Treatment of mycoplasma contamination in a large panel of cell cultures

Safe, Effective, and Inexpensive Clearance of Mycoplasma Contamination from Cultures of Apicomplexan Parasites with Sparfloxacin

Most commercial products cannot be used for clearance of Mycoplasma contamination from cultures of apicomplexan parasites due to the parasites' dependence on the apicoplast, an essential organelle with DNA replication and translation machinery of cyanobacterial origin. The lone exception, mycoplasma removal agent (MRA), is relatively expensive, and some mycoplasma strains have shown resistance to clearance with MRA. Here, we report that the fluoroquinolone antibiotic sparfloxacin is a safe, effective, and inexpensive alternative for treatment of mycoplasma contamination in cultures of apicomplexan parasites. Sparfloxacin cleared both MRA-sensitive and MRA-resistant mycoplasma species from P. falciparum cultures at 1 and 4 μg/mL, respectively. We show that cultures of three different apicomplexan parasites can be maintained at concentrations of sparfloxacin required to clear mycoplasma without resulting in substantial deleterious effects on parasite growth. We also describe an alternative low-cost, in-house PCR assay for detecting mycoplasma. These findings will be useful to laboratories maintaining apicomplexan parasites in vitro, especially in low-resource environments, where the high cost of commercial products creates an economic barrier for detecting and eliminating mycoplasma from culture. IMPORTANCE These findings will be useful to laboratories maintaining apicomplexan parasites in vitro, especially in low-resource environments, where the high cost of commercial products creates an economic barrier for detecting and eliminating Mycoplasma from culture.

Peroxidase-linked assay for detection of antibodies against bovine leukosis virus

A peroxidase linked assay (PLA) was designed to screen bovine sera for the presence of specific antibodies against bovine leukosis virus (BLV). Out of 201 samples of bovine sera analyzed, 52.2% were considered positive by PLA, 26.4% by AGID, and 38.9% by ELISA. Western blotting analyses excluded 27 samples found to be positive by PLA. PLA showed 100% of sensitivity when compared with AGID and ELISA. Specificity was 64.8% and 78%, respectively (kappa coefficients were 0.70 and 0.83). These findings indicate that PLA can be used as an alternative method for the diagnosis of BLV infection in cattle.

Mycoplasma contamination of cell cultures: Incidence, sources, effects, detection, elimination, prevention

The contamination of cell cultures by mycoplasmas remains a major problem in cell culture. Mycoplasmas can produce a virtually unlimited variety of effects in the cultures they infect. These organisms are resistant to most antibiotics commonly employed in cell cultures. Here we provide a concise overview of the current knowledge on: (1) the incidence and sources of mycoplasma contamination in cell cultures, the mycoplasma species most commonly detected in cell cultures, and the effects of mycoplasmas on the function and activities of infected cell cultures; (2) the various techniques available for the detection of mycoplasmas with particular emphasis on the most reliable detection methods; (3) the various methods available for the elimination of mycoplasmas highlighting antibiotic treatment; and (4) the recommended procedures and working protocols for the detection, elimination and prevention of mycoplasma contamination. The availability of accurate, sensitive and reliable detection methods and the application of robust and successful elimination methods provide powerful means for overcoming the problem of mycoplasma contamination in cell cultures.

Efficiency of Plasmocin™ on various mammalian cell lines infected by mollicutes in comparison with commonly used antibiotics in cell culture: a local experience

Mycoplasma contamination is a deleterious event for cell culture laboratories. Plasmocin™ is used to prevent and eradicate mycoplasma infections from cell. In this study, 80 different mammalian cell lines from various sources; human, monkey, mice, hamster and rat were used to study and evaluate plasmocin™ efficiency and compare it to commonly used antibiotics such as BM-cyclin, ciprofloxacin and mycoplasma removal agent (MRA). It was shown that mycoplasma infections were eradicated by plasmocin™, BM-cyclin, ciprofloxacin and MRA in 65%, 66.25%, 20%, and 31.25%, respectively, of infected cell cultures. However, re-infection with mycoplasmas after the period of 4 months occurred in 10-80% of the studied cell lines. Cell cytotoxicity and culture death was observed in 25, 17.5 and 10% of the treated cells, for plasmocin™, BM-cyclin and MRA, respectively. In this study, Plasmocin™ showed strong ability to eradicate mollicutes from our cell lines with minimal percentage of regrowth. However, due to its high cell cytotoxicity it should be used with caution especially when dealing with expensive or hard-to-obtain cell lines. Amongst the antibiotics tested, BM-cyclin was shown to remove mycoplasma with the highest efficiency.

