Plasmid analysis and antimicrobial susceptibilities of Peptostreptococcus species

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 degrees C followed by proteinase K (0.2 mg/ml) for 1 h at 37 degrees C. In addition we report, the occurrence of clindamycin or metronidazole-resistant peptostreptococci, but these phenotypes were not correlated with plasmid carriage.