Emergence of penicillin resistance among Fusobacterium nucleatum populations of commensal oral flora during early childhood

Abstract

Penicillin resistance due to β-lactamase production is surprisingly common among oral bacteria in childhood. Fusobacterium nucleatum, a Gram-negative anaerobic bacillus, is a member of the developing oral commensal flora. As part of the investigation on the emergence of oral bacterial resistance, the aim of the present study was to examine longitudinally the penicillin resistance among salivary F. nucleatum populations as related to age, day care attendance and sibling history, and exposure to antimicrobial agents. Altogether 1492 F. nucleatum isolates from saliva of 44 healthy infants followed at a study clinic at 2, 6, 12, 18 and 24 months of age were tested for β-lactamase production. Furthermore, the 276 β-lactamase-positive isolates were examined for their in vitro susceptibility to penicillin G by the NCCLS-approved agar dilution method. Statistical analysis of the associations between penicillin-resistant isolates and infants' age, day care attendance, number of siblings and their ear infections, and exposure to antimicrobial agents was performed by SPSS Windows Version 10. The prevalence of infants harbouring β-lactamase-producing F. nucleatum strains increased from 2% to 49% during the follow-up time. In nearly all cases β-lactamase-producing F. nucleatum isolates were found simultaneously with β-lactamase-negative isolates. Most β-lactamase-producing isolates (80%) showed an MIC of ≥8 mg/L. In conclusion, the prevalence of infants harbouring penicillin-resistant F. nucleatum, due to β-lactamase production increased with age and usage of antimicrobial agents during the first year of life.