Antibiotic Sensitivity and β-Lactamase Activity of Penicillin G Resistant Capnocytophaga in Saliva of Children with Infantile Acute Lymphatic Leukemia

Abstract

     We studied antibiotic sensitivity, and the role of β-lactamase activity and outer membrane permeability in the mechanism of β-lactam antibiotic resistance of Capnocytophaga and Prevotella in saliva of children with infantile acute lymphatic leukemia. The 90% minimum inhibitory concentration (MIC₉₀) of imipenem (IPM), cefteram-pivoxil (CFTM-PI), clindamycin (CLDM) and ofloxicin (OFLX) against penicillin G (PCG) resistant Capnocytophaga and Prevotella was 1.56–100μg/ml. The MIC₉₀ of other antibiotics tested was ≥ 200μg/ml. β-Lactamase activity was detected in all strains of both microorganisms. The β-lactamase of Capnocytophaga and Prevotella dissolved ampicillin (ABPC) and cefazolin (CEZ) substrates, respectively. The activity of Capnocytophaga β-lactamase was 7–33mU/mg for ABPC and 22–94mU/mg for CEZ, while these values for Prevotella were 6–149mU/mg for the two substrates. The β-lactamase of both microorganisms dissolved more CEZ substrate than ABPC substrate. The number of isolates was calculated that had both a MIC of ≥ 50μg/ml and β-lactamase activity of ≥ 30mU/mg. The percentage of these isolates was low for IPM and CFTM-PI. However, the percentages were high for other antibiotics tested. Obstruction of outer membrane permeability was observed with ethylendiaminetetraacetic acid disodium salt in the MIC of PCG, CEZ and LMOX in Capnocytophaga, and in the MIC of ABPC and CER in Prevotella.
     These results suggest that multi-resistant isolates of Capnocytophaga and Prevotella were isolated from oral cavities of children with infantile acute lymphatic leukemia, and β-lactamase was closely related to the mechanism of β-lactam antibiotic resistance in these microorganisms.