Cloned mycoplasma ribosomal RNA genes for the detection of mycoplasma contamination in tissue cultures

A Beginner's Guide to Cell Culture: Practical Advice for Preventing Needless Problems

The cultivation of cells in a favorable artificial environment has become a versatile tool in cellular and molecular biology. Cultured primary cells and continuous cell lines are indispensable in investigations of basic, biomedical, and translation research. However, despite their important role, cell lines are frequently misidentified or contaminated by other cells, bacteria, fungi, yeast, viruses, or chemicals. In addition, handling and manipulating of cells is associated with specific biological and chemical hazards requiring special safeguards such as biosafety cabinets, enclosed containers, and other specialized protective equipment to minimize the risk of exposure to hazardous materials and to guarantee aseptic work conditions. This review provides a brief introduction about the most common problems encountered in cell culture laboratories and some guidelines on preventing or tackling respective problems.

Comparison of Nucleic Acid Hybridization and Fluorometry for Measurement of the Relationship between RNA/DNA Ratio and Growth Rate in a Marine Bacterium

Continuous culture of Pseudomonas stutzeri Zobell, a marine denitrifying bacterium, was used to determine the relationship between growth rate and nucleic acid content. The trend of decreasing RNA content with decreasing growth rate, well known for enteric organisms, was found to occur in P. stutzeri Zobell as well, even at very long generation times such as those thought to occur in the oligotrophic ocean. When assayed by ethidium bromide fluorescence, the total RNA/DNA ratio was linear for generation times between 6 and 60 h. We also developed a 200-bp nucleic acid probe (with species-specific potential) for a portion of the 23S rRNA gene of P. stutzeri Zobell, which was used to quantify rRNA and rDNA by hybridization in the same continuous cultures. The rRNA/rDNA ratio also exhibited a decrease with decreasing growth rate, but the relationship, although significant, was not simply linear. The sensitivity and accuracy of the two methods are compared, and the potential for species specificity in future hybridizations is discussed.

Regulation of mouse immuno-responses by a natural suppressor cell clone from bone marrow

Natural suppressor (NS) activity is mediated by several kinds of cell lineages in bone marrow. We demonstrated that a NS cell, clone 7-31, was obtained after limiting dilution with bone marrow culture supplemented with WEHI supernatant. Clone 7-31, was capable of non-specific suppression of the generation of cytotoxic T lymphocytes without major histocompatibility complex restriction. Suppression of cytotoxic thymus-dependent lymphocyte (CTL) generation was also induced with a cell-free supernatant from the 7-31 cells. Interleukin-2 (IL-2) containing concanavallin-A-conditioned medium could not reverse the suppression. The supernatant did not inhibit the proliferation of IL-2-dependent CTLL-2 cells and rapidly growing tumour cells and fibroblasts. Thus, this bone marrow suppressor cell produces a soluble factor that inhibits the generation of CTL in vitro, and prolongs the acceptance of skin allografts in in vivo.

In vitro analysis of mutations causing myoclonus epilepsy with ragged-red fibers in the mitochondrial tRNA(Lys)gene: two genotypes produce similar phenotypes

Cytoplasts from patients with myoclonus epilepsy with ragged-red fibers harboring a pathogenic point mutation at either nucleotide 8344 or 8356 in the human mitochondrial tRNA(Lys) gene were fused with human cells lacking endogenous mitochondrial DNA (mtDNA). For each mutation, cytoplasmic hybrid (cybrid) cell lines containing 0 or 100% mutated mtDNAs were isolated and their genetic, biochemical, and morphological characteristics were examined. Both mutations resulted in the same biochemical and molecular genetic phenotypes. Specifically, cybrids containing 100% mutated mtDNAs, but not those containing the corresponding wild-type mtDNAs, exhibited severe defects in respiratory chain activity, in the rates of protein synthesis, and in the steady-state levels of mitochondrial translation products. In addition, aberrant mitochondrial translation products were detected with both mutations. No significant alterations were observed in the processing of polycistronic RNA precursor transcripts derived from the region containing the tRNA(Lys) gene. These results demonstrate that two different mtDNA mutations in tRNA(Lys), both associated with the same mitochondrial disorder, result in fundamentally identical defects at the cellular level and strongly suggest that specific protein synthesis abnormalities contribute to the pathogenesis of myoclonus epilepsy with ragged-red fibers.

