The polymerase chain reaction for Mycoplasma pulmonis

Pathogenesis of murine astrovirus in experimentally infected mice

Astroviruses are often associated with gastrointestinal diseases in mammals and birds. Murine astrovirus (MuAstV) is frequently detected in laboratory mice. Previous studies on MuAstV in mice did not report any symptoms or lesions. However, little information is available regarding its pathogenicity in immunodeficient mice. Therefore, in this study, we experimentally infected germ-free NOD.Cg-PrkdcscidIl2rgtm1Sug/ShiJic (NOG) mice, which are severely immunodeficient, with MuAstV. Germ-free mice were used for experimental infection to eliminate the effects of intestinal bacteria. Mice in each group were then necropsied and subjected to PCR for MuAstV detection, MuAstV RNA quantification in each organ, and histopathological examination at 4 and 28 days post inoculation (DPI). Tissue samples from the small intestine were examined by transmission electron microscopy. No symptoms or abnormalities were detected in any mice during necropsy. The MuAstV concentration was highest in the lower small intestine, where it increased approximately 8-fold from 4 to 28 DPI. Transmission electron microscopy revealed circular virus particles of approximately 25 nm in diameter in the cytoplasm of the villous epithelial cells of the lower small intestine. Histopathological examination did not reveal any abnormalities, such as atrophy, in the intestinal villi. Our results suggest that MuAstV proliferates in the villous epithelial cells of the lower small intestine and has weak pathogenicity.

Detection of Mycoplasma pulmonis in laboratory rats and technicians

Five species of mycoplasma are associated with several rat diseases. Mycoplasma pulmonis is the most important and most studied, possibly causing disease in rats and undermining the validity of laboratory experiments. M. pulmonis was isolated in 144/240 laboratory rats and identified by PCR in 155/240. This species was also detected in 12 human individuals (technicians of a laboratory animal house hold) in contact with these rats. The results were confirmed by sequencing of DNA products. Mycoplasma species are host specific; however, M. pulmonis was identified in humans, suggesting a case of unspecific colonization. Statistical analysis shows a greater risk for M. pulmonis colonizing individuals who are exposed to infected rats in animal facilities than individuals who do not. The detection of M. pulmonis in humans indicates a new status for this mollicute mycoplasmas in animal-holding facilities.

Polymerase chain reaction with a primer pair in the 16S-23S rRNA spacer region for detection of Mycoplasma pulmonis in clinical isolates

To develop a diagnostic tool to identify Mycoplasma pulmonis (M. pulmonis) in clinical isolates, we developed a polymerase chain reaction (PCR) assay using primers specific for the 16S-23S rRNA intergenic spacer region (SR) of M. pulmonis. One pair of PCR primers reacted specifically with two reference strains of M. pulmonis tested and seven samples isolated from naturally infected rats. The primer pair did not produce PCR products of the correct size from any other rodent or human mycoplasmas or cellular DNA from rodent lungs. Specificity of the PCR assay was confirmed by Southern blotting with probe specific for the SR of M. pulmonis. The PCR assay for detection of M. pulmonis established in this study is suitable for diagnosis of M. pulmonis infection in clinical cases.

Detection of Mycoplasma pulmonis in cilia-associated respiratory bacillus isolates and in respiratory tracts of rats by nested PCR

