Species-specific PCR for identification of common contaminant mollicutes in cell culture

Minimal Bacterial Cell JCVI-syn3B as a Chassis to Investigate Interactions between Bacteria and Mammalian Cells

Mycoplasmas are atypical bacteria with small genomes that necessitate colonization of their respective animal or plant hosts as obligate parasites, whether as pathogens, or commensals. Some can grow axenically in specialized complex media yet show only host-cell-dependent growth in cell culture, where they can survive chronically and often through interactions involving surface colonization or internalization. To develop a mycoplasma-based system to identify genes mediating such interactions, we exploited genetically tractable strains of the goat pathogen Mycoplasma mycoides (Mmc) with synthetic designer genomes representing the complete natural organism (minus virulence factors; JCVI-syn1.0) or its reduced counterpart (JCVI-syn3B) containing only those genes supporting axenic growth. By measuring growth of surviving organisms, physical association with cultured human cells (HEK-293T, HeLa), and induction of phagocytosis by human myeloid cells (dHL-60), we determined that JCVI-syn1.0 contained a set of eight genes (MMSYN1-0179 to MMSYN1-0186, dispensable for axenic growth) conferring survival, attachment, and phagocytosis phenotypes. JCVI-syn3B lacked these phenotypes, but insertion of these genes restored cell attachment and phagocytosis, although not survival. These results indicate that JCVI-syn3B may be a powerful living platform to analyze the role of specific gene sets, from any organism, on the interaction with diverse mammalian cells in culture.

A spatial statistical framework for the parametric study of fiber networks: Application to fibronectin deposition by normal and activated fibroblasts

Due to the complex architectural diversity of biological networks, there is an increasing need to complement statistical analyses with a qualitative and local description of their spatial properties. One such network is the extracellular matrix (ECM), a biological scaffold for which changes in its spatial organization significantly impact tissue functions in health and disease. Quantifying variations in the fibrillar architecture of major ECM proteins should considerably advance our understanding of the link between tissue structure and function. Inspired by the analysis of functional magnetic resonance imaging (fMRI) images, we propose a novel statistical analysis approach embedded into a machine learning paradigm, to measure and detect local variations of meaningful ECM parameters. We show that parametric maps representing fiber length and pore directionality can be analyzed within the proposed framework to differentiate among various tissue states. The parametric maps are derived from graph-based representations that reflect the network architecture of fibronectin (FN) fibers in a normal, or disease-mimicking in vitro setting. Such tools can potentially lead to a better characterization of dynamic matrix networks within fibrotic tumor microenvironments and contribute to the development of better imaging modalities for monitoring their remodeling and normalization following therapeutic intervention.

Three induced pluripotent stem cell lines (TRNDi033-A, TRNDi034-A, TRNDi035-A) generated from lymphoblasts of three apparently healthy individuals

Expanded human lymphoblast cells from three different aged healthy individuals, 8-year-old male, 0-year-old newborn (NB) male, and 26-year-old female, were used to generate induced pluripotent stem cell (iPSC) lines TRNDi033-A, TRNDi034-A and TRNDi035-A, respectively, by exogenous expression of five reprogramming factors, human OCT4, SOX2, KLF4, L-MYC and LIN28. The authenticity of established iPSC lines was confirmed by the expressions of stem cell markers, karyotype analysis, embryoid body formation, and scorecard analysis. These iPSC lines could serve as healthy donor controls that are age and sex matched for the studies involving patient-specific iPSCs.

Development and Evaluation of a New qPCR Assay for the Detection of Mycoplasma in Cell Cultures

In recent years, cell culture has become an important tool not only in research laboratories, but also in diagnostic and biotechnological development laboratories. Mycoplasma contamination is present in up to 35% of cell cultures used in research and in cell therapies. This fact represents a significant problem since such contamination can cause disastrous effects on eukaryotic cells by altering their cellular parameters, which, in turn, can lead to unreliable experimental results. For this reason, it is mandatory to carry out continuous testing for the presence of Mycoplasma in cell culture and the development of appropriate methodologies for this purpose. An ideal detection methodology should be fast, sensitive, and reliable. In this study, we propose an alternative detection method based on real-time PCR in conjunction with a novel combination of primers and probes that have been improved to increase their efficiency. The new PCR method demonstrates 100% sensitivity and specificity results in the detection of common Mycoplasma species that contaminate cell cultures. Whilst 11 of 45 tested supernatants were positive for Mycoplasma (24.4%) using the new PCR method (corresponding to 5 of the 14 lines tested (35.71%)), only 10 of 45 supernatants showed positive results with the commercial Venor®GeM qEP and Plasmotest® kit. In addition, the new PCR method exhibits a high capacity to detect less-frequent Mycoplasma species, such as those related to the M. mycoides cluster. The use of an alternative Mycoplasma-detection method in cell culture labs can guarantee the detection of Mycoplasma contamination, especially in cases when dubious results are recorded.

Coalescent RNA-localizing and transcriptional activities of SAM68 modulate adhesion and subendothelial basement membrane assembly

Endothelial cell interactions with their extracellular matrix are essential for vascular homeostasis and expansion. Large-scale proteomic analyses aimed at identifying components of integrin adhesion complexes have revealed the presence of several RNA binding proteins (RBPs) of which the functions at these sites remain poorly understood. Here, we explored the role of the RBP SAM68 (Src associated in mitosis, of 68 kDa) in endothelial cells. We found that SAM68 is transiently localized at the edge of spreading cells where it participates in membrane protrusive activity and the conversion of nascent adhesions to mechanically loaded focal adhesions by modulation of integrin signaling and local delivery of β-actin mRNA. Furthermore, SAM68 depletion impacts cell-matrix interactions and motility through induction of key matrix genes involved in vascular matrix assembly. In a 3D environment SAM68-dependent functions in both tip and stalk cells contribute to the process of sprouting angiogenesis. Altogether, our results identify the RBP SAM68 as a novel actor in the dynamic regulation of blood vessel networks.

Identification of cell culture contamination by an unusual species of Mycoplasma related to the M. mycoides cluster

Mycoplasma contamination is a significant problem in cell culture replication and maintenance. From more than 200 known species, a limited number of Mycoplasma species have been detected in cell cultures, representing new species or variants that can escape detection systems. A qPCR commercial kit was used for Mycoplasma detection in cell cultures. Furthermore, an amplified Mycoplasma species was sequenced and summited for sequence assembly, clustering, and evolutionary analysis study. Our work has identified a new and unusual variant or species of Mycoplasma that possesses a high degree of homology with species related with M. mycoides cluster. This variant is usually associated with cattle but has been detected contaminating a cell culture. Mycoplasma testing (even for unusual species) in cell cultures is essential to ensure the validity and reproducibility of research that uses cell cultures and to ensure the quality of cell line deposits in biobanks. For this reason, it is necessary to perform continuous checks for the absence of Mycoplasma in cell cultures and engage in the continuous adaptation of relevant detection systems.

