Molecular variability of the adhesin-encoding gene pvpA among Mycoplasma gallisepticum strains and its application in diagnosis

Insights on Mycoplasma gallisepticum and Mycoplasma synoviae infection in poultry: a systematic review

Avian mycoplasmosis mainly caused by Mycoplasma gallisepticum and M. synoviae is an economically important disease of poultry industry. It causes huge economic losses in terms of decrease in weight gain, feed conversion efficiency, egg production, hatchability; increase in embryo mortality, carcass condemnation, prophylaxis and treatment cost in broiler, layer and breeder flocks. The disease is caused by four major pathogenic mycoplasmas viz., M. gallisepticum (MG), M. synoviae (MS), M. meleagradis (MM) and M. iowae (MI). The MG and MS are World Organization for Animal Health listed respiratory pathogens. MG causes chronic respiratory disease in chicken and infectious sinusitis in turkey; however, MS causes synovitis and airsacculitis in birds. The infection is transmitted both horizontally and vertically. Prevention and control measures of avian mycoplasmosis mainly comprises of biosecurity, treatment and vaccination. For vaccination of birds, inactivated bacterins, live attenuated and/or recombinant live poxvirus vaccines are commercially available against MG and MS infection. The present systematic review summarizes the different epidemiological studies carried out on MG and MS infection in poultry in different geographical locations of India and abroad over the last decade (2010-2020), economic impact, diagnosis and prevention and control.

Targeted sequencing analysis of Mycoplasma gallisepticum isolates in chicken layer and breeder flocks in Thailand

Mycoplasma gallisepticum (MG) is one of the most economically important pathogens worldwide. MG affects the respiratory system and impairs growth performance in poultry. In developing countries, the most widely used technique to identify MG is the conventional PCR assay. In this study, 24 MG isolates collected from Thailand farms with unvaccinated chickens during 2002–2020 were characterized by gene-targeted sequencing (GTS), followed by phylogenetic analysis using unweighted pair group method with arithmetic mean. These 24 Thai MG isolates differed from vaccine strains, including the F, ts-11 and 6/85 strains. One isolate showed 99.5–100% genetic similarity to the F strain with 4 partial gene analyses. This result may have been due to contamination from vaccinated flocks because the F strain is the most commonly used vaccine strain in Thailand. However, the GTS analysis using the partial MG genes in this study showed that the isolates could be grouped into different patterns based on individual gene sequences. The phylogenetic analysis of partial mgc2, gapA, pvpA and lp gene sequences classified the Thai MG isolates into 7, 11, 7 and 2 groups, respectively. In conclusion, at least 2 partial MG genes, especially partial gapA and mgc2 genes, are needed to differentiate MG isolates.

Rapid and specific detection of Mycoplasma gallisepticum and Mycoplasma synoviae infection in poultry using single and duplex PCR assays

Avian mycoplasmosis, mainly caused by Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS), is an economically important disease of poultry industry. The present study was aimed to develop duplex PCR as a rapid, specific and economical method for accurate detection of MG and MS in poultry and its comparison with single (monoplex) MG/MS PCR. During present investigation, a total of 146 poultry flocks having clinical history of respiratory disease were screened. Pooled tissue samples (trachea, lungs and air sacs) from 4-5 birds of each flock were collected during necropsy at disease investigation laboratories, Hisar, Haryana, India. The single and duplex PCR assays were standardized using primers of intergenic spacer region (IGSR; 16S-23S rRNA) for MG and hemagglutinin vlhA gene for MS, with expected amplicon size of 812 bp and 1200 bp products, respectively. In single PCR, 6.85%, 2.74% and 2.74% tissue samples were found positive for MG, MS and both MG and MS, respectively. However, duplex PCR showed, 7.53%, 2.74% and 1.37% positivity for MG, MS and both MG and MS, respectively. Taking the results of monoplex PCR as a gold standard, sensitivity and specificity of the developed duplex PCR was found to be 94.44% and 100%, respectively. Moreover, Cohen's kappa statistic (k = 0.97) measured a 'perfect' agreement between monoplex and duplex PCR assays. The positive and negative predictive values of duplex PCR was found to be 1.0 and 0.9922, respectively at 95% confidence interval (CI), as compared to monoplex PCR. The simultaneous use of two genes in a duplex PCR was more rapid and economical than two separate single PCR reactions.

Comparative evaluation of indirect-ELISA and DOT blot assay for serodetection of Mycoplasma gallisepticum and Mycoplasma synoviae antibodies in poultry

Avian mycoplasmosis, mainly caused by Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) is an economically important disease of the poultry industry. The present study was aimed to develop whole cell based indirect-ELISA (i-ELISA) and DOT blot assay (DOT-ELISA) as rapid, sensitive, specific and economical sero-detection tests for MG and MS. A total of 306 blood samples were collected from birds slaughtered at local meat shops of different districts of Haryana, India to detect MG and MS antibodies. Sonicated antigens prepared from freshly grown culture of MG and MS were used to develop i-ELISA and DOT blot assay. In i-ELISA, 50.32% and 61.76% serum samples were found to be positive for MG and MS antibodies, respectively. However in DOT blot assay, 41.83% and 53.92% serum samples were found positive for MG and MS antibodies, respectively. The relative diagnostic sensitivity and specificity of DOT-ELISA were measured considering i-ELISA as a reference test. The relative diagnostic sensitivity of the DOT blot assay was found to be 69.48% and 82.01%; whereas relative diagnostic specificity was 86.18% and 91.45% for the detection of MG and MS antibodies, respectively. The developed serological assays may be used as rapid and economical diagnostic tools for large scale screening of poultry sera for MG and MS antibodies.

