gga-miR-146c Activates TLR6/MyD88/NF-κB Pathway through Targeting MMP16 to Prevent Mycoplasma Gallisepticum (HS Strain) Infection in Chickens

Mycoplasma gallisepticum (MG), a pathogen that infects chickens and some other birds, triggers chronic respiratory disease (CRD) in chickens, which is characterized by inflammation. The investigation of microbial pathogenesis would contribute to the deep understanding of infection control. Since microribonucleic acids (miRNAs) play a key role in this process, gga-mir-146c, an upregulated miRNA upon MG infection, was selected according to our previous RNA-sequencing data. In this paper, we predicted and validated that MMP16 is one of gga-miR-146c target genes. Results show that MMP16 is the target of gga-miR-146c and gga-miR-146c can downregulate MMP16 expression within limits. gga-miR-146c upregulation significantly increased the expression of TLR6, NF-κB p65, MyD88, and TNF-α, whereas the gga-miR-146c inhibitor led to an opposite result. gga-miR-146c upregulation effectively decreased apoptosis and stimulated DF-1 cells proliferation upon MG infection. On the contrary, gga-miR-146c inhibitor promoted apoptosis and repressed the proliferation. Collectively, our results suggest that gga-miR-146c upregulation upon MG infection represses MMP16 expression, activating TLR6/MyD88/NF-κB pathway, promoting cell proliferation by inhibiting cell apoptosis, and, finally, enhancing cell cycle progression to defend against host MG infection.

Detection of infectious bronchitis virus 793B, avian metapneumovirus, Mycoplasma gallisepticum and Mycoplasma synoviae in poultry in Ethiopia

A survey was conducted into respiratory infectious diseases of poultry on a chicken breeder farm run by the Ethiopian Institute of Agricultural Research (EIAR), located in Debre Zeit, Ethiopia. Oropharyngeal swabs were collected from 117 randomly selected birds, and blood was taken from a subset of 73 of these birds. A combination of serological and molecular methods was used for detection of pathogens. For the first time in Ethiopia, we report the detection of variant infectious bronchitis virus (793B genotype), avian metapneumovirus subtype B and Mycoplasma synoviae in poultry. Mycoplasma gallisepticum was also found to be present; however, infectious laryngotracheitis virus was not detected by PCR. Newcastle disease virus (NDV) was not detected by PCR, but variable levels of anti-NDV HI antibody titres shows possible exposure to virulent strains or poor vaccine take, or both. For the burgeoning-intensive industry in Ethiopia, this study highlights several circulating infectious respiratory pathogens that can impact on poultry welfare and productivity.

Application of Molecular and Serological Methods for Rapid Detection of Mycoplasma gallisepticum Infection (Avian mycoplasmosis)

Mycoplasma infection is a major problem in veterinary medicine and in poultry production. The pathogen has many strains, so that diagnosis of the disease using culture method is not effective. The objective of this work was to evaluate the prevalence of Mycoplasma gallisepticum (MG) in Kuwait poultry farms using serology and molecular methods in comparison to the culture under specific conditions. A total of 50 swab samples from choanal cleft and tracheal samples and blood samples were obtained from three different local farms, the blood samples were processed for an Enzyme Linked Immunosorbent Assay (ELISA) detection and the swab samples for Polymerase Chain Reaction (PCR) and culture methods detection. A PCR diagnostic kit (VenoMGs) and ELISA diagnostic kit (ProFLOK), were used in comparison to the traditional culture method, to study the spread of this disease in samples from broiler and layer flocks. Fifty chicken samples were tested for mycoplasmosis, samples tested with ELISA gave 24 positive (48%) and 29 were positive by PCR (58%) and only seven (14%) were positive with culture methods. Swab samples obtained from the choanal cleft gave more positive (60%) with PCR than tracheal samples (56.6%). The culture gave 20 and 5% positive, respectively for tracheal and choanal samples. The methods reported here are of high sensitivity and specificity for Mycoplasma. Both the PCR and ELISA methods are superior to culture method for detection of avian mycoplasmosis. This study showed that MG infection is prevalent in commercial broiler and layer chickens in Kuwait poultry farms. The use of these methods for surveillance of the disease will establish data concerning the predominant Mycoplasmosis diseases in Kuwait if done on a large scale.

