title: Spheroplast induction in clinical isolates of Serratia marcescens in the presence of Ca2+ or Mg2+.
abstract: Serratia marcescens was easily induced to form spheroplasts by beta-lactam antibiotics in the presence of Ca2+ or Mg2+ without an osmotic stabilizer such as sucrose. The spheroplasts grew in volume, although they could not divide. They were stable for more than 10 h at 37 degrees C in a medium containing a high concentration of antibiotic, and they had the ability to revert to the original bacillary form. Ca2+ was more effective in spheroplast induction than Mg2+. The effect was proportional to the concentration of cations. In 40% of 180 clinical isolates of S. marcescens, more than 40% of the original bacterial cells were induced to form spheroplasts by ceftizoxime in a medium supplemented with 40 mM Ca2+. A high spheroplast induction rate was observed even in medium with 10 mM Ca2+. Few isolates that were supersusceptible to ceftizoxime (MIC, less than 0.2 microgram/ml) were induced to form spheroplasts at a high rate. No difference in spheroplast induction rate or extent between antibiotic-resistant strains and relatively susceptible strains (MIC, greater than 0.2 microgram/ml) was found. The serotype of S. marcescens had no effect on the spheroplast induction rate. Monocations (Na+ and K+) had little effect on spheroplast induction.
authors.affiliation: Department of Bacteriology, Kinki University School of Medicine, Osaka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tada
authors.forename: J
authors.initials: J
authors.lastname: Yamaguchi
mesh_terms: D000372:Agglutination Tests; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D003470:Culture Media; D004352:Drug Resistance, Microbial; D006801:Humans; D007769:Lactams; D008274:Magnesium / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D009997:Osmotic Pressure; D012703:Serotyping; D012706:Serratia marcescens / Q000145:classification / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D013104:Spheroplasts / Q000648:ultrastructure*
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D007769:Lactams; D008274:Magnesium; D002118:Calcium