This prospective study was designed to investigate amoxicillin-resistant oral anaerobes, and to identify their beta-lactamase-encoding genes. Three subgingival bacterial samples were collected from 12 patients suffering from periodontitis. One to seven beta-lactamase-producing strains were obtained from each patient, mostly belonging to the Prevotella genus (Bacteroides eggerthii, 2/35 strains; Prevotella sp., 33/35 strains). PCR assays were used to detect cfxA and cepA/cblA, the genes encoding class A/group2e beta-lactamases previously described in the Bacteroides fragilis group. The present investigation confirmed the role of Prevotella species as beta-lactamase producers in periodontal pockets. Additionally, this PCR screening showed (1): the high prevalence of CfxA beta-lactamase production by aminopenicillin-resistant Prevotella (32/33: 97.0% positive strains) vs. cepA/cblA (1/33: 3.0% positive strains), and (2) the presence of cfxA in the periodontal reservoir in the absence of antimicrobial therapy during the previous 6 months.

Chromosome-and plasmid-encoded CfxA2 and CfxA3 ␤-lactamases were detected in Capnocytophaga spp. from oral sources in France, Norway, and the United States. Unidentified chromosome-encoded ␤-lactamases were present in Capnocytophaga sputigena. Nucleotide sequence analysis of the CfxA3-encoding plasmid from C. ochracea revealed an unreported insertion sequence (ISCoc1) upstream of the cfxA gene.

No abstract

Sixty-two strains of oral (32) and non-oral (30) Prevotella producing beta-lactamases were screened for cfxA by PCR, using an intragenic primer pair. All 62 were cfxA/cfxA2 positive. Fourteen of these strains, representing seven pigmented and seven non-pigmented Prevotella species were submitted to further PCR with specific primers that amplified the whole beta-lactamase structural gene (966 bp). After cloning and sequencing, the deduced amino acid sequences were compared with that of Bacteroides vulgatus CfxA beta-lactamase. All 14 sequences possessed the E272K substitution characteristic of CfxA2. CfxA sensu stricto was not observed in the present series. G83D, F/V189L, W193L and D239Y substitutions were observed more than once, without species specificity. This sequence analysis indicates that most oral and non-oral beta-lactamase-producing Prevotella isolates from French patients produce variants of the CfxA enzyme.