beta-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 t he 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 s elected and asked to report on: current systemic disorders and medications, history of use of antibiotics, and smoking habits. Clinical variables incl uded probing pocket depth, clinical attachment level, plaque, bleeding on p robing, and suppuration. Pooled subgingival samples of 4 selected sites wer e anaerobically cultured in blood agar plates with and without amoxicillin, and amoxicillin/clavulanate. Bacterial colonies growing on amoxicillin pla tes but not on amoxicillin/clavulanate plates were tested for beta-lactamas e production. beta-lactamase producing bacteria were isolated and identifie d. 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 a ntibiotic use revealed that, in the previous 12 months, 54.8% of patients i n 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 diff erent beta-lactamase producing colonies per patient (p<0.001), and the numb er of amoxicillin resistant colonies (p<0.001) were significantly higher in the Spanish group. 74 beta-lactamase producing strains in the Spanish grou p 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 grou p belonged to Prevotella genus. Conclusions: A high prevalence of beta-lactamase producing bacteria has bee n evaluated in two distinct populations, belonging to two European countrie s with clear differences in antibiotic usage policy. A higher prevalence an d a more complex beta-lactamase producing microflora, were found in the Spa nish group, associated with a higher antibiotic consumption. This study sho ws that a higher use of beta-lactam antibiotics is reflected in the % of be ta-lactamase producing bacteria in the subgingival microflora of patients w ith periodontitis. This information may be important in the treatment of se vere periodontitis.