Azithromycin in the treatment of periodontal disease. Effect on microbial flora.

Azithromycin is an azalide antibiotic with excellent in vitro activity against a wide variety of oral bacteria. It has a long half-life, good tissue penetration and is preferentially taken up by phagocytes. We investigated the microbiological efficacy of azithromycin as an adjunct to the non-surgical treatment of adult chronic periodontitis; its clinical efficacy is dealt with in a separate paper. 46 patients were treated in a double-blind placebo controlled trial. Microbiological assessment of the same periodontal pocket (initially > 6 mm) was made at weeks 0, 2, 3, 6, 10 and 22. Either azithromycin 500 mg 1 x daily for 3 days or placebo was given at week 2. Particular attention was paid to the numbers of black pigmented anaerobes and spirochaetes present since these are the most commonly implicated pathogens in periodontal disease. Pigmented anaerobes were significantly reduced at weeks 3 and 6 in patients who received azithromycin compared to placebo and remained lower, although not significantly so, throughout the study. Counts of spirochaetes were significantly reduced throughout the study in patients who received azithromycin compared to placebo. Our microbiological study suggests that azithromycin may be useful as an adjunct in the treatment of periodontal disease.

Degradation and utilisation of chondroitin sulphate by Streptococcus intermedius.

Streptococcus intermedius, part of the 'Streptococcus milleri group', has the ability to produce glycosaminoglycan depolymerising enzymes (hyaluronidase and chrondroitin sulphate depolymerase) which is unique amongst the viridans streptococci and may contribute to their virulence in brain and liver abscesses. The growth of S. intermedius strain UNS 35 was studied in basal medium supplemented with chondroitin sulphate A (CS-A, sulphated at position 4 of the N-acetylgalactosamine moiety) or chondroitin sulphate C (CS-C, sulphated at position 6 of the N-acetylgalactosamine moiety) as the major carbohydrate source. CS-A but not CS-C supported the growth of S. intermedius. Extracellular degradation of CS-A resulted in the initial accumulation of 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-delta-enepyranosyluronic acid)-D-galactose (deltaUA GalNAc-0S), and low levels of 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-delta-enepyranosyl uronic acid)-4-O-sulpho-D-galactose (deltaUA GalNAc-4S) in the medium with GalNAc-0S being subsequently utilised during bacterial growth. Metabolic end-products included formate and ethanol but not lactate, indicating that growth was probably carbon-limited. The CS-A contained 30% CS-C, which was also depolymerised resulting in the formation of 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-delta-enepyranosyluronic acid)-6-O-sulpho-D-galactose (deltaUA GalNAc-6S) in the culture supernate, but this unsaturated disaccharide was apparently not utilised during growth. The results indicate that S. intermedius produced CS-AC depolymerase, which was inducible and extracellular, and sulphatase activity. Experiments with authentic deltaUA GalNAc-4S and deltaUA GalNAc-6S demonstrated that deltaUA GalNAc4S rather than deltaUA GalNAc-6S was the preferred substrate for the sulphatase. Therefore, it is suggested that the CS-AC depolymerase of S. intermedius may play a role in the destruction of CS in host tissues, facilitating bacterial spread, and also in bacterial nutrition by the liberation of nutrients at the site of infection.

Purification and properties of a novel glycosaminoglycan depolymerase from Streptococcus intermedius strain UNS 35.

A glycosaminoglycan (GAG) depolymerase that acts on chondroitin sulphate A (CS-A), chondroitin sulphate C (CS-C) and hyaluronic acid (HA) was purified to apparent homogeneity from a culture of Streptococcus intermedius, strain UNS 35, grown in minimal medium supplemented with CS-A as the sole carbon source. The enzyme was purified by ammonium sulphate precipitation followed by serial chromatography on DEAE Trisacryl M, CM Trisacryl M and heparin-agarose. SDS-PAGE analysis of the purified enzyme yielded a single band with a mol.wt of c. 83000. The purified GAG depolymerase was unusual in its substrate specificity. The enzyme was initially regarded as a CS depolymerase because of its induction by CS-A. However, the GAG depolymerase exhibited greatest activity against HA, whereas the degradation rates of CS-A and CS-C were c. 8% and 2%, respectively, of the rate with HA. On this basis the enzyme could be classified as a hyaluronidase rather than a CS depolymerase. The pH optimum was around neutrality and the enzyme was unusual in having a high pI of approximately 9.3.

Comparative in-vitro activity of azithromycin, macrolides (erythromycin, clarithromycin and spiramycin) and streptogramin RP 59500 against oral organisms.

The in-vitro activities of azithromycin, clarithromycin, spiramycin and RP 59500 were compared with erythromycin against a wide range of oral organisms which have been implicated in oral infections and/or endocarditis (clindamycin was included for oral streptococci). All compounds tested showed good activity against many of these organisms, although some variation was observed with different species. Clarithromycin was the most active of the antibiotics tested against Gram-positive anaerobes, including Actinomyces spp., Propionibacterium spp., Lactobacillus spp. and Bifidobacterium dentium. Azithromycin was slightly less active than erythromycin against these species. In general, RP 59500 had higher MICs than the macrolides, other than spiramycin, against these organisms, but was superior in activity against Peptostreptococcus spp., inhibiting all isolates at 2 mg/L. Azithromycin was, in general, the most active antibiotic tested against the Gram-negative anaerobes: Fusobacterium spp., Bacteroides spp., Wolinella spp., Actinobacillus actinomycetemcomitans, Selenomonas spp. and Mitsuokella multiacida, including those isolates which were insusceptible to erythromycin. Clarithromycin showed similar activity to erythromycin against most Gram-negative species, but was superior against Capnocytophaga ochraceus and Eikenella corrodens. RP 59500 was less active than the macrolides against most Gram-negative anaerobes, but was superior to erythromycin and clarithromycin against Fusobacterium spp. and Leptotrichia buccalis, some strains of which were moderately resistant to erythromycin. The macrolides and clindamycin were about equally active against the oral streptococci, whereas RP 59500 showed lower inhibitory activity. The in-vitro results suggest that azithromycin and clarithromycin may be of value in the treatment of dental sepsis and the prophylaxis of endocarditis. RP 59500 showed useful activity against Gram-positive anaerobes and, because of its bactericidal activity against oral streptococci, may also prove to have a role in these areas.