Isolation of a mycoplasma-specific binding peptide from an unbiased phage-displayed peptide library

An important goal in medicine is the development of methods for cell-specific targeting of therapeutic molecules to pathogens or pathogen-infected cells. However, little progress has been made in cell-specific targeting of bacterially infected cells. Using a phage display approach, we have isolated a 20-mer peptide that binds to Mycoplasma arginini infected pancreatic beta-cells in tissue culture. This peptide binds to M. arginini infected beta-cells 200 times better than a control phage and is specific for the infected cells. Furthermore, transferring the M. arginini contamination to another cell line renders the newly infected cell line susceptible to peptide binding. Immunolocalization experiments suggest that the peptide is binding to M. arginini adhered to the cell surface. The free synthetic peptide retains its binding in the absence of the phage vehicle and tetramerization of the peptide increases its affinity for the infected cells. Efforts have been made to use this peptide to eliminate Mycoplasma from infected cell lines using ferromagnetic beads coated with the selected peptide. A ten-fold reduction of infection was accomplished with one fractionation via this approach. Our results suggest that this peptide, isolated from an unbiased selection, may be of utility for the detection and reduction of Mycoplasma infection in cultured cells. Furthermore, a general implication of our findings is that phage display methods may be useful for identifying peptides that target a broad array of other biological pathogens in a specific fashion.

Comparative antibiotic eradication of mycoplasma infections from continuous cell lines

Accumulating data implicate mycoplasma contamination as the single biggest problem in the culture of continuous cell lines. Mycoplasma infection can affect virtually every parameter and functional activity of the eukaryotic cells. A successful alternative to discarding infected cultures is to attempt to eliminate the contaminants by treatment with specific and efficient antimycoplasma antibiotics. The addition of antibiotics to the culture medium during a limited period of time (1-3 wk) is a simple, inexpensive, and very practical approach for decontaminating continuous cell lines. Here, we examined the effectiveness of several antibiotic treatment protocols that we have employed routinely in our cell lines bank. On an aggregate, 673 cultures from 236 chronically mycoplasma-positive cell lines were exposed to one of the following five antibiotic regimens: mycoplasma removal agent (quinolone; a 1-wk treatment), enrofloxacin (quinolone; 1 wk), sparfloxacin (quinolone; 1 wk), ciprofloxacin (quinolone; 2 wk), and BM-Cyclin (alternating tiamulin and minocycline; 3 wk). The mycoplasma infection was permanently (as determined by three solid mycoplasma detection assays) eliminated by the various antibiotics in 66-85% of the cultures treated. Mycoplasma resistance was seen in 7-21%, and loss of the culture as a result of cytotoxically caused cell death occurred in 3-11% of the cultures treated. Overall, 223 of the 236 mycoplasma-positive cell lines could be cured in a first round of antibiotic treatment with at least one regimen. Taken together, 95% of the mycoplasma-infected cell lines were permanently cleansed of the contaminants by antibiotic treatment, which validates this approach as an efficient and technically simple mycoplasma eradication method.

