PhD ceremony Mr. T.E. Rams: Antibiotic resistance in human periodontitis and peri-implant microbiota

PhD ceremony: Mr. T.E. Rams, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Antibiotic resistance in human periodontitis and peri-implant microbiota

Promotor(s): prof. A.J. van Winkelhoff, prof. J.E. Degener

Faculty: Medical Sciences

The extent of in vitro antibiotic resistance of subgingival bacterial pathogens in chronic periodontitis and peri-implantitis patients in the United States was studied in this thesis.

Study 1 found clindamycin most active against periodontal Streptococcus constellatus, and amoxicillin most active against periodontal Streptococcus intermedius. Study 2 found substantial in vitro resistance of periodontal Enterococcus faecalis to tetracycline, erythromycin, clindamycin, and metronidazole, but 100% susceptibility to ampicillin, amoxicillin/clavulanate, vancomycin, and teicoplanin. Study 3 revealed 52.1% of 564 chronic periodontitis patients yielded β-lactamase enzyme producing subgingival bacterial test species, which raises questions about the therapeutic potential of β-lactam antibiotics in periodontal therapy. Study 4 found subgingival periodontal pathogens resistant in vitro to doxycycline, amoxicillin, metronidazole, or clindamycin, in 55%, 43.3%, 30.3%, and 26.5%, of 400 chronic periodontitis subjects, respectively. However, only 15% of subjects harbored subgingival pathogens resistant to both amoxicillin and metronidazole. Study 5 found considerable in vitro spiramycin resistance among subgingival periodontal pathogens, but that spiramycin in combination with metronidazole had an antimicrobial potential similar to amoxicillin plus metronidazole. Study 6 found peri-implantitis patients to frequently harbor submucosal bacterial pathogens resistant in vitro to individual therapeutic concentrations of clindamycin, amoxicillin, doxycycline or metronidazole, but only rarely to both amoxicillin and metronidazole.

These findings indicate that chronic periodontitis and peri-implantitis patients in the United States frequently yield subgingival periodontal pathogens resistant in vitro to therapeutic concentrations of individual antibiotics, but less so with antibiotic combinations, and demonstrate a wide variability in periodontal pathogen antibiotic resistance patterns.