Prevalence of blood parasites in eastern versus Western house finches: are eastern birds resistant to infection?

The rapid spread of the bacterial disease, Mycoplasma gallisepticum (MG), throughout the introduced range of house finches (Carpodacus mexicanus) in eastern North America, compared to its slower spread through the native western range, has puzzled researchers and highlights the need to understand the relative differences in health state of finches from both populations. We conducted a light-microscope survey of hemoparasites in populations of finches from Arizona (within the western range) and from Alabama (within the eastern range), and compared our estimates of prevalence to published reports from house finches sampled in both ranges. Of the 33 Arizona birds examined, we recorded hematozoan infections in 16 (48.5%) individuals, compared to 1 infected Alabama bird out of 30 birds examined (3.3%). Based on independent surveys of seven western North American and five eastern North American populations of house finches the average prevalence of blood parasites in western populations is 38.8% (±17.9 SD), while the average prevalence within the eastern range is only 5.9% (±6.1 SD). The average rate of infection among all songbirds sampled in the east is 34.2% (±4.8 SD). Thus, our surveys of wild birds as well as previously published observations point to eastern house finches having a much lower prevalence of blood parasite infections than their western counterparts. Combined with the fact that eastern finches also tend to have lower rates of avian pox infections than do western birds (based on a literature review), these observations suggest that eastern birds have either strong resistance to these infections or high susceptibility and associated mortality.

Aerosolization of Mycoplasma synoviae compared with Mycoplasma gallisepticum and Enterococcus faecalis

In order to study the airborne transmission of an arthropathic strain of Mycoplasma synoviae, preliminary aerosol experiments were performed. They were conducted in duplicate in an empty isolator (1.3 m3) to assess the yield and viability of M. synoviae with time compared with Mycoplasma gallisepticum and Enterococcus faecalis. After aerosol generation air samples were taken with two different devices using gelatine or cellulose nitrate filters. There was no difference between the devices, but cellulose nitrate filters yielded very low bacterial counts. The aerosolized dose per isolator for M. synoviae was 3.4 x 10(10) colony-forming units (cfu), for M. gallisepticum was 2.6 x 10(10) cfu and for E. faecalis was 3 x 10(10) cfu. Immediately after aerosolization, concentrations of about 10(6) to 10(7) cfu/m3, 10(7) to 10(8) cfu/m3 and 10(8) to 10(9) cfu/m3 air of M. synoviae, M. gallisepticum and E. faecalis were found, respectively. At 25 min M. synoviae concentrations dropped below the detection level (<4 x 10(4) cfu), while 10(5) to 10(6) and 10(8) to 10(9) cfu were found for M. gallisepticum and E. faecalis, respectively. The average M. synoviae concentration during the experiment was estimated at 10(2) to 10(3) cfu/l. The M. gallisepticum and E. faecalis aerosol generated an average of approximately 10(3) to 10(4) cfu/l air and 10(5) to 10(6) cfu/l air, respectively. Thus mycoplasma and E. faecalis aerosols were successfully generated despite considerable initial loss as measured by culture. The loss was greater in the mycoplasma aerosols, especially those of M. synoviae.

Differentiation of Mycoplasma gallisepticum strains using PCR and high-resolution melting curve analysis