Cloning of cytadhesin protein gene (pvpA) and expression analysis of recombinant fusion protein of Mycoplasma gallisepticum

Chronic respiratory disease (CRD) caused by Mycoplasma gallisepticum (MG) is one of the major respiratory tract infections of the poultry, resulting in significant economic loss to the poultry farmers. Diagnosis of such ailment is highly necessary for effective control measures. In addition, promising molecular tools are warranted for efficient epidemiological tracing of the outbreaks. The study was focused on the elucidation of phase variable cytadhesin protein gene (pvpA) of MG through cloning and expression analysis. A set of primers targeting the pvpA gene of MG was designed. The complete pvpA gene was amplified and cloned into pUC-derived expression vector pRSETA. Finally, the recombinant clones were examined through colony PCR and restriction endonuclease (RE) analysis with EcoR1 and BamH1 enzymes followed by sequencing. The expression of the recombinant pvpA gene was optimized at 1.4mM/μl concentration of Isopropyl-β-D-thiogalactoside induction at 30°C. The recombinant fusion protein was purified by immobilized metal affinity chromatography and characterized by SDS-PAGE followed by confirmation of recombinant cytadhesin fusion protein through western blot analysis. The pvpA gene was successfully cloned and expressed. The deduced amino acid sequence analysis had shown the presence of two direct repeats (DR1 and DR2) along with predicted PRP motifs repeatedly with high proline encoding regions at the carboxy-terminal of pvpA gene indicating its scope for epidemiological studies.

Complete Sequence-Based Genotyping of mgc2/pvpA Genes in Chicken-Derived Mycoplasma gallisepticum Isolates of Iran

Mycoplasma gallisepticum (MG) is a major pathogen of the poultry industry throughout the world. MG causes chronic respiratory disease in chickens and infectious sinusitis in turkeys. Despite constant improvements in the biosecurity of the poultry industry in Iran, MG infection still occurs and causes significant economic issues. To evaluate genetic variability, 10 Iranian MG isolates along with 17 available sequences were characterized by gene-targeted sequencing (GTS) analysis of complete mgc2/pvpA genes. According to the findings, 21 different sequence types within the sample set of 27 strains were typed by this method. The discriminatory power of this typing assay was established to be 0.97. Although no insertions and deletions of nucleotides were observed in the mgc2 gene among the Iranian strains, different lengths of pvpA genes with 1086, 1095, and 1101 nucleotides were detected within direct repeats (DRs) 1 and 2. Generally, eight tetrapeptides Pro-Arg-Pro-Met/Gln/Asn were found in the DRs of PvpA. Analysis of the carboxyl ends of PvpA proteins exhibited various repeats of prolines. In the phylogenetic tree of partial and complete mgc2/pvpA genes, all Iranian MG isolates were clustered into two distinct groups. Because this typing assay could provide a higher discriminatory power than the previously reported GTS scheme of partial mgc2/ pvpA genes, these results can be considered a blueprint for future national control and diagnostic strategies. Furthermore, consistent surveillance with larger datasets will be needed to clarify the epidemiologic characteristics of MG outbreaks in different poultry hosts.

Molecular detection and characterization of Mycoplasma gallisepticum and Mycoplasma synoviae strains in backyard poultry in Italy

Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) represent the most important avian Mycoplasma species in the poultry industry, causing considerable economic losses. In Italy, the presence of MG or MS has been investigated especially in commercial poultry farms. To our knowledge, no systematic investigations on MG or MS presence using highly specific diagnostic assays have been performed in backyard poultry. The aim of this study was to detect and molecularly characterize MG and MS strains in 11 backyard poultry flocks located in different regions of Italy. Tracheal swabs were collected and DNA was extracted. For MS, a PCR targeting a vlhA gene fragment was performed, and typing and subtyping was attempted. The presence of MG was investigated by a screening PCR, then MG typing by gene-targeted sequencing (GTS). All the amplicons were sequenced, then MG and MS dendrograms were constructed. All the flocks examined resulted Mycoplasma positive: 5 out of 11 (45.45%) were MG and MS positive, 3 (27.27%) were MG positive, and the remaining 3 (27.27%) were MS positive. The MS detections were assigned to types C, D, and F. All strains of type D belonged to subtype D1 and 2 unknown subtypes were identified. A MS sequence showed peculiar characteristics, which did not allow assignment to a known MS type or subtype. MG GTS analysis identified 6 MG strains belonging to 5 subclusters circulating in Italian backyards chicken flocks. The results of this study provide evidence of a risk for commercial poultry farms, especially in areas where backyard and commercial farms are close, suggesting the implementation of biosecurity measures.

Molecular Identification and Sequencing of <I>Mycoplasma gallisepticum</I> Recovered from Broilers in Egypt

BACKGROUND AND OBJECTIVES

Avian mycoplasmosis, particularly Mycoplasma gallisepticum (MG) is one of the infectious diseases associated with economic losses in Egyptian poultry industry. Thus, this study was aimed to determine the prevalence, serological identification, molecular characterization, sequencing and minimum inhibitory concentration of M. gallisepticum isolated from diseased broilers in Egypt.

MATERIALS AND METHODS

A total of 351 samples (227 tissue samples "tracheas and air sacs" and 124 tracheal swabs) and 71 sera were collected from diseased broilers. The conventional (isolation and biochemical) and molecular methods (PCR) were performed for detection of M. gallisepticum and virulence-associated gene (mgc2). The serum plate agglutination (SPA) test and enzyme-linked immunosorbent assay (ELISA) were applied on sera for determination of the presence of antibodies against M. gallisepticum. The minimal inhibitory concentration test (MIC) was used to determine the sensitivity of two sequenced M. gallisepticum strains to anti-mycoplasma agents.

RESULTS

The total recovery rate of Mycoplasma from 351 samples from broilers was 45.29% (159) in which M. gallisepticum showed a prevalence of 62.89% (100/159). Serological identification of M. gallisepticum in 71 collected sera using SPA and ELISA were 54.9 and 40.8% with the highest geometric mean titer of ELISA for M. gallisepticum (699.08 and 495.92). Molecular characterization of Mycoplasma using PCR showed that 50% (3/6) of tested isolates were identified as M. gallisepticum based on 16SrRNA. Also, the mgc2 gene was detected in 50% (3/6) M. gallisepticum isolates. Two positive PCR mgc2 specific genes of M. gallisepticum isolates were subjected to gene target sequencing (GTS) to verify that these two isolates were M. gallisepticum. The minimal inhibitory concentration test (MIC) was applied to determine the sensitivity of these two sequenced M. gallisepticum strains to anti-mycoplasma agents. The first M. gallisepticum isolate was sensitive to tilmicosin, tiamulin and spiramycin. The second M. gallisepticum isolate showed sensitivity to tiamulin, spiramycin and tilmicosin.

