β-Lactamase activity and outer membrane permeability of β-lactam antibiotic resistant Prevotella in saliva of elementary school children

Abstract

We studied the relation between the resistance to β-lactam antibiotics and β-lactamase activity, and the role of the outer membrane permeability of β-lactam antibiotic resistant Prevotella in the saliva of elementary school children. Strains which had a higher antibiotic minimum inhitory concentration (MIC) also had high β-lactamase activity. The number of strains was calculated that had both on MIC of 50 μg/ml or greater and β-lactamase activity of 30 mU/mg or more. The percentage of these strains was 17-57% for penicillin G, 0-61% for ampicillin, 50-83% for cefaclor, 0-57% for cefazolin and 0-50% for aztreonam. However, the percentages for cefmetazole, latamoxef and cefteram were low, and the value for imipenem was zero. Nine of the 58 strains tested had a cefaclor MIC with EDTA that was 1/4 or less the cefaclor MIC without EDTA. These results suggest that β-lactamase plays an important role in the mechanism of β-lactam antibiotic resistance in the Prevotella tested, and that outer membrane permeability is related to this mechanism in some of the strains.