of RNA and protein synthesis for invasion using specific inhibitors.
- Evaluating the effect of cytochalasin D on bacterial invasion.
Main Results:
- Two of nine C. diversus strains demonstrated significant invasion of HEp-2 cells; none effectively invaded HUVEC.
- C. diversus survived intracellularly within HEp-2 cells for over 20 hours.
- Type 1 fimbriae enhanced adhesion to HEp-2 cells but did not correlate with increased invasion.
- Bacterial invasion required ongoing protein synthesis and was inhibited by cytochalasin D, indicating an active host cell-dependent process.
- A specific 32-kDa protein in cerebrospinal fluid isolates was not linked to invasion.
Conclusions:
- Bacterial invasion of host cells, dependent on protein synthesis, is a critical step in C. diversus-induced brain abscess formation.
- Adhesion mediated by type 1 fimbriae is a distinct process from invasion, which requires active host cell participation.
- Further research into the specific invasion mechanisms and host-pathogen interactions is warranted to combat C. diversus meningitis complications.