Detection of Mycoplasma Contamination in Transplanted Retinal Cells by Rapid and Sensitive Polymerase Chain Reaction Test

Contamination of cells/tissues by infectious pathogens (e.g., fungi, viruses, or bacteria, including mycoplasma) is a major problem in cell-based transplantation. In this study, we tested a polymerase chain reaction (PCR) method to provide rapid, simple, and sensitive detection of mycoplasma contamination in laboratory cultures for clinical use. This mycoplasma PCR system covers the Mycoplasma species (spp.) listed for testing in the 17th revision of the Japanese Pharmacopoeia, and we designed it for use in transplantable retinal cells. Here, we analyzed mycoplasma contamination in induced pluripotent stem cell (iPS cell)-derived transplantable retinal pigment epithelium (RPE) cells. In the spike tests to RPE cells with nine species of class Mollicutes bacteria, including seven Mycoplasma spp. and one of each Acholeplasma spp. and Ureaplasma spp., contamination at the concentration of 100 and 10 CFU/mL were detected with 100% probability in all cases, while 1 CFU/mL had a detection rate of 0–75%. DNA prepared from bacteria species other than class Mollicutes species was not detectable, indicating the specificity of this PCR. While iPS cells and iPS-RPE cells established in our laboratory were all negative by this PCR, some of the commercially available cell lines were positive. Cells for transplantation should never have infection, as once pathogens are implanted into the eyes, they can cause severe intraocular inflammation. Thus, it is imperative to monitor for infections in the transplants, although generally, mycoplasma infection is difficult to detect.

A low-cost simple test for weekly detection of Mycoplasma hyorhinis and arginini contaminations in cell cultures and viral preparations

Mollicutes (Mycoplasma and Acholeplasma) are parasitic bacteria that adhere to cellular surfaces, naturally resistant to many antibiotics and extremely small. They are often found as contaminants in cultured cells, where they go unnoticed. They may be present in viral stocks because they are present in supernatants of cells where cultured viruses are released. The best way to keep laboratories free of Mycoplasma is to discard infected cultures, but, as judged by the very common finding of Mycoplasma-contaminated cultures in many laboratories, this is not done as often as it should be. A possible reason is that most procedures recommended take as long as performing a simple experiment and many laboratories delay testing to save money and time. Indeed, many methods exist to detect Mycoplasma infection of cell lines, but they take at least a couple of hours of hands-on work, if not more. Here we describe a procedure to screen viral stocks and tissue cultures for Mycoplasma presence. It relies on isolation of Mycoplasma on ordinary horse blood agar directly from exhausted tissue culture supernatants and does not require experienced personnel or expensive equipment. It only requires minutes of hands-on work, and, for this, it may be useful for weekly screening of cultures. It yields semiquantitative results in roughly 5 days, which is the time that usually passes between one subculture passage of cells in vitro to another. Because of its simplicity, it may be useful for detecting Mycoplasma in viral stocks and for frequent screening of cultures in research laboratories.

Mycoplasma bovis Infections in Free-Ranging Pronghorn, Wyoming, USA

Mycoplasma bovis is 1 of several bacterial pathogens associated with pneumonia in cattle. Its role in pneumonia of free-ranging ungulates has not been established. Over a 3-month period in early 2019, »60 free-ranging pronghorn with signs of respiratory disease died in northeast Wyoming, USA. A consistent finding in submitted carcasses was severe fibrinosuppurative pleuropneumonia and detection of M. bovis by PCR and immunohistochemical analysis. Multilocus sequence typing of isolates from 4 animals revealed that all have a deletion in 1 of the target genes, adh-1. A retrospective survey by PCR and immunohistochemical analysis of paraffin-embedded lung from 20 pronghorn that died with and without pneumonia during 2007–2018 yielded negative results. These findings indicate that a distinct strain of M. bovis was associated with fatal pneumonia in this group of pronghorn.

Development of New PCR Assay with SYBR Green I for Detection of Mycoplasma, Acholeplasma, and Ureaplasma sp. in Cell Cultures

Mycoplasma, Acholeplasma, and Ureaplasma sp. are atypical bacteria responsible for in vitro cell culture contaminations that can warp the results. These bacteria also cause human and animal infections and may lead to chronic diseases. In developed polymerase chain reaction (PCR) in this study a quantitative PCR with SYBR Green I fluorochrome was applied to facilitate the Mycoplasma, Acholeplasma, and Ureaplasma sp. DNA detection and identification. Screening Test-1 v.1 (triplex qPCR) allowed for the detection of 11 species. Test-1 v.2 (three single qPCRs) pre-identified three subgroups, allowing for the reduction of using single qPCRs in Test-2 for species identification. The range of both tests was consistent with pharmacopeial requirements for microbial quality control of mammal cells and included detection of M. arginini, M. orale, M. hyorhinis, M. fermentans, M. genitalium, M. hominis, M. pneumoniae, M. salivarium, M. pirum, A. laidlawii, and U. urealyticum. Limit of detection values varied between 125–300 and 50–100 number of copies per milliliter in Test-1 and Test-2, respectively. Test-1 and Test-2 showed fully concordant results, allowed for time-saving detection and/or identification of selected species from Mycoplasma, Acholeplasma, and Ureaplasma in tested cell cultures.

Prevalence Determination of m. Hominis and m. Genitalium in the Semen Samples in the Northeast of Iran Using Culture and Multiplex Polymerase Chain Reaction

Infertility has recently become a growing social and economic world problem. Genital mycoplasmas, such as Mycoplasma hominis and M. genitalium, are most frequently associated with several adverse effects on men’s fertility. The present study aimed to determine the prevalence of M. hominis and M. genitalium in the semen samples in thenortheast of Iran. During thiscross-sectional study from February to May, 2018, 100 semen samples were collected from 100 infertile men in Mashhad, Khorasan Razavi province, northeast of Iran. The presence of M. hominis and M. genitalium was detected by cultivation, polymerase chain reaction (PCR), and Multiplex PCR assays. The colony of mycoplasma was confirmed by Diene’s stain; moreover, arginine hydrolysis, glucose, and urea utilization were evaluated. The following semen indices were analyzed according to World Health Organization guidelines for semen analysis: color, volume, appearance, liquefaction, viscosity, concentration, pH, leukocyte concentration, progressive motility, morphological normality, motile sperm concentration, functional sperm concentration, sperm motility index, and functional sperm. The gene of 16SrRNA (GPO1& MGSO primers) was used as the target gene of the Mycoplasma genus in PCR assay. Multiplex-PCR was performed with a specific primer for conserved regions in the 16SrRNA gene for M. hominis (RNAH1& RNAH2 primers) and the 140-kDa Adhesion Protein Gene for M. genitalium (MG1 & MG2 primers).According to the results,9 (9%) samples were PCR-positive for Mycoplasma spp , while there were 7 (7%) cases isolated by cultivation. M. hominis was detected in 8 (8%) samples by Multiplex PCR, while there was no evidence for M. genitalium. The mean age scores of all infertile and infected men were obtained at 31 and 30 years, respectively. The study could not show any statistical correlation between mycoplasma infection and abnormal semen parameters. The heterogeneity of mycoplasma prevalence in the reports can be ascribed to differences in geographic areas, the sensitivity of the identification method, condition of the group (fertile/infertile), sample size, and operator proficiency. Various results have been reported in numerous studies conducted on the relationship between mycoplasma infection and abnormal semen parameters.

