title: Prophage induction in lysogenic Aggregatibacter actinomycetemcomitans cells co-cultured with human gingival fibroblasts, and its effect on leukotoxin release.
abstract: Lysogeny is common among strains of the periodontal pathogen Aggregatibacter actinomycetemcomitans. Since lysogenic induction is known to result in the increased synthesis and release of bacterial toxins from lysogens, it would be important to elucidate the conditions under which induction of these bacteria may occur. Co-cultures of A. actinomycetemcomitans strains (either lysogenic or non-lysogenic) and human cells (either gingival fibroblasts or pharyngeal epithelial cells) were prepared. Following incubation, bacteriophage titers of up to 6.2 × 10(7) pfu/ml were detected in the cell-free, spent culture media from the co-cultures of the lysogenic A. actinomycetemcomitans strains and the fibroblasts. Little (maximum of 2 × 10(0) pfu/ml) or no titers of phage could be detected in the mono-cultures of the lysogenic A. actinomycetemcomitans strains alone. In contrast, no phage were detectable in the cell-free spent culture media of the lysogens cocultured with the epithelial cells. Futhermore, co-culture of the A. actinomycetemcomitans lysogens with the fibroblasts resulted in enhanced release of the A. actinomycetemcomitans leukotoxin into the culture medium, in comparison with the spent culture media from mono-cultures of the lysogens alone. These results are consistent with the concept that interaction with fibroblasts may mediate prophage induction in lysogenic strains of A. actinomycetemcomitans, and that leukotoxin release is greatly augmented following induction of the lysogens.
authors.affiliation: Laboratory of Oral Infectious Diseases, Temple University School of Dentistry, 3223 North Broad Street, Philadelphia, PA 19140, USA. rstevens@dental.temple.edu
authors.forename: Roy H
authors.initials: RH
authors.lastname: Stevens
authors.forename: Caroline
authors.initials: C
authors.lastname: de Moura Martins Lobo Dos Santos
authors.forename: David
authors.initials: D
authors.lastname: Zuanazzi
authors.forename: Marcelo Barbosas
authors.initials: MB
authors.lastname: de Accioly Mattos
authors.forename: Davis Fernandes
authors.initials: DF
authors.lastname: Ferreira
authors.forename: Scott C
authors.initials: SC
authors.lastname: Kachlany
authors.forename: Eduardo M B
authors.initials: EM
authors.lastname: Tinoco
mesh_terms: D001435:Bacteriophages / Q000302:isolation & purification*; D002478:Cells, Cultured; D018920:Coculture Techniques; D004847:Epithelial Cells / Q000382:microbiology; D005098:Exotoxins / Q000378:metabolism*; D005347:Fibroblasts / Q000382:microbiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D008242:Lysogeny; D015661:Pasteurellaceae / Q000254:growth & development / Q000821:virology*; D014775:Virus Activation
chemical_list: D005098:Exotoxins; C018579:leukotoxin