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1.
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.  相似文献   

2.
A live attenuated Mycoplasma gallisepticum vaccine, ts-11, has been used for control of M gallisepticum in several countries. The rapid serum agglutination test is usually used as an indicator of flock response to vaccination; however, in some flocks, the detected response may be weak or absent. We investigated whether the low level, or lack, of systemic antibodies in ts-11-vaccinated flocks is correlated with susceptibility to infection after challenge with a virulent M. gallisepticum strain. Birds from 2 separate ts-11-vaccinated commercial flocks with no, or weak, rapid serum agglutination responses (at 11 or 14 wk postvaccination) were randomly selected and subjected to aerosol challenge with either M gallisepticum strain Ap3AS or sterile mycoplasma broth. A group of nonvaccinated specific-pathogen-free chickens at similar age were also exposed to aerosolization with M. gallisepticum strain Ap3AS and used as positive controls. Postmortem examination of the birds, performed 2 wk after challenge, revealed no significant difference in microscopic tracheal lesions or mucosal thicknesses between the ts-11-vaccinated field birds irrespective of their aerosolization treatment. However, both microscopic tracheal lesions and tracheal mucosal thicknesses of nonvaccinated challenged birds were significantly greater than those of ts-11 vaccinates. Hence, broiler breeders vaccinated in the field showed significant protection against virulent M. gallisepticum challenge even when no serum antibody was detected by rapid serum agglutination test. These results reveal that seroconversion detected by rapid serum agglutination test after ts-11 vaccination is not a reliable predictor of protection against M. gallisepticum infection. The possible significance of local antibody response and cell-mediated immunity against M. gallisepticum infection is discussed.  相似文献   

3.
Two cases of Mycoplasma gallisepticum infection in different avian species in backyard gamebird operations in Slovenia were investigated. In the first case, M gallisepticum was associated with severe respiratory disease with almost 20 per cent mortality in pheasants, whereas the infection was less pathogenic for chickens and turkeys reared at the same site. The M gallisepticum isolates from pheasants had a unique pMGA gene sequence containing a repeat of 12 nucleotides, and they contained only small amounts of the cytadhesins MGC1 and MGC3 and no PvpA protein. However, they expressed some typical M gallisepticum proteins and several proteins which were immunogenic for pheasants, chickens and turkeys. A strain of M gallisepticum isolated from the sinus of a pheasant was highly pathogenic for chicken embryos. In the second case, the M gallisepticum strain that was associated with respiratory disease and mortality in peafowl also affected chickens. M gallisepticum strain ULB 992 was isolated from the infraorbital sinus of a dead peafowl. The ULB 992 strain synthesised a small amount of MGC3, a truncated form of MGC1 and lacked PvpA. However, it expressed several proteins which were immunogenic for the birds infected with M gallisepticum at both gamebird operations.  相似文献   

4.
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.  相似文献   

5.
Specific pathogen free day-old chicks were inoculated with a virulent strain of Mycoplasma gallisepticum. Birds received either danofloxacin (50 ppm), tylosin (500 ppm) or no medication in the drinking water from 24 hours after infection for three days. The effects of medication on mortality, weight gain, serology, lesions and reisolation of M gallisepticum 21 days following infection were studied. Treatment with danofloxacin and tylosin significantly decreased mortality and increased weight gain compared with infected unmedicated birds. Twenty-one days after infection, M gallisepticum was isolated from 96 per cent of unmedicated birds compared with only 6 per cent of danofloxacin-treated and 40 per cent of tylosin-treated birds, and the percentage showing positive serological tests was reduced from 100 per cent of unmedicated birds to 0 per cent of danofloxacin-treated and 29 per cent of tylosin-treated birds. In both cases, the proportion of positive birds from the danofloxacin-treated group was significantly lower than that from the tylosin-treated group. The occurrence of air sac lesions was also significantly lower in danofloxacin-treated than in tylosin-treated birds.  相似文献   