Fibronectin Extra Domains tune cellular responses and confer topographically distinct features to fibril networks

Cellular fibronectin (FN; also known as FN1) variants harboring one or two alternatively spliced so-called extra domains (EDB and EDA) play a central bioregulatory role during development, repair processes and fibrosis. Yet, how the extra domains impact fibrillar assembly and function of the molecule remains unclear. Leveraging a unique biological toolset and image analysis pipeline for direct comparison of the variants, we demonstrate that the presence of one or both extra domains impacts FN assembly, function and physical properties of the matrix. When presented to FN-null fibroblasts, extra domain-containing variants differentially regulate pH homeostasis, survival and TGF-β signaling by tuning the magnitude of cellular responses, rather than triggering independent molecular switches. Numerical analyses of fiber topologies highlight significant differences in variant-specific structural features and provide a first step for the development of a generative model of FN networks to unravel assembly mechanisms and investigate the physical and functional versatility of extracellular matrix landscapes.This article has an associated First Person interview with the first author of the paper.

Molecular genetic techniques and oligonucleotides for mycoplasma identification – a review

Control of distribution of mycoplasmal infections in cattle herds is essential in the majority of countries world-wide. Various PCR procedures are available to detect mycoplasmas in cell cultures and bovine mycoplasma in different types of samples. We reviewed some common PCR techniques and specific primers targeted to different bacterial genetic regions of mycoplasma. Several researchers used the same PCR approach and Mycoplasma spp. as a target but their results could not be compared because different primer pairs were used. These methods and primers were first developed to identify mycoplasma species that contaminate animal cell cultures, and then were used by other researchers to differentiate mycoplasmas as a cow infecting agent. Our analysis of the specificity of these primer pairs to nucleotide sequences of five Mycoplasma spp. showed that oligonucleotides have less specificity to them. Numerous commercially available PCR kits are applicable to find mycoplasma contamination in cell cultures and fewer of them can be used in veterinary diagnostics. Although serological and culture techniques are still used, it is necessary to develop a new multiplex PCR technique with a more specific primer set especially in agrarian countries.

Sterility Testing for Cellular Therapies: What Is the Role of the Clinical Microbiology Laboratory?

Sterility testing of cellular therapy products along with the associated environmental monitoring requirements for aseptic facilities, including compounding pharmacies, continues to impact clinical microbiology laboratories, as evidenced by the numerous discussions recurring on American Society for Microbiology Division C and ClinMicroNet listservs. This minireview provides an overview of this complex field of current good manufacturing practices (cGMP) based on biopharmaceutical industry standards and summarizes the compendial and alternative rapid microbial test methods available for product sterility and Mycoplasma testing. In addition, this minireview highlights major overarching regulatory requirements governing any laboratory performing product testing as regulated by the United States Food and Drug Administration (FDA). These requirements are different from the more familiar clinical requirements of the Clinical Laboratory Improvement Act of 1988 (CLIA '88), the College of American Pathologists (CAP), and the Joint Commission on Accreditation of Healthcare Organizations (JCAHO), all of which have no jurisdiction in this area. As the cellular therapy field continues to advance and an increasing number of medical centers participate in clinical trials of these novel therapies, it is critical that laboratories have a sound understanding of the major regulations and cGMP practices governing microbiological testing in the biopharmaceutical industry.

High-Throughput Sequencing (HTS) of newly synthetized RNAs enables one shot detection and identification of live mycoplasmas and differentiation from inert nucleic acids

Mycoplasma contamination threatens both the safety of biologics produced in cell substrates as well as the quality of scientific results based on cell-culture observations. Methods currently used to detect contamination of cells include culture, enzymatic activity, immunofluorescence and PCR but suffer from some limitations. High throughput sequencing (HTS) can be used to identify microbes like mycoplasmas in biologics since it enables an unbiased approach to detection without the need to design specific primers to pre-amplify target sequences but it does not enable the confirmation of microbial infection since this could reflect carryover of inert sequences. In order to unambiguously differentiate the presence of live or dead mycoplasmas in biological products, the present method was developed based on metabolic RNA labelling of newly synthetized mycoplasmal RNAs. HTS of labelled RNA detected A549 cell infection with Acholeplasma laidlawii in a manner similar to both PCR and culture and demonstrated that this technique can unambiguously identify bacterial species and differentiates infected cells from cells exposed to a high inoculum of heat-inactivated mycoplasmas. This method therefore combines the advantage of culture (that detects only live microorganisms) with those of molecular tests (rapidity) together with a very broad range of bacterial detection and identification.

Cancer Cell Lines Are Useful Model Systems for Medical Research

Cell lines are in vitro model systems that are widely used in different fields of medical research, especially basic cancer research and drug discovery. Their usefulness is primarily linked to their ability to provide an indefinite source of biological material for experimental purposes. Under the right conditions and with appropriate controls, authenticated cancer cell lines retain most of the genetic properties of the cancer of origin. During the last few years, comparing genomic data of most cancer cell lines has corroborated this statement and those that were observed studying the tumoral tissue equivalents included in the The Cancer Genome Atlas (TCGA) database. We are at the disposal of comprehensive open access cell line datasets describing their molecular and cellular alterations at an unprecedented level of accuracy. This aspect, in association with the possibility of setting up accurate culture conditions that mimic the in vivo microenvironment (e.g., three-dimensional (3D) coculture), has strengthened the importance of cancer cell lines for continuing to sustain medical research fields. However, it is important to consider that the appropriate use of cell lines needs to follow established guidelines for guaranteed data reproducibility and quality, and to prevent the occurrence of detrimental events (i.e., those that are linked to cross-contamination and mycoplasma contamination).

Generation and Characterization of Eptesicus fuscus (Big brown bat) kidney cell lines immortalized using the Myotis polyomavirus large T-antigen

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Eptesicus fuscus kidney cells immortalized using Myotis polyomavirus T-antigen.

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E. fuscus interferon competent kidney cell line supports the growth of vesicular stomatitis virus, porcine epidemic diarrhea virus, herpes simplex virus and Middle-East respiratory syndrome coronavirus.

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All cell lines exhibit a marker for fibroblasts (vimentin), some also exhibit an epithelial marker (cytokeratin).

It is speculated that bats are important reservoir hosts for numerous viruses, with 27 viral families reportedly detected in bats. Majority of these viruses have not been isolated and there is little information regarding their biology in bats. Establishing a well-characterized bat cell line supporting the replication of bat-borne viruses would facilitate the analysis of virus-host interactions in an in vitro model. Currently, few bat cell lines have been developed and only Tb1-Lu, derived from Tadarida brasiliensis is commercially available. Here we describe a method to establish and immortalize big brown bat (Eptesicus fuscus) kidney (Efk3) cells using the Myotis polyomavirus T-antigen. Subclones of this cell line expressed both epithelial and fibroblast markers to varying extents. Cell clones expressed interferon beta in response to poly(I:C) stimulation and supported the replication of four different viruses, namely, vesicular stomatitis virus (VSV), porcine epidemic diarrhea coronavirus (PED-CoV), Middle-East respiratory syndrome coronavirus (MERS-CoV) and herpes simplex virus (HSV). To our knowledge, this is the first bat cell line from a northern latitude insectivorous bat developed using a novel technology. The cell line has the potential to be used for isolation of bat viruses and for studying virus-bat interactions in culture.