Mycoplasma gallisepticum (MG) is an economically important pathogen of poultry worldwide, causing chronic respiratory disease in chickens and turkeys. Differentiation of MG strains is critical, especially in countries where poultry flocks are vaccinated with live vaccines. In this study, oligonucleotide primers were designed based on a region preceding the trinucleotide repeat of a member of the vlhA gene family, and amplicons of 145-352 bp were generated from cultures of 10 different MG strains, including the ts-11, F and 6/85 vaccine strains. High-resolution melting (HRM) curve analysis of the resultant amplicons could differentiate all MG strains. Analysis of the nucleotide sequences of the amplicons from each strain revealed that each melting curve profile related to a unique DNA sequence. The HRM curve profiles (for ts-11) remained consistent after at least five passages under laboratory conditions. PCR-HRM curve analysis of 33 DNA extracts derived from respiratory swabs, or mycoplasma cultures grown from respiratory swabs, of ts-11-vaccinated commercial or specific pathogen-free chickens identified all these specimens, according to their sequences, as ts-11. The potential of the PCR-HRM curve analysis was also shown in the genotyping of 30 additional MG isolates from Europe, the USA and Israel. The results presented in this study indicate that PCR followed by HRM curve analysis provides a rapid and robust technique for genotyping of MG isolates/strains using both MG cultures and clinical swabs.

[Prevalence of Mycoplasmas in commercial layer flocks during laying period]

Within this study's range, laying hens from different housing systems were investigated on prevalence of Mycoplasma sp. for the duration of one laying period, with an emphasis on the two clinically relevant species M. synoviae and M. gallisepticum. Tracheal swabs were analysed for mycoplasms by genus- and species-specific amplification after DNA extraction. Of 919 collected tracheal swabs, 84% were positive for the genus-specific test, while 75% turned out positive for M. synoviae. Mycoplasms were detected at some time during the laying period in all 19 flocks included in this investigation. Using a species-specific PCR, only one flock of a free-range system was free of M. synoviae. On the contrary, PCR analysis did not detect M. gallisepticum in any of the collected samples. Individual and flock examinations revealed no correlation between clinical symptoms and the presence of M. synoviae in hens and flocks, respectively. As the majority of the examined flocks were already positive for M. synoviae upon entry, the establishment of a control regime for Mycoplasma sp. would be advisable for parent stock and rearing facilities.

Effects of supplemental dietary phytase and 25-hydroxycholecalciferol on the blood characteristics of commercial layers inoculated before or at the onset of lay with the F-strain of Mycoplasma gallisepticum

In 3 trials, the effects of dietary supplementation with phytase (PHY) and 25-hydroxycholecalciferol on BW and the blood characteristics of commercial layers that were inoculated prelay (12 wk of age) or at the onset of lay (22 wk of age) with F-strain Mycoplasma gallisepticum were assessed at 34, 50, and 58 wk of age. Experimental layer diets, which included either a basal control diet or the same diet supplemented with 0.025% PHY and 25-hydroxycholecalciferol, were fed from 20 through 58 wk of age. The supplemented diet decreased blood hematocrit values across bird age, inoculation type (sham vs. F-strain M. gallisepticum), and age of inoculation (prelay vs. onset of lay). Phytase- and 25-hydroxycholecalciferol-supplemented diets reduced bird BW in sham-inoculated control birds across bird age and age of inoculation. This effect was not observed in F-strain M. gallisepticum-inoculated birds. Furthermore, across diet (control vs. supplemented) and inoculation type, total plasma protein concentration at 34 wk of age was higher in birds that were inoculated at the onset of lay compared with those inoculated prelay. Diet, inoculation type, and inoculation age had no effect on mortality, reproductive organ histopathological lesion scores, or serum cholesterol and Ca concentrations. In conclusion, throughout lay, the supplementation of commercial layer diets with PHY may lower hematocrit, and inoculation with F-strain M. gallisepticum prelay or at the onset of lay may ameliorate the depressing effects of dietary PHY and 25-hydroxycholecalciferol supplementation on hen BW.

