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Journal of Clinical Microbiology, January 2006, p. 172-176, Vol. 44, No. 1
0095-1137/06/$08.00+0     doi:10.1128/JCM.44.1.172-176.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Detection of cfxA and cfxA2, the ß-Lactamase Genes of Prevotella spp., in Clinical Samples from Dentoalveolar Infection by Real-Time PCR

Kaori Iwahara,¹ Tomoari Kuriyama,^2* Satoshi Shimura,³ David W. Williams,⁴ Maki Yanagisawa,¹ Kiyomasa Nakagawa,^1,2 and Tadahiro Karasawa³

Department of Oral and Maxillofacial Surgery, Kanazawa University Graduate School of Medical Science,¹ Department of Oral and Maxillofacial Surgery, Kanazawa University Hospital,² Department of Clinical Laboratory Science, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan,³ Department of Oral Surgery, Medicine and Pathology, School of Dentistry, Cardiff University, Cardiff, United Kingdom⁴

Received 19 July 2005/ Returned for modification 10 September 2005/ Accepted 29 October 2005

While most bacteria involved in dentoalveolar infection are highly susceptible to penicillin, some Prevotella strains exhibit resistance to this agent through the production of ß-lactamase. The production of ß-lactamase by Prevotella spp. is in turn associated with the expression of the genes cfxA and cfxA2. The aim of the present study was to determine the prevalence of cfxA and cfxA2 in Prevotella strains by use of real-time PCR and to assess the performance of this molecular method for the direct detection of the genes in 87 clinical samples (pus and root canal exudates) from dentoalveolar infection. Production of ß-lactamase by each isolate was determined using a nitrocefin disk. ß-Lactamase production was seen in 31% of Prevotella isolates, while all isolates of other species were ß-lactamase negative. The penicillin resistance of isolates strongly correlated with the production of ß-lactamase. Real-time PCR was found to detect the cfxA and cfxA2 genes from at least five cells per reaction mixture (5 x 10³ CFU/ml of pus). Using real-time PCR, the presence of cfxA and cfxA2 was evident for all 48 ß-lactamase-positive Prevotella strains. In contrast, neither ß-lactamase-negative Prevotella (n = 91) or non-Prevotella (n = 31) strains were positive for the genes. In this study, 31 of the 87 samples yielded ß-lactamase-positive Prevotella results, and cfxA and cfxA2 were detected in all 31 samples. Of the 56 culture-negative samples, 8 (14%) were positive for cfxA and cfxA2 by the real-time PCR. This sensitive and specific molecular method offers a rapid clinical test for aiding in the selection of an appropriate antibiotic for treatment of dentoalveolar infection. Although penicillin remains largely effective in the treatment of dentoalveolar infection, ß-lactamase-stable antibiotics should be considered in cases in which ß-lactamase-positive Prevotella strains are involved.

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* Corresponding author. Mailing address: Department of Oral and Maxillofacial Surgery, Kanazawa University Hospital, 13-1 Takara-machi, Kanazawa 920-8640, Japan. Phone: (81) 762652444. Fax: (81) 762344268. E-mail: tomoari{at}oral.m.kanazawa-u.ac.jp.

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Journal of Clinical Microbiology, January 2006, p. 172-176, Vol. 44, No. 1
0095-1137/06/$08.00+0     doi:10.1128/JCM.44.1.172-176.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.