To improve the detection of Mycoplasma pulmonis contamination of isolates of cilia-associated respiratory (CAR) bacillus, we developed a nested PCR method using primers for 16S rRNA gene sequences. Of 140 samples of 16 different CAR bacillus isolates, 73 (52%) were inhibitory in the first PCR, as indicated by the absence of amplicons of the internal control, but only 11 of 140 (7.9%) were inhibitory in the second PCR. Of 27 samples known to contain M. pulmonis, only 12 (44%) were positive in the first PCR, but 25 of 27 (93%) were positive in the second PCR. Nested PCR also detected M. pulmonis in 21 of 61 (34%) CAR bacillus samples from which M. pulmonis could not be cultured and identified 2 additional M. pulmonis-contaminated CAR bacillus isolates. Of 359 respiratory and reproductive tract lavage samples from rats and mice, 35 (9.8%) were inhibitory in the first PCR, but only 15 (4.2%) were inhibitory in the second PCR. Of 72 lavage specimens from rats inoculated with an avirulent, poorly infective M. pulmonis strain, 14 (19%) were positive by nested PCR, but only 2 of 72 (2.8%) were positive by culture. Nested PCR also detected M. pulmonis in 14 of 20 (70%) paraffin sections of lung and trachea from rats and mice inoculated with CAR bacillus isolates known to contain M. pulmonis, whereas single PCR gave no positive results. We conclude that nested PCR is superior to single PCR or culture for detecting M. pulmonis, and that M. pulmonis is present in all but four CAR bacillus isolates in our collection that were from naturally infected rats; the four isolates that were exceptions were obtained from rats from a single colony.

Detection of mycoplasma contaminations by the polymerase chain reaction

The polymerase chain reaction (PCR) has been used for the general detection of Mollicutes. 25 Mycoplasma and Acholeplasma species were detected including important contaminants of cell cultures such as M. orale, M. arginini, M. hyorhinis, M. fermentans, A. laidlawii and additional human and animal mycoplasmas. PCR reactions were performed using a set of nested primers defined from conserved regions of the 16S rRNA gene. The detection limit was determined to be 1 fg mycoplasma DNA, which is equivalent to 1-2 genome copies of the 16S rRNA coding region. The identity of the amplification products was confirmed by agarose gel electrophoresis and restriction enzyme analysis. DNA from closely and distantly related micro-organisms did not give rise to specific amplification products. The method presented here offers a much more sensitive, specific and rapid assay for the detection of mycoplasmas than the existing ones.

Development of a selective and sensitive polymerase chain reaction assay for the detection of Mycoplasma pirum

A new assay using the polymerase chain reaction to amplify a 173-nucleotide DNA fragment within the 16S ribosomal RNA gene of Mycoplasma pirum has been developed. The assay selectively amplified DNA from all strains of M. pirum tested with a high level of sensitivity, even in a context of human DNA. DNA from other mollicute species, including those closely related to M. pirum, from bacteria phylogenetically close to mollicutes (Clostridium innocuum, C. ramosum and Bacillus subtilis), from Escherichia coli and from human peripheral blood mononuclear cells, did not produce the amplified DNA product specific for M. pirum.

Genus- and species-specific identification of mycoplasmas by 16S rRNA amplification

Systematic computer alignment of mycoplasmal 16S rRNA sequences allowed the identification of variable regions with both genus- and species-specific sequences. Species-specific sequences of Mycoplasma collis were elucidated by asymmetric amplification and dideoxynucleotide sequencing of variable regions, using primers complementary to conserved regions of 16S rRNA. Primers selected for Mycoplasma pneumoniae, M. hominis, M. fermentans, Ureaplasma urealyticum, M. pulmonis, M. arthritidis, M. neurolyticum, M. muris, and M. collis proved to be species specific in the polymerase chain reaction. The genus-specific primers reacted with all mycoplasmal species investigated as well as with members of the genera Ureaplasma, Spiroplasma, and Acholeplasma. No cross-reaction was observed with members of the closely related genera Streptococcus, Lactobacillus, Bacillus, and Clostridium or with any other microorganism tested. On the basis of the high copy number of rRNA, a highly sensitive polymerase chain reaction assay was developed in which the nucleic acid content equivalent to a single organism could be detected.

Detection of Mycoplasma hyopneumoniae DNA by the polymerase chain reaction

DNA amplification by the polymerase chain reaction (PCR) was examined to detect DNA of Mycoplasma hyopneumoniae, an etiological agent of porcine pneumonia. A pair of synthetic primers was selected that specify the amplification of a 520-basepair DNA fragment in a reiterative sequence of M. hyopneumoniae genome. The PCR product was detected by direct gel electrophoresis or by blot hybridization to a synthetic oligonucleotide probe. The specificity of PCR for M. hyopneumoniae was confirmed by lack of cross-reactivity to DNA from other porcine mycoplasmas.