CONCLUSION

These results summarized the necessity of monitoring the Egyptian poultry farms for avian mycoplasmosis. Also, further studies are required for controlling of mycoplasma in all stages of the poultry industry production chain to avoid different losses in Egypt.

Application of high-resolution melting-curve analysis on pvpA gene for detection and classification of Mycoplasma gallisepticum strains

Mycoplasma gallisepticum (MG) is an avian species pathogen which causes heavy economic losses in the poultry industry. The purpose of this study was to determine genomic diversity of 14 MG field strains from chicken, Chuker partridge and peacock collected during 2009-2012 in Iran by polymerase chain reaction and partial sequencing of the pvpA gene. A High-Resolution Melting (HRM) technique was also developed and applied to differentiate between field and vaccine strains. Sequencing of the pvpA gene revealed a 51 nucleotide deletion, within DR-1 and DR-2, among MG strains from chicken and partridge whilst 63 nucleotides were deleted in MG strain from peacock. One nucleotide substitution was also observed among chicken MG strains. Phylogenetic analysis of the sequences clustered all of the Iranian MG strains into two clades or phylogeny groups; the strains from chicken and partridge in one group (group 1) and the strain from peacock into another group (group 4). HRM analysis has also produced comparable outcome to those of sequencing; four distinct melting curves which correspond to the three MG strains from chicken, Chukar partridge and peacock and ts-11 vaccine strain. Overall, findings of this study point towards a single source of infection for the chicken and partridge MG strains and likelihood of the strains being native and endemic in Iran. Peacock considered as an exotic species in Iran, hence the genetic distance for the pvpA gene. MG can be transmitted easily among different avian species and this distinct peacock strain may pose a threat to poultry industry. Our findings also show that molecular variation among pvpA gene of MG strains could be revealed using the relatively rapid and affordable HRM technique.

Real-time Loop-mediated Isothermal Amplification (LAMP) of mgc2 Gene of Mycoplasma Gallisepticum

Introduction

Mycoplasma gallisepticum is considered the most pathogenic and economically significant avian Mycoplasma spp. for the worldwide poultry industry. The aim of this study was to develop a novel and sensitive real-time loop-mediated isothermal amplification (LAMP) assay based on the amplification of its mgc2 gene sequence for its rapid molecular detection in poultry.

Material and Methods

Blood samples from 300 broiler and layer chickens were screened using a rapid serum agglutination (RSA) test. A real-time LAMP reaction was conducted with seropositive swab samples at 60ºC for 90 min in an ESEQuant tube scanner using 6-carboxyfluorescein as the reporting dye.

Results

The sensitivity of the developed assay was 10 fg/µL of DNA. The assay was found 100% specific, showing no cross-reactivity with other avian Mycoplasma species. The proportion found of the positive samples by the real-time LAMP was 58%. In comparison, the RSA was found to detect 52% of positive cases.

Conclusion

The mgc2 real-time LAMP emerged as a more sensitive and accurate method for molecular detection of M. gallisepticum than RSA. Robustness and precision give it applicability as a potential field diagnostic tool for M. gallisepticum control. The study will be beneficial in reducing economic losses that M. gallisepticum inflicts on the poultry industry. This is the first reported development of a real-time LAMP assay based on the amplification of the mgc2 gene sequence using an ESEQuant tube scanner for galline M. gallisepticum detection.

A survey of Mycoplasma gallisepticum and Mycoplasma synovaie with avian influenza H9 subtype in meat-type chicken in Jordan between 2011-2015

Commercial chickens in Jordan suffer from respiratory disease of undetermined etiology. This study was designed to document the involvement of avian influenza virus (AIV) H9 subtype, Mycoplasma gallisepticum (MG), and Mycoplasma synoviae (MS) in this respiratory disease. In this study, trachea swabs from 350 commercial broiler chicken flocks that suffered from respiratory disease were tested for AIV H9 subtype by using reverse transcription (RT)-PCR and for MG and MS by using PCR. PCR and RT-PCR results showed that 23.7, 8.9, and 6.6% of these flocks were infected with AIV H9 subtype, MS, and MG, respectively, whereas 12.9 and 5.7% of these flocks were infected with both AIV H9 subtype and MS and AIV H9 subtype and MS, respectively. Furthermore, 42.3% of these flocks were negative for the above mentioned respiratory diseases. Further epidemiological studies are recommended to determine risk factors and evaluate the economic consequences of AIV H9 subtype, MG, and MS infections in the region. Furthermore, studies are required to isolate AIV H9 subtype, MG, and MS and develop vaccines against the local field isolates.

Cloning, expression, and antigenic characterization of recombinant protein of Mycoplasma gallisepticum expressed in Escherichia coli

Mycoplasma gallisepticum (MG) is a member of the most important avian mycoplasmas, causing chronic respiratory disease in chickens and leading to important economic losses in the poultry industry. Recombinant technology represents a strategic approach used to achieve highly reliable and specific diagnostic tests in veterinary diseases control: in particular this aspect is crucial for confirming mycoplasma infection and for maintaining mycoplasma-free breeder flocks. In this study, we identified a component of the pyruvate dehydrogenase dihydrolipoamide acetyltransferase (i.e., E2) protein by 2-dimensional electrophoresis (2-DE), characterized it in immunoblotting assays, and analyzed its recombinant (r-E2) in a rec-ELISA test. For full-length protein expression in Escherichia coli (EC) a point mutation was introduced. A rabbit antiserum produced against r-E2 was tested in a Western Blot using different samples of Mycoplasma species. The results showed the applicability of site-directed mutagenesis, with a good yield of the r-E2 after purification. Also, anti-E2 serum reacted with all the tested MG strains showing no cross reaction with other mycoplasmas. The developed E2 ELISA test was capable of detecting MG antibodies in the sera examined. Those results demonstrate the antigenic stability of the E2 protein which could represent a recombinant antigen with potential diagnostic applications.

