Evaluation of Minimum Inhibitory Concentrations for 154 Mycoplasma synoviae isolates from Italy collected during 2012-2017

Mycoplasma synoviae (MS) is a highly prevalent bacterial species in poultry causing disease and severe economic losses. Antibiotic treatment is one of the control strategies that can be applied to contain clinical outbreaks in MS-free flocks, especially because this bacterium can be transmitted in ovo. It becomes, then, very important for veterinarians to know the antibiotic susceptibility of the circulating strains in order to choose the most appropriate first-line antibiotic molecule as a proactive role in fighting antibiotic resistance. We evaluated the Minimum Inhibitory Concentrations (MICs) of enrofloxacin, oxytetracycline, doxycycline, erythromycin, tylosin, tilmicosin, spiramycin, tiamulin, florfenicol and lincomycin for MS isolates collected between 2012 and 2017 in Italy. A total of 154 MS isolates from different poultry commercial categories (broiler, layer, and turkey sectors) was tested using commercial MIC plates. All MS isolates showed very high MIC values of erythromycin (MIC90 ≥8 μg/mL) and enrofloxacin (MIC90 ≥16 μg/mL). MIC values of doxycycline and oxytetracycline obtained were superimposable to each other with only a one-fold dilution difference. Discrepancies between MIC values of tylosin and tilmicosin were observed. Interestingly, seven isolates showed very high MIC values of lincomycin and tilmicosin, but not all of them showed very high MIC values of tylosin. Most of the MS isolates showed low MIC values of spiramycin, but seven strains showed a MIC ≥16 μg/mL. In the observation period, the frequency of the different MIC classes varied dependently on the tested antibiotic. Interestingly, tilmicosin MICs clearly showed a time-dependent progressive shift towards high-concentration classes, indicative of an on-going selection process among MS isolates. Until standardized breakpoints become available to facilitate data interpretation, it will be fundamental to continue studying MIC value fluctuations in the meantime in order to create a significant database that would facilitate veterinarians in selecting the proper drug for treating this impactful Mycoplasma.

Development of mismatch amplification mutation assays for the differentiation of MS1 vaccine strain from wild-type Mycoplasma synoviae and MS-H vaccine strains

Mycoplasma synoviae is an economically significant pathogen in the poultry industry, inducing respiratory disease and infectious synovitis in chickens and turkeys, and eggshell apex abnormality in chickens. Eradication, medication and vaccination are the options for controlling M. synoviae infection. Currently there are two commercial, live, attenuated vaccines available against M. synoviae: the temperature sensitive MS-H vaccine strain and the NAD independent MS1 vaccine strain. Differentiation of vaccine strains from field isolates is essential during vaccination and eradication programs. The present study provides melt-curve and agarose gel based mismatch amplification mutation assays (MAMA) to discriminate the MS1 vaccine strain from the MS-H vaccine strain and wild-type M. synoviae isolates. The assays are based on the A/C single nucleotide polymorphism at nt11 of a HIT family protein coding gene. The melt- and agarose-MAMAs reliably distinguish the MS1 vaccine strain genotype from the MS-H vaccine strain and wild-type M. synoviae isolate genotype from 10² template number/DNA sample. No cross-reactions with other avian Mycoplasma species were observed. The assays can be performed directly on clinical samples and they can be run simultaneously with the previously described MAMAs designed for the discrimination of the MS-H vaccine strain. The developed assays are applicable in laboratories with limited facilities and promote the rapid, simple and cost effective differentiation of the MS1 vaccine strain.

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.

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.

[Mycoplasma synoviae-associated egg-pole shell defects in laying hens]

Hens laying eggs with egg-pole shell defects (EPS) were examined in a clinical prospective study. 86 hens with EPS and 72 hens without EPS from three flocks were selected for this study. It could be proven serologically that hens with EPS had significant (p < 0.05) higher titers against Mycoplasma (M.) synoviae then hens without EPS. PCR tested cloacal swabs for M. synoviae were more frequently positive from hens with EPS (87%; n=72) then from hens without EPS (18%; n=13). Furthermore, M. synoviae could be cultivated from the oviduct of five hens with EPS. Additionally, M. synoviae-DNA was detectable in the albumen of nearly all eggs with EPS (n=48; 98%), contrary to the eggs without EPS (n=11; 26%). Ultrastructural investigation revealed that eggs with EPS showed considerable differences of the egg shell structure as well as the cross section dimension according to eggs without EPS. Due to the significantly more frequent detection of M. synoviae-DNA from the cloaca of chickens with EPS, is an involvement of M. synoviae in laying of EPS in the surveyed herds likely. Further infection experiments with the isolated M. synoviae were not perfomed, therefore about the causal pathogenic role of M. synoviae in the development of eggs with EPS in the surveyed herds can only be speculated.