Comparative antibiotic eradication of mycoplasma infections from continuous cell lines

Accumulating data implicate mycoplasma contamination as the single biggest problem in the culture of continuous cell lines. Mycoplasma infection can affect virtually every parameter and functional activity of the eukaryotic cells. A successful alternative to discarding infected cultures is to attempt to eliminate the contaminants by treatment with specific and efficient antimycoplasma antibiotics. The addition of antibiotics to the culture medium during a limited period of time (1-3 wk) is a simple, inexpensive, and very practical approach for decontaminating continuous cell lines. Here, we examined the effectiveness of several antibiotic treatment protocols that we have employed routinely in our cell lines bank. On an aggregate, 673 cultures from 236 chronically mycoplasma-positive cell lines were exposed to one of the following five antibiotic regimens: mycoplasma removal agent (quinolone; a 1-wk treatment), enrofloxacin (quinolone; 1 wk), sparfloxacin (quinolone; 1 wk), ciprofloxacin (quinolone; 2 wk), and BM-Cyclin (alternating tiamulin and minocycline; 3 wk). The mycoplasma infection was permanently (as determined by three solid mycoplasma detection assays) eliminated by the various antibiotics in 66-85% of the cultures treated. Mycoplasma resistance was seen in 7-21%, and loss of the culture as a result of cytotoxically caused cell death occurred in 3-11% of the cultures treated. Overall, 223 of the 236 mycoplasma-positive cell lines could be cured in a first round of antibiotic treatment with at least one regimen. Taken together, 95% of the mycoplasma-infected cell lines were permanently cleansed of the contaminants by antibiotic treatment, which validates this approach as an efficient and technically simple mycoplasma eradication method.

Continuous hematopoietic cell lines as model systems for leukemia-lymphoma research

Along with other improvements, the advent of continuous human leukemia-lymphoma (LL) cell lines as a rich resource of abundant, accessible and manipulable living cells has contributed significantly to a better understanding of the pathophysiology of hematopoietic tumors. The first LL cell lines, Burkitt's lymphoma-derived lines, were established in 1963. Since then, more than 1000 cell lines have been described, although not all of them in full detail. The major advantages of continuous cell lines is the unlimited supply and worldwide availability of identical cell material, and the infinite viable storability in liquid nitrogen. LL cell lines are characterized generally by monoclonal origin and differentiation arrest, sustained proliferation in vitro under preservation of most cellular features, and specific genetic alterations. The most practical classification of LL cell lines assigns them to one of the physiologically occurring cell lineages, based on their immunophenotype, genotype and functional features. Truly malignant cell lines must be discerned from Epstein-Barr virus (EBV)-immortalized normal cells, using various distinguishing parameters. However, the picture is not quite so straightforward, as some types of LL cell lines are indeed EBV+, and some EBV+ normal cell lines carry also genetic aberrations and may mimic malignancy-associated features. Apart from EBV and human T-cell leukemia virus in some lines, the majority of wild-type LL cell lines are virus-negative. The efficiency of cell line establishment is rather low and the deliberate establishment of new LL cell lines remains by and large an unpredictable random process. Difficulties in establishing continuous cell lines may be caused by the inappropriate selection of nutrients and growth factors for these cells. Clearly, a generally suitable microenvironment for hematopoietic cells, either malignant or normal, cannot yet be created in vitro. The characterization and publication of new LL cell lines should provide important and informative core data, attesting to their scientific significance. Large percentages of LL cell lines are contaminated with mycoplasma (about 30%) or are cross-contaminated with other cell lines (about 15-20%). Solutions to these problems are sensitive detection, effective elimination and rigorous prevention of mycoplasma infection, and proper, regular authentication of cell lines. The underlying cause, however, appears to be negligent cell culture practice. The willingness of investigators to make their LL cell lines available to others is all too often limited. There is a need in the scientific community for clean and authenticated high-quality LL cell lines to which every scientist has access. These are offered by various institutionalized public cell line banks. It has been argued that LL cell lines are genetically unstable (both cytogenetically and molecular genetically). For instance, cell lines are supposed to acquire numerical and structural chromosomal alterations and various types of mutations (e.g. point mutations) in vitro. We present evidence that while nearly 100% of all LL cell lines indeed carry genetic alterations, these alterations appear to be stable rather than unstable. As an example of the practical utility of LL cell lines, the recent advances in studies of classical and molecular cytogenetics, which in large part were made possible by cell lines, are highlighted. A list of the most useful, robust and publicly available reference cell lines that may be used for a variety of experimental purposes is proposed. Clearly, by opening new avenues for investigation, studies of LL cell lines have provided seminal insights into the biology of hematopoietic neoplasia. Over a period of nearly four decades, these initially rather exotic cell cultures, known only to a few specialists, have become ubiquitous powerful research tools that are available to every investigator.

