This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We hypothesize that systemically administered antibiotics will alter the microbial composition of biofilms and their antibiotic resistance patterns. We will examine the composition of subgingival biofilm samples in conjunction with the administration of antibiotic agents and determine the proportion and identity of antibiotic resistant species in subjects receiving different antibiotics. Biofilms are important because some resident species have the potential to cause disease, whereas other species contribute to the maintenance of oral health. Certain microbial complexes, and members within the complexes, relate strongly to inflammation and periodontal destruction. Bacteria within biofilms are particularly resistant to antibiotics. The reasons for increased resistance are not fully understood, although a number of factors may play a role. The biofilm matrix can act as a barrier preventing entry of antibiotics. Bacteria in the outer region of the biofilm may enzymatically inactivate antibiotics or exclude antibiotics due to their altered cell surfaces. In some biofilms, the matrix prevents inward diffusion of antibiotics. This study will evaluate the effects of scaling and root planing (SRP) in conjunction with antibiotic administration on the microbiological composition of plaque samples. Changes in bacterial species will be evaluated along with antibiotic resistance characteristics. Specifically, the effects of metronidazole, azithromycin, and low dose doxycycline will be investigated against placebo in 4 groups of subjects with adult periodontitis.
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