LAUSR

Streptococcus agalactiae (Group B Streptococcus, GBS) is a pathogen causing neonatal sepsis, meningitis, and invasive infections in the elderly and people with medical conditions. Macrolide and lincosamide resistance rates of GBS are increasing worldwide. A macrolide resistance gene, erythromycin ribosomal methylase (erm), typically confers MLSB phenotype. However, in this study, we recovered and characterized three clinical ermB-PCR-positive isolates of GBS with L phenotype. PCR of ermB and lnuB (lincosamide nucleotidyltransferase) genes were positive in all three clinical isolates. The ermB gene of the clinical isolates harbored C222T (N74N), T224C (I75T), and A299G (N100S) nucleotide (amino acid) substitutions and insertion of an IS1216E element at nucleotide position 643, resulting in the deletion between 643th-738th nucleotide positions of ermB gene, and suggesting loss-of-function of ErmB protein in the three clinical isolates. Since these clinical isolates are pitfalls of PCR method for detecting antimicrobial drug resistance genes, partial deletion of antimicrobial drug resistance genes, which confer contradiction between PCR detection of antimicrobial drug resistance genes and antimicrobial drug resistance phenotypes, must be considered.