1 Laboratory of Oral Biology, School of Dental Medicine, Toulouse; 2 Laboratoire Aventis, Paris, France
Received 18 June 2004; returned 6 August 2004; revised 1 December 2004; accepted 8 December 2004
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Abstract |
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Methods: We measured the MICs of spiramycin and metronidazole for the recovered pathogens and the gingival crevice fluid antibiotic concentrations of both antibiotics, and attempted to correlate them with bacterial eradication.
Results: The concentrations of metronidazole consistently exceeded the MICs for the pathogens isolated in the corresponding sites, even at the usual metronidazole (250 mg three times/day) dose. All the bacterial species were eradicated during treatment and at follow-up, although Fusobacterium spp. eradicated during treatment reappeared in a majority of the cases at follow-up, 30 days after treatment, in both groups.
Conclusions: The results of antibiotic therapy with metronidazole or the spiramycin/metronidazole combination are consistent with their in vitro antibacterial activity and with the local antibiotic concentrations; they suggest that the currently used metronidazole dose (250 mg, three times/day) alone or as part of the spiramycin/metronidazole combination, could be sufficient for the treatment of active periodontitis.
Keywords: oral anaerobic bacteria , gingival crevice fluid , pharmacodynamics
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Introduction |
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The objective of this study was to test the in vivo antibacterial efficacy of the currently used metronidazole dose (as contained in the fixed spiramycin/metronidazole combination) in patients with active periodontitis, and of a high dose (1500 mg/day) of metronidazole alone, to measure the gingival crevice fluid concentrations, and to attempt to correlate the bacterial eradication results with the antibacterial activity of these agents in vitro and the concentrations measured in the gingival crevice fluid.
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Patients and methods |
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The crevice fluid was collected by adsorption on a sterile paper tip inserted as above, and according to the previous description by Rotzetter et al.5 A sample from the same sites was taken for the concentration assay of metronidazole and spiramycin on days 2, 6 (3 h after the morning dose) and 7 (24 h after the last dose), and frozen at 80 °C until the end of the study. The measurements of both compounds in the gingival crevice fluid were made using a specific liquid chromatography method with simultaneous detection by mass spectrometry (LCMS/MS) developed by CEPHAC, Saint-Benoît, France, with a 150 mg/L quantification limit. The imprecision and inaccuracy of the method were, for metronidazole, < 7% and ±3%, respectively; for spiramycin I, the imprecision and inaccuracy were < 9% and ±6%, respectively (inter-assay variation). The range of concentrations for the controls was 0.540 mg/L.
The protocol was approved by the local Ethics Committee and the patients gave informed consent to participation in the study prior to enrolment.
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Results |
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The bacterial eradication on day 6 and day 30, according to the species found at enrolment, are presented in Table 1. All bacterial species were eradicated on day 6 in the spiramycin/metronidazole group, except for A. actinomycetemcomitans and one strain of Capnocytophaga spp., but Fusobacterium spp. colonized a large number of sites on day 30. All bacterial species were eradicated on day 6 in the metronidazole group, except for Capnocytophaga spp., and E. corrodens. P. intermedia was often present on day 6 and, like Fusobacterium spp. colonized a large number of sites on day 30.
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The distribution of the MICs of metronidazole and spiramycin for each bacterial species isolated at enrolment is presented in Tables 2 and 3. P. gingivalis and P. intermedia appeared susceptible to both agents, whereas Fusobacterium spp. was susceptible to metronidazole, but not to spiramycin. M. micros was susceptible to metronidazole, but not to spiramycin. A. actinomycetemcomitans and E. corrodens are resistant to both agents. Capnocytophaga spp. was resistant to metronidazole, but also frequently to spiramycin for which a wide distribution of MICs of this agent was observed. C. rectus strains appeared susceptible to metronidazole, but not to spiramycin.
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Concentration in the gingival crevice fluid
In the spiramycin/metronidazole group, the mean, median and extreme (minimum/maximum) concentrations of metronidazole in the gingival crevice fluid (affected and spared sites together) were 36.7 and 22.5 mg/L (min/max: 2.5/148 mg/L) at D2, 44.7 and 21.5 mg/L (min/max: 6.2/144 mg/L) at D6 and 43.9 and 3.4 mg/L (min/max: 0/350 mg/L) at D7. In the high-dose metronidazole group, they were 72.0 and 41.5 mg/L (min/max: 3.6/260 mg/L) at D2, 51.8 and 19.7 mg/L (min/max: 1.95/253 mg/L) at D6, 31.9 and 10.4 mg/L (min/max: 3.75/130 mg/L) at D7.