A synthetic biology standard for Chinese Hamster Ovary cell genome monitoring and contaminant detection by polymerase chain reaction

Background

Chinese Hamster Ovary (CHO) cells are the current industry standard for production of therapeutic monoclonal antibodies at commercial scales. Production optimisation in CHO cells hinges on analytical technologies such as the use of the polymerase chain reaction (PCR) to quantify genetic factors within the CHO genome and to detect the presence of contaminant organisms. PCR-based assays, whilst sensitive and accurate, are limited by (i) requiring lengthy sample preparation and (ii) a lack of standardisation.

Results

In this study we directly assess for the first time the effect of CHO cellular material on quantitative PCR (qPCR) and end-point PCR (e-pPCR) when used to measure and detect copies of a CHO genomic locus and a mycoplasma sequence. We also perform the first head-to-head comparison of the performance of a conventional qPCR method to that of the novel linear regression of efficiency (LRE) method when used to perform absolute qPCR on CHO-derived material. LRE qPCR features the putatively universal ‘CAL1’ standard.

Conclusions

We find that sample preparation is required for accurate quantitation of a genomic target locus, but mycoplasma DNA sequences can be detected in the presence of high concentrations of CHO cellular material. The LRE qPCR method matches performance of a conventional qPCR approach and as such we invite the synthetic biology community to adopt CAL1 as a synthetic biology calibration standard for qPCR.

Measuring E. coli and bacteriophage DNA in cell sonicates to evaluate the CAL1 reaction as a synthetic biology standard for qPCR

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We establish the effect of E. coli cellular material on sensitivity of qPCR for detection and quantitation of a lone genomic sequence.

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We demonstrate that LRE qPCR matches performance of the conventional Standard Curve qPCR method with respect to absolute quantitation of a genomic E. coli sequence.

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We characterise the effect of E. coli cellular material on performance of qPCR for detection and quantitation of a bacteriophage DNA sequence.

We measured the impact of the presence of total Escherichia coli (E. coli) cellular material on the performance of the Linear Regression of Efficiency (LRE) method of absolute quantitative PCR (LRE qPCR), which features the putatively universal CAL1 calibration reaction, which we propose as a synthetic biology standard. We firstly used a qPCR reaction in which a sequence present in the lone genomic BirA locus is amplified. Amplification efficiency for this reaction, a key metric for many quantitative qPCR methods, was inhibited by cellular material from bioreactor cultivation to a greater extent than material from shake flask cultivation. We then compared LRE qPCR to the Standard Curve method of absolute qPCR (SC qPCR). LRE qPCR method matched the performance of the SC qPCR when used to measure 417–4.17 × 10⁷ copies of the BirA target sequence present in a shake flask-derived cell sonicates sample, and for 97–9.7 × 10⁵ copies in the equivalent bioreactor-derived sample. A plasmid-encoded T7 bacteriophage sequence was next used to compare the methods. In the presence of cell sonicates from samples of up to OD₆₀₀ = 160, LRE qPCR outperformed SC qPCR in the range of 1.54 × 10⁸–1.54 × 10¹⁰ copies of the T7 target sequence and matched SC qPCR over 1.54 × 10⁴–1.54 × 10⁷ copies. These data suggest the CAL1 standard, combined with the LRE qPCR method, represents an attractive choice as a synthetic biology qPCR standard that performs well even when unpurified industrial samples are used as the source of template material.

Detection of Mycoplasma Contamination Directly from Culture Supernatant Using Polymerase Chain Reaction

Ensuring mycoplasma-free cell culture is of prime importance as they severely affect cellular characteristics leading to experimental artefacts and spurious results. Various methods persist for mycoplasma detection; out of the whole array of methods polymerase chain reaction (PCR) is the most favoured one because it is highly sensitive, specific and quick. The PCR-based detection procedure involves three steps: cell culture supernatant collection, DNA isolation, and PCR. We have modified this procedure so that cell culture supernatant can directly be used for PCR without the need for DNA extraction. This modification makes the procedure quicker and more sensitive because loss of mycoplasma DNA is prevented and this loss becomes more significant when the level of mycoplasma contamination is very low.

Experimental infection of BHK21 and Vero cell lines with different Mycoplasma spp

Mycoplasma spp, belongs to the class Mollicutes and is capable to produce alterations in cellular cultures causing damages to the biotechnological industry. Bioproducts generally require two essential inputs, bovine serum and cells. The study herein aims to evaluate the mycoplasma concentrations that affect the growing of BHK21 and Vero cells. The species used were: Mycoplasma orale, M. salivarium, M. arginini and M. hyorhinis, cultivated in a SP4 media. Two contamination tests were performed with BHK21 and Vero cells and one of them applied different concentrations of mycoplasma. In the first one, mycoplasma was applied at the day zero and, in the second one, the contamination was performed after the monolayer establishment. The both cellular cultures presented cytopathic effects with mycoplasma contamination, but the Vero cells suffered more damages than the BHK21 ones. It was also observed that the severity of the cytopathic effect depended on the mycoplasma specie, on the concentration and on the time of contact with the cellular culture, which evidences the importance of controlling the presence of mycoplasma in biotechnological industries.

Isolation and molecular identification of Mycoplasma equigenitalium from equine genital tracts in northern India

Although Mycoplasma equigenitalium has been implicated in equine reproductive problems, its prevalence is largely unexplored due to the lack of specific diagnostic tests. To address this limitation, the authors developed and optimized species-specific primer pairs that target M. eguigenitalium rpoB (RNA polymerase B subunit) gene sequences. The specificity of the PCR assay developed in this study was determined using 12 field isolates including the type strain of M. equigenitalium and other Mycoplasma species. In the field study, a total of 122 mare and stallion samples comprising of 50 clinical and 72 random samples were subjected to species-specific PCR assay to detect M. equigenitalium in equine genital tracts. Mycoplasma equigenitalium (MEG) species-specific PCR detected 22.13% positive samples; however, only 9.01% of the samples were found to be positive using the conventional culture technique. The PCR established in this study could be used for rapid, specific and accurate diagnosis of M. equigenitalium strains. To the authors' knowledge, this is the first report addressing the development and evaluation of species-specific PCR to detect M. equigenitalium.

Development of a PCR assay to detect mycoplasma contamination in cord blood hematopoietic stem cells

BACKGROUND AND OBJECTIVES

Contamination of cell lines and biological products is one of the major problems of cell culture techniques. Rapid detection of mycoplasma contamination in cell culture is an important part of quality control standards in related laboratories. The aim of this study was to evaluate the efficacy of PCR in detection of myroplasma as contaminants in cell cultures and other biological products.

METHOD

PCR assays were optimized for 16 S rRNA target gene. Also the utilized PCR method was evaluated in terms of sensitivity and specificity. Finally, a simple DNA extraction and PCR analysis of 164 cell culture of adipose tissue derived mesenchymal stem cells were performed.

RESULTS

A 715 bp product was amplified and subsequently was confirmed by sequencing. The technique could detect 10 copies of the target DNA. No cross-reactivity with genomic DNA of other microorganisms was observed.

CONCLUSIONS

The PCR technique in this study was based on 16S rRNA gene. It was highly sensitive and specific since it was able to detected Mycoplasma contamination in cell cultures.

