EPITHELIAL-CELL INVASION BY ACTINOBACILLUS-ACTINOMYCETEMCOMITANS STRAINS FROM RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM GROUPS ASSOCIATED WITH JUVENILE PERIODONTITIS OR CARRIER STATUS

The epithelial cell invasiveness of Actinobacillus actinomycetemcomita ns Strains of different restriction fragment-length polymorphism (RFLP ) groups associated with disease conversion and asymptomatic carrier s tatus in localized juvenile periodontitis was examined. Twenty clinica l isolates were studied for their ability to invade KB monolayers, usi ng the quantitative gentamicin killing assay Five isolates were found to be invasive; five were not invasive; and the other 10 did not invad e better than an invasion negative control Haemophilus aphrophilus str ain ATCC 19415, Using probe-specific DNA fingerprinting, 11 strains we re assigned to RFLP group TI (disease-associated); 4 to RFLP type XIII (carrier status-associated); and the others to groups III, IV, V and VII. Eight isolates, all RFLP group TI, were leukotoxin producers as d etermined by PCR amplification of the lkt promoter region. No correlat ion was found between invasiveness and RFLP group. Leukotoxin producti on was more associated with noninvasive than invasive strains.