Comparison of multiple genes and 16S-23S rRNA intergenic space region for their capacity in high resolution melt curve analysis to differentiate Mycoplasma gallisepticum vaccine strain ts-11 from field strains

Mycoplasma gallisepticum (MG) is an important avian pathogen causing significant economic losses in the global poultry industry. In an attempt to compare and evaluate existing genotyping methods for differentiation of MG strains/isolates, high resolution melt (HRM) curve analysis was applied to 5 different PCR methods targeting vlhA, pvpA, gapA, mgc2 genes and 16S-23S rRNA intergenic space region (IGSR). To assess the discriminatory power of PCR-HRM of examined genes and IGSR, MG strains ts-11, F, 6/85 and S6, and, initially, 8 field isolates were tested. All MG strains/isolates were differentiated using PCR-HRM curve analysis and genotype confidence percentage (GCP) values of vlhA and pvpA genes, while only 0, 3 and 4 out of 12 MG strains/isolates were differentiated using gapA, mgc2 genes and IGSR, respectively. The HRM curve analysis of vlhA and pvpA genes was found to be highly correlated with the genetic diversity of the targeted genes confirmed by sequence analysis of amplicons generated from MG strains. The potential of the vlhA and pvpA genes was also demonstrated for genotyping of 12 additional MG strains from Europe and the USA. Results from this study provide a direct comparison between genes previously used in sequencing-based genotyping methods for MG strain identification and highlight the usefulness of vlhA and pvpA HRM curve analyses as rapid and reliable tools specially for diagnosis and differentiation of MG strains used here.

Mycoplasma gallisepticum experimental infection and tissue distribution in chickens, sparrows and pigeons

The most effective approaches to control the spread of Mycoplasma gallisepticum include strict biosecurity measures, continuous surveillance and eradication of infected flocks. The rapid expansion of the poultry industry worldwide in restricted geographical areas and severe economic losses due to M. gallisepticum outbreaks make it crucial to identify and better control the vectors responsible for the transmission of the disease. In the present study we evaluated the susceptibility of sparrows and pigeons to M. gallisepticum and the tissue distribution of M. gallisepticum in these species as compared with chickens. This information will further define the role of these common avian species in M. gallisepticum transmission. Twenty-six chickens, pigeons, and sparrows were experimentally inoculated with a field strain of M. gallisepticum and were monitored for the development of clinical signs, seroconversion, productive infection by culture, and M. gallisepticum distribution in their tissues by immunohistochemistry. All M. gallisepticum-inoculated chickens showed mild respiratory signs, seroconverted (haemagglutination inhibition geometric mean titre = 494) and shed M. gallisepticum in their tracheas. M. gallisepticum antigens were observed at high levels by immunohistochemistry in their tracheas, conjunctivas, nasal turbinates, and air sacs. The pigeons and sparrows did not show clinical signs or seroconvert but M. gallisepticum was reisolated up to 7 days post inoculation from pigeons and intermittently from sparrows. M. gallisepticum antigens were observed at low level in the conjunctiva of some pigeons and sparrows, as well as in the trachea of some sparrows. We conclude that pigeons and sparrows are partially susceptible to M. gallisepticum infection but do not seroconvert or maintain a steady carrier state similar to chickens and that these species may play a role in M. gallisepticum transmission between poultry farms as mechanical vectors.

Pathologic lesions caused by coinfection of Mycoplasma gallisepticum and H3N8 low pathogenic avian influenza virus in chickens

Chickens were infected under experimental conditions with Mycoplasma gallisepticum and low pathogenic avian influenza (LPAI) strain A/mallard/Hungary/19616/07 (H3N8). Two groups of chickens were aerosol challenged with M. gallisepticum strain 1226. Seven days later, one of these groups and one mycoplasma-free group was challenged with LPAI H3N8 virus; one group without challenge remained as negative control. Eight days later, the birds were euthanized and examined for gross pathologic and histologic lesions. The body weight was measured, and the presence of antimycoplasma and antiviral antibodies was tested before the mycoplasma challenge, before the virus challenge, and at the end of the study to confirm both infections. Chickens in the mycoplasma-infected group developed antibodies against M. gallisepticum but not against the influenza virus. Chickens of the group infected with the influenza virus became serologically positive only against the virus, while the birds in the coinfected group developed antibodies against both agents. The LPAI H3N8 virus strain did not cause decrease in body weight and clinical signs, and macroscopic pathological lesions were not present in the chickens. The M. gallisepticum infection caused respiratory signs, airsacculitis, and peritonitis characteristic of mycoplasma infection. However, the clinical signs and pathologic lesions and the reduction in weight gain were much more significant in the group challenged with both M. gallisepticum and LPAI H3N8 virus than in the group challenged with M. gallisepticum alone.

Development and immunogenicity of recombinant GapA(+) Mycoplasma gallisepticum vaccine strain ts-11 expressing infectious bronchitis virus-S1 glycoprotein and chicken interleukin-6

Mycoplasma gallisepticum (MG) is a major pathogen of poultry that causes chronic respiratory disease in chickens and infectious sinusitis in turkeys. A live attenuated vaccine, ts-11, has been used for the control of MG in several countries. The efficacy of this vaccine is highly dose dependent and the flock antibody response is weak. To improve the functionality of the vaccine and investigate its potential as a delivery vector for foreign antigens and immunomodulatory proteins, we developed a derivative of ts-11 expressing infectious bronchitis virus-S1 glycoprotein (IBV-S1) and releasing chicken interleukin-6 into the extracellular milieu (MG ts-11 C3 (+CS)) using a transposon-based delivery vector. Following administration of MG ts-11 C3 (+CS) to chickens by eye-drop, an antibody response to MG and IBV-S1, as determined by the rapid serum agglutination test (RSA) and Western blotting, respectively, could be detected. Birds inoculated with the recombinant vaccine had significantly enhanced weight gain and were partially protected against damage by pathogenic IBV. These results indicate that the ChIL-6 released by MG ts-11 C3 (+CS) may have had a non-specific effect on growth rate. They also suggest that ts-11 is a promising vaccine vector, capable of delivering heterologous protective antigens, and may also provide non-specific benefits when engineered to express immunomodulatory proteins. With some improvements in the expression system, it could be used to induce a targeted immune response against specific mucosal pathogens, and co-expression of several antigens would allow development of a novel multivalent vaccine.