A sensible technique to detect mollicutes impurities in human cells cultured in GMP condition

In therapeutic trials the use of manipulated cell cultures for clinical applications is often required. Mollicutes microorganism contamination of tissue cultures is a major problem because it can determine various and severe alterations in cellular function. Thus methods able to detect and trace cell cultures with Mollicutes contamination are needed in the monitoring of cells grown under good manufacturing practice conditions, and cell lines in continuous culture must be tested at regular intervals. We here describe a multiplex quantitative polymerase chain reaction assay able to detect contaminant Mollicutes species in a single-tube reaction through analysis of 16S-23S rRNA intergenic spacer regions and Tuf and P1 cytoadhesin genes. The method shows a sensitivity, specificity, and robustness comparable with the culture and the indicator cell culture as required by the European Pharmacopoeia guidelines and was validated following International Conference on Harmonization guidelines and Food and Drug Administration requirements.

Detection of Mycoplasma contamination in cell cultures

Mycoplasma contamination of cell lines is a major problem in cell culture technology. This unit presents protocols involving either the polymerase chain reaction (PCR) or fluorescent in situ hybridization (FISH) to provide independent, fast, and sensitive techniques to monitor mycoplasma contamination in laboratory cultures. Special emphasis is placed on the integration of control reactions to prevent false-negative as well as false-positive results due to reaction inhibition or contamination and background staining, respectively.

A single-tube real-time PCR assay for Mycoplasma detection as a routine quality control of cell therapeutics

BACKGROUND

Contamination of cell culture and biological material by mollicute species is an important safety issue and requires testing. We have developed a singletube real-time polymerase chain reaction (PCR) assay for rapid detection of Mollicutes species stipulated by the European Pharmacopeia.

METHODS

Primers and TaqMan probes (FAM-labeled) were deduced from 16S rDNA sequence alignment of 18 mollicutes species. A synthetic internal control (IC) DNA and an IC-specific TaqMan probe (VIC-labeled) were included. The analytical sensitivity of the assay was determined on DNA dilutions from 12 mollicute strains. Specificity was proven by the use of DNA from other bacteria.

RESULTS

Analytical sensitivities of the PCR assay were in the range of 405-2,431 genomes/ml for 11 of the 12 tested mollicute DNA samples. The lowest sensitivity was found for Ureaplasma urealyticum (19,239 genomes/ml). Negative results for DNA samples from 3 different ubiquitous bacteria demonstrated the specificity of the PCR assay for Mollicutes. Direct testing of cell culture supernatants spiked with Mycoplasma orale revealed similar sensitivity compared to isolated DNA.

CONCLUSIONS

Our single-tube real-time PCR assay with internal reaction control enables rapid and specific detection of mollicute contaminants. The test protocol is suitable for routine quality control of cell therapeutics.

Bovine mammary epithelial cell cultures for the study of mammary gland functions

In the present study, the analysis of epithelial cells derived from various sources was undertaken, beginning from the mammary gland tissue through the primary cultures and their subsequent passages. The objective of the study was the comparative analysis of the stage in which the epithelial cells obtained from individuals in different lactation cycles and disparate phases of cell culture growth are the most suitable for morphological research and analysis of gene expression activity. The cultures of primary bovine mammary epithelial cells and passages were identified morphologically using immunocytochemical methods. After positive identification, real-time PCRs were performed for the analysis of the expression level of casein genes, whey protein genes, and butyrophilin gene. The most stable reference genes in real-time PCRs for the mammary gland tissue and cell cultures were also determined. Of the reference genes, the UXT and GAPDH genes appeared to be the most stable ones for the mammary gland tissue samples and epithelial cell cultures. The results obtained allowed concluding that the mammary gland samples collected from heifers constituted the most effective material for the initiation of primary cultures. The primary cultures formed characteristic for the mammary gland tissue dome structures, which images were obtained using confocal microscopy. The highest levels of expression of the CSN1S1, CSN1S2, CSN2, and CSN3 genes were detected in primary cultures. The levels of expression of whey protein genes (LALBA and BGL) were highest in the second passage. The most abundant expression of the BTN1A1 gene was observed in primary cultures and the third passage. On the basis of the whole experiment, it can be concluded that primary cultures and cells of the second passage derived from heifer individuals appeared to be the best materials for the analysis of mammary gland function and gene expression activity.

Treatment of mycoplasma contamination in cell cultures with Plasmocin

A high percentage of cell lines are chronically infected with various mycoplasma species. The addition of antibiotics that are particularly effective against these contaminants to the culture medium during a limited period of time is a simple, inexpensive, and very practical approach for decontaminating cell cultures. Here, we examined the effectiveness of the new antimycoplasma compound Plasmocin that has been employed routinely to cleanse chronically infected cell lines. In a first round of treatment 45 out of 58 (78%) mycoplasma-positive cell lines could be cured. In a second attempt using back-up cryopreserved original cells, four additional cell lines were cured; thus, the overall cure rate was 84%. Even if the mycoplasma contamination was not eradicated by Plasmocin, the parallel treatment with several other antibiotics (Baytril, BM-Cyclin, Ciprobay, MRA, or MycoZap) led to the cure of all 58 cell lines. The successful decontamination was permanent as mycoplasmas were no longer detected at day +14 posttreatment and at later time points as examined by PCR which is the most sensitive and specific mycoplasma detection method. Collectively, our results highlight certain antibiotics as effective antimycoplasma reagents and support the therapeutic rationale for their use in the eradication of this notorious cell culture contaminant.

Causes of pneumonia epizootics among bighorn sheep, Western United States, 2008-2010

Mycoplasma ovipneumoniae is a primary pathogen.

Epizootic pneumonia of bighorn sheep is a devastating disease of uncertain etiology. To help clarify the etiology, we used culture and culture-independent methods to compare the prevalence of the bacterial respiratory pathogens Mannheimia haemolytica, Bibersteinia trehalosi, Pasteurella multocida, and Mycoplasma ovipneumoniae in lung tissue from 44 bighorn sheep from herds affected by 8 outbreaks in the western United States. M. ovipneumoniae, the only agent detected at significantly higher prevalence in animals from outbreaks (95%) than in animals from unaffected healthy populations (0%), was the most consistently detected agent and the only agent that exhibited single strain types within each outbreak. The other respiratory pathogens were frequently but inconsistently detected, as were several obligate anaerobic bacterial species, all of which might represent secondary or opportunistic infections that could contribute to disease severity. These data provide evidence that M. ovipneumoniae plays a primary role in the etiology of epizootic pneumonia of bighorn sheep.

Development and validation of a multiplex quantitative polymerase chain reaction assay for the detection of Mollicutes impurities in human cells, cultured under good manufacturing practice conditions, and following European Pharmacopoeia requirements and the International Conference on Harmonization guidelines

BACKGROUND AIMS

The clinical applications of in vitro manipulated cultured cells and their precursors are often made use of in therapeutic trials. However, tissue cultures can be easily contaminated by the ubiquitous Mollicutes micro-organisms, which can cause various and severe alterations in cellular function. Thus methods able to detect and trace Mollicutes impurities contaminating cell cultures are required before starting any attempt to grow cells under good manufacturing practice (GMP) conditions.