PCR-based preparation of 23S rRNA-targeted group-specific polynucleotide probes

DNA coding for a variable region within domain III of bacterial 23S rRNA was used as the target for group-specific polynucleotide hybridization probes. The corresponding rDNA was amplified in vitro by the PCR technique in combination with a pair of primers specific for flanking conserved target sites. The amplified fragments were cloned or used directly as probes. RNA probes were generated by in vitro transcription of cloned or amplified rDNA. The probes were labeled by incorporating modified nucleotides during in vitro DNA amplification or in vitro transcription or by random priming. The use of in vitro transcribed single-stranded RNA probes instead of double-stranded DNA probes provided stronger hybridization signals. Group-specific probes were prepared from genomic DNAs or directly from cells of Acinetobacter calcoaceticus, Alcaligenes faecalis, Aeromonas hydrophila, Nannocystis exedens, Pseudomonas aeruginosa, Pseudomonas fluorescens, and Pseudomonas stutzeri.

Detection of mycoplasma contamination in cell cultures by a mycoplasma group-specific PCR

The suitability of a 16S rRNA-based mycoplasma group-specific PCR for the detection of mycoplasma contamination in cell cultures was investigated. A total of 104 cell cultures were tested by using microbiological culture, DNA fluorochrome staining, DNA-rRNA hybridization, and PCR techniques. A comparison of the results obtained with these techniques revealed agreement for 95 cell cultures. Discrepant results, which were interpreted as false negative or false positive on the basis of a comparison with the results obtained with other methods, were observed with nine cell cultures. The microbiological culture technique produced false-negative results for four cell cultures. The hybridization technique produced false-negative results for two cell cultures, and for one of these cell cultures the DNA staining technique also produced a false-negative result. The PCR may have produced false-positive results for one cell culture. Ambiguous results were obtained with the remaining two cell cultures. Furthermore, the presence of contaminating bacteria interfered with the interpretation of the DNA staining results for 16 cell cultures. For the same reason the hybridization signals of nine cell cultures could not be interpreted. Our results demonstrate the drawbacks of each of the detection methods and the suitability of the PCR for the detection of mycoplasmas in cell cultures.

Mycoplasma detection by PCR analysis

The polymerase chain reaction (PCR) method was used to detect mycoplasma contamination in a panel of 42 continuous cell lines. According to the microbiological cultivation assay on agar, 29 cell lines were chronically infected and 13 cell lines were negative. Sets of outer and inner primers (nested double-step PCR) were applied which anneal to DNA sequences coding for conserved regions of the 16S rRNA. These oligonucleotides allow for the amplification of DNA regions found in at least 25 mycoplasma species (including the ones most commonly found in cell cultures), but do not cross-hybridize with DNA from eukaryotic cells. Mycoplasma-positive cell lines showed distinctive bands in ethidium bromide-stained gels, both after the first round of amplification as well as after the second PCR; all agar-negative cell lines were also unambiguously negative in the PCR assay. Thus, neither false-positive nor false-negative results occurred. Provided that the proper PCR working conditions are scrupulously observed, the PCR amplification has several outstanding advantages: high sensitivity, specificity, reliability, objectivity, speed, and simplicity.

Specificity and sensitivity of polymerase chain reaction (PCR) in comparison with other methods for the detection of mycoplasma contamination in cell lines

The polymerase chain reaction (PCR) amplification was used for the detection of mycoplasma contamination in 42 continuous cell lines. Using the microbiological cultivation on agar as the reference method, 29 cell lines were regarded as positive and 13 cell lines as negative. The double-step PCR analysis employed nested primers that anneal to gene sequences coding for the evolutionarily conserved 16 S rRNA of some 25 different mycoplasma species (including the ones most commonly found in cell cultures). In terms of the positivity or negativity of mycoplasma infection the results were identical for the agar assay and PCR amplification. All positive cell lines displayed distinct, unequivocal, objectively discernible bands on agarose gels while the non-infected specimens showed no DNA amplification. A simultaneously performed comparison with four other commonly used detection methods (DNA-RNA hybridization in solution, DAPI DNA fluorescence staining, immunostaining with a monoclonal antibody and an ELISA) showed that PCR produced significantly less false-negative or false-positive results than all the other methods. Furthermore, in dilution experiments, PCR correctly detected the infecting mycoplasmas at the lowest level of 1/10(4) whereas the other assays were less sensitive. It is concluded that double-step PCR employing nested primers is superior to other mycoplasma detection methods in many respects: simplicity and speed, high specificity and extreme sensitivity, objectivity and accuracy.