Interlaboratory comparison of ability to detect nucleic acid of Mycoplasma gallisepticum and Mycoplasma synoviae by polymerase chain reaction

In recent years polymerase chain reaction (PCR) assays have become widely used as methods to confirm the presence of Mycoplasma gallisepticum and Mycoplasma synoviae in poultry flocks, but there has been limited standardization of the protocols used. Thirteen laboratories from five different countries participated in an interlaboratory comparison of detection of M. gallisepticum and M. synoviae DNA by PCR in samples that contained 10-fold dilutions of these bacteria. The concentration of bacteria ranged from 10(5) to 10(2) genome copies/100 microl sample, as quantified by real-time PCR, and the samples were supplied on dry cotton swabs. Each laboratory was asked to use its standard method for PCR testing of these pathogens. A questionnaire was supplied with the samples to obtain details of the methods that were used in testing. One-half of the laboratories used a commercially available test kit, while the others used an in-house protocol. The protocols used for DNA extraction varied greatly, even among those using commercially available test kits. Two laboratories had developed the primers for nucleic acid amplification themselves, and one of these used real-time PCR for amplification. While the majority of the laboratories detected M. synoviae down to the 100 copy limit of the comparison, the detection limit for M. gallisepticum was somewhat higher. Furthermore, different results were obtained from laboratories that used the same commercial test kit. To the best of our knowledge this is the first investigation of its kind in the field of avian diseases.

The Mycoplasma gallisepticum 16S–23S rRNA Intergenic Spacer Region Sequence as a Novel Tool for Epizootiological Studies

Mycoplasma gallisepticum (MG) contains two sets of rRNA genes (5S, 16S and 23S) in its genome, but only one of the two is organized in an operon cluster and contains a unique 660-nucleotide intergenic spacer region (IGSR) between the 16S and the 23S rRNA genes. We designed a polymerase chain reaction (PCR) for the specific amplification of the complete MG IGSR segment. The MG IGSR PCR was tested on 18 avian mollicute species and was confirmed as MG specific. The reaction sensitivity was demonstrated by comparing it to the well-established MG mgc2 PCR. The MG IGSR sequence was found to be highly variable (discrimination [D] index of 0.950) among a variety of MG laboratory strains, vaccine strains, and field isolates. The sequencing of the MG IGSR appears to be a valuable single-locus sequence typing (SLST) tool for MG isolate differentiation in diagnostic cases and epizootiological studies.

Experimental evidence for transmission of Mycoplasma gallisepticum in house finches by fomites

Ever since Mycoplasma gallisepticum emerged among house finches in North America, it has been suggested that bird aggregations at feeders are an important cause of the epidemic of mycoplasmal conjunctivitis because diseased birds could deposit droplets of pathogen onto the feeders and thereby promote indirect transmission by fomites. In this paper we bring the first experimental evidence that such transmission (bird-to-feeder-to-bird) does actually take place. House finches infected via this route, however, developed only mild disease and recovered much more rapidly than birds infected from the same source birds but directly into the conjunctiva. While it is certainly probable that house finch aggregations at artificial feeders enhance pathogen transmission, to some degree transmission of M. gallisepticum by fomites may serve to immunize birds against developing more severe infections. Some such birds develop M. gallisepticum antibodies, providing indication of an immune response, although no direct evidence of protection.

Molecular characterization of MG isolates using RAPD and PFGE isolated from chickens in Brazil

In the present study, 27 primers were screened under different cycles by random amplified polymorphic DNA (RAPD) method. Mathematical models were used for analysis of the genetic relationships among strains, including vaccinal, reference strains and nine field isolates previously characterized as Mycoplasma gallisepticum (MG)F by RAPD and pulsed field gel electrophoresis (PFGE). The PFGE was considered as laborious, expensive and time-consuming than RAPD method. These methods improved the typeability for epidemiological studies of MG with regard to differentiation from vaccinal and field strains.

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.

Differentiation of mycoplasma gallisepticum strains using molecular methods

Increasing use of Mycoplasma gallisepticum (MG) live vaccines has led to a need for the differentiation of MG strains. The MG strains MK-7, MS-16, S6, FS-9 and R strains and the MG live vaccine strain F were compared by random amplification of polymorphic DNA (RAPD) in this study. Using RAPD, different patterns were found among the MG strains. In addition to this, we examined the differentiating potential of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) primers targeted at the crmA, crmB, crmC, gapA, mgc2 and pvpA genes encoding cytadherence-related surface proteins. These proteins may take part in the pathogenesis of MG-induced disease. Differentiation of strain F is based on the identification of restriction enzyme sites in the PCR amplicons. Using HphI enzyme, crmC PCR amplicons produced different RFLP patterns. Digestion of amplicons of gapA-specific PCR with MboI enzyme also produced distinct patterns. Differences were observed among strains R and F by digestion of mgc2 PCR amplicons with HaelIl and VspI enzymes and digestion of pvpA PCR amplicons with AccI, PvulI and ScrFI endonucleases. This method can be used for the rapid differentiation of vaccine strain from wild strains. Differentiation of MG strains is a great advantage for diagnosticians or practitioners and it is useful for epidemiological studies.

