Bacterins and vaccines for the control of Mycoplasma gallisepticum

The preferred method for the control of Mycoplasma gallisepticum is eradication. Unfortunately, the advent of multiple-age farms for poultry production has made eradication impractical after the organism has been introduced. Live vaccination with the F strain of M. gallisepticum during the rearing period has been used to prevent egg production losses. More recently, an inactivated oil emulsion bacterin has become available commercially. Vaccine and bacterin offer protection against egg production losses, respiratory signs and lesions, and egg transmission. Vaccination of broilers, however, is not yet feasible, Bacterin offers minimal protection against infection. The use of bacterins and vaccines on multiple-age farms is being studied as a potential eradication tool.

Improving the Mycoplasma gallisepticum and M. synoviae antigen yield by readjusting the pH of the growth medium to the original alkaline state

The pH of Mycoplasma gallisepticum (MG) and M. synoviae (MS) growth medium was readjusted back to the original alkaline state when the pH reached 6.1 (for MG) and 6.7 (for MS), and the medium was reincubated until the pH of the medium returned to 6.7 to 6.9. The result was that MG and MS antigen yields were 43 and 54% higher than yields obtained at the usual harvest time.

Correlation of titer, preservation method, and storage of Mycoplasma gallisepticum F strain and the immune response in chickens

The F strain of Mycoplasma gallisepticum (MG) was used either fresh or after lyophilization or freezing at -60 C to vaccinate young leghorn chickens. Vaccine stored either frozen or lyophilized for 22 months was also used. Each vaccine preparation was given at dosages ranging from 10(5) to 10(9) colony-forming units/ml. All dosage levels of MG significantly (P less than 0.05) reduced air-sac lesion scores after aerosol challenge with the R strain of MG at 6 weeks postvaccination, regardless of the method of vaccine preservation or storage.

Evaluation of attenuated strains of Mycoplasma gallisepticum as vaccines in young chickens

Five trials were conducted to evaluate the virulence and the vaccination efficacy of the F, R, S6, and A5969 strains of Mycoplasma gallisepticum (MG) at different in vitro passage levels. Vaccination was done by eye-drop or aerosol, and efficacy was evaluated in terms of air-sac lesions after aerosol challenge with the R strain of MG. Continuing medium passage of these strains of MG resulted in gradual attenuation. Aerosol vaccination with highly attenuated MG at 21 days of age was more effective in stimulating the development of immunity than was eye-drop vaccination at 7 days, but aerosol vaccination induced more air-sac lesions. Aerosol vaccination with high-passaged F or S6 strain provided good immunity against MG challenge. Back-passage in chickens of the F strain of over 300 medium passages did not substantially increase the virulence, but back-passage of the S6 strain at the 258th passage and F strain at the 11th and 252nd passage did result in increased virulence. Both low- and high-passaged F and S6 strains were virulent for turkey poults, but only the high-passage F strain did not significantly (P less than 0.05) affect body weight.

Transferred humoral immunity in chickens to Mycoplasma gallisepticum

Progeny chicks of Mycoplasma gallisepticum (MG)-infected and MG-free white leghorns were used to evaluate the protective effects of maternal antibodies against aerosol challenge with the virulent R strain of MG at 3, 7, or 14 days of age. Interference by maternal antibodies with day-1 vaccination with the F strain of MG was also studied. In another trial, 8, 4, or 2 ml of high- or low-titered antiserum was given to 20-day-old commercial white leghorn chicks. Protection was measured in terms of air-sac lesions post-challenge with the R strain of MG as above. Maternal antibody in the chicks conferred very little protection against challenge and did not interfere with day-1 vaccination with the F strain of MG. Low-titered antibody gave no protection against growth of MG in the tracheas, but the high-titered MG antiserum did confer some protection against airsacculitis. This protection might be due to growth-inhibition antibody in the transferred serum.

Evaluation of the microagglutination test in the diagnosis of Mycoplasma gallisepticum infection in chickens

The sensitivity and specificity of the microagglutination (MA), serum-plate-agglutination (SP), and hemagglutination-inhibition (HI) test for Mycoplasma gallisepticum (MG) were compared in groups of chickens infected with MG, M. synoviae, or Pasteurella multocida or inoculated with bacterins prepared from Staphylococcus aureus or Erysipelothrix rhusiopathiae. Of the three tests evaluated, the HI test had the highest specificity, but it was the least sensitive. Both the MA and SP tests were more sensitive than the HI test but lower in specificity. The MA test was less sensitive than the SP test in detecting antibodies against heterologous MG strains.

