β-lactamase producing bacteria in the subgingival microflora of adult patients with periodontitis.: A comparison between Spain and The Netherlands

Background/aims: Countries with a high per capita antibiotic use frequently demonstrate a high level of drug resistance. The aim of this study was to compare the prevalence and levels of beta-lactamase producing bacteria in the subgingival microflora in adult patients with periodontitis in Spain and The Netherlands, and to characterise beta-lactamase producing bacteria in both patient samples. Method: Patients with moderate to severe periodontitis were consecutively selected and asked to report on: current systemic disorders and medications, history of use of antibiotics, and smoking habits. Clinical variables included probing pocket depth, clinical attachment level, plaque, bleeding on probing, and suppuration. Pooled subgingival samples of 4 selected sites were anaerobically cultured in blood agar plates with and without amoxicillin, and amoxicillin/clavulanate. Bacterial colonies growing on amoxicillin plates but not on amoxicillin/clavulanate plates were tested for beta-lactamase production. beta-lactamase producing bacteria were isolated and identified. Results: 31 patients were studied in the Spanish group and 30 in the Dutch group. Comparable mean gender and ages were found. Evaluation of previous antibiotic use revealed that, in the previous 12 months, 54.8% of patients in the Spanish group and 10% in the Dutch group reported antibiotic use (p<0.001). The prevalence of beta-lactamase producing bacteria was 87.1% in the Spanish group and 73.3% in the Dutch group. Total counts of beta-lactamase producing bacteria on amoxicillin plates (p<0.01), the mean number of different beta-lactamase producing colonies per patient (p<0.001), and the number of amoxicillin resistant colonies (p<0.001) were significantly higher in the Spanish group. 74 beta-lactamase producing strains in the Spanish group and 33 in the Dutch group were isolated for identification. 23 out of 35 identified strains in the Spanish group, and 32 out of 33 in the Dutch group belonged to Prevotella genus. Conclusions: A high prevalence of beta-lactamase producing bacteria has been evaluated in two distinct populations, belonging to two European countries with clear differences in antibiotic usage policy. A higher prevalence and a more complex beta-lactamase producing microflora, were found in the Spanish group, associated with a higher antibiotic consumption. This study shows that a higher use of beta-lactam antibiotics is reflected in the % of beta-lactamase producing bacteria in the subgingival microflora of patients with periodontitis. This information may be important in the treatment of severe periodontitis.