Rapid serodiagnosis with the use of surface plasmon resonance imaging for the detection of antibodies against major surface protein A of Mycoplasma synoviae in chickens

Mycoplasma synoviae, a major worldwide pathogen in poultry, causes respiratory tract infection and arthritis in chickens and turkeys. Two major surface antigens of M. synoviae are encoded by a single gene, vlhA (variably expressed lipoprotein and hemagglutinin). The gene product is cleaved post-translationally to yield the lipoprotein major surface protein (MSP) B (MSPB) and the hemagglutinin MSPA. The availability of MSPA as an antigen for serodiagnosis was studied by means of a protein chip based on surface plasmon resonance imaging (SPRi). The diagnostic potential of SPRi for measurement of levels of antibody to MSPA was compared with that of a conventional enzyme-linked immunosorbent assay (ELISA) kit. The results from SPRi, a process that took only 1 h, were similar to those from ELISA. Therefore, MSPA can be used as an antigen for serologic studies, and SPRi, a label-free and high-throughput method, may be a valuable tool in avian serodiagnostic studies.

[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.

Identification of major immunogenic proteins of Mycoplasma synoviae isolates

Mycoplasma synoviae isolates differ in patterns of immunogenic proteins, but most of them have not been identified yet. The main aim of this study was their identification in two closely related M. synoviae isolates, ULB 02/P4 and ULB 02/OV6, recovered recently from chickens in Slovenia. N-terminal sequencing identified 17 M. synoviae proteins. Amongst them were 14 major, highly expressed but previously unidentified proteins, including enzymes, chaperones and putative lipoproteins. ULB 02/P4 proteins with increasing molecular weight (M(w)) in the region above the lipoprotein MSPB (approximately 40 kDa) were elongation factor EF-Tu, enolase, NADH oxidase, haemagglutinin MSPA, ATP synthase beta chain, trigger factor, pyruvate kinase and chaperone DnaK. Enolase (approximately 47 kDa) seemed to be immunogenic for chickens infected with M. synoviae, whereas EF-Tu, which might cross-react with antibodies to the P1 adhesin of Mycoplasma pneumoniae, was not. ULB 02/OV6 synthesized several immunogenic proteins and those with M(w) of approximately 70, 78, 82, 90, 110 and 160 kDa, cross-reacted with antibodies to Mycoplasma gallisepticum. They remain to be identified, because besides putative lipoproteins, protein bands of 78, 82, 85 and 110 kDa contained also dehydrogenase PdhD, elongation factor EF-G, enzyme PtsG and putative neuraminidase, respectively.

Classification of Mycoplasma synoviae strains using single-strand conformation polymorphism and high-resolution melting-curve analysis of the vlhA gene single-copy region

Mycoplasma synoviae is an economically important pathogen of poultry worldwide, causing respiratory infection and synovitis in chickens and turkeys. Identification of M. synoviae isolates is of critical importance, particularly in countries in which poultry flocks are vaccinated with the live attenuated M. synoviae strain MS-H. Using oligonucleotide primers complementary to the single-copy conserved 5' end of the variable lipoprotein and haemagglutinin gene (vlhA), amplicons of approximately 400 bp were generated from 35 different M. synoviae strains/isolates from chickens and subjected to mutation scanning analysis. Analysis of the amplicons by single-strand conformation polymorphism (SSCP) revealed 10 distinct profiles (A-J). Sequencing of the amplicons representing these profiles revealed that each profile related to a unique sequence, some differing from each other by only one base-pair substitution. Comparative high-resolution melting (HRM) curve analysis of the amplicons using SYTO 9 green fluorescent dye also displayed profiles which were concordant with the same 10 SSCP profiles (A-J) and their sequences. For both mutation detection methods, the Australian M. synoviae strains represented one of the A, B, C or D profiles, while the USA strains represented one of the E, F, G, H, I or J profiles. The results presented in this study show that the PCR-based SSCP or HRM curve analyses of vlhA provide high-resolution mutation detection tools for the detection and identification of M. synoviae strains. In particular, the HRM curve analysis is a rapid and effective technique which can be performed in a single test tube in less than 2 h.

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.

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.

Development and evaluation of a diagnostic PCR for Mycoplasma synoviae using primers located in the intergenic spacer region and the 23S rRNA gene

Mycoplasma synoviae (Ms) is an important pathogen of poultry, causing economic losses to this industry. Early and reliable diagnosis is a key to controlling the spread of this organism. In this study, a polymerase chain reaction with one primer based on the intergenic spacer region (ISR) was validated for detection of Ms. The ISR primer was paired with a general primer from within the 23S rRNA gene. The PCR primers were tested with the 22 other recognised avian Mycoplasma species to check the specificity and with 21 field isolates of Ms from various hosts and countries, and with several swab samples. The PCR appeared to be specific and sensitive. Four different sample preparation methods were compared for use in this PCR, and the amplification protocol was compared with three others, confirming the comparative sensitivity of the new PCR.