Development and Validation of a Real-Time Taqman®Polymerase Chain Reaction Assay for the Detection of Mycoplasma gallisepticum in Naturally Infected Birds

In this study, we report the development and validation of a real-time polymerase chain reaction (PCR) assay using a Taqman-labeled probe for the detection of Mycoplasma gallisepticum (MGLP assay). The MGLP assay was highly specific with a detection limit of 25 template copies per reaction and a quantification limit of 100 template copies per reaction. Validation of the assay was completed with 1247 samples (palatine cleft and tracheal swabs) from M. gallisepticum-positive and -negative chicken flocks. The MGLP assay was compared to an enzyme-linked immunosorbent assay (ELISA), a conventional polymerase chain reaction assay (mgc2 PCR), and isolation of M. gallisepticum from naturally infected flocks. A total of 805 samples collected from negative flocks, as verified by ELISA and/or mgc2 PCR, were negative by the MGLP assay. A total of 442 samples were collected from positive flocks, of which a total of 228 samples were positive by the MGLP assay. These results agreed for 98.87% of the samples when tested by mgc2 PCR. When comparing the MGLP assay with M gallisepticum isolation, the MGLP assay was more sensitive than isolation for detecting positive birds from a positive flock, 172/265 and 50/265, respectively. Overall, the MGLP assay and M. gallisepticum isolation agreed for 52.8% of the samples tested. In conclusion, the MGLP assay was highly specific, sensitive, and reproducible, and allowed the quantification of template copies directly from clinical samples.

Further Western Spread of Mycoplasma gallisepticum Infection of House Finches

Mycoplasma gallisepticum, an important pathogen of poultry, especially chickens and turkeys, emerged in 1994 as the cause of conjunctivitis in house finches (Carpodacus mexicanus) in their eastern range of North America. The resulting epidemic of M. gallisepticum conjunctivitis severely decreased house finch abundance and the continuing endemic disease in the eastern range has been associated with repeating seasonal peaks of conjunctivitis and limitation of host populations. Mycoplasma gallisepticum conjunctivitis was first confirmed in the western native range of house finches in 2002 in a Missoula, Montana, population. Herein, we report further western expansion of M. gallisepticum conjunctivitis in the native range of house finches based on positive polymerase chain reaction results with samples from birds captured in 2004 and 2005 near Portland, Oregon.

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.

Real-time polymerase chain reaction for the qualitative and quantitative detection ofMycoplasma gallisepticum

The aim of this study was to evaluate the sensitivity and the detection limit of a real-time polymerase chain reaction (Q-PCR) developed for the qualitative and quantitative detection of Mycoplasma gallisepticum. No cross-reactivity was observed with DNA from other important avian mycoplasmas, including Mycoplasma synoviae and Mycoplasma meleagridis. However, the Q-PCR could not distinguish between M. gallisepticum and Mycoplasma imitans. The Q-PCR had detection limits 10 to 1000 times lower than a conventional commercial PCR method and than culture. The Q-PCR was used quantitatively by incorporating a set of external M. gallisepticum DNA standards, derived from a M. gallisepticum log-phase culture of a known concentration. The number of colony-forming unit equivalents per millilitre in tracheal swabs from experimentally infected birds could be determined from a single sample. The method had good reproducibility and correlated well with standard counting techniques using culture. It can be concluded that the Q-PCR described is suitable for qualitative and quantitative detection of M. gallisepticum in clinical samples.

