Based on this study, changes in clinical parameters during pregnancy are reversible, indicating that pregnancy gingivitis does not predispose or proceed to periodontitis.

In the oral cavity of relatively young women without periodontitis, P. nigrescens, unlike P. intermedia, is a frequent finding. Conceivably, pregnant women harbor increasing numbers of P. nigrescens associated with pregnancy gingivitis.

The in vitro susceptibility of ActinobaciUlus actinomycetemcomitans to azithromycin, a new macrolide antibiotic of a new class known as azalides, was compared with that of erythromycin by the agar dilution method on Mueller-Hinton Haemophilus test medium. Eighty-two A. actinomycetemcomitans strains, 79 recent clinical isolates obtained from 40 periodontally healthy or diseased subjects, and 3 type strains were included in the study. Erythromycin showed poor in vitro activity against A. actinomycetemcomitans. Azithromycin, however, was highly effective against A. actinomycetemcomitans: all strains were inhibited at 2.0 ,ug/ml. Azithromycin exhibited the best in vitro activity against the serotype a subpopulation of A. actinomycetemcomitans: 1O0o of the strains were inhibited at 1.0 ,ug/ml. The lowest MICs were, however, recorded by serotype b strains. Since azithromycin has favorable pharmacokinetic properties, including excellent distribution into tissues, it could be expected to pass into gingival crevicular fluid at levels sufficient to inhibit A. actinomycetemcomitans in vivo. Therefore, it is a good candidate for future clinical trials in A. actinomycetemcomitans-associated periodontitis.Actinobacillus actinomycetemcomitans is a capnophilic gram-negative coccobacillus which has been associated with localized juvenile periodontitis and with some cases of refractory and rapidly progressing periodontitis (33). The distribution ofA. actinomycetemcomitans serotypes in periodontally healthy and diseased subjects has lately been reported by Asikainen et al. (3), who demonstrated that serotype b was dominant in the subjects with periodontal disease and that serotype c was the most common serotype in the healthy subjects. Patients with a positive finding forA. actinomycetemcomitans often fail to respond adequately to mechanical therapy only (21). Many antibiotics have been administered in the treatment ofA. actinomycetemcomitansassociated periodontal diseases. Despite the good in vitro susceptibility ofA. actinomycetemcomitans to tetracyclines (4,30), the clinical response has been variable (2, 27, 31). The favorable clinical results obtained with metronidazole are thought to be due to the better in vitro activity of the hydroxy metabolite of metronidazole against A. actinomycetemcomitans and the possible synergistic effects of these compounds in vivo (16). However, in some patients metronidazole alone may not be effective enough for the eradication of A. actinomycetemcomitans from the oral cavity (20,25). On the other hand, the production of 13-lactamase by other bacterial species in periodontal pockets may compromise the use of ,-lactamase-susceptible penicillins (32). Furthermore, the old macrolide antibiotic erythromycin penetrates insufficiently into gingival crevicular fluid (24). Thus, it is necessary to screen for alternative antimicrobial agents that would be active against A. actinomycetemcomitans to find potential candidates for therapeutical trials.During recent years, an extensive development has occurre...