zithromax and Actinobacillus-Infections

Although polymicrobial infections, such as peri-implantitis or periodontitis, were postulated in the literature to be caused by synergistic effects of bacteria, these effects remain unclear looking at antibiotic susceptibility. The aim of this study is to compare the antibiotic susceptibilities of pure cultures and definite cocultures.. Laboratory strains of Aggregatibacter actinomycetemcomitans (Aa) (previously Actinobacillus actinomycetemcomitans), Capnocytophaga ochracea (Co), and Parvimonas micra (Pm) (previously Peptostreptococcus micros) were cultivated under anaerobic conditions, and their susceptibilities to 10 antibiotics (benzylpenicillin G, ampicillin, amoxicillin, ampicillin/sulbactam, amoxicillin/clavulanic acid, minocycline, metronidazole, linezolid, azithromycin, and moxifloxacin) were tested using the Epsilometertest. Cocultures, each consisting of two or three bacteria, were treated analogously.. All four cocultures showed lower susceptibilities to azithromycin and minocycline than to pure cultures. The coculture Aa-Co showed a lower susceptibility to moxifloxacin as did the coculture Aa-Pm to benzylpenicillin G; the coculture Co-Pm showed a lower susceptibility to amoxicillin, amoxicillin/clavulanic acid, metronidazole, and benzylpenicillin G. However, the coculture Co-Pm showed a higher susceptibility to ampicillin, linezolid and moxifloxacin as did Aa-Pm and Aa-Co-Pm to linezolid.. In addition to established in vitro assays, it was demonstrated that antimicrobial cocultures caused antibiotic susceptibilities that differed from those of pure cultures. Bacterial cocultures frequently showed lowered susceptibilities to antibiotics.

Topics: Acetamides; Actinobacillus Infections; Aggregatibacter actinomycetemcomitans; Amoxicillin; Amoxicillin-Potassium Clavulanate Combination; Ampicillin; Anti-Bacterial Agents; Anti-Infective Agents; Aza Compounds; Azithromycin; Capnocytophaga; Coculture Techniques; Coinfection; Drug Resistance, Bacterial; Fluoroquinolones; Gram-Negative Bacterial Infections; Gram-Positive Bacterial Infections; Humans; Linezolid; Metronidazole; Microbial Interactions; Minocycline; Moxifloxacin; Oxazolidinones; Penicillin G; Peptostreptococcus; Peri-Implantitis; Periodontitis; Quinolines; Sulbactam

The in vitro susceptibility of Actinobacillus 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 micrograms/ml. Azithromycin exhibited the best in vitro activity against the serotype a subpopulation of A. actinomycetemcomitans: 100% of the strains were inhibited at 1.0 micrograms/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.

Topics: Actinobacillus; Actinobacillus Infections; Azithromycin; Colony Count, Microbial; Erythromycin