Species-specific oligonucleotide probes complementary to 16S rRNA of Mycoplasma gallisepticum and Mycoplasma synoviae

Mycoplasma gallisepticum and M synoviae are important avian pathogens causing respiratory diseases which result in great economic losses in poultry farming. Two oligonucleotide probes, complementary to the variable region V8 of 16S rRNA from the avian mycoplasmas M gallisepticum and M synoviae have, therefore, been designed and used in direct filter hybridisation experiments. Both probes gave strong hybridisation signals with their homologous targets, whereas no cross-hybridisations were obtained with any of the other avian mycoplasmas tested. It was possible to detect 2-3 x 10(4) mycoplasma organisms by direct filter hybridisation experiments with radiolabelled probes. The probes were also used to analyse several laboratory strains and field isolates of M gallisepticum and M synoviae with complete agreement between the probe technique and the other methods used for species determination. Atypical M gallisepticum strains also gave strong hybridisation signals with the M gallisepticum specific probe.

Oligonucleotide probes complementary to 16S rRNA for rapid detection of mycoplasma contamination in cell cultures

Mycoplasma contamination of cell cultures is a menace to diagnostic and research procedures. Rapid and reliable detection methods are, therefore, sorely needed. After comparing 16S rRNA sequences from those mycoplasmas that contaminate cell cultures, three different oligonucleotide probes were constructed. Two of these probes were designed to be group-specific and one to be species-specific. The three oligonucleotide probes were designed to cover all mycoplasmas commonly isolated from cell cultures. Contaminated cell lines could easily be detected by a direct filter hybridization assay in which the probes were incubated jointly. The assay proved to be rapid and sensitive with the possibility to perform and evaluate the mycoplasma testing within one working day.

Specificity of oligonucleotide probes complementary to evolutionarily variable regions of 16S rRNA from Mycoplasma hyopneumoniae and Mycoplasma hyorhinis

Mycoplasma is the common name for the smallest free-living microorganisms, the Mollicutes. Mycoplasma hyopneumoniae is of great importance in veterinary medicine, causing enzootic pneumonia in pigs. M hyorhinis can cause polyserositis and may cause pneumonia in piglets. Oligonucleotides complementary to variable regions of 16S rRNA from these mycoplasmas were designed and used as probes for detection and identification of these mycoplasmas. The probe complementary to 16S rRNA of M hyorhinis gave a very weak cross-hybridisation with M hyosynoviae in filter hybridisation experiments, but not with any of the other porcine mycoplasmas tested. Three oligonucleotide probes complementary to M hyopneumoniae 16S rRNA were tested. One of the probes (Mhp6/30) was found to be specific to M hyopneumoniae, but the other two gave cross-hybridisation with M flocculare. Using the Mhp6/30 probe in direct filter hybridisation experiments, it proved possible to detect M hyopneumoniae in lung biopsies from experimentally infected pigs.

Defects in mitochondrial protein synthesis and respiratory chain activity segregate with the tRNA(Leu(UUR)) mutation associated with mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes

