R Plasmids in Streptococcus agalactiae (Group B)

Abstract

Two plasmids determining resistance to tetracycline .(RIP500) and to chloramphenicol, erythromycin, lincomycin, and pristinamycin I (RIP501) were isolated from a strain of Streptococcus agalactiae. The frequency-of-resistance loss is very low for RIP500 (<3 x 104) but higher for RIP501 (the efficiency was dependent upon the curing agents and incubation temperature and varied between 0.5 and 96%). Derivatives susceptible to all drugs were also obtained. RIP500 and RIP501 have similar molecular weights (17.9 x 106 and 20 x 106, respectively) and represent different percentages of total deoxyribonucleic acid (0.4 and 4%, respectively). The number of copies of RIP500 and RIP501 per cell is different, and these plasmids are likely replicated under different kinds of control (stringent and/or relaxed). No plasmid deoxyribonucleic acid was found in a derivative of strain B96 susceptible to all drugs.

Characterization of a Small Plasmid Determining Resistance to Erythromycin, Lincomycin, and Vernamycin B α in a Strain of Streptococcus sanguis Isolated from Dental Plaque

“…pyogenes (6,25,28), and a group B streptococcus (20). In several cases, the molecular masses of these plasmids are similar, with plasmid DNA being of a size of approximately 17 megadaltons (6,9,13,26).…”

The Plasmidome of Firmicutes: Impact on the Emergence and the Spread of Resistance to Antimicrobials

“…The Inc18 group is traditionally represented by three emblematic plasmids: pSM19035 (101) and pIP501 from S. agalactiae and pAMβ1 from E. faecalis (64,(101)(102)(103)(104). It gets its name from the apparent incompatibility of these plasmids with each other described in seminal studies in the field and following the nomenclature of Inc groups started by Richard Novick for staphylococcal plasmids (50,60,64,105).…”

The TraA relaxase autoregulates the putative type IV secretion-like system encoded by the broad-host-range Streptococcus agalactiae plasmid pIP501

“…pIP501 is a 30 599 bp conjugative Inc18 plasmid, originally isolated from Streptococcus agalactiae (Horodniceanu et al, 1976), conferring resistance to the MLS group of antibiotics (erythromycin) and to chloramphenicol. pIP501 exhibits a very broad host range for conjugative transfer, including streptococci, lactobacilli, enterococci, lactococci, staphylococci, bacilli, Listeria and clostridia.…”