Bi-antigenic immunoassay models based on the recombinant PvpA proteins for Mycoplasma gallisepticum diagnosis in chickens

The present study aimed to produce the relatively conserved central fragment of the Mycoplasma gallisepticum PvpA cytadhesin as recombinant antigen and to determine its species-specific diagnostic potential in comparison with the full-length recombinant rPvpA336 protein. For this purpose, a recombinant protein (rPvpA134) consisting of 134 amino acids with apparent molecular mass of 27 kD was produced and highly purified. The rPvpA134 protein was composed of the amino acid residues at positions 133-265 with respect to the wild-type PvpA. Two bi-antigenic diagnostic models based on Western blot and enzymatic rapid immunofiltration assay (ERIFA) were developed to compare simultaneously the diagnostic potential of the recombinant antigens rPvpA134 and rPvpA336. Although 40% of the confirmed rPvpA336-positive chicken sera were detected as reactive with rPvpA134, this protein would be a useful secondary diagnostic antigen with which to confirm species-specific antibody response for monitoring M. gallisepticum infections. It can be concluded from the present study that 2 bi-antigenic models were successfully adapted to the specific diagnosis of chicken M. gallisepticum. Furthermore, by virtue of its simplicity and rapidity, the ERIFA model has multi-antigenic application potential, making it an alternative field test that is widely applicable in the veterinary diagnostic field.

Comparative genomic analyses of attenuated strains of Mycoplasma gallisepticum

Mycoplasma gallisepticum is a significant respiratory and reproductive pathogen of domestic poultry. While the complete genomic sequence of the virulent, low-passage M. gallisepticum strain R (R(low)) has been reported, genomic determinants responsible for differences in virulence and host range remain to be completely identified. Here, we utilize genome sequencing and microarray-based comparative genomic data to identify these genomic determinants of virulence and to elucidate genomic variability among strains of M. gallisepticum. Analysis of the high-passage, attenuated derivative of R(low), R(high), indicated that relatively few total genomic changes (64 loci) occurred, yet they are potentially responsible for the observed attenuation of this strain. In addition to previously characterized mutations in cytadherence-related proteins, changes included those in coding sequences of genes involved in sugar metabolism. Analyses of the genome of the M. gallisepticum vaccine strain F revealed numerous differences relative to strain R, including a highly divergent complement of vlhA surface lipoprotein genes, and at least 16 genes absent or significantly fragmented relative to strain R. Notably, an R(low) isogenic mutant in one of these genes (MGA_1107) caused significantly fewer severe tracheal lesions in the natural host compared to virulent M. gallisepticum R(low). Comparative genomic hybridizations indicated few genetic loci commonly affected in F and vaccine strains ts-11 and 6/85, which would correlate with proteins affecting strain R virulence. Together, these data provide novel insights into inter- and intrastrain M. gallisepticum genomic variability and the genetic basis of M. gallisepticum virulence.

Flock-level prevalence of Clostridium colinum in broiler flocks with digestive disease in Jordan by polymerase chain reaction

A cross-sectional study was conducted from May to September of the year 2008 in broiler flocks in the southern and northern area of Jordan, to determine the flock-level prevalence of Clostridium colinum infection. Intestinal swabs were collected from 170 broiler flocks and tested by PCR. Among the study population, 20 flocks in both areas (11.8%, 95% confidence interval: 10 to 22%) were positive for C. colinum infection. The prevalence of positive intestinal samples in the southern and northern area of Jordan were 4.7 and 7.1%, respectively, which was statistically significant (chi(2) = 3.9 df = 1, P = 0.0482). It is recommended to conduct further epidemiologic studies to determine risk factors and to evaluate the economic consequences of the C. colinum infection in the region.

Differentiation of Mycoplasma gallisepticum vaccine strains ts-11 and 6/85 from commonly used Mycoplasma gallisepticum challenge strains by PCR

Mycoplasma gallisepticum (MG) is an important avian pathogen causing significant economic losses within the poultry industry. In an effort to develop tools to aid in MG research and diagnostics, we have compared sequences of the attenuated MG vaccine strain ts-11 to those of commonly used pathogenic challenge strains in search of a simple means of differentiation. Via gapA sequence alignments and comparisons, we have identified and designed primers facilitating strain differentiation. When applied to conventional polymerase chain reaction (PCR) assay at low annealing temperature, the primer sets allow for the differentiation of MG attenuated vaccine strains ts-11 as well as the attenuated MG vaccine strain 6/85 from the commonly utilized MG challenge strains R(low), R, and S6. Conventional PCR differentiation is based on the visualization of sole products with the attenuated MG strains ts-11 and 6/85 and the lack of the corresponding products from MG strains R(low), R, and S6. When applied to MG strain F, product visualization varies with the applied primer set. The differentiation of MG strains ts-11 and 6/85 from the pathogenic challenge strains was also accomplished via real-time analyses, however, the primer sets were not able to differentiate MG strains ts-11 and 6/85 from selected MG field isolates.

Separating Mycoplasma gallisepticum Field Strains from Nonpathogenic Avian Mycoplasmas

Mycoplasma gallisepticum (MG) has repeatedly emerged as a serious problem in U.S. broiler, layer, and turkey industries. Tracing the source of an outbreak is essential if MG control is to be accomplished. Amplified fragment length polymorphism (AFLP), random amplification of polymorphic DNA (RAPD), and restriction fragment length polymorphism (RFLP) are valuable tools used to study MG epidemiology, allowing diagnosticians to determine the source of MG infections. In some past outbreaks, AFLP, RAPD, and RFLP fingerprinting, which require pure MG cultures, were not successful because of contaminating nonpathogenic mycoplasmas from field samples. The objective of this research was to develop a method to separate rapidly growing nonpathogenic avian mycoplasma species from slower-growing MG field strains. Mixtures of MG and three separate nonpathogenic avian mycoplasmas were inoculated onto chick embryo fibroblasts cells (CEF) allowing MG to penetrate the CEF cells. Later, gentamicin sulphate was added to the culture, eliminating the nonpathogenic mycoplasmas and allowing MG to be isolated in pure culture. Mixtures of Mycoplasma synoviae (MS) and MG could not be separated in this assay. However, removal of nicotinamide adenine dinucleotide and cysteine hydrochloride during serial passage in Frey broth medium successfully eliminated growth of MS.

