Spheroplast Formation in Clinical Isolates of Gram-Negative Bacteria by fi-lactam Antibiotic in the Presence of Ca²⁺ or Mg²⁺

Abstract

Induction to cell wall-deficient bacteria has been suggested to be a cause of intractable and opportunistic infection after chemotherapy. Spheroplast formation by β-lactam antibiotic in not so high osmotic pressure was investigated in six species of gram-negative bacteria. Some species of gram-negative bacteria were induced to form spheroplast at a high rate by 1: 10 concentration of ceftizoxime in the presence of Ca²⁺ or Mg²⁺. Especially in 38% of Prosteus mirabi is and P. vulgaris, more than 40% of the original cells were induced to form spheroplast by ceftizoxime in a medium supplemented with 40mM Ca²⁺. The same formation rate was also found in 22% of Serratia marcescens. Formation rates in the drug sensitive strains of S. marcescens were enhanced as the drug concentration increased. Ca²⁺ was more effective in spheroplast formation than Mg²⁺.