title: Polymyxin B-induced cocarde growth phenomenon of Serratia marcescens due to cationic detergent-like activity of polymyxin B.
abstract: 14 of 74 test strains of Serratia marcescens yielded reproducible cocarde-like growths (coc+) around 30-micrograms disks of polymyxin B (PB) on Müller-Hinton, brain heart infusion and tryptic soy agar. The coc+ phenomenon was not due to nutrient effects of growth medium nor did it correlate with either group A (phage tail) bacteriocinogeny or colicinogeny as determined with 32 selected test strains; mitomycin C failed to give rise to coc+ growths. The anionic bile salts of MacConkey agar as well as aqueous sodium deoxycholate neutralized the coc+ activity of PB. Benzalkonium chloride, chlorhexidine digluconate, and cetyltrimethylammonium bromide by themselves did not produce cocardes. Rather, these cationic detergents enhanced PB activity somewhat against selected coc+ and coc- strains of S. marcescens. It was concluded that the PB-induced growth phenomenon of S. marcescens was due to the cationic detergent-like activity of this polypeptide antibiotic.
mesh_terms: D003470:Culture Media; D003902:Detergents / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D011112:Polymyxin B / Q000494:pharmacology*; D011113:Polymyxins / Q000494:pharmacology*; D012706:Serratia marcescens / Q000187:drug effects* / Q000254:growth & development; D013501:Surface-Active Agents / Q000494:pharmacology*
chemical_list: D003470:Culture Media; D003902:Detergents; D011113:Polymyxins; D013501:Surface-Active Agents; D011112:Polymyxin B