Genotyping of Mycoplasma gallisepticum and M. synoviae by Amplified Fragment Length Polymorphism (AFLP) analysis and digitalized Random Amplified Polymorphic DNA (RAPD) analysis

Mycoplasma gallisepticum (MG) and M. synoviae (MS) are the cause of considerable economic losses in the poultry industry. Molecular differentiation of avian Mycoplasma strains may be helpful in tracing infections and in the evaluation of implemented intervention strategies. Amplified Fragment Length Polymorphism (AFLP) has shown to be a powerful typing technique but the application for poultry Mycoplasma strains is very limited. The aim of this study was to evaluate the reproducibility and discriminatory power of AFLP HindIII/HhaI and AFLP BglII/Mfel for the inter- and intraspecies differentiation of avian mycoplasmas and to compare these test characteristics with digitalized Random Amplified Polymorphic DNA (RAPD) analysis. The reproducibility of RAPD, AFLP HindIII/HhaI and AFLP BglII/Mfel was 50-100, 97-98 and 86-99%, respectively. RAPD and both AFLP enzyme combinations were able to differentiate between five avian Mycoplasma species. For AFLP, five MG and four MS clusters could be identified. The phylogenetic tree for both enzyme combinations was comparable. For RAPD, four MG clusters could be identified. For MS, however, due to the poor reproducibility of the RAPD technique, no clear genogroups could be identified. On basis of the results of this study it can be concluded that AFLP is a powerful technique for the genotyping of avian mycoplasmas and that, although AFLP HindIII/HhaI generated patterns with less fragments, the final results showed homologous results.

Use of mgc2-polymerase chain reaction-restriction fragment length polymorphism for rapid differentiation between field isolates and vaccine strains of Mycoplasma gallisepticum in Israel

Increasing use of Mycoplasma gallisepticum (MG) live vaccines has led to a need for a rapid test for differentiation of MG field strains from the live vaccine strains ts-11 and 6/85. We examined the differentiating potential of diagnostic polymerase chain reaction (PCR) primers targeted to the gene mgc2, encoding a cytadherence-related surface protein uniquely present in MG. The mgc2-PCR diagnostic primers are specific for MG in tests of all avian mycoplasmas or bacteria present in the chicken trachea and are sensitive enough to readily detect MG in tracheal swabs from field outbreaks. Differentiation of vaccine strain ts-11 was based on identification of restriction enzyme sites in the 300-base-pair (bp) mgc2-PCR amplicon present in ts-11 and missing in MG isolates from field outbreaks in Israel. Restriction sites for the enzymes HaeII and SfaN1 were identified in the amplified region in strain ts-11 and were not found in 28 field isolates of MG, comprising a representative cross section of all the MG isolates from the period 1997-2003. In practice, differential diagnosis of MG is achieved within 1 day of submission of tracheal swab samples by mgc2-PCR amplification and restriction of the amplicon with HaeII, giving a 270-bp fragment for ts-11 or no restriction for other MG strains tested. Application of the mgc2-PCR-restriction fragment length polymorphism (mgc2-PCR-RFLP) assay enabled differential diagnosis of both components of a mixture of ts-11 and non-ts-11 DNA, detecting the field strain in the presence of a large excess of ts-11. The test was successfully applied in vivo for monitoring vaccinates in a ts-11 vaccine trial. In principle, the test may also be used to identify the 6/85 vaccine strain, which yields a 237-bp product, readily differentiated from the approximately 300-bp PCR product of all other strains tested. Further testing of field isolates will be necessary to determine the applicability of this test in the United States and other countries.

Safety and efficacy ofMycoplasma gallisepticumTS-11 vaccine for the protection of layer pullets against challenge with virulentM. gallisepticumR-strain

Mycoplasma gallisepticum TS-11 vaccine was studied for its safety and protective ability in 49-day-old M. gallisepticum-free and Mycoplasma synoviae-free commercial Tetra SL layer chickens. Sixty birds were distributed into four groups: 15 were unvaccinated but were challenged with M. gallisepticum R-strain, 15 were vaccinated by eye drop and then challenged with virulent M. gallisepticum R-strain 4 weeks post vaccination, 15 were designated as controls without vaccination and challenge, and 15 received TS-11 vaccine but no challenge. Based on the post-challenge clinical signs, body weight gain, gross pathological examination of air sacs and peritoneum, histological examination of the trachea, lung, spleen and liver, and reisolation of mycoplasmas from inner organs, the TS-11 vaccine is safe and does not produce clinical signs, a major decrease of body weight gain or pathological lesions. Vaccination induced a slight serological response to M. gallisepticum antigen in serum plate agglutination and blocking enzyme-linked immunosorbent assay tests and prevented development clinical signs of airsacculitis, peribronchitis and interstitial pneumonia on M. gallisepticum challenge.

