Detection and characterization of β-lactamase genes in subgingival bacteria from patients with refractory periodontitis

Fifty-three β-lactamase-producing strains of oral bacteria isolated from patients with refractory periodontitis in Norway and USA were screened for the presence of the blaTEM, blaSHV, blaOXA, blaampC, blacfxA, and blacepA/cblA genes by the polymerase chain reaction (PCR). The PCR products were characterized by direct sequencing of the amplified DNA. Thirty-four of the 53 enzyme-producing strains (64%) were positive in one of the PCR assays. All β-lactamase-producing Prevotella and Capnocytophaga spp. were CfxA positive. TEM-type β-lactamases were identified in one strain each of Escherichia coli and Neisseria sp., and one strain of Citrobacter freundii possessed an AmpC-type β-lactamase. Screening for gene cassettes and genes known to be associated with integrons did not reveal the presence of integrons in these oral bacteria. Sequence analyses showed that most CfxA positive Prevotella and Capnocytophaga isolates from patients with refractory periodontitis harboured variants of the CfxA2 and CfxA3 enzyme. The present study also showed that many different genetic determinants of β-lactamase production are found in bacteria isolated from refractory periodontitis, many of which remain to be characterized.