Establishment of a Collection and Detection Technology of Mycoplasma hyopneumoniae in Aerosol

ObjectiveThis study was to establish a simple method for collecting and detecting Mycoplasma hyopneumoniae （Mhp） in aerosol. MethodBased on the mechanisms of liquid impinger and filtration sampler, a double concentration aerosol sampler was designed for collecting Mhp aerosol. Firstly, the collection was performed in a closed environment full of artificial aerosol of Mhp. Secondly, collection efficiency was detected by real-time PCR. Thereafter, the clinical feasibility of the designed equipment was tested by collecting aerosol samples in different pig herds. In one assay, the samples were collected at different times from one pig house challenged with Mhp. In another assay, the samples was collected from the delivery room, nursery and fattenning house of a MPS outbreak farm as well as a Mhp infection positive pig farm without obvious clinical symptoms. All the aerosol samples were then detected by real-time PCR or nested PCR. ResultThe collection efficiency of the designed bioaerosol sampler was （37.04±6.43） %, Mhp could be detected 7 d after intratracheal challenge with pneumonic lung homogenate suspension. Aerosol samples of 11 pig houses from the two Mhp positive pig farms with or without clinical symptoms all showed a positive result of PCR, the positivity rate was 100%. ConclusionA high sensitive collecting and detecting technology of aerosol was successfully established, which can be applied to clinical detection of Mhp in aerosol.

Effect of Osmotic Pressure on Mycoplasma hyopneumoniae Strain 168

[Objective] This study aimed to investigate the effect of hypertonic solution on the morphology,size,incubation time and cell viability of Mycoplasma hyopneumoniae（Mhp）.[Method] Mhp was stimulated by using NaCl hypertonic solution with a final concentration of 1.8% for 1,2,4,6 and 8 min,respectively.After staining and microscopic examination,the particle size and CCU（color change unit） were determined,and PCR identification was conducted.[Result] After treated with hypertonic solution for different time,Mhp was shrunken and turned round,the particle size was reduced,and the cell number rapidly decreased or even disappeared after 2 min.CCU was reduced by a gradient,and the observation time was extended for 1 d.The target band of Mhp could be amplified from samples after treated with hypertonic solution for different time.After treated with 1.8% NaCl solution for 1-6 min,Mhp changed in the morphology and size but still had viability.[Conclusion] This study provided reference data for exploring the entrance of Mhp into blood circulation after intramuscular injection and a new immunization route of swine Mycoplasma pneumonia vaccine.

Advances in the Detection of Mycoplasma hyopneumoniae by Polymerase Chain Reaction (PCR) Technology

Mycoplasma hyopneumoniae is an important pathogen causing Mycoplasmal pneumonia of swine, which generally causes secondary infections and mixed infections, thus seriously threats the development of swine industry and resulting in huge economic losses. Using PCR technology has very important significance to the correct diagnosis of Mycoplasmal pneumonia at the early stage. In this paper, specific target genes of Mycoplasma hyopneumoniae, methods for clinical sample collection, key technical factors of DNA sample processing method, and the research progress, main advantages and disadvantages, and application of general PCR technology, multiple PCR technology, nested-PCR technology, real-time fluorescence quantitative PCR technology, gene chip detection technology and loop-mediated isothermal amplification in detection of Mycoplasma hyopneumoniae were summarized, which provided convenience for the effective diagnosis and prevention of Mycoplasmal pneumonia of swine.

Development and Application of a Quantitative Competitive PCR Assay for Detecting Mycoplasma hyopneumoniae

[Objective] This study aimed to develop a quantitative competitive assay for detecting Mycoplasma hyopneumoniae in culture. [Method] One pair of Mhp-specific primers was designed for detecting Mhp in culture. Another pair of primers was designed based on the conserved gene sequences of Mycoplasma. The competitive template, which carried the same primer binding site with the target fragment, was constructed using enzyme digestion method. [Result] The logarithm of concentration of competitive template was treated as the abscissa（X-axis）, and the logarithm of corrected optical density ratio between amplification products by competitive template and target template was treated as the ordinate（Y-axis）. Thus the standard curve was drawn, and the regression equation was also obtained. When Y was assigned as 0, the concentration of the competitive plate was calculated, and then the concentration of Mhp was deduced. The logarithms of Color change unit（CCU） were treated as the abscissa（X-axis）, and the copy numbers of Mhp were treated as the ordinate（Y-axis）, so the standard curve was generated. It was found that the copy number of Mhp was highly correlated to CCU. [Conclusion] A quantitative competitive PCR assay was successfully established for the rapid detection of Mhp in culture.

