Plasmid analysis and antimicrobial susceptibilities of Peptostreptococcus species

Abstract There are no published methods on plasmid isolation from Peptostreptococcus spp., therefore two methods of plasmid isolation from this genera were analysed: the boiling and alkaline-SDS methods. Plasmid DNA was not recovered by the boiling method, however, with the alkaline-SDS method, cryptic plasmid DNA was detected in two P. asaccharolyticus and one P. magnus strains. To achieve optimum lysis, Peptostreptococcus cells were treated with lysozyme (2 mg/ml) for 15 min. at 37°C followed by proteinase K (0.2 mg/ml) for 1 h at 37°C. In addition we report, the occurence of clindamycin or metronidazole-resistant peptostreptococci, but these phenotypes were not correlated with plasmid carriage.