title: Surprisingly fast disappearance of beta-lactam selection pressure in cultivation as detected with novel biosensing approaches.
abstract: Tetracycline and beta-lactam resistances among others are used as selection markers in the production of recombinant proteins. The beta-lactam resistance is based on degradation, i.e. the selection pressure gradually disappears from the culture, whereas tetracycline resistance is based on active efflux. We have studied the kinetics of the stability of antibiotic selection pressure in culture using a simple model system (pBR322 in Escherichia coli). Concentrations of ampicillin, carbenicillin and tetracycline were measured with novel sensor cells developed in our lab. These cells are specifically induced to produce light in the presence of the drugs and here their performance was shown to be excellent in monitoring antibiotic concentrations in cell culture. The sensor cells are cheap to produce and use and a high number of samples can be analysed simultaneously. To our surprise, ampicillin and carbenicillin were completely degraded after 2.5-3.0 h of culture, although it has been widely claimed that especially carbenicillin is a good selective agent, whereas tetracycline was stable in culture. beta-lactamase activity in culture was found to correlate with the kinetics of ampicillin degradation.
authors.affiliation: Department of Biotechnology, Sixth Floor, University of Turku, Tykistökatu 6, FIN-20520 Turku, Finland. teemu.korpimak@utu.fi
authors.forename: Teemu
authors.initials: T
authors.lastname: Korpimäki
authors.forename: Jussi
authors.initials: J
authors.lastname: Kurittu
authors.forename: Matti
authors.initials: M
authors.lastname: Karp
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015374:Biosensing Techniques / Q000379:methods* / Q000639:trends; D003470:Culture Media / Q000737:chemistry; D004355:Drug Stability; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D013752:Tetracycline / Q000032:analysis / Q000494:pharmacology; D013753:Tetracycline Resistance / Q000235:genetics; D013997:Time Factors; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000032:analysis / Q000378:metabolism; D047090:beta-Lactams / Q000032:analysis / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D047090:beta-Lactams; D001618:beta-Lactamases; D013752:Tetracycline