6.
Harderian glands of one-day-old chickens were surgically removed. At one week old, these chickens and controls from which these tissues were not removed, were vaccinated intranasally with a temperature-sensitive mutant of Mycoplasma gallisepticum. Humoral and local immunity were measured by means of antibody in sera and tracheal washings, respectively. Protection was measured by resistance to intra-air-sac challenge with the S6 strain of M gallisepticum. There was no discernible difference in either humoral or local antibody response between vaccinated chickens from which the glands had been removed and control birds. In addition, both groups were significantly protected against air-sac challenge compared with unvaccinated controls. These results indicate that removal of the Harderian glands neither affects the production of antibody to M gallisepticum, nor alters the effectiveness of temperature-sensitive M gallisepticum vaccination. The role that the Harderian glands play in resistance to M gallisepticum is therefore questioned.  相似文献   

7.
Mycoplasma gallisepticum was isolated from 2 wild-type turkeys (Meleagris gallopavo) and 1 domestic turkey living in close contact on a farm in Tehama County, California. Sinusitis was detected in 2 of 14 wild-type turkeys and in 1 of 12 feral broad-breasted bronze turkeys, but in none of several chickens on the premises. The entire mixed flock was captured, sinus aspirates were collected from affected birds, and blood samples were obtained from all birds for serologic testing. Blood samples also were obtained from 10 domestic turkeys on adjacent premises from which breeding stock had been borrowed. The M gallisepticum isolated from sinus aspirates was typed and inoculated into susceptible chickens, resulting in airsacculitis. California wild turkeys with and without histories of exposure to domestic fowl and wild turkeys shipped into California from Texas for release were tested for antibodies to M gallisepticum, using the plate agglutination test. Evidence of M gallisepticum infection was not found in wild turkeys at any location other than the original premises.  相似文献   

8.
The clinical and microbial efficacy of antimicrobial treatments of avian colibacillosis was studied, using an experimental model on chickens previously inoculated with multiresistant commensal Escherichia coli strains. One E. coli with pMG252 plasmid containing bla(FOX5) and qnrA1 genes and another E. coli with pMG298 plasmid containing bla(CTX-M15) and qnrB1 genes were first orally inoculated to chickens Both isolates were also resistant to chloramphenicol, sulphamethoxazole, trimethoprim, streptomycin, gentamicin, kanamycin, and tetracycline. The birds were then experimentally infected with an avian pathogenic E. coli (APEC), via the air sac. Treatments (oxytetracycline (OTC), trimethoprim-sulfadimethoxin (SXT), amoxicillin (AMX) or enrofloxacin (ENR) were then offered at the therapeutic doses. Symptoms, lesions in dead or sacrificed birds, and isolation and characterization of APEC from internal organs were studied. Results showed that OTC, SXT or ENR treatments could control the pathology. AMX worsened the disease, possibly due to endotoxin shock. All APEC re-isolated from internal organs showed the same antimicrobial susceptibility as the APEC inoculated strain, except for one APEC isolate from an infected OTC-treated bird, which acquired tetracycline resistance only, and one APEC isolate recovered from the air sacs of a chicken in the infected SXT-treated group, which acquired the pMG252 plasmid and became multi-resistant. Thus three antimicrobials could control the disease but the experimental model enabled, to our knowledge, the first observation of plasmid transfer from a bacterium of the intestinal tract to a pathogenic isolate from the respiratory tract.  相似文献   

9.
The objective of the present study was to determine whether selection of fluoroquinolone resistance could be easily induced in Campylobacter jejuni-colonized chickens by treatment with enrofloxacin of representative fluoroquinolones at the inherent dosage licensed in Japan (50 ppm in drinking water for 3 days). In the case of isolates from chickens of study 1, an increase in the population of susceptible isolates appeared after the cessation of treatment and maintained throughout the experiments. On the contrary, our results of study 2 demonstrated that administration of enrofloxacin generated a rapid increase of fluoroquinolone resistance in C. jejuni showing the mutation of Asp-90-Asn in the gyrA gene. Present results indicate that the enrofloxacin treatment for broilers at the inherent dosage is able to select fluoroquinolone resistance in C. jejuni. We conclude that whatever enrofloxacin dosage is used, an emergence of fluoroquinolone resistant of C. jejuni occurs.  相似文献   