Duplex PCR to differentiate between Mycoplasma synoviae and Mycoplasma gallisepticum on the basis of conserved species-specific sequences of their hemagglutinin genes

We developed a duplex PCR assay targeting the hemagglutinin multigene families, vlhA and pMGA, of Mycoplasma synoviae and Mycoplasma gallisepticum, respectively. The assay proved to be specific and sensitive enough to justify its use for the simultaneous detection of the two major avian mycoplasma species from field isolates.

Comparison of Culture, PCR, and Different Serologic Tests for Detection of Mycoplasma gallisepticum and Mycoplasma synoviae Infections

In this study, the technical performance of culture, two commercially available polymerase chain reaction (PCR) tests, rapid plate agglutination (RPA) test, hemagglutination inhibition (HI) test, and eight commercially available enzyme-linked immunosorbent assays (ELISAs) were compared for the detection of avian mycoplasma infections from 3 days postinfection (d.p.i.) through 35 d.p.i. The tests were carried out on samples from specified pathogen-free layers that were infected at 66 wk of age with recent Mycoplasma synoviae (MS) and Mycoplasma gallisepticum (MG) field strains, MS and MG ATCC strains, and Mycoplasma imitans (MIM), respectively. Results showed a high percentage of positive samples in the homologous infected groups and a high percentage of negative samples (100%) in the uninfected and heterologous infected groups during 35 d.p.i. of both culture and PCR tests. For the group infected with the MG 15302 ATCC strain, serology was more sensitive than bacteriology. All MG and MS tests, with the exception of MG ELISA kit D showed a lower percentage of positive samples during 35 d.p.i. for the detection of the MG and MS ATCC strain infection compared with that of the field strains. Also, the number of cross-reactions (false positives) in the serologic tests was lower after infection with an ATCC strain than after an infection with the MG or MS field strain. Contradictory to other studies, the ELISAs and the RPA test using undiluted serum showed a relatively high number of false-positive results. The MG ELISAs (except ELISA kit D) showed more false-positive results (up to 37%) in the MIM-infected group than in the MS-infected groups. This was not unexpected, as MIM and MG have a close antigenic relationship. The results of the serologic tests in this study showed that a certain level of false-positive results can be expected in about any serologic test. Although the level of false-positive results varied between several serologic tests, this study showed that it is not advisable to rely completely on one test (system) only.

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.

Induced expression of the antimicrobial peptide melittin inhibits experimental infection by Mycoplasma gallisepticum in chickens

The in vivo action of the antimicrobial peptide melittin, expressed from a recombinant plasmid vector, on chickens experimentally infected with Mycoplasma gallisepticum was studied. The plasmid vector pBI/mel2/rtTA includes the melittin gene under the control of an inducible tetracycline-dependent human cytomegalovirus promoter and the gene coding for the trans-activation protein rtTA. Aerosol administration of the vector, followed by infecting the chickens with M. gallisepticum 1226, is shown to inhibit development of infection. The inhibitory action was confirmed by a complex of clinical, pathomorphological, histological and serological studies, and also by comparing the M. gallisepticum reisolation frequency from the respiratory tract and internal organs. The data suggest that plasmid vectors expressing genes of antimicrobial peptides can be considered as potential agents for the prevention and treatment of mycoplasma infections in poultry farming.

Carotenoid-based plumage coloration predicts resistance to a novel parasite in the house finch

The Hamilton-Zuk hypothesis proposes that the bright colours displayed by many species of birds serve as signals of individual resistance to parasites. Despite the popularity of this hypothesis, only one previous study has tested whether plumage coloration predicts how individuals respond to a disease challenge. We inoculated 24 male house finches (Carpodacus mexicanus) of variable plumage hue with a novel bacterial pathogen, Mycoplasma gallicepticum (MG). We found no relationship between plumage hue and time to first symptoms following inoculation, but we found a significant negative relationship between plumage hue and clearance of disease: males with redder plumage cleared MG infection significantly better than did males with yellower plumage. The hue of carotenoid-based plumage coloration has been shown to be a primary criterion in female mate choice in the house finch. These observations suggest that one benefit to females for choosing redder males is obtaining mates with better resistance to parasites.

