Introduction

Periodontal disease (PD) affects the tooth support tissue and the periodont and it is the main cause of tooth loss in small animals (Williams 1997). Bacterial plaque is responsible for most oral affections (Gioso & Correa 2003, Meira et al. 2007), which prevalence increases with age, reaching about 80% of dogs over five years old (Harvey & Emilly 1993, Marreta 2001). Treatment of PD and odontogenic diseases is based on removal of sub and supragingival bacterial plaque, polishing of dental crowns and correct antibiotic therapy (Nelson & Couto 2001, Salinas et al. 2006). Effective antibiotics against anaerobic bacteria, like clindamycin and metronidazole + esperamycin, are recommended in periodontal treatment pre and postoperative (Addy & Martin 2005, Carneiro et al. 2005, Meira et al. 2007). However, a comparative study about the effectiveness of antibiotic therapy has not yet been made in veterinary medicine. Thus, the purpose of this study was to determine microbiota of the subgingival bacterial plaque of dogs with PD and establish the effect of antibiotic therapy on its reduction.

Materials and Methods

Twenty Labrador retriever dogs were evaluated, being 4 males and 6 females, with mean weight 35.4kg and ages between 1 and 8 years old. The animals were randomly assigned in two groups with 10 animals each (G1 and G2) and identified by numbers from 1 to 20. On day zero, animals were submitted to physical and laboratorial exams. On odontological evaluation, they were clinically classified accordingly to their PD degree. Each animal was submitted to two collections of subgingival bacterial plaque samples, being the first on day zero (G1) and the second (G2) 15 days after the start of antibiotic therapy. Samples were collected by introducing paper cones in subgingival space on periodontal sites with clinical signs of inflammation. After collection, the samples were submitted to culture, bacterial isolation, identification by morphocellular analysis, biochemical tests and antibiogram. Antibiotic therapy was initiated three days before periodontal treatment and lasted for a total seven days. Animals in G1 were given clindamycin (Antirobe®) in 10mg/kg dose rate and animals in G2 were given metronidazole + espiramycin (Periodontil®) in 12.5mg/kg de metronidazole and 25mg/kg esperamycin doses rate. For periodontal treatment, animals were administered acepromazine (0.1 mg/kg) and morphine (0.5 mg/ kg) and anesthesia was induced with propofol (3 mg/kg) and maintained with isoflurane in oxygen. Routine periodontal treatment was performed, with sub and supragingival dental plaque removal and dental polishing.

Results

In odontological clinical evaluation, 6 (30%) animals presented discrete degree, 10 (50%) presented moderate degree and 4 presented advanced degree of periodontal disease. Mean age in animals with discrete degree was 3.1 years old, in animals with moderate degree was 3.9 years old and in animals with advanced degree was 6.5 years old. On C1, 17 (85%) samples presented bacterial growth and 20 strains were isolated. On C2, 13 (65%) samples presented bacterial growth and 15 strains were isolated. Of the 13 (65%) samples on C2 which presented growth, 7 (53.84%) were harvested from animals in G1 (9 isolated strains) and 6 (46.15%) from animals in G2 (6 isolated strains). Of 20 isolated colonies on C1, 11 (55%) were identified as Staphylococcus spp, 4 (20%) as Pasteurella spp, 3 (15%) as Bacillus spp, 1 (5%) as Levedura and 1 (5%) as Streptococcus spp. Of 15 isolated colonies on C2, 5 (33.33%) were identified as Staphylococcus spp, 4 (26.66%) as Pasteurella spp, 3 (20%) as Escherichia coli, 2 (13.33%) as Bacillus spp and 1 (6.66%) as Streptococcus spp. Two samples (10%) presented the same microorganism on C1 and C2, 9 samples (45%) presented different microorganisms, 6 samples presented growth only on C1, 2 samples (10%) presented growth only on C2 and 1 sample (5%) did not presented growth on neither collection. On antibiogram of the 20 isolated strains on C1, 6 strains (30%) were sensitive and 2 (10%) were low sensitive to clindamycin; 4 (20%) were sensitive and 2 (10%) were low sensitive to esperamycin; all strains were resistant to metronidazole. On antibiogram of the 15 isolated strains on C2, 1 strain (6.66%) was sensitive to clindamycin; 1 (6.66%) was sensitive and 1 (6.66) was low sensitive to esperamycin; all strains were resistant to metronidazole. In G2, none of the strains were sensitive to any of the antibiotics.

Discussion and Conclusions

On clinical odontological evaluation, advanced degree was more frequently observed on older animals, also related by Sorensen et al. (1980), Genco et al. (1998), Logan & Boyce (1994) and Rezende et al. (2004). According to Eurides et al (1996), conversely, levels of plaque were similar on different age groups of dogs. After antibiotic therapy, there was a 20 and 28% reduction in the number of samples with bacterial growth and in the number of isolated strains, respectively, which suggests that antibiotics acted on the control of microbiota related do PD. However, other factors should be considered, like failure on bacterial growth due to the collection methodology and reduction of microorganisms rate after mechanical removal of bacterial plaque. All isolated microorganisms were facultative anaerobic and resistant to metronidazole. Loesche et al. (1992) believe unsuccessful treatment with metronidazole is related to inadequate prescriptions, when the biological agent is not precisely identified. According to Vergani et al. (2004), metronidazole is more effective against anaerobic bacteria, present in more advanced PD degrees, which explains the low effect of the antibiotic in this study. This suggests that clindamycin may be a better recommendation in initial stages of PD, when there is a predominance of facultative anaerobic bacteria, and metronidazole in more advanced stages, when there is a predominance of strict anaerobic bacteria. Al-Haroni et al. (2006) and Gaetti-Jardim et al. (2007) studies sustain this conclusion, as metronidazole was effective against strict anaerobic bacteria, but did not present inhibitory activity against facultative bacteria.

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