Use of molecular diversity of Mycoplasma gallisepticum by gene-targeted sequencing (GTS) and random amplified polymorphic DNA (RAPD) analysis for epidemiological studies

A total of 67 Mycoplasma gallisepticum field isolates from the USA, Israel and Australia, and 10 reference strains, were characterized by gene-targeted sequencing (GTS) analysis of portions of the putative cytadhesin pvpA gene, the cytadhesin gapA gene, the cytadhesin mgc2 gene, and an uncharacterized hypothetical surface lipoprotein-encoding gene designated genome coding DNA sequence (CDS) MGA_0319. The regions of the surface-protein-encoding genes targeted in this analysis were found to be stable within a strain, after sequencing different in vitro passages of M. gallisepticum reference strains. Gene sequences were first analysed on the basis of gene size polymorphism. The pvpA and mgc2 genes are characterized by the presence of different nucleotide insertions/deletions. However, differentiation of isolates based solely on pvpA/mgc2 PCR size polymorphism was not found to be a reliable method to differentiate among M. gallisepticum isolates. On the other hand, GTS analysis based on the nucleotide sequence identities of individual and multiple genes correlated with epidemiologically linked isolates and with random amplified polymorphic DNA (RAPD) analysis. GTS analysis of individual genes, gapA, MGA_0319, mgc2 and pvpA, identified 17, 16, 20 and 22 sequence types, respectively. GTS analysis using multiple gene sequences mgc2/pvpa and gapA/MGA_0319/mgc2/pvpA identified 38 and 40 sequence types, respectively. GTS of multiple surface-protein-encoding genes showed better discriminatory power than RAPD analysis, which identified 36 pattern types from the same panel of M. gallisepticum strains. These results are believed to provide the first evidence that typing of M. gallisepticum isolates by GTS analysis of surface-protein genes is a sensitive and reproducible typing method and will allow rapid global comparisons between laboratories.

Differentiation of Mycoplasma gallisepticum strains using amplified fragment length polymorphism and other DNA-based typing methods

Amplified fragment length polymorphism (AFLP) was used to type 34 strains of Mycoplasma gallisepticum (MG) including vaccine strains ts-11, 6/85, and F. Using AFLP, a total of 10 groups, with 30 distinguishable AFLP typing profiles, were generated in the analysis. The AFLP method was able to identify and differentiate both MG field strains from recent outbreaks and those that were epidemiologically related. The AFLP procedure will provide assistance in identifying the sources of mycoplasma infections. Vaccine strains were also differentiated from other field strains, which will be useful in the evaluation of vaccination programs. The AFLP discrimination potential was compared to other molecular typing techniques such as gene-targeted typing by DNA sequence analysis of the MG cytadhesin-like protein encoding gene, mgc2, and random amplified polymorphic DNA assay on the same MG isolates. The three assays correlated well with one another, with AFLP analysis having a much higher discriminatory power and reproducibility.

Specific detection and typing of Mycoplasma synoviae strains in poultry with PCR and DNA sequence analysis targeting the hemagglutinin encoding gene vlhA

Mycoplasma synoviae is a major pathogen of chickens and turkeys, causing economic losses to the poultry industry worldwide. In this study, we validated and applied polymerase chain reaction (PCR) and DNA sequence analysis on the N-terminal end of the hemagglutinin encoding gene vlhA as an alternative for the detection and initial typing of field strains of M. synoviae in commercial poultry. PCR primers were tested against isolates of M. synoviae from various sources along with other avian mycoplasma and other bacterial species. The vlhA gene-targeted PCR assay was highly specific in the identification of M. synoviae, with a detection limit of 4.7 x 10(2) color changing units/ml. DNA sequence analysis of amplified products was also conducted to validate the potential for typing M. synoviae strains using the N-terminal region of the vlhA gene. To evaluate the test, we applied the PCR assay to tracheal swabs collected from chickens challenged with M. synoviae strain K1968 and compared the results to the serologic detection. The PCR assay was also evaluated directly on tracheal samples collected from commercial layers. Overall, this vlhA gene-targeted PCR is a useful tool for detection and initial typing of M. synoviae and can be applied in the preliminary identification of M. synoviae isolates directly from clinical samples.

Molecular characterization of Mycoplasma gallisepticum isolates from turkeys

Mycoplasma gallisepticum was isolated from several turkey flocks at different locations in the United States that were clinically affected with respiratory disease. Five of these isolates from four series of outbreaks had patterns similar to the 6/85 vaccine strain of M. gallisepticum by random amplified polymorphic DNA (RAPD) analysis using three different primer sets, whereas with a fourth primer set (OPA13 and OPA14), only two of the isolates were similar to 6/85. Results obtained by sequencing portions of the pvpA, gapA, and mgc2 genes and an uncharacterized surface lipoprotein gene indicated that the field isolates had DNA sequences that ranged from 97.6% to 100%, similar to the 6/85 results. In some of the outbreaks there was an indirect association with the presence of commercial layers in the area that had been vaccinated with this vaccine strain, but there was no known close association with vaccinated birds in any of the outbreaks. Turkeys were challenged with two of the field isolates and with 6/85 vaccine strain. Turkeys challenged with the field isolates developed respiratory disease with airsacculitis and a typical M. gallisepticum antibody response, whereas birds challenged with 6/85 developed no respiratory signs or lesions and developed only a weak antibody response. Although these isolates were very similar to the 6/85 vaccine strain, it was not possible to prove that they originated from the vaccine strain-it is possible that they could be naturally occurring field isolates.

Characterization of a naturally occurring infection of a Mycoplasma gallisepticum house finch-like strain in turkey breeders

An outbreak of Mycoplasma gallisepticum (MG) in commercial turkeys involving very mild clinical signs was difficult to confirm by routine methods. In the first part of this study (trial A), we conducted a bioassay to increase the likelihood of detecting MG. Susceptible turkeys were inoculated with sinus exudates from four different affected commercial turkey flocks. Turkeys were evaluated for clinical signs, as well as by serology and culture of tracheal swabs, at 21 and 42 days postchallenge. An MG isolate from one of the sinus exudates used for inoculation, designated K5054, was very similar to isolates from house finches when characterized by random amplified polymorphic DNA analysis as well as DNA sequence analysis of portions of the phase-variable putative adhesin protein (pvpA) gene, a lipoprotein gene, and the cytadhesin gapA/mgc1 gene. The turkeys inoculated with the K5054 sinus exudate seroconverted in the absence of severe clinical signs. There was a single reisolation of K5054 from these turkeys 42 days postchallenge. Susceptible contact turkeys were commingled with the K5054-inoculated turkeys at 49 days postchallenge. We found no evidence of transmission of MG to the contacts by culture or serology at 7, 21, or 35 days after commingling. In the second part of this study (trial B), we challenged the contacts and K5054 sinus exudate-inoculated turkeys from trial A with virulent R strain 88 days after the K5054 sinus exudate inoculation. On necropsy 10 days postchallenge, the evaluation of gross and microscopic lesions, serology, and culture showed that the turkeys previously inoculated with K5054 sinus exudate were protected against disease and reinfection.

