Development of plaque and gingivitis following antibiotic therapy in dogs

Abstract Changes in the subgingival microbiota were studied during a 4-week period of plaque accumulation in beagles which initially had clean teeth and healthy gingiva. The effect of Clindamycin, Metronidazole and Vancomycin on the microbiota and associated gingivitis was also determined. Fifteen 1-year-old beagle dogs were used. During two subsequent periods of plaque accumulation, one without (control) and one with (test) antibiotic therapy, the animals were allowed to accumulate plaque. Plaque and gingivitis development was assessed by clinical measurements. Plaque samples were harvested from the gingival sulcus region and the percentage distribution of different bacteria was determined following aerobic and anaerobic incubation in selected media. Following microbial sampling, biopsies of the gingiva and surrounding soft and hard tissues were removed and the size of the inflammatory cell infiltrate assessed. The results demonstrated that beagle dogs with a normal gingiva harbored a microbiota within the gingival sulcus region dominated by gram-positive and gram-negative rods. After 4 weeks of undisturbed plaque accumulation, the number of sulcus bacteria had increased 100-fold. This increase was the result of a proliferation of gram-negative anaerobic rods. Concomitant with this change of the microflora, an inflammatory reaction developed in the gingiva. When the dogs during a similar 4-week period were given Metronidazole, no increase of the subgingival microbiota occurred. The inflammatory response of the gingiva was minute. Treatment with Clindamycin and Vancomycin did not entirely prevent the proliferation of the subgingival bacteria. The number of microorganisms harbored after 4 weeks of Clindamycin and Vancomycin treatment was, however, only 50% of that of the control period. Even if the number of colony forming units was similar at the end of Vancomycin and Clindamycin treatment the quality of the two subgingival microbiotas was different. Vancomycin treatment resulted in a plaque dominated by gram-negative bacteria while Clindamycin allowed gram-positive bacteria to increase in number. Gingival inflammation resulting in the Vancomycin group was more pronounced than the gingivitis response in the Clindamycin group.