Growth of cell-wall-deficient variants of Enterobacter cloacae facilitates beta-lactamase derepressed mutants

Int J Antimicrob Agents. 2002 May;19(5):397-404. doi: 10.1016/s0924-8579(02)00008-0.

Abstract

The degree to which cell-wall-deficient bacteria (CWDB) are involved in the generation of beta-lactamase derepressed mutants (DM) was measured using Enterobacter cloacae 3624. The frequency of DM in non-permissive isotonic ticarcillin medium was compared with their frequency in hypertonic ticarcillin medium that supports CWDB growth. DM were resistant to extended spectrum penicillins and cephalosporins and had a basal beta-lactamase activity of >300 units/mg protein. Anaerobic growth of CWDB increased the relative risk of DM 2 x 10(6)-fold. Aerobic incubation produced fewer CWDB colonies but the risk of DM was still increased 400-fold over non-permissive controls. These results define a new role for CWDB as intermediaries in the emergence of resistance.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Cell Division
  • Cell Wall / genetics*
  • Colony Count, Microbial
  • Culture Media / chemistry
  • Drug Resistance, Bacterial*
  • Drug Stability
  • Enterobacter cloacae / cytology*
  • Enterobacter cloacae / drug effects
  • Enterobacter cloacae / enzymology
  • Enterobacter cloacae / genetics*
  • Gene Expression Regulation, Bacterial
  • Hypertonic Solutions
  • Microbial Sensitivity Tests
  • Mutation / genetics*
  • Risk Factors
  • Ticarcillin / pharmacology
  • beta-Lactamases / genetics
  • beta-Lactamases / metabolism*

Substances

  • Anti-Bacterial Agents
  • Culture Media
  • Hypertonic Solutions
  • beta-Lactamases
  • Ticarcillin