10.
Monitoring of susceptibility to antibiotics in field isolates of pathogenic avian mycoplasmas is important for appropriate choice of treatment. Our study compared in vitro susceptibility to enrofloxacin and difloxacin in recent (2005-2006) isolates of Mycoplasma gallisepticum and Mycoplasma synoviae from meat-type turkey flocks with archived (1997-2003) isolates and reference strains. Comparison of minimal inhibitory concentration (MIC) values determined by microtest, agar dilution and commercial Etest showed good agreement, but underscored the need for standardized methods for testing. Notably, while the commercial Etest was convenient and accurate for determining MICs for enrofloxacin in the range 0.002-0.094mug/ml, the endpoint of inhibition for M. gallisepticum and M. synoviae strains with MIC values >/=1.0mug/ml could not be determined. A decrease in susceptibility to both fluoroquinolones was detected in archived strains but to a greater degree in recent isolates, most of which had MICs above the NCCLS susceptibility breakpoint for these antibiotics (相似文献   

11.
The interaction between Mycoplasma gallisepticum (MG) and the tracheal mucosa of the young chicken was studied. The use of a selective plating method permitted differentiation between a pathogenic tylosin-resistant strain (227) and a less pathogenic tylosin-sensitive vaccine strain (F). Both MG strains adhered to the tracheal mucosa and colonized equally well. In mixed infection, the presence or absence of the second strain did not change the efficiency of colonization by either strain. When chickens were exposed to the vaccine strain 24 hr or 2 weeks before superinfection by the pathogen, there was no significant reduction in the efficiency of superinfection, despite the presence of 10(6) colony-forming units of MG strain F in the trachea. However, chickens had an increased ability to resist superinfection 5 weeks after exposure via the air sac. These results suggest that the biological mechanism underlying protection of F-strain-vaccinated chickens against adventitious infection by the homologous species does not involve competition for adherence sites or blockage by prior colonization.  相似文献   

12.
House sparrows were infected by aerosol with Mycoplasma gallisepticum (MG) or M. synoviae (MS). MG was reisolated from 5 to 11 sparrows 10 days postinfection, but infection appeared to be temporary. Mycoplasma-free chickens reared in the experimental house became infected with MG during the trial. MS was recovered from only one sparrow. Serological tests were unsatisfactory for diagnosing infected birds. The results suggest that house sparrows may be temporary biological carriers of MG.  相似文献   

13.
In a series of experiments chickens were treated with chemicals which block the production of corticosterone by the adrenal cortex prior to being challenged with respiratory disease (and other) agents in order to determine if the course of the diseases could be altered. Some chickens received a single intramuscular injection (14 mg/kg) of 1,1-dichloro-2,2-bis/p-chlorophenyl/ethane (ABC) dissolved in corn oil (20 mg/mL) at least 12 h before challenge. Other chickens received feed containing 500 mg/kg of metyrapone for at least 12 h before and during the challenge infection. Treated chickens were more resistant than the untreated controls to Newcastle disease virus, Mycoplasma gallisepticum, combined M. gallisepticum-Newcastle disease virus infection, and avian adenovirus group II infection. The feeding of erythromycin (1 g/kg of feed), one day before and during the challenge, reduced the severity of M. gallisepticum infection. The effects of feeding both metyrapone and erythromycin resulted in a further increase in resistance. Chickens which had been treated with ABC had less severe lesions and greater postchallenge weight gain than the controls in response to a secondary Escherichia coli infection.  相似文献   