Cytoplasts from two unrelated patients with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes) harboring an A----G transition at nucleotide position 3243 in the tRNA(Leu(UUR)) gene of the mitochondrial genome were fused with human cells lacking endogenous mitochondrial DNA (mtDNA) (rho 0 cells). Selected cybrid lines, containing less than 15 or greater than or equal to 95% mutated genomes, were examined for differences in genetic, biochemical, and morphological characteristics. Cybrids containing greater than or equal to 95% mutant mtDNA, but not those containing normal mtDNA, exhibited decreases in the rates of synthesis and in the steady-state levels of the mitochondrial translation products. In addition, NADH dehydrogenase subunit 1 (ND 1) exhibited a slightly altered mobility on polyacrylamide gel electrophoresis. The mutation also correlated with a severe respiratory chain deficiency. A small but consistent increase in the steady-state levels of an RNA transcript corresponding to 16S rRNA + tRNA(Leu(UUR)) + ND 1 genes was detected. However, there was no evidence of major errors in processing of the heavy-strand-encoded transcripts or of altered steady-state levels or ratios of mitochondrial rRNAs or mRNAs. These results provide evidence for a direct relationship between the tRNALeu(UUR) mutation and the pathogenesis of this mitochondrial disease.

Defects in mitochondrial protein synthesis and respiratory chain activity segregate with the tRNA(Leu(UUR)) mutation associated with mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes

Cytoplasts from two unrelated patients with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes) harboring an A----G transition at nucleotide position 3243 in the tRNA(Leu(UUR)) gene of the mitochondrial genome were fused with human cells lacking endogenous mitochondrial DNA (mtDNA) (rho 0 cells). Selected cybrid lines, containing less than 15 or greater than or equal to 95% mutated genomes, were examined for differences in genetic, biochemical, and morphological characteristics. Cybrids containing greater than or equal to 95% mutant mtDNA, but not those containing normal mtDNA, exhibited decreases in the rates of synthesis and in the steady-state levels of the mitochondrial translation products. In addition, NADH dehydrogenase subunit 1 (ND 1) exhibited a slightly altered mobility on polyacrylamide gel electrophoresis. The mutation also correlated with a severe respiratory chain deficiency. A small but consistent increase in the steady-state levels of an RNA transcript corresponding to 16S rRNA + tRNA(Leu(UUR)) + ND 1 genes was detected. However, there was no evidence of major errors in processing of the heavy-strand-encoded transcripts or of altered steady-state levels or ratios of mitochondrial rRNAs or mRNAs. These results provide evidence for a direct relationship between the tRNALeu(UUR) mutation and the pathogenesis of this mitochondrial disease.

Newly discovered mycoplasma isolated from patients infected with HIV

Mycoplasmas have been isolated from patients with acquired immunodeficiency syndrome (AIDS) and they may contribute to the pathogenesis of this disease. We have isolated repeatedly a previously unknown mycoplasma from the urine of an HIV-positive male homosexual and, subsequently, from the urine of 5 HIV-positive patients with AIDS. The mycoplasma was not found in the urine of 98 healthy control subjects. The organism has an unusual tip-like structure with densely packed fine granules and metabolizes both glucose and arginine for growth. Antigenic and DNA analyses show the organism to be distinct from other known mycoplasmas. The mycoplasma displays in-vitro activities associated with virulence in vivo. In addition, electronmicroscopy shows that the mycoplasma can invade and attach to various human and animal cells. We are investigating whether the new mycoplasma has a role in human disease.

Clinical and biological characteristics of Ureaplasma urealyticum induced polyarthritis in a patient with common variable hypogammaglobulinaemia

Persistent infectious polyarthritis caused by Ureaplasma urealyticum in a patient with common variable hypogammaglobulinaemia is described. The patient developed a symmetrical, destructive polyarthritis and tenosynovitis associated with a markedly depressed synovial fluid glucose concentration and characteristic soft tissue abscesses. The ureaplasma organism developed resistance to multiple antibiotics and persisted for five years. The organism was identified repeatedly in many joints by culture, confirmed by DNA hybridisation, and mycoplasma-like structures were shown in synovial tissues by electron microscopy.

The retinoblastoma gene functions as a growth and tumor suppressor in human bladder carcinoma cells