METHODS

We developed a multiplex quantitative polymerase chain reaction (qPCR) assay specific for the 16S-23S rRNA intergenic spacer regions, for the Tuf and P1 cytoadhesin genes, able to detect contaminant Mollicutes species in a single tube reaction. The system was validated by analyzing different cell lines and the positive samples were confirmed by 16S and P1 cytoadhesin gene dideoxy sequencing.

RESULTS

Our multiplex qPCR detection system was able to reach a sensitivity, specificity and robustness comparable with the culture and the indicator cell culture method, as required by the European Pharmacopoeia guidelines.

CONCLUSIONS

We have developed a multiplex qPCR method, validated following International Conference on Harmonization (ICH) guidelines, as a qualitative limit test for impurities, assessing the validation characteristics of limit of detection and specificity. It also follows the European Pharmacopoeia guidelines and Food and Drug Administration (FDA) requirements.

A multi-laboratory profile of Mycoplasma contamination in Lawsonia intracellularis cultures

Background

During the routine laboratory cultivation of Lawsonia intracellularis, Mycoplasma contamination has been a frequent problem. When Mycoplasma contamination occurs in laboratories that study L. intracellularis, the cultures must be discarded for 4 reasons: 1) Mycoplasma is inevitably concentrated along with L. intracellularis during the passage of L. intracellularis; 2) Mycoplasma inhibits the growth of L. intracellularis; and 3) it is impossible to selectively eliminate Mycoplasma in L. intracellularis cultures. In this study, we observed the contamination of Mycoplasma species during L. intracellularis cultivation among multiple laboratories.

Results

The presence of a Mycoplasma infection in the L. intracellularis cultures was verified using polymerase chain reaction (PCR), and a sequence analysis of the partial 16S rRNA and 23S rRNA genes was performed. A PCR-based assay using genus-specific universal primers revealed that 29 (85.3%) of the 34 cultures were contaminated with Mycoplasma, including 26 with M. hyorhinis (89.2%), 2 with M. orale (6.9%), and 1 with M. fermentans (3.4%). The Mycoplasma contamination was not the result of infection with material of pig origin. McCoy cells, which are required for the cultivation of L. intracellularis, were also ruled out as the source of the Mycoplasma contamination.

Conclusions

In this study, M. hyorhinis was identified as the most common mollicute that contaminated L. intracellularis cultures. Whether L. intracellularis enhances the biological properties of Mycoplasma to promote infection in McCoy cells is not known. Because the McCoy cell line stocks that were used simultaneously were all negative for Mycoplasma, and the same worker handled both the McCoy cells to maintain the bacteria and the L. intracellularis cultures, it is possible that the L. intracellularis cultures are more vulnerable to Mycoplasma contamination. Taken together, these results suggest that continuous cultures of L. intracellularis must be tested for Mycoplasma contamination at regular intervals.

The GenBank accession numbers for the sequences reported in this paper are JN689375 to JN689377.

A specific statistical model and algorithm related to the detection of Mollicutes in contaminated biological samples by Real-Time Transcription Mediated Amplification

Among all nucleic acid amplification technologies, Real-Time Transcription Mediated Amplification (Real-Time TMA) is an isothermal method that can amplify RNA targets a billion-fold in less than one hour's time. By using this method, a new assay was developed for detecting the presence of Mollicutes in mammalian cell cultures and biologics. Production of amplicons is monitored in real time by measuring continuously a fluorescence signal during the reaction. The shape of this signal curve is a sigmoid, where an initial baseline phase precedes an exponential phase ending with a maximum followed by a linear decreasing phase. The aim of this study was to develop a curve-analysis tool to unambiguously assign a Mollicutes positive or negative status to a biological sample. In this context, a statistical analysis of the data combined with the selection of the best predictors allowed the development of an algorithm which removes erroneous data and applies the best predictors to generate the Mollicutes status prediction. Our results demonstrate that this algorithm assigns positive/negative/invalid status coming from Real-Time TMA fluorescence signal analysis with a confidence (true predictions) in the results close to 100%.

Multiplex polymerase chain reaction-based reverse line blot hybridization assay to detect common genital pathogens

The objective of the present paper is to develop and apply a multiplex polymerase chain reaction (mPCR) based reverse line blot (RLB) hybridization assay to facilitate the diagnosis of genital infections by detection of seven recognized or putative genital pathogens (Neisseria gonorrhoeae, Chlamydia trachomatis, Ureaplasma urealyticum, Ureaplasma parvum, Mycoplasma genitalium, Mycoplasma hominis and Trichomonas vaginalis). Species-specific biotin-labelled primer pairs were used in a single mPCR to amplify target regions in each of seven pathogens. The amplified biotin-labelled PCR products were hybridized with membrane-bound-specific oligonucleotide probes and were detected by chemiluminescence. Two hundred and eleven specimens (104 male urethral and 107 female vaginal swabs), collected from patients with suspected genital infections attending the Wuhan First Hospital Sexually Transmitted Diseases (STD) clinic, were tested by mPCR/RLB and results were confirmed by single PCR using different species-specific targets. The sensitivity of the assay was assessed using dilutions of positive DNA controls with known copy numbers, for each target. The assay correctly identified all reference strains and detected potential pathogens in a high proportion of clinical specimens. There was no cross-reaction between the seven pathogens. The mPCR/RLB can detect <or= 10(2) copies of the target gene fragments. Comparison of mPCR/RLB and single PCR assays showed discrepant results in six of 211 (2.8%) clinical specimens, which were positive by mPCR/RLB assay, but negative by the corresponding single PCR. Nested PCR on the six discrepant specimens gave results consistent with those of mPCR/RLB. In conclusion, the mPCR/RLB hybridization assay is sensitive and specific, and able to rapidly detect genital pathogens in clinical specimens.

Rapid and sensitive detection of Mollicutes in cell culture by polymerase chain reaction

Infections with Mollicutes species (such as Mycoplasma, Acholeplasma, and Ureaplasma) can induce a variety of problems in living organisms and laboratory cell cultures. Therefore, it is necessary to establish a routine diagnostic protocol for Mycoplasma infection in order to ensure reliable research results, as well as the safety of commercial biological products. For that purpose a novel PCR-based procedure using specific designed primers complementary to 16S rRNA genome region of mollicute species was evaluated. PCR was optimized and sensitivity and specificity was evaluated by defined cell count concentrations (2-31250 CFU/ml) of different strains of Mycoplasma, Acholeplasma and Ureaplasma. Amplicon (272 bp) was cloned by PCR-cloning and sequenced by dideoxy chain termination. PCR, was found to be able to detect 10 copies of mollicute target DNA. No cross-reactivity with genomic DNA of non-mollicute bacteria or human cell lines was observed. Forty seven human and animal cell lines were evaluated for mollicute contamination. Twenty five cell lines (53%) were correctly identified as contaminated by this molecular approach. The results of this study demonstrated that this PCR-based method is not only fast and reproducible, but also highly sensitive and specific for detecting contaminant mycoplasmas in cell cultures.

Detection of Mollicutes in bioreactor samples by real-time transcription-mediated amplification

AIM

Contamination by Mollicutes is a significant challenge for research laboratories and biopharmaceutical industry. It leads to alteration of results or production quality as well as loss of time, materials and revenue. These organisms can czoriginate from mammalian, avian, insect, plant or fish cells. Culture-based methods may require 28 days to detect Mollicutes. Traditional microbiology could advantageously be replaced by nucleic acid testing for earlier detection.

