Characterization of the Tn916-like transposon Tn3872 in a strain of Abiotrophia defectiva (Streptococcus defectivus) causing sequential episodes of endocarditis in a child

Clinical blood isolates from three sequential episodes of endocarditis occu rring over a 6-month period in a child with a malformative cardiopathy were investigated. All isolates identified as Abiotrophia defectiva were resist ant to erythromycin-clindamycin and to tetracycline-minocycline, due to the presence of sequences homologous to the erythromycin resistance gene ermB and to the tetracycline resistance gene tet(M), respectively. These resista nce genes were located on a chromosomally borne composite Tn916-related tra nsposon. These results demonstrate the involvement of conjugative transposo ns in the dissemination of antibiotic resistance in the genus Abiotrophia.