In the spiramycin/metronidazole group, the mean, median and extreme (minimum/maximum) concentrations of spiramycin were 5.5 and 2.8 mg/L (min/max: 0/68.4 mg/L) at D2, 3.6 and 3.2 mg/L (min/max: 0/10.2 mg/L) at D6, and 4.3 and 3.2 mg/L (min/max: 0/26.9 mg/L) at D7. The concentrations were below the quantification limit in one patient (in the spared site only) at all dates (D2, D6 and D7), and in another patient (in an affected site) at D6 and D7.
Inhibitory ratio
For metronidazole, the MICs for A. actinomycetemcomitans, Capnocytophaga spp. and E. corrodens frequently exceeded the upper value tested (8 mg/L), but were not precisely measured. In consequence, when the in situ concentration of metronidazole in the corresponding sites exceeded 8 mg/L, the inhibitory ratio could not be calculated. In the remaining cases, the inhibitory ratio of metronidazole was constantly superior or equal to 1 for all pathogens in both groups, except for two strains of Capnocytophaga spp. in both groups. The inhibitory ratio of spiramycin (spiramycin/metronidazole group) was superior to 1 only for P. gingivalis and P. intermedia (2/2 and 10/10 strains, respectively); it was inferior to 1 for a large majority of Fusobacterium spp., A. actinomycetemcomitans, C. rectus and E. corrodens strains; it was superior to 1 in 7/14 Capnocytophaga spp. strains.
Clinical efficacy and tolerance
The clinical activity, evaluated by the evolution of the loss of attachment under treatment and at follow-up, showed an improvement or stabilization on day 6 in 16/20 affected sites in the spiramycin/metronidazole group and in 14/16 sites in the metronidazole group, and similarly on day 30 in 18/20 and 15/16 affected sites, respectively. Three patients in the high-dose metronidazole group presented a spontaneously resolving, mild or moderate adverse event (nausea, headache, cutaneous rash), whereas none was reported in the spiramycin/metronidazole group (P=0.07).
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Discussion |
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The concentrations of metronidazole reached in the gingival crevice fluid of the patients in our study were particularly high, exceeding those measured by Rotzetter et al.,5 which were in the order of 10 mg/L after a single administration of 4 500 000 U/750 mg (spiramycin/metronidazole), or after a dose regimen of three daily administrations of 1 500 000 U/250 mg. No clear explanation can be offered for this discrepancy. In any case, the concentrations measured in our study largely exceeded the MICs of this agent for the involved pathogens, including with the usual dose regimen (250 mg unit doses).
The results of the in vitro susceptibility tests of the above pathogens to spiramycin and metronidazole are generally consistent with the data already known for these agents by Poulet et al.9 in patients with periodontal disease and Dubreuil et al.10 in patients with infections from dental origin. Poulet et al.9 and Dubreuil et al.10 reported a low level of susceptibility to erythromycin of Fusobacterium spp., but good activity by metronidazole.
To our knowledge, although a number of in vitro, descriptive bacteriological studies have been performed on the pathogens involved in periodontitis, and some clinical studies have described the in vivo, including long-term, bacteriological efficacy of different antibiotics, only few data are available on the pharmacodynamic rationale of the antibiotic treatment of this pathology. The concentrations of the agents in the gingival fluid have been described, but no correlation between the in vivo bacteriological efficacy and the antibiotic dose used, or the concentration reached in the gingival crevice fluid has yet been published. Our study provides an insight into the in vivo pharmacodynamic activity of antibacterial agents used in periodontitis, such as metronidazole or the spiramycin/metronidazole combination.
In conclusion, the spiramycin/metronidazole combination (1 500 000 U/250 mg) and high dose metronidazole (500 mg), three times/day for 6 days, eliminate most of the bacterial pathogens on treatment and at follow-up (except for Fusobacterium spp.) with only slight differences between the groups. The concentrations of metronidazole are very high in the gingival crevice fluid and exceed the MICs for the involved pathogens, even at the usual metronidazole (250 mg three times/day) dose, and these results are consistent with the in vivo efficacy. These findings, together with the adverse events recorded in the high-dose metronidazole group, suggest that the use of metronidazole at the usual dose, alone or as part of the spiramycin/metronidazole combination, could be sufficient for the treatment of active periodontitis.
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Acknowledgements |
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References |
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