The product of the human retinoblastoma gene (RB) is a nuclear phosphoprotein that is thought to function as a tumor suppressor. Mutations of RB frequently occur in human bladder carcinoma. To investigate the significance of the functional loss of this gene in bladder cancer, an RB expression plasmid (pBARB) under control of the human beta-actin promoter was transfected into the bladder carcinoma cell line HTB9, which lacks RB expression. Marker-selected transfectants that expressed RB protein were identified by immunoblotting and immunohistochemical staining. In selected clones, stable RB expression has persisted over 1 yr under standard culture conditions with 10% serum. However, RB expression caused major alterations of HTB9 growth properties both in vitro and in vivo. RB+ transfectants lacked the ability to form colonies in semi-solid medium, and their growth rate was significantly decreased in 3% serum. In addition, the tumorigenicity of these transfectants was markedly decreased. Tumors that formed in nude mice were much smaller and had a longer latency period but were indistinguishable microscopically from those produced by parental cells. Slower growing tumors were RB+, as measured by nuclear staining of their RB protein and by a normal RB protein pattern on immunoblots. These findings support the concept that the RB gene acts as both a growth and tumor suppressor in bladder cancer cells.

Detection of Mycoplasma bovis and Mycoplasma agalactiae by oligonucleotide probes complementary to 16S rRNA

The partial sequences of 16S rRNA from Mycoplasma bovis and M. agalactiae were determined by dideoxynucleotide sequencing using reverse transcriptase. Two oligonucleotides complementary to different evolutionary variable regions of 16S rRNA from these two species were synthesized. The oligonucleotides were end-labelled with 32P and used as probes in filter hybridization experiments with different bovine, caprine and ovine mycoplasmas as samples. One of the probes, complementary to a sequence of the V8-region of both M. bovis and M. agalactiae, did not cross-hybridize to any bovine, caprine or ovine mycoplasmas except M. bovigenitalium and M. californicum. This probe is thus not useful for analysis of bovine samples, but can be used for detection of M. agalactiae in samples from goats and sheep, since M. bovigenitalium and M. californicum have never been isolated from these hosts and M. bovis only occasionally. The other probe, complementary to a sequence of the V6-region of M. bovis, gave some cross-hybridization with M. agalactiae but not with bovine mycoplasmas. M. agalactiae has never been isolated from cattle and this probe is therefore useful for rapid screening of bovine samples for M. bovis.

Effects of growth phase and antibiotics on quantitative DNA/RNA hybridization

Synthetic probes complementary to ribosomal RNA are increasingly used in the detection of bacteria. Many applications, however, require the quantitation of bacteria. We therefore tested the influence of growth phase and representative antibiotics (ampicillin, chloramphenicol and gentamycin) on the outcome of DNA/RNA filter hybridization using radiolabelled probes and a multisample digital autoradiograph for quantitative monitoring. Hybridization efficiency seemed influenced by the binding capacity of the membrane, availability of target molecules and physiological growth control. For chloramphenicol the absolute hybridization signal remained constant over the experimental period. Only a slight decrease was found in experiments with gentamycin whereas viable counts dropped 10,000-fold. For ampicillin a decrease in viable counts was paralleled by diminishing signal strengths. Relative signal strengths (counts per viable cell) increased in all experiments with antibiotics. In conclusion; (i) RNA probes seem to detect bacteria even after onset of antimicrobial therapy; (ii) DNA/RNA filter hybridization appears not suitable for accurate quantitation of bacteria.

Evaluation of different hybridization procedures for the detection of mycoplasma contamination in cell cultures

Cell culture samples were analysed for mycoplasma contaminations with two different DNA probes which have been described earlier. One probe (the H900 probe), derived from the 23S rRNA gene of Mycoplasma hyorhinis, cross-hybridized with virtually all mycoplasmas (including the acholeplasmas). The other probe (the T2 probe), derived from a protein gene of Acholeplasma laidlawii, cross-hybridized with most acholeplasmas. The two probes were compared in three different direct filter hybridization procedures without previous isolation of DNA or RNA. One of the procedures, developed in the present study, gave the highest sensitivity in DNA-RNA hybridization but also worked satisfactorily in DNA-DNA hybridization. The sensitivity of the H900 probe in filter hybridization experiments was compared with the sensitivity of a commercial probe for detection of mycoplasma contaminations in cell cultures. The H900 probe was found to be at least 25 times more sensitive for all cell culture mycoplasmas except for A. laidlawii, for which they were equally sensitive.