Preparation of Monoclonal Antibody against P65 Protein of Mycoplasma hyopneumoniae

P65 protein, the major immunodominant protein of Mycoplasma hyopneu-moniae （Mhp） exhibiting no cross-reaction with other mycoplasmas, is general y used as a target protein for Mhp detection. In this study, BALB/c mice were immunized with prokaryotical y expressed P65 recombinant protein to prepare monoclonal anti-body. After screening with Mhp whole-cel protein and P65 protein, a specific hy-bridoma cel line, 3G12, was obtained by ELISA. Identification results indicated that the antibody secreted by 3G12 hybridoma cel s could react with P65 protein and Mhp whole-cel protein. According to indirect ELISA assay, 3G12 cel culture super-natant possessed a titer of 1∶12 800 against P65 protein and 1∶3 200 against Mhp whole-cel protein; 3G12 ascites possessed a titer of above 1∶4 000 000 against P65 protein and above 1∶20 000 against Mhp 168 whole-cel protein. After long-term in vitro culture and continuous freezing-thawing, 3G12 cel line could stably secrete antibodies. A monoclonal antibody against P65 protein and Mhp whole-cel protein was successful y obtained in the present study, which provided basis for further in-vestigating the pathogenic mechanism of Mhp and establishing diagnostic methods of Mycoplasmal pneumonia of swine （MPS）.

Comparative Analysis for the Detection and Monitoring of Mycoplasma hyopneumoniae Infection by Nested PCR(n-PCR) and Real time PCR(q-PCR) from Field Swine Herds

[Objective] 303 nasal swabs samples were collected from pigs in farms located in Taizhou city, Jiangsu Province, China from March to December 2012 for the purpose of detecting the presence of Mycoplasma hyopneumoniae, the primary agent of Enzootic porcine pneumonia （EPP） in pig herds using the nested PCR and Real time PCR techniques. [Method] Nasal swabs were collected from pigs of different ages＇ i.e. 7, 14, 21, 28, 30 and 35 days old, soaked in sterile 1 xPBS overnight at 4 ℃ and DNA extracted using the TIANamp（R） bacterial DNA kit. The DNA samples underwent amplification under the Mhyo 183 q-PCR and P36 primer Nested PCR systems. [Result] With the Nested PCR assay, 38 （12.5%） out of 303 samples tested positive for the presence of M. hyopneumoniae; with the real time PCR assay 152 （50.2%） tested positive for M. hyopneumoniae. The two assays matched to positively detect Mhyo in 22 （7.3%） samples and again matched in 127 （41.9%） samples negative for Mhyo infection. The pattern of infection in both assays was similar where 7- and 35-day-old piglets in both assays had the highest rates of infection i.e. 15.6% and 18.4% for n-PCR and 53.1% and 56.6% for q-PCR for 7- and 35-day-old piglets respectively. [Conclusion] The results highlight the suitability of both PCR assays in establishing the herd infection status of pigs in field conditions.

Immune Responses to the Attenuated Mycoplasma hyopneumoniae 168 Strain Vaccine by Intrapulmonic Immunization in Piglets

To investigate the immune responses to the attenuated Mycoplasma hyopneumoniae 168 strain vaccine, 8-15 d old piglets were immunized with M. hyopneurnoniae 168 strain vaccine by intrapulmonic route. And the specific IgG antibody in serum, lymphoproliferation, IFNT, and specific secretory IgA （SIgA） antibody in bronchoalveolar lavage fluid were detected on 30 and 60 d post-immunization （DPI）, respectively. On 60 DPI, all the pigs except for those in health control group were challenged with a field M. hyopneumoniae strain JS. Necropsy was performed on 30 d post-challenge （DPC）. The results showed that IFN7 and specific SIgA were stimulated on surface of respiratory tract after immunization. And peripheral blood mononuclear cells could also be proliferated about 1.81 and 2.12 fold on 30 and 60 DPI when stimulated by M. hyopneumoniae protein in vitro. However, no serum IgG antibody against M. hyopneumoniae was detected during the whole immune phage. After challenge, vaccinated pigs were observed with only very slight histological lesion in individual lobes. None of vaccinated pigs showed any clinical signs. While the unvaccinated pigs from challenge control group showed varying degrees of clinical sign and severe macroscopical lesion of mycoplasmal pneumonia of swine （MPS）. The result suggested that the attenuated M. hyopneumoniae 168 strain vaccine inoculated by intrapulmonic route could activate the systemic cellular immunity, the local mucosal immunity and IFNγ secretion in respiratory tract to against M. hyopneumoniae infection in piglets.