The complete genome sequence of the avian pathogen Mycoplasma gallisepticum strain R(low)

The complete genome of Mycoplasma gallisepticum strain R(low) has been sequenced. The genome is composed of 996,422 bp with an overall G+C content of 31 mol%. It contains 742 putative coding DNA sequences (CDSs), representing a 91 % coding density. Function has been assigned to 469 of the CDSs, while 150 encode conserved hypothetical proteins and 123 remain as unique hypothetical proteins. The genome contains two copies of the rRNA genes and 33 tRNA genes. The origin of replication has been localized based on sequence analysis in the region of the dnaA gene. The vlhA family (previously termed pMGA) contains 43 genes distributed among five loci containing 8, 2, 9, 12 and 12 genes. This family of genes constitutes 10.4% (103 kb) of the total genome. Two CDSs were identified immediately downstream of gapA and crmA encoding proteins that share homology to cytadhesins GapA and CrmA. Based on motif analysis it is predicted that 80 genes encode lipoproteins and 149 proteins contain multiple transmembrane domains. The authors have identified 75 proteins putatively involved in transport of biomolecules, 12 transposases, and a number of potential virulence factors. The completion of this sequence has spawned multiple projects directed at defining the biological basis of M. gallisepticum.

Molecular Variability of House Finch Mycoplasma gallisepticum Isolates as Revealed by Sequencing and Restriction Fragment Length Polymorphism Analysis of the pvpA Gene

Mycoplasma gallisepticum, a major pathogen of chickens and turkeys, has caused significant declines in house finch (Carpodacus mexicanus) populations in the eastern United States since it was first observed in this species in 1994. There is evidence that M. gallisepticum infection is now endemic among eastern house finches, although disease prevalence has declined, suggesting an evolving host-parasite relationship. Studies based on randomly amplified polymorphic DNA (RAPD) have documented the presence of a single, unique RAPD profile in house finch M. gallisepticum isolates, suggesting a single point source of origin, which agrees with the known epidemiologic observations. In the present study, we evaluated the molecular variability of 55 house finch isolates as well as 11 chicken and turkey isolates including reference strains of M. gallisepticum. Molecular variability was evaluated by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) analysis and nucleotide sequencing of the pvpA gene, which encodes for the putative cytadhesin protein PvpA. Three different RFLP groups and 16 genotypes were evident from the 55 house finch isolates evaluated. Sequence analysis of pvpA gene PCR products showed that although most house finch M. gallisepticum isolates clustered more closely to each other, others clustered more closely to either turkey or chicken field isolates. These findings suggest that house finch isolates are more polymorphic than previously recognized by RAPD studies. This feature may allow us to learn more about the molecular evolution and epidemiology of this emerging disease host-parasite relationship.

Isolation and characterization of a 6/85-like Mycoplasma gallisepticum from commercial laying hens

Eighty-three-week-old table egg layers with swollen sinuses were presented with a history of increased mortality. Serology revealed positive titers to Mycoplasma gallisepticum (MG). The birds were part of a flock in which some birds had been vaccinated with 6/85 live MG vaccine at 18 wk of age. Tracheal cultures were obtained from both vaccinated and unvaccinated birds within the flock. The cultures were indistinguishable from 6/85 vaccine by both random amplified polymorphic DNA analysis and DNA sequence analysis. Challenge studies were performed to compare the field isolates with 6/85 vaccine and the R strain of MG. The field isolates produced a greater antibody response by serum plate agglutination than did the 6/85 vaccine. The isolates effectively colonized the trachea without increasing the tracheal mucosal thickness; however, they did not extensively colonize the air sacs or cause airsacculitis in the experimental birds.

Haemagglutinins of pathogenic avian mycoplasmas

The pathogenic avian mycoplasmas, Mycoplasma gallisepticum, Mycoplasma synoviae, Mycoplasma meleagridis, Mycoplasma iowae and Mycoplasma imitans, synthesize haemagglutinins that are immunogenic, variably expressed, surface proteins. The haemagglutinins of M. gallisepticum (pMGA), M. synoviae (VlhA) and M. imitans are lipoproteins, encoded by related multigene families that appear to have arisen by horizontal gene transfer. M. gallisepticum also has genes encoding cytadhesins in its genome but these are present as a single copies, while the pMGA gene family contains 30 to 70 genes. The switch in expression of distinct pMGA genes (e.g. pMGA1.1 to pMGA1.9) generates antigenic variation, which is thought to be important in immune evasion but also has significance in the preparation of M. gallisepticum antigens for serological diagnosis. In the majority of M. synoviae strains, post-translational cleavage of the VlhA protein generates an amino-terminal part (the lipoprotein MSPB) and a carboxyl-terminal part (MSPA), which mediates binding to erythrocytes. The 5'vlhA gene region, which encodes proline-rich repeats in the amino-terminal part of MSPB, is highly polymorphic among M. synoviae strains. Insertions or deletions in the part of vlhA encoding the proline-rich repeats cause MSPB length variation in different M. synoviae strains. Recombination between the 5'vlhA gene and pseudogenes in the genome generates changes in antigenic determinants in the carboxyl two-thirds of the MSPB molecule, and in MSPA, resulting in changes in the domains involved in the binding of M. synoviae to erythrocytes. Variant haemagglutinins of M. gallisepticum (pMGA1.7) and M. synoviae (diverse VlhA forms) share sequences that may be responsible for antigenic cross-reactions between M. gallisepticum and M. synoviae. Shared epitopes have been demonstrated using specific antibodies against MSPB that also recognize proteins of M. gallisepticum and of M. iowae (serotype N). Size and antigenic variants have also been reported for M. meleagridis and M. iowae proteins, but it is not known if these are their haemagglutinins. Advances in the molecular characterization of M. gallisepticum (pMGA, pvpA) and M. synoviae (vlhA) genes and their sequencing in numerous strains is likely to enable significantly improved epidemiological studies and improved tracing of M. gallisepticum and M. synoviae strains in different flocks.