Alexandre Arredondo1,2, Vanessa Blanc1, Carolina Mor3, José Nart3, Rubén León1. 1. Department of Microbiology, Dentaid Research Center, Cerdanyola del Vallès, Spain. 2. Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, Spain. 3. Department of Periodontology, Universitat Internacional de Catalunya, Barcelona, Spain.
Abstract
OBJECTIVES: To study oral Prevotella spp. isolated from patients with chronic periodontitis, to determine their susceptibility to azithromycin and erythromycin and to screen the presence of macrolide resistance genes therein. MATERIAL AND METHODS: Isolates with a Prevotella-like morphology were obtained from subgingival samples of 52 patients with chronic periodontitis. Each isolate was identified to the species level by sequencing of the 16S rRNA gene. In 100 Prevotella spp. isolates, azithromycin and erythromycin susceptibility was determined using the E test method, and the screening of erm(A), erm(B), erm(C), erm(F), erm(G), erm(Q) and mef(A) genes was done by PCR. RESULTS: Prevotella intermedia and Prevotella nigrescens were the most identified species (33% each). Minimum inhibitory concentrations (MICs) ranges for both antibiotics were 0.016/0.032 to >256 μg/ml. MIC50 values for azithromycin and erythromycin were 1.5 and 1 μg/ml, respectively, and MIC90 values were >256 μg/ml for both antibiotics. Nineteen per cent of the isolates carried erm(B), and 51% carried erm(F). CONCLUSIONS: The MIC values found were high compared to previous studies. erm(F) was greatly prevalent, and we describe for the first time the erm(B) gene in Prevotella spp. The presence of either of the genes seems to be associated with a higher degree of resistance to azithromycin and erythromycin.
OBJECTIVES: To study oral Prevotella spp. isolated from patients with chronic periodontitis, to determine their susceptibility to azithromycin and erythromycin and to screen the presence of macrolide resistance genes therein. MATERIAL AND METHODS: Isolates with a Prevotella-like morphology were obtained from subgingival samples of 52 patients with chronic periodontitis. Each isolate was identified to the species level by sequencing of the 16S rRNA gene. In 100 Prevotella spp. isolates, azithromycin and erythromycin susceptibility was determined using the E test method, and the screening of erm(A), erm(B), erm(C), erm(F), erm(G), erm(Q) and mef(A) genes was done by PCR. RESULTS:Prevotella intermedia and Prevotella nigrescens were the most identified species (33% each). Minimum inhibitory concentrations (MICs) ranges for both antibiotics were 0.016/0.032 to >256 μg/ml. MIC50 values for azithromycin and erythromycin were 1.5 and 1 μg/ml, respectively, and MIC90 values were >256 μg/ml for both antibiotics. Nineteen per cent of the isolates carried erm(B), and 51% carried erm(F). CONCLUSIONS: The MIC values found were high compared to previous studies. erm(F) was greatly prevalent, and we describe for the first time the erm(B) gene in Prevotella spp. The presence of either of the genes seems to be associated with a higher degree of resistance to azithromycin and erythromycin.