Health survey of house finches (Carpodacus mexicanus) from Wisconsin

We conducted a health survey of house finches (Carpodacus mexicanus) without evidence of Mycoplasma gallisepticum infection in order to establish baseline population health measures and estimate prevalence of potential pathogens likely to influence host susceptibility to mycoplasmosis. Seasonal changes in several physiologic parameters were observed. Weights were greater in winter compared with the breeding season (P < 0.01), fat scores were greater in winter than during fall migration (P < 0.01) or the breeding season (P < 0.01), and packed cell volume and total plasma protein measures during fall migration (P < 0.05) and winter (P < 0.01) were greater than during the breeding season. Culture of voided fecal material yielded 13 bacterial isolates likely representative of normal gastrointestinal flora. Avian pox lesions and blood and gastrointestinal parasite infections were at low prevalence (< or = 4%) compared with Proctophyllodes spp. feather mite infestations (32%) in the population. All parasites occurred at generally low levels in individual hosts. A logistic regression analysis of our data suggests that greater fat scores, tarsal length, and being male are potential risk factors for mite infestation in house finches.

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.

Real-time polymerase chain reaction for Mycoplasma gallisepticum in chicken trachea

In this work, we describe a rapid detection procedure for Mycoplasma gallisepticum from chicken tracheal swabs by real-time polymerase chain reaction (PCR) by LightCycler system, where we were able to monitor the amplification of the newly synthesized M. gallisepticum-specific PCR product as a proportionally increasing fluorescent signal by using the double-stranded DNA binding dye SYBR Green I and have identified M. gallisepticum-specific PCR products by DNA melting curve analysis by plotting the first negative derivative (-d[F1]dT) of fluorescence over temperature. Detection limits of the PCR were found to be 3 and 3000 colony-forming units ml(-1) with pure culture of M. gallisepticum and artificially spiked samples, respectively. Out of 96 tracheal swabs, 68 were taken from live chickens and 28 were taken by scraping the mucosal surface of the trachea (SMST) of necropsied chickens. All of the 18 PCR-positive results were from the swabs taken by the SMST method, whereas all of the samples taken from live chickens were negative. Thus, the PCR with the SMST method had a sensitivity and a specificity of 64.2% (18 of 28 chickens) and 100%, respectively. The total time required for template preparation from tracheal swab samples and real-time PCR was approximately 65 min. These results indicate that real-time PCR with the LightCycler technology is a rapid and sensitive test to identify M. gallisepticum-infected flocks if a proper sampling is applied.

Effects of F-strain Mycoplasma gallisepticum inoculation on serum very low density lipoprotein diameter and fractionation of cholesterol among lipoproteins in commercial egg-laying hens

Experimental inoculation with the F-strain of Mycoplasma gallisepticum (FMG) at 12 wk of age has been shown to affect the performance, liver, reproductive organs, and yolk lipid characteristics of commercial layers. Therefore, this study was conducted to determine the serum lipoprotein characteristics of commercial egg-laying hens at 16 wk of age and throughout lay after inoculation with FMG at 12 wk of age. Mean diameters of very low density lipoproteins (VLDL) were determined for the 10th, 50th, and 90th percentiles of serum total VLDL of each hen. Percentages of total serum cholesterol recovered in VLDL and low and high density lipoprotein particle classes were also determined. Inoculation of birds with FMG at 12 wk did not change the physical properties or relative concentrations of their circulating lipoproteins. However, the age of the bird had significant differential effects on all the parameters examined. These data demonstrate that FMG-inoculation at 12 wk of age does not affect the lipoproteins of laying hens, but because these birds were housed in biological isolation units, these results do not preclude the possibility that these yolk precursors may be affected in FMG-infected birds that are housed in facilities in which there are increased levels of environmental stress. These data further suggest that alterations in liver, reproductive organs, and yolk lipid characteristics in response to FMG, as noted in previous reports on commercial layers, are not mediated through changes in circulating VLDL diameters.