New bacteriophage vectors for the large scale production of single stranded insert DNA

SSEV 18 and SSEV 19, derivatives of the bacteriophages M13mp18/19, are new versatile cloning vectors allowing the large scale preparation of single stranded (ss) insert DNA. Replacing the original multiple cloning site by a synthetic 96 bp DNA fragment, a new polylinker region has been introduced containing complementary sequences designed to form a stem structure where single stranded insert fragments can be excised via a 'master restriction' site. The usefulness of such a vector has been demonstrated by the cloning of a 900 bp HindIII fragment derived from the Mycoplasma hyorhinis 23 S rRNA gene. After excision the single stranded insert was labeled isotopically and tested for sensitivity and specificity in detecting homologous sequences in pure DNA or cellular material immobilized on filters.

Evaluation and practical aspects of the use of a commercial DNA probe for detection of mycoplasma infections in cell cultures

Cell cultures have been analyzed for mycoplasma infections by using a commercial DNA-probe based on rRNA genes from mycoplasmas. Both the original version, Mycoplasma T.C. Detection Kit, and the improved version of the kit, Mycoplasma T.C. II Rapid Detection System, were used. The sensitivities of the two tests were found to be adequate in most cases and the improved version of the kit was 10-100 times more sensitive than the original one. A batch variation was observed with the improved version, which is not satisfactory. This batch variation can, however, be checked and the performance of the method with a properly working lot was found to be good.

AdoP assay detection of mycoplasmal contamination in biological media

The AdoP assay has been shown to be reliable in controlling the absence of mycoplasmas in filtered sera. We therefore compared its effectiveness with that of other tests in the detection of animal cell contamination by mycoplasmas.

Detection and quantitation of Anaplasma marginale in carrier cattle by using a nucleic acid probe

Cattle which have recovered from acute infection with Anaplasma marginale, a rickettsial hemoparasite of cattle, frequently remain persistently infected with a low-level parasitemia and serve as reservoirs for disease transmission. To fully understand the role of these carriers in disease prevalence and transmission, it is essential that low levels of parasitemia can be accurately detected and quantitated. We have developed a nucleic acid probe, derived from a portion of a gene encoding a 105,000-molecular-weight surface protein, that can detect A. marginale-infected erythrocytes. The probe is specific for A. marginale and can detect 0.01 ng of genomic DNA and 500 to 1,000 infected erythrocytes in 0.5 ml of blood, which is equivalent to a parasitemia of 0.000025%. This makes the probe at least 4,000 times more sensitive than light microscopy. Hybridization of the probe with treated blood from animals proven to be carriers of anaplasmosis showed that parasitemia levels were highly variable among carriers, ranging from greater than 0.0025 to less than 0.000025%. Parasitemia levels of individual animals on different dates were also variable. These results imply that, at any given time, individuals within a group of cattle may differ significantly in their abilities to transmit disease.

Distinction of species and strains of mycoplasmas (mollicutes) by genomic DNA fingerprints with an rRNA gene probe

Genomic fingerprints of Acholeplasma laidlawii, Mycoplasma hominis, and Mycoplasma pneumoniae strains were obtained by Southern blot hybridization of the digested mycoplasmal DNAs with an rRNA gene probe. The hybridization patterns revealed genotypic heterogeneity among A. laidlawii and M. hominis strains and a remarkable degree of homogeneity among M. pneumoniae strains isolated from pneumonia patients during a 10-year period. Genomic fingerprints with the rRNA gene probe can thus serve as indicators of intraspecies genetic homogeneity or heterogeneity and can provide a new, sensitive tool for strain identification with a potential for application in epidemiology.

A species-specific DNA probe for the detection of Mycoplasma gallisepticum

An 800-base-pair DNA fragment from a partial genomic library of Mycoplasma gallisepticum was selected and used as a probe for the selective detection of this avian pathogen. The specificity and sensitivity of this probe were demonstrated by using dot blot and Southern hybridizations.

Nucleic acid probes in clinical microbiology

The infectious disease applications of nucleic acid probe have been described. In addition, the basic procedures of nucleic acid probe technology have been discussed, as have the factors affecting implementation of probe technology in diagnostic laboratories. Despite the questions raised, nucleic acid probes will become part of the diagnostic laboratory in the near future. Commercial interests are developing and marketing new probes, reagents, and kits which will expedite the employment of this technology. High-volume reference laboratories will first use probes as part of a battery of tests which will include ELISA and monoclonal antibody methods. In all probability, probes will replace methods: that have proven to be ineffective, difficult, or costly such as culturing for some enteric pathogens and Legionella, that require long incubation periods, such as mycobacteria, or that have high costs and low yields, such as virology.