Characterization of Mycoplasma hominis mutations involved in resistance to fluoroquinolones

Fluoroquinolone-resistant mutants of Mycoplasma hominis were selected in vitro from the PG21 susceptible reference strain either by multistep selection on increasing concentrations of various fluoroquinolones or by one-step selection on agar medium with ofloxacin. The quinolone resistance-determining regions (QRDR) of the structural genes encoding the A and b subunits of DNA gyrase were amplified by PCR, and the nucleotide sequences of eight multistep-selected resistant strains were compared to those of susceptible strain PG21. Four high-level resistant mutants that were selected on norfloxacin or ofloxacin contained a C-to-T transition in the gyrA QRDR, leading to substitution of Ser-83 by Leu in the GyrA protein. Analysis of the sequence of the gyrB QRDR of the eight multistep-selected mutants did not reveal any difference compared to that of the gyrB QRDR of the reference strain M. hominis PG21. Similar analyses of eight one-step-selected mutants did not reveal any base change in the gyrA and gyrB QRDRs. These results suggest that in M. hominis, like in other bacterial species, a gyrA mutation at Ser-83 is associated with fluoroquinolone resistance.

Application of a Mycoplasma group-specific PCR for monitoring decontamination of Mycoplasma-infected Chlamydia sp. strains

Mycoplasma contamination of biological materials remains a major problem. Most contaminations are caused by the use of Mycoplasma-contaminated cell lines. We adapted a Mycoplasma group-specific PCR to detect Mycoplasma contamination in cell lines and demonstrate its use in monitoring decontamination procedures with Mycoplasma-contaminated suspensions of Chlamydia spp. Three different methods were investigated: the use of Mycoplasma-specific antiserum in cell culture, physical separation by the combined use of enzymatic treatment and differential centrifugation, and the use of detergents. With these methods only incubation with Triton X-100 resulted in decontamination of Mycoplasma-contaminated suspensions of several laboratory strains of Chlamydia pneumoniae, C. pecorum, and C. trachomatis. Only one C. pneumoniae strain, UZG-1, was sensitive to Triton X-100 treatment. Since 39 of 40 throat swabs from patients with symptoms of an upper respiratory tract infection had positive reactions in the Mycoplasma group-specific PCR, this procedure could also have clinical significance in attempts to propagate C. pneumoniae strains from clinical specimens.

Isolation and characterization of a novel human prostatic stromal cell culture: DuK50

A novel human prostatic stromal cell culture, designated DuK50, has been passed in vitro > 12 mo. Tissue cultures were obtained from material harvested within a normal region of a radical prostatectomy specimen. These monolayers exhibited normal fibroblastic characteristics with each cell having a flattened, elongated appearance. Karyotypic analysis revealed a normal, male 46, XY chromosomal content with no numerical or structural abnormalities. DNA analysis using a Cell Analysis Systems Image Analyzer confirmed a euploid DNA content (7.9 pg DNA). Cellular markers for verification of stromal cell type were performed by immunohistochemical techniques. DuK50 stained positive for vimentin and fibronectin. Immunostains for epithelial cytokeratins and prostate-specific antigen were negative, which ruled out contamination with prostatic epithelial cells. Negative immunostaining with desmin monoclonal antibody and light staining with smooth muscle actin alpha is consistent with the staining pattern of myofibroblasts. Response to various androgens, measured by a microculture tetrazolium assay technique, revealed a significant growth stimulation of DuK50. Soft agar invasiveness assays and tumorigenicity studies in nude mice were negative. DuK50 exhibits a rapid doubling time with excellent plating efficiency, thrives in a readily available media supplemented with fetal bovine serum, and passes with routine trypsin protocols. The availability of this prostatic stromal cell culture may facilitate studies on this cell type's role in growth factor modulation, drug and steroid metabolism, and stromal-epithelial interactions in the prostate.