14.
Experimental groups of 15 susceptible 3-week-old turkeys were inoculated oculonasally with avian metapneumovirus (APV) subtype A and susceptible Escherichia coli O2:K1 and Ornithobacterium rhinotracheale (ORT) bacteria, with a 3 days interval between viral and bacterial inoculation and approximately 8h between the two bacterial inoculations. The aims of the present study were to assess the efficacy of drinking-water administration of enrofloxacin for 3 and 5 days, amoxicillin for 5 days and florfenicol for 5 days for the treatment of the resulting respiratory disease, based on clinical and bacteriological examinations. Antimicrobial treatment started 1 day after dual bacterial inoculation. After infection, the birds were examined and scored for clinical signs daily, weighed at different times, and their tracheae swabbed daily. Five birds were euthanised and examined for macroscopic lesions at necropsy at 5 days post-bacterial inoculation (dpbi) and the remainder at 15dpbi. Samples of the turbinates, trachea, lungs, sinuses, air sacs, heart, pericardium and liver were collected for bacteriological examination. Recovery from respiratory disease caused by an APV/E. coli/ORT triple infection in 3-week-old turkey poults was overall most successful after enrofloxacin treatment, irrespective of treatment duration, followed by florfenicol treatment. Compared with the untreated group, clinical signs as well as ORT and E. coli multiplication in the respiratory tract were significantly reduced by both enrofloxacin treatments and the florfenicol treatment, with the enrofloxacin treatments showing significantly better reductions than the florfenicol treatment. Five-day treatment with amoxicillin, compared with the untreated group, did not cause a significant reduction in any of the aforementioned parameters.  相似文献   

15.
An indirect enzyme-linked immunosorbent assay (ELISA) was developed and tested for its ability to detect humoral response to Mycoplasma gallisepticum in chickens. Two antigens were used in the solid phase of the assay. Antigen 1 was a membrane-derived sodium dodecyl sulfate (SDS)-solubilized preparation; Antigen 2 was prepared in the same manner as Antigen 1 but was passed through an immunoadsorbent column containing rabbit anti-medium antibodies. Test conditions were optimized for incubation times and temperatures. Antigen, serum, and enzyme conjugate concentrations were standardized, and reproducibility was determined. A baseline value, representing a positive or negative result, was established independently for both antigens. The assay was then used to detect anti-M. gallisepticum antibodies in experimentally infected chickens. Serum samples collected at 0, 2, 5, 7, 10, 14, 21, 28, and 35 days postinfection (PI) were analyzed by serum plate agglutination (SPA), hemagglutination-inhibition (HI), and ELISA with both Antigens 1 and 2. ELISA was found to be less sensitive but more specific than SPA and more sensitive than HI. The ELISA was more sensitive with Antigen 1 than with Antigen 2. The former assay correctly identified 79% of the serum samples positive for M. gallisepticum by 7 days PI and 100% of the positive birds by 35 days PI. When the absorbance values for each group of birds were averaged, the ELISA successfully identified the M. gallisepticum-infected birds as uniformly positive 7 through 35 days PI and correctly identified all other groups negative for M. gallisepticum through 35 days PI.  相似文献   

16.
The humoral immune response over time of White Leghorn chickens experimentally infected with Mycoplasma gallisepticum or M. synoviae by an aerosol inoculation or a contact exposure were compared by immunoblotting. The response of chickens infected with M. gallisepticum were similar with respect to proteins recognized and intensity of response, regardless of mode of infection. On the other hand, chickens infected by aerosolization of M. synoviae responded to more proteins and with greater intensity than did M. synoviae contact-exposed birds. Chickens infected with M. gallisepticum responded with antibodies to over 20 proteins, while chickens infected with M. synoviae responded with antibodies to 12 proteins. Field sera from chickens naturally infected on commercial poultry farms with M. gallisepticum or M. synoviae were analyzed by immunoblotting and were found to react with a number of mycoplasma proteins. However, no correlation was seen when comparing intensity of immunoblot staining and hemagglutination-inhibition titer of the field sera. The experimental antisera were used to identify species-specific proteins of M. gallisepticum and M. synoviae. Six immunogenic species-specific proteins of M. gallisepticum with relative molecular masses of 82 (p82), 65-63 (p64), 56 (p56), 35 (p35), 26 (p26), and 24 (p24) kilodaltons (kDa) were identified. Two species-specific proteins of M. synoviae with relative molecular masses of 53 (p53) and 22 (p22) kDa were identified. Additionally, a highly immunogenic 41 (p41) kDa protein of M. synoviae was identified. Species-specific proteins identified in these mycoplasmas and the 41 kDa protein of M. synoviae were purified by preparative SDS-PAGE in amounts sufficient for further characterization and for use in serodiagnostic tests.  相似文献   