METHODS AND RESULTS

A membrane filtration-based concentration of the Mollicutes has been coupled to real-time transcription-mediated amplification (real-time TMA) to demonstrate these advantages. The eight species required by European Pharmacopoeia have been tested and were detected with sensitivity below 100 CFU per 20-ml sample. Co-culture experiments, in which Mollicutes are grown with CHO-S (suspension) or HEK 293 (adherent) cells, were also performed to respectively mimic a bioreactor or flask contamination. Despite the fact that Mollicutes can attach to or invade mammalian cells, they were consistently detected over multiple days.

CONCLUSIONS

the sample preparation and amplification method used in this study increases sensitivity and reduces time-to-result for detection of Mollicutes.

SIGNIFICANCE AND IMPACT OF THE STUDY

the described system allows real-time monitoring for microbial contamination of cell-based processes and products for the biopharmaceutical industry.

PCR-based detection and eradication of mycoplasmal infections from various mammalian cell lines: a local experience

A total of 200 cell lines including different human, monkey, mice, hamster and rat cell types were examined for mycoplasma infection status. PCR assay using generic-specific universal primers showed that 40 (20%) of the cell lines are contaminated with mycoplasma. Employment of species-specific primers within these infected cell lines revealed infection with M. hyorhinis (42.5%), M. fermentas (37.5%), M. arginini (37.5%), M. orale (12.5%) and A. laidlawii (7.5%). A number of the cultures were coinfected with 2 or 3 different species. Contaminated samples were treated with BM-Cyclin, Ciprofloxacin and mycoplasma removal agent (MRA). Mycoplasma eradication was subsequently checked by PCR following 2 weeks continuous culture of treated cells in antibiotic free culture medium. Mycoplasmal infections were eradicated in 100, 70 and 42% of infected cell lines when the samples were treated with BM-Cyclin, MRA and Ciprofloxacin, respectively. However, 12% (BM-Cyclin), 62.5% (MRA) and 82.5% (Ciprofloxacin) of mycoplasma regrowth was observed 4 months after the treatment. Notably, the risk of spontaneous culture death was 17.5, 12.5 and 0% for BM-Cyclin, MRA and Ciprofloxacin, respectively.

Ex utero harvest of hematopoietic stem cells from placenta/umbilical cord with an automated collection system

Hematopoietic stem cells (HSCs) from the human placenta and umbilical cord blood (UCB) provide a rich source of highly proliferative cells for many clinical uses with advantages over traditional sources like the bone marrow and periphery blood. However, the key current constraint with this source of HSCs is the inadequate number of HSCs cells that can be harvested in a single collection using current approaches, which render a large number of collections unusable on their own, even for pediatric patients. This paper will present the development of a device to enable more efficient harvesting of HSCs from placentas, which can be used ex utero, upon the discharge of placentas after deliveries. The device can be used to facilitate a two-fraction collection process. Results, in terms of mononucleated cells (MNCs) count, CD34+ cells count, as well as flow cytometry, will be furnished to verify the effectiveness of the developed system.

The cytostatic activity of pyrimidine nucleosides is strongly modulated by Mycoplasma hyorhinis infection: Implications for cancer therapy

Nucleoside analogues are widely used as chemotherapeutic agents in the treatment of cancer. Several cancers are reported to be associated with mycoplasmas (i.e. Mycoplasma hyorhinis), which contain a number of nucleoside-metabolizing enzymes. Pyrimidine nucleoside analogues, such as 5-fluoro-2'-deoxyuridine (FdUrd), 5-trifluorothymidine (TFT) and 5-halogenated 2'-deoxyuridines can be degraded by thymidine phosphorylase (TP) to their inactive bases. We found in M. hyorhinis-infected MCF-7 breast carcinoma cells (MCF-7/HYOR) a mycoplasma-encoded TP that dramatically (20-150-fold) reduces the cytostatic activity of these compounds. The reduction in cytostatic activity could be fully restored in the presence of TPI (5-chloro-6-[1-(2-iminopyrrolidinyl)methyl]uracil hydrochloride), a known inhibitor of human TP. This observation is in agreement with the markedly decreased formation of active metabolite (i.e. FdUMP for FdUrd) or diminished drug incorporation into nucleic acids (i.e. for TFT and 5-bromo-2'-deoxyuridine) in MCF-7/HYOR cells compared with uninfected MCF-7 cells. Antimetabolite formation is fully restored in the presence of TPI. In contrast, 5-fluoro-5'-deoxyuridine (5'DFUR), an intermediate metabolite of capecitabine, was markedly more cytostatic in MCF-7/HYOR cells than in uninfected cells, due to the activation of this prodrug by the mycoplasma-encoded TP. Thus, our data reveal that M. hyorhinis expresses a TP that activates 5'DFUR but inactivates FdUrd, TFT and 5-halogenated 2'-deoxyuridines, and that is highly sensitive to the inhibitory effect of the TP inhibitor TPI. Given the association of M. hyorhinis with several human cancers, our findings suggest that pyrimidine nucleoside-based but not 5FU-based anti-cancer therapy might be more effective when combined with a mycoplasmal TP inhibitor.

Tandem use of immunofluorescent and DNA staining assays to validate nested PCR detection of mycoplasma

Mycoplasma contamination in cell culture is a serious setback to cell culturists across the world with a very high rate of reported occurrence particularly because of difficult early detection. Out of a variety of detection methods known, the double-step nested polymerase chain reaction (PCR)-based detection of mycoplasma in cell culture has been critically viewed upon because of chances of producing reliable results. A nested PCR technique, described to detect a large range of cell-culture-contaminating mycoplasma species, with greater sensitivity to detect as low a contamination as a few organisms, was compared with the results from two cytological techniques employed in tandem. These are DNA staining using Hoechst, the gold standard, and an immunofluorescent assay using a highly specific monoclonal antibody. The study undertaken on randomly collected cell cultures revealed a false-negative and several false-positive results in comparison to the cytological methods employed. The observations were particularly more unambiguous with the immunofluorescent assay employed in the study while simultaneously employed Hoechst staining serving as an indicator of bacterial contamination. There is a general apprehension that genus-specific PCR approaches could be associated with inaccurate outcome and only species-specific PCRs may be satisfactory in routine screening for mycoplasma contamination in cell cultures. At this juncture, it may be suggested that caution must be exercised while adopting the two-step nested PCR-based detection approaches, and the simultaneous employment of cytological methods used in this investigation could prove to be practicable in the proper interpretation of results.

