Transferable Plasmids Mediating Multiple-Antibiotic Resistance in Streptococcus faecalis subsp. liquefaciens

Abstract

In strain HK187 ( Streptococcus faecalis subsp. liquefaciens ) four plasmids were isolated. The molecular weights, as analyzed in neutral sucrose gradients and by electron microscopy, were found to be about 36 × 10 ⁶ , 31 × 10 ⁶ , 26 × 10 ⁶ , and 4 × 10 ⁶ . Plasmid 3, also designated pFK14, with a molecular weight of 26 × 10 ⁶ , was found to be responsible for resistance to chloramphenicol and erythromycin and also for high-level resistance to streptomycin and lincomycin. In mixed cultures these four resistances could be transferred with high frequency to a plasmid-free recipient, S. faecalis strain JH2-2.