17.
Mycoplasma gallisepticum infection results in numerous clinical signs including a reduction in egg production in laying chickens. Attempts to prevent mycoplasmosis have included vaccination with both killed and attenuated live M. gallisepticum strains. Live vaccines provide reduction in clinical signs and have been shown to replace indigenous strains when used in a consistent program for several placements. Antibiotic therapy is another option for controlling losses associated with mycoplasmosis. Therapeutic antibiotics with activity against mycoplasma approved for use in poultry include tetracyclines and tylosin. These drugs also are approved for feed efficiency when administered in the feed at levels below the therapeutic index for mycoplasma. The data presented here suggest that birds vaccinated with the live 6/85 strain of M. gallisepticum and then fed tylosin, at the approved level for feed efficiency, exhibit a serologic vaccine response similar to that of unmedicated birds but show improved feed efficiency.  相似文献   

18.
Specific-pathogen-free layer hens in maximum lay were exposed by aerosol to a broth culture of Mycoplasma gallisepticum R' strain. Egg-production loss of greater than 50% was evident 7-14 days following challenge of unvaccinated chickens, with a gradual recovery during the next several days. Various vaccine preparations were tested to determine the effect in the model. All vaccinated chickens exhibited significantly (P < or = 0.05) lower egg-production loss than the unvaccinated controls. The model provides a method for testing treatment effects on egg-production losses resulting from controlled exposure to M. gallisepticum and may be useful in simulating field exposure.  相似文献   

19.
The in vitro emergence of resistance to enrofloxacin, erythromycin, tylosin, tiamulin, and oxytetracycline in three avian Mycoplasma species, Mycoplasma gallisepticum, Mycoplasma synoviae and Mycoplasma iowae was studied. Mutants were selected stepwise and their MICs were determined after 10 passages in subinhibitory concentrations of antibiotic. High-level resistance to erythromycin and tylosin developed within 2-6 passages in the three Mycoplasma species. Resistance to enrofloxacin developed more gradually. No resistance to tiamulin or oxytetracycline could be evidenced in M. gallisepticum or M. synoviae after 10 passages whereas, resistant mutants were obtained with M. iowae. Cross-sensitivity tests performed on mutants demonstrated that mycoplasmas made resistant to tylosin were also resistant to erythromycin, whereas mutants made resistant to erythromycin were not always resistant to tylosin. Some M. iowae tiamulin-resistant mutants were also resistant to both macrolide antibiotics. Enrofloxacin and oxytetracycline did not induce any cross-resistance to the other antibiotics tested. These results show that Mycoplasma resistance to macrolides can be quickly selected in vitro, and thus, providing that similar results could be obtained under field conditions, that development of resistance to these antibiotics in vivo might also be a relatively frequent event.  相似文献   

20.
To monitor the existence of avian pathogens in laying chicken flocks, specific pathogen-free (SPF) chickens were introduced into two layer farms and reared with laying hens for 12 months. SPF chickens were bled several times after their introduction and examined for their sero-conversion to avian pathogens. As a result, antibodies to eight or ten kinds of pathogens were detected in SPF chickens on each farm. Antibodies to infectious bronchitis virus (IBV), avian nephritis virus, Mycoplasma gallisepticum and M. synoviae were detected early within the first month. Antibody titer to IBV suggested that the laying chickens were infected with IBV repeatedly during the experiment on both farms. However, antibodies to infectious bursal disease virus and 6 pathogens were not detected.  相似文献   

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