Continuous cell lines are frequently contaminated with microorganisms, mycoplasmas being the most prominent and cumbersome. In our experience, of the 300 cell lines examined more than one third was infected with mycoplasmas. Mycoplasma contamination can affect virtually every parameter and functional activity of a cultured cell. An alternative to the recommended disposal of infected cultures is an attempt to eliminate the contaminants. Adding
antibiotics with strong activity against mycoplasmas to the culture medium is a simple, inexpensive and efficient decontamination method. Here, we studied the effectiveness of the new
antibiotic enrofloxacin (
Baytril) developed specifically for use against mycoplasmas.
Baytril is a new synthetic agent from the group of
quinolone derivatives that are
DNA gyrase inhibitors. Thirty-two chronically infected cell lines (27 human
leukemia-
lymphoma cell lines) were treated with
Baytril in a prospective study in direct comparison with three other well-established anti-mycoplasma regimens, the
antibiotics BM-Cyclin, Ciprobay and MRA (
Mycoplasma Removal Agent). Mycoplasmas were detected by
DNA staining,
agar colony growth,
DNA-
RNA hybridization, polymerase chain reaction, and
monoclonal antibody staining. Treatment with
Baytril eliminated the contaminants in 30/32 cultures (94%). The cure rates for Ciprobay,
BM-Cyclin and MRA were 91%, 81%, and 75%, respectively. The IC50 values of
Baytril for cell lines varied over a wide range depending on the type of hematopoietic cell lineage with T- and B-cell lines being more sensitive targets.
Baytril-treated cell lines remained mycoplasma-negative over a 12-week
antibiotic-free culture period. Low levels of
mycoplasma infection were shown not to persist by repeat testing after growth without
antibiotics. A retrospective analysis of anti-mycoplasma treatments with
BM-Cyclin, Ciprobay, MRA or
Baytril showed that 265/351 cultures (75%) were immediately cured of mycoplasma; however, all of the remaining, mycoplasma-positive cultures harboring mycoplasms resistant to the first
antibiotic could be cleaned up by a second round with a different
antibiotic.
Baytril is an efficient anti-mycoplasma
antibiotic and based on its high cure rate might be the treatment of first choice.