Plasmid loss testing

Plasmid Loss testing service, also known as Marker Retention service, is offered as part of our Non-integrated Cell Bank Characterization services package to determine the percentage of cells in a cell  sample that contains a selectable marker such as antibiotic resistant gene. In microbial cell culture process, a bacteria stain may lose its antibiotic resistance due to the loss of its resistant-coding plasmid, an undesirable event in biologics manufacturing.
This service is available at Research, GLP, and GMP grade.

Assay Description

Test sample will be tested for the presence or absence of the selective marker, such as an antibiotic resistant gene coded in the plasmid in E. Coli. Test sample, positive, and negative cells will be plated to obtain isolated colonies. Results will be reported as the percentage of cells retaining the marker, or percentage of plasmid loss.


  • A report with the following information will be delivered:
  • Images of selective and non-selective growth plates
  • Colony counts
  • Calculation of percentage of marker retention or plasmid loss
  • Turn-around Time: 4 weeks
  • Contact our customer service to discuss your needs in non-integrated cell bank characterization.