In vitro antimicrobial susceptibilities of three Porphyromonas spp and in vivo responses in the oral cavity of cats to selected antimicrobial agents.

摘要

25 isolates of 3 feline Porphyromonas spp. (P. gingivalis, P. salivosa and P. circumdentaria) from the oral cavity and oral-associated disease were tested for their in vitro susceptibility to amoxycillin, amoxycillin-clavulanate, benzylpenicillin, clindamycin, doxycycline, erythromycin and metronidazole using agar dilution and Epsilometer test methods. Digoxigenin-labelled whole chromosomal DNA probes directed against P. gingivalis VPB 3492, P. circumdentaria NCTC 12469T and P. salivosa VPB 3313 were used to quantify organisms obtained from 2 sample sites at the gingival margins of these cats before and 5 days after, treatment with 1 of 4 common antimicrobials (amoxycillin-clavulanate, clindamycin, doxycycline or spiramycin-metronidazole). The response to treatment was assessed clinically for each cat. All isolates were susceptible in vitro to all 7 antimicrobial agents using both methods. The numbers of P. gingivalis were not reduced at the gingival sample sites by administration of amoxycillin-clavulanate for 5 days, although this treatment reduced the numbers of P. salivosa and P. circumdentaria to below detection levels in 6 of 8 and 2 of 3 sample sites, respectively; clinical improvement was not observed in cats treated with amoxycillin-clavulanate. Treatment with clindamycin, doxycycline or spiramycin-metronidazole resulted in clinical improvement and a marked reduction of all Porphyromonas isolates at the sample sites. It is concluded that the Epsilometer test is a simple and accurate method for determining the minimum inhibitory concentration for P. gingivalis, P. salivosa and P. circumdentaria. All strains were susceptible in vitro to all the antimicrobial agents tested although clinical improvement of gingival disease was not noted with amoxycillin-clavulanate when given for 5 days at usual doses. This appears to be the first report of the disparity between the in vivo and in vitro susceptibility of oral bacterial strains to amoxycillin-clavulanate in the veterinary dental literature. This also appears to be the first report in which clinical and microbiological responses to commonly used antimicrobial agents for periodontal disease in cats has been documented and quantified. It is shown that treatment with clindamycin, spiramycin-metronidazole or doxycycline not only produce a substantial reduction in the number of Porphyromonas spp. (in most cases to below detection levels), but also result in substantial clinical improvement. It is suggested that these antimicrobial agents areuseful adjunctive therapy to mechanical debridement in domestic cats.