Egg transmission of two strains of Mycoplasma gallisepticum in chickens

The egg transmissibility of strains F and R of Mycoplasma gallisepticum (MG) was studied in 53 pullets by isolating MG from the eggs and embryos. MG was isolated at rates of 3.19% and 1.59% from the eggs of hens exposed by aerosol to the R or F strain, respectively. However, MG was isolated at rates of 0.19% and 0.00% from the eggs of chickens exposed by eye drop to the R or F strain, respectively. A statistically significant reduction in egg production was observed during the first 4 weeks postexposure in the group exposed to the R strain of MG by aerosol. An unexpected finding was significantly lower fertility of eggs from all MG-infected groups.

Cross-immunity and antigenic relationships among five strains of Mycoplasma gallisepticum in young Leghorn chickens

Five strains of Mycoplasma gallisepticum (MG) were tested for their cross-protection, virulence, and antigenic relationship in young leghorn chickens. Chickens vaccinated at 1 day of age by eye drop with the F or R strain of MG had good protection against aerosol challenge with the F, R, or S-6 strain at 4 weeks postvaccination. Chickens vaccinated at 1 day of age with the 503 or 730 strain had only partial protection against challenge with R, F, or S-6; the degree of cross-protection was related to the virulence of the vaccine strain used. In the hemagglutination-inhibition test, serum from chickens with single infection (vaccination and/or challenge with only one strain) with the F, S-6, or R strain reacted strongly with antigens prepared from S-6 and A5969 and reacted weakly with 730 and 503 antigens. Chickens with a single infection with the 503 or 730 strain reacted only with antigen prepared from the homologous strain. Serum from chickens with a two-strain mixed infection had a wider spectrum of HI activities. In the serum-plate-agglutination test, serum from chicken infected with the S-6, F, or R strain reacted with all antigens. Chickens infected with the 503 or 730 strain reacted more strongly with the homologous antigen. Antigen prepared from the S-6 strain of MG detected antibodies against the 503 and 730 strains more efficiently than did antigen prepared from the A5969 strain.

Pathogenicity of two strains of Mycoplasma gallisepticum in turkeys

Strains F and R of Mycoplasma gallisepticum (MG) were compared for their pathogenicity in broad-breasted white turkey poults in terms of induction of airsacculitis, depression of growth rate, and induction of antibody production against MG. Eye-drop inoculation with the F or R strain produced only minimal lesions. However, aerosol exposure with either MG strain resulted in a significantly higher incidence and severity of air-sac lesions (P less than 0.001), reduction of growth rate (P less than 0.005), and hemagglutination-inhibition (HI) antibody titers against MG than did eye-drop inoculation. There were no significant differences between the two MG strains in effects on incidence of air-sac lesions or on growth rate.

Viability of the F strain of Mycoplasma gallisepticum after storage in the frozen or lyophilized state

Strain F of Mycoplasma gallisepticum was stored frozen at -60 C or -20 C in liquid medium with or without cryoprotective agents or was lyophilized with or without stabilizers and stored at 4 C. The titer was determined before, during, and after the subsequent storage period. In cultures frozen at -60 C or lyophilized, the titer had not significantly declined by the end of 371 days of storage. At -20 C, the titer of frozen cultures declined rapidly, and no mycoplasma had survived 282 days of storage. The addition of cryoprotective agents (10% glycerol or 8% dimethyl sulfoxide) or freeze-drying stabilizers (12% sucrose, or 7.5% glucose, 8% skim milk, or SPA) did not help maintain the viability of the mycoplasmas during freezing or freeze-drying process and the subsequent storage.

In vitro activity of rifampin alone and in combination with nafcillin and Vancomycin against pathogenic strains of Staphylococcus aureus

Twenty strains of Staphylococcus aureus isolated from patients with endocarditis were examined in vitro for susceptibility to rifampin, nafcillin, and vancomycin and to combinations of rifampin with nafcillin or vancomycin. Minimum bactericidal concentrations of rifampin ranged from 0.0031 to 0.0125 mug/ml, of nafcillin ranged from 0.078 to 0.312 mug/ml, and of vancomycin ranged from 0.312 to 1.25 mug/ml. The combination of rifampin with nafcillin was synergistic for 12 strains; the combination of rifampin plus vancomycin was synergistic for 5 of the isolates.

Methadone: antimicrobial activity and interaction with antibiotics

We studied the effect of methadone, alone and in combination with antimicrobial agents, on two strains each of Staphylococcus aureus, Pseudomonas aeruginosa, and Serratia marcescens isolated from blood streams of parenteral drug abusers with bacterial endocarditis. Methadone has its own antibacterial effect, although at supraphysiological concentrations, and is even synergistic with antimicrobial agents against some organisms. Thus, methadone does not interfere with the antibacterial effects of antibiotics in vitro.