Persistence of Mycoplasma synoviae in hens after two enrofloxacin treatments and detection of mutations in the parC gene

The ability of Mycoplasma synoviae, an avian pathogen, to persist despite fluoroquinolone treatments was investigated in hens. Groups of Mycoplasma-free hens were experimentally infected with the M. synoviae 317 strain and treated twice with enrofloxacin at the therapeutic dose. The results show that the two treatments did not have any influence on this strain of M. synoviae recovery from tracheal swabs. Mycoplasmas were isolated from tracheal swab cultures, but not from inner organs such as the liver or spleen, suggesting that this strain of M. synoviae was not able to cross the mucosal barrier to disseminate throughout the host. A significant increase of the resistance level to enrofloxacin of five re-isolated mycoplasma clones, was observed after the second treatment. This increase was associated in two clones to a Ser81-->Pro substitution, found in the ParC quinolone-resistance determining region (QRDR) of DNA topoisomerase IV. This is the first time that a mutation in a gene coding for topoisomerase IV is described in M. synoviae after in vivo enrofloxacin treatments in experimentally infected hens.

Epidemiological study on Mycoplasma synoviae infection in layers

Mycoplasma synoviae infection occurs worldwide in commercial poultry flocks and may result in severe economic losses. The prevalence of this mycoplasma in standard layers older than 60 weeks was studied in a French department and the characteristics of infected or free flocks were compared. The genomic profiles of isolates from 36 infected flocks were studied by pulsed-field gel electrophoresis and random amplified polymorphic DNA methods in order to investigate possible routes of transmission. The minimum inhibitory concentrations of antibiotics were determined. Results showed that infection was more frequent in multi-age farms. Egg production and mortality of infected flocks were respectively lower and higher than in non-infected flocks but the differences were not statistically significant. The genomic profiles of isolates were quite homogeneous, a feature which does not facilitate the understanding of routes of transmission. All isolates were susceptible to tetracyclines, macrolides (except erythromycin), spectinomycin and fluoroquinolones.

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.

Systemic Mycoplasma synoviae infection in broiler chickens

Systemic Mycoplasma synoviae infection in 47-day-old broiler chickens with septicaemic lesions and increased carcass condemnation rate is reported. The clinical history included respiratory signs and an enlarged keel bursa. Condemnations at the processing plant were due to airsacculitis and keel bursitis. Involvement of several organs, including the keel bursa, liver, spleen, brain, choroid of the eye, nerves and skeletal muscle associated with vasculitis, and the isolation of M. synoviae from the liver and keel bursa are only occasionally seen in field cases. Random amplified polymorphic DNA analysis of the M. synoviae isolated from the broiler chickens in this study had a different pattern when compared with the reference M. synoviae strains, WVU-1853, MS-H and F10-2AS, and another M. synoviae isolated from broiler breeders from the same company, but had a similar DNA pattern to an M. synoviae isolated from broiler chickens and turkeys owned by the same company. This finding suggests a horizontally acquired infection rather than vertical transmission.

Experimental evidence of indirect transmission of Mycoplasma synoviae

The aim of the study was to analyse experimental transmission of Mycoplasma synoviae, an avian pathogen. Three experiments using specific pathogen-free day-old chicks placed in isolators were conducted. In the first experiment, the birds were introduced in an isolator previously contaminated with a M. synoviae broth culture. After 34 days, these birds were eliminated and, for the second trial, the chicks were introduced in the same isolator without disinfecting. In the third assay, the chicks were placed in an isolator containing a mixture of food, feathers and dust collected less than an hour earlier from a M. synoviae infected laying hen flock. In the second and third experiments in order to exacerbate the M. synoviae infection, the birds were inoculated with infectious bronchitis (IB) virus. The presence of M. synoviae in the environment and in tracheal swabs was monitored by culture, a multiplex PCR (mPCR) detecting M. synoviae and Mycoplasma 16S rDNA and a multiplex RT-PCR (mRT-PCR) detecting the M. synoviae mRNA coding for a membrane protein and Mycoplasma 16S rRNA. In in vitro experimental conditions, M. synoviae mRNA and 16S rRNA were detected up to 20 min and 23 h respectively after mycoplasma death. In the first assay, the first infected bird was detected on the 13th day. In the second trial, culturable M. synoviae or viable M. synoviae were detected in the isolator for 3 or 4 to 5 days respectively after depopulation of the birds of the first assay whereas the first culture positive tracheal swabs were detected on the 33rd day, after IB inoculation. In the third experiment, the first infected birds were detected on the 54th day. Thus, the different assays showed that M. synoviae contaminated material (dust, feathers and food) can infect chicks, sometimes after remarkably long silent periods.

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.