DNA hybridization probe for the Pseudomonas fluorescens group

Plasmid pHF360 was constructed from cloned rRNA genes (rDNA) of Pseudomonas aeruginosa and used as hybridization probe for the Pseudomonas fluorescens group. The probe was tested by dot and in situ colony hybridizations to chromosomal DNAs from a wide variety of organisms. pHF360 DNA hybridized exclusively to chromosomal DNAs from bacteria representing the P. fluorescens group and separated them clearly from all other bacteria tested in the present study. Determination of the nucleotide sequence of the cloned DNA showed that it is a fragment from a 23S rRNA gene of P. aeruginosa. It was compared with the published 23S RNA sequence from Escherichia coli.

Comparative studies to determine the efficiency of 6 methylpurine deoxyriboside to detect cell culture mycoplasmas

Studies were performed to compare three methods to detect mycoplasmal infection of cell cultures. The methods included microbiological assay by inoculation into broth and onto agar with anaerobic incubation, fluorescent DNA staining by Hoechst 33258, and mycoplasmal mediated cytotoxicity by 6 methylpurine deoxyriboside (6MPDR). Fluorescent DNA staining and 6MPDR assays were performed in an indicator cell culture system. A total of 2589 cell cultures were assayed. Mycoplasmas were detected in 174, an incidence of 6.7%. Species isolated were: Acholeplasma laidlawii, Mycoplasma orale, M. arginini, M. hyorhinis, M. fermentans, M. pirum, and M. pneumoniae. In separate studies, 6MPDR also detected infection with Spiroplasma mirum when this organism was deliberately inoculated into cell cultures. The efficiencies of microbiological testing, fluorescent DNA assays, and 6MPDR were 43.1, 98.8, and 97.1%, respectively.

Detection of cell culture mycoplasmas by a genetic probe

The utility of a genetic probe prepared against mycoplasmal ribosomal RNA was evaluated. The probe consisted of a tritiated DNA probe prepared with reverse transcriptase against Mycoplasma and Acholeplasma. Using a batch process without Southern blots and autoradiography, the probe assay detected mycoplasma infection in 27 of 52 cell cultures, an incidence of 51.9%. No false-positives were detected. Two false-negatives occurred; these were unusual mycoplasma infections of cell cultures grown in serum-free media. The sensitivity of the probe varied with mycoplasma species, from 9.3 X 10(3) for M. arginini to 2.6 X 10(6) for M. orale. The assay is rapid, taking only 2-3 h.

Antigen detection for the rapid diagnosis of mycoplasma and Legionella pneumonia

Immunologic attempts to detect mycoplasma antigens in fluids of infected patients have been rare and largely unsuccessful. Nucleic acid hybridization procedures appear promising on the basis of successes in detecting mycoplasmal contamination of tissue culture cells; results of attempts to apply these techniques to human infections have not been reported. Antigens can be detected in the urine of about 80% of patients with serogroup 1 Legionella pneumophila pneumonia and of some patients with serogroup 4 Legionella pneumophila and Legionella dumoffii pneumonia. The specificity of these assays is greater than 99%. In a test population in which the prevalence of Legionella pneumophila was 4%, the posterior probabilities of positive and negative results of tests for antigen were 86.5% and 99.3%, respectively. Antigen is detectable within the first 3 days of illness approximately as often as at later periods, and antigen may remain detectable for a few days to 1 yr after successful therapy. Antigen is detectable in serum, but the concentrations are considerably lower than in urine. Combining urinary antigen detection with direct fluorescent antibody examination of secretions increases the rapid diagnostic yield by 10%-20%. Monoclonal antibody studies demonstrate that subgroup specificities are present among the serogroup 1 urinary antigens. Radiometric and enzyme immunoassays detect antigen in equal proportions of patients. Latex agglutination results are positive in about 80% of those cases positive by the other methods.

Molecular biology and genetics of mycoplasmas (Mollicutes)

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