Rapid detection of mycoplasma contamination in cell cultures using SYBR Green-based real-time polymerase chain reaction

We have developed a simple method for rapid detection of mycoplasma contamination in cell cultures using SYBR Green-based real-time polymerase chain reaction (PCR). To detect eight common contaminant mollicutes, including Mycoplasma (M. arginini, M. fermentans, M. orale, M. hyorhinis, M. hominis, M. salivarium, M. pirum) and Acholeplasma laidlawii, four primers were prepared based on the 23S rRNA regions. Using these primers and a minimum of 100 fg of mycoplasma genomic DNA, the 23S rRNA regions of these eight mycoplasma species were consistently amplified by real-time PCR. In contrast, no specific amplification product was observed using DNA templates prepared from various mammalian cell lines. Frozen and cultured samples of several cell lines were tested for mycoplasma contamination to evaluate the utility of this method. Of 25 samples that tested positive for mycoplasma by Hoechst staining, which requires two passages of cell cultures started from frozen samples, mycoplasma was detected by real-time PCR in 24 samples of cell extracts prepared directly from frozen samples. When cultured samples were used for this assay, the accuracy of the diagnoses was further improved. Thus, this technique, which is simple, rapid, and sensitive enough for practical application, is suitable for handling many samples and for routine screening for mycoplasma contamination of cell cultures.

Prevalence of mycoplasmas in the semen and vaginal swabs of Danish stallions and mares

The reproduction rate of horses is one of the lowest within domestic livestock despite advances the veterinary medicine. Infertility in horses may be due mainly to the lack of suitable selection criteria in the breeding of horses. However, acquired infertility due to genital, bacterial infections may occur. Mycoplasmas have been implicated in genital disorders and infertility of many species including humans and horses. However, their role as commensals or pathogens of the genital tract of horses is still not determined. Bacteriological examinations made on the fossa glandis, urethra, penis and semen of stallions, showed the presence of different Mycoplasma species. Therefore our study aimed to find the prevalence of Mycoplasma species and a possible association with fertility problems in Danish riding horses. Eighty semen samples from stallions and 19 vaginal swab samples from mares were tested by PCR for presence of mycoplasmal DNA. The vaginal swab samples were also cultured in the Mycoplasma specific medium. None of the samples were positive for presence of genital mycoplasmas during the screen. The lack of genital mycoplasmas observed in this study may be due to a very extensive use of artificial insemination of modern sport horses.

Introduction of a validation concept for a PCR-based Mycoplasma detection assay

BACKGROUND

Mycoplasma contamination is amongst the most frequently occurring problems associated with cell cultures. In order to meet the legal requirements (European Pharmacopoeia and FDA) for Mycoplasma testing of cell lines and therapeutics, we have developed a PCR-based method to detect mycoplasms and introduce a validation concept.

METHODS

The PCR assay specifically amplifies a 280-bp DNA fragment of the gene coding for the 16S rDNA. Simultaneous amplification of an artificial oligonucleotide containing primer-binding sites allowed control of the efficacy of the PCR. The validation of the PCR assay was performed with two Mycoplasma reference strains, M. orale and M. pneumoniae. The validation concept included (i) cultivation of M. orale and M. pneumoniae in medium with an indicator for bacterial metabolism, (ii) determination of the color-changing units (CCU) in repeated dilution experiments and (iii) correlation of the PCR results with CCU values.

RESULTS

The detection range was found to include all Mycoplasma species most commonly found in cell cultures. The analytical sensitivity of the PCR was the CCU equivalent of 100 for M. orale and M. pneumoniae. Probit analysis revealed a detection probability of 9% for a mean concentration of 1222 (935-1844) CCU/mL for M. pneumoniae and 2547 (1584-10,352) CCU/mL for M. orale.

DISCUSSION

The validation of the Mycoplasma detection assay supported PCR as an attractive diagnostic tool that will help manage the important issue of Mycoplasma contamination of cell cultures.

Development of a PCR method for mycoplasma testing of Chinese hamster ovary cell cultures used in the manufacture of recombinant therapeutic proteins

Chinese hamster ovary (CHO) cell cultures used to produce biopharmaceuticals are tested for mycoplasma contamination as part of the ensurance of a safe and pure product. The current U.S. Food and Drug Administration (FDA) regulatory guideline recommends using two procedures: broth/agar cultures and DNA staining of indicator cell cultures. Although these culture methods are relatively sensitive to most species, theoretically capable of detecting as few as 1-10 cfu/ml of most species, the overall procedure is lengthy (28 d), costly and less sensitive to noncultivable species. The detection of mycoplasma using the polymerase chain reaction (PCR) method has been considered an alternative method because it is relatively fast (1-2 d), inexpensive, and independent of culture conditions, however, limitations in sensitivity (limit of detection >/=1000 cfu/ml) and the risk of false positive and false negative results have prevented PCR from replacing the traditional culture methods in the industrial setting. In this report, we describe a new PCR assay for mycoplasma detection that appears to resolve these issues while being sufficiently simple and inexpensive for routine use. This assay applies readily available techniques in DNA extraction together with a modified single-step PCR using a previously characterized primer pair that is homologous to a broad spectrum of mycoplasma species known to infect mammalian cell cultures. Analysis is made easy by the detection of only a single amplification product within a narrow size range, 438-470 bp. A high sensitivity and specificity for mycoplasma detection in CHO cell production cultures is made possible through the combination of three key techniques: 8-methoxypsoralen and UV light treatment to decontaminate PCR reagents of DNA; hot-start Taq DNA polymerase to reduce nonspecific priming events; and touchdown- (TD-) PCR to increase sensitivity while also reducing nonspecific priming events. In extracts of mycoplasma DNA, the limit of detection for eight different mycoplasma species is 10 genomic copies. In CHO cell production cultures containing gentamicin, the limit of detection for a model organism, gentamicin-resistant M. hyorhinis, is 1 cfu/ml. The sensitivity and specificity of this PCR assay for mycoplasma detection in CHO cell production cultures appear similar to the currently used culture methods and thus should be considered as an alternative method by the biopharmaceutical industry.

Simultaneous detection and identification of common cell culture contaminant and pathogenic mollicutes strains by reverse line blot hybridization

We have developed a reverse line blot (RLB) hybridization assay to detect and identify the commonest mollicutes causing cell line contamination (Mycoplasma arginini, Mycoplasma fermentans, Mycoplasma hyorhinis, Mycoplasma orale, and Acholeplasma laidlawii) and human infection (Mycoplasma pneumoniae, Mycoplasma hominis, Mycoplasma genitalium, Ureaplasma parvum, and Ureaplasma urealyticum). We developed a nested PCR assay with "universal" primers targeting the mollicute 16S-23S rRNA intergenic spacer region. Amplified biotin-labeled PCR products were hybridized to membrane-bound species-specific oligonucleotide probes. The assay correctly identified reference strains of 10 mollicute species. Cell cultures submitted for detection of mollicute contamination, clinical specimens, and clinical isolates were initially tested by PCR assay targeting a presumed mollicute-specific sequence of the 16S rRNA gene. Any that were positive were assessed by the RLB assay, with species-specific PCR assay as the reference method. Initially, 100 clinical and 88 of 92 cell culture specimens gave concordant results, including 18 in which two or more mollicute species were detected by both methods. PCR and sequencing of the 16S-23S rRNA intergenic spacer region and subsequent retesting by species-specific PCR assay of the four cell culture specimens for which results were initially discrepant confirmed the original RLB results. Sequencing of amplicons from 12 cell culture specimens that were positive in the 16S rRNA PCR assay but negative by both the RLB and species-specific PCR assays failed to identify any mollicute species. The RLB hybridization assay is sensitive and specific and able to rapidly detect and identify mollicute species from clinical and cell line specimens.