Standardization of a Real-time PCR System for Quantitative Detection of Mycoplasma hyopneumoniae

This study was conducted to develop a method for accurate quantification of Mycoplasma hyopneumoniae during vaccine production or experimental research. Primer and probe concentration that gave the highest ΔRn and the lowest Ct were selected to establish the real-time PCR system for the detection of M. hyopneumoniae. Template DNA of M. hyopneumoniae was extracted by boiling under different conditions and detected by real-time PCR to determine the optimal conditions for DNA extraction. Thereafter, intra-and inter-batch reproducibility tests were carried out using a standard plasmid to evaluate the stability of the PCR system. Subsequently, the effect of medium composition on the quantitative detection was evaluated. Finally, the correlation between real-time PCR and CCU method was explored. The optimal primer and probe concentration for real-time PCR were 0.4 and 0.2 μmol/L, respectively. The intra-and inter-batch coefficients of variation(CV) in Ct value of 10~4-10~9 copies/μl standard plasmid were <5%, indicating good reproducibility of the real-time PCR system. Following incubation in a boiling water bath for 10 min, M. hyopneumoniae samples can be used directly as a template in subsequent real-time PCR assays,and good intra-batch and inter-batch reproducibility was observed. The working concentration of KM2 medium should be less than the 1/10 of the concentration of the stock solution to minimize its influence on the quantitative detection. Spearman's correlation analysis revealed that the log of CCU and the log of DNA copy number had a significant positive relationship(r=0.797,P=0.000). Thus, the two methods can be used in combination in the quantitative detection of M. hyopneumoniae. In summary, a rapid, stable and accurate quantitative PCR system for detecting M. hyopneumoniae culture was established in this study, which provides a technical means for accurate quantification of M. hyopneumoniae in vaccine production and laboratory tests.

Establishment of a model of Mycoplasma hyopneumoniae infection using Bama miniature pigs

Mycoplasma hyopneumoniae(M.hyopneumoniae),is the primary aetiological agent of enzootic pneumonia leading to chronic respiratory disease prevalent worldwide.Conventional pigs are the only animals used for pathogenicity studies and vaccine evaluations of M.hyopneumoniae.Considering that the challenge animals have better genetic stability and a smaller body size to operate with,an alternative experimental animal model of M.hyopneumoniae infection with Bama miniature pigs was established.Nine seven-week-old snatch-farrowed,porcine colostrum-deprived(SF-pCD)Bama miniature pigs and nine conventional pigs were randomly divided into two infected groups(Bama miniatureinfected(BI)and conventional-infected groups(CI),BI and CI,n=6)and two control groups(Bama miniature control(BC)and conventional control(CC)groups,BC and CC,n=3).Every piglet was tracheally inoculated with 5×10^(8) CCU/mL containing 10%suspension of a stock of frozen lung homogenate from SF-pCD pigs infected with virulent strain JS or sterilized KM2 medium.Typical lung lesions appeared in all infected pigs after necropsy,and the mean gross lung lesions was 17.3 and 13.7 in groups of BI and CI.Serum IgG and nasal sIgA antibody titres were increased significantly.Cilia shedding and mucus staining increased greatly in JS-infected bronchi.Obvious reddish gross lesions and M.hyopneumoniae antigen were detected,especially apparently observed in group of BI.Moreover,DNA copies of M.hyopneumoniae from bronchoalveolar lavage fluid(BALF)of each JS-infected piglet reached more than 10^(8),and M.hyopneumoniae could be re-isolated from each infected BALF.These results indicate that Bama miniature pigs could be used as an alternative and more maneuverable experimental infection model for M.hyopneumoniae and display typical clinical and pathological features consistent with those in conventional pigs.

