β-Lactamase Production by Oral Anaerobic Gram-Negative Species in Infants in Relation to Previous Antimicrobial Therapy

Abstract

ABSTRACT The frequency of β-lactamase production in gram-negative bacteria has increased considerably during recent years. In this study, β-lactamase production by oral anaerobic gram-negative rods isolated from saliva was longitudinally examined for 44 Caucasian infants at the ages of 2, 6, and 12 months in relation to their documented exposure to antibiotics. Isolates showing decreased susceptibility to penicillin G (1 μg/ml) were examined for β-lactamase production by using a chromogenic cephalosporin disk test. β-Lactamase-positive, gram-negative anaerobic species were found in 11, 55, and 89% of each age group, respectively. β-Lactamase production was most frequent among organisms of the Prevotella melaninogenica group. At 12 months, 73% of the infants harbored β-lactamase-producing members of the P. melaninogenica group, 55% had nonpigmented Prevotella species, 25% had Porphyromonas catoniae , 23% had Fusobacterium nucleatum , and 5% had Capnocytophaga species. Several β-lactamase-producing species could be simultaneously found in the infants’ mouths. The presence of β-lactamase-producing species was significantly associated with the infants’ exposure to antibiotics through antimicrobial treatments given to the infants and/or their mothers.