Secretory Expression of Mycoplasma hyopneu-moniae P97R1 Gene in Pichia pastoris and Primary Application of the Expression Product

[Objective] This study aimed to investigate the secretory expression of P97R1 gene of Mycoplasma hyopneumoniae（Mhp） in Pichia pastoris expression system and the primary application; of the expression product. [Method] A pair of specific primers was designed to conduct PCR according to the Mhp P97R1 gene sequence in Genbank, and the amplified P97R1 gene was cloned into the pPICZa-A yeast expression vector to construct the secretory recombinant expression vector pPICZa-A-P97R1. The plasmid pPICZa-A-p97R1 linearized by Sac I was transformed into P. pastoris GSl15 by electroporation. Positive transformant identified by PCR was incubated to express P97R1 protein after methanol induction. And the expression product was identified using SDS-PAGE and Western-blotting anal.wsis. [Result] P97R1 protein was successfully expressed in the P. pastoris system, with a secre- tory amount of 499μg/ml, and revealed good reactogenicity. Meanwhile, an indirect ELISA method was established with P97R1 protein after the optimization of each reaction factor, which showed good specificity and repeatability according to repeated tests. [Conclusion] This study provides bases for developing the ELISA Kit for anti- body detection and genetically engineered vaccine to Mhp.

Preventive Effects of Five Drugs on Mycoplasma Pneumonia of Swine (MPS)

The paper was to explore the preventive effects of five drugs on mycoplasma pneumonia of swine （MPS） and to provide reference for clinical medication of pig farms in Hainan Province. A total of 444 health piglets were randomly divided into 6 groups, including five medication groups （72 piglets in group A, 74 pig- lets in group B, 72 piglets in group C, 76 piglets in group D, 76 piglets in group E） and one control group （74 piglets）. The piglets in experimental groups were treated drugs once a day for successive 5 days at 30, 60, 90, 120 and 150 of age. The piglets in control group were free of medication. At 70 and 140 days of age, 15 piglets of each group were randomly selected to collect their blood sermn. The Mycoplasma hyopneumoniae （M-Hyo） antibodies in serum were measured by en- zyme-linked immunosorbent assay （ELISA）. During the experiment, the incidence rates of respiratory disease, lung lesion, feed conversion rate, average daily gain （ADG）, and mortality rate of pigs were also observed and recorded. The results showed that the five drugs had significant difference in preventative effects. Group C （Zhiyuanjing group） received the best preventive effect and the highest economic benefits. Compared with control group, the ADG and feed conversion rate in group C were increased by 7.53% and 9.09%, respectively; the incidence rate of respiratory disease was reduced by 13.44% and lung lesion was alleviated by 81.43% ; and the earnings of each pig could rise by 132.70 yuan. The preventative effect and economic benefit of the drugs was sequenced by Chansu Kechuanling and Bingchan Kechuanwang. Wante Feilin and amoxicillin had weaker preventive effects against MPS but greatly influenced growth performance of pigs, so they should be used alternatively with other drugs.

A Sensitive Competitive ELISA for Determination of Biotin in Transformed Yeast Culture Media

Aim To develop a sensitive competitive ELBA for the determination of biotinin transformed yeast culture media. Methods The ELBA plate was firstly coated with Mycoplasmahyopneumoniae, and then successively incubated with rabbit anti-Mycoplasma hyopneumoniae serum andgoat anti-rabbit IgG-biotin to form the solid biotin, which competed with the biotin in the solution(standard or sample) for the limited streptavidin-horse radish peroxidase conjugate. The standardcalibration curve for biotin analysis was constructed in the range of 50 - 2000 ng·L^(-1). ResultsThe detection limit for biotin was found to be 83 ng·L^(-1), which was about 1000 times lower thanthe lowest determination concentration in the reported ELISA for biotin analysis. The relativestandard deviations for the spiked samples at biotin concentrations of 200 ng·L^(-1), 500ng·L^(-1), and 1000 ng·L^(-1) were 24.87%, 6.15% , and 7.86% , respectively, with the averagerecovery of 101.13% . The wild yeast and its sixty-three transformed yeast culture media wereapplied to the developed ELBA for the determination of biotin. It was found that the biotinconcentrations in more than 85% of the tested samples were enhanced with different increase factorsafter transformation. Conclusion Utilization of Mycoplasma hyopneumoniae as the coating proteinimproves the precision and accuracy of the ELBA assay, which might be used for the biotin assay inother media.