Adaptation of the Sensititre broth microdilution technique to antimicrobial susceptibility testing of Mycoplasma gallisepticum.

A technique is described for determining the antimicrobial susceptibility of Mycoplasma gallisepticum, using the Sensititre broth microdilution system. Fourteen M. gallisepticum field isolates and one reference isolate (R-strain) were tested in duplicate against seven antimicrobials. Isolates were susceptible to oxytetracycline, furaltadone, and lincomycin/spectinomycin, but not to amoxycillin and apramycin. Susceptibility to erythromycin and tylosin varied. These data are in agreement with those reported by other workers using more traditional methods, but this adaptation of the broth microdilution technique eliminates any variation attributable to the time-consuming preparation of antimicrobial dilutions associated with these methods.     

Experimental alveolar echinococcosis in pigs, lesion development and serological follow up

Liver lesions were found in 6/6 pigs 7 months after oral inoculation with 5000 or 35,000 Echinococcus multilocularis eggs. However, lesion morphology differed considerably among the animals. The largest lesions (3–8 mm in diameter) were found in a single pig and smaller lesions (1.5–3 mm) in three pigs. These lesions were clearly circumscribed and had pronounced central necroses and dystrophic calcifications. In contrast, most of the smallest (usually <1.5 mm in diameter) found in two other pigs, had small compact fibrotic areas and blurred borders with obvious fibrous infiltrations into the interlobular tissues. E. multilocularis specific DNA was detected by PCR in all lesion types, but metacestode viability, as assessed by in vivo intraperitoneal inoculations in jirds, could not be demonstrated. Within 1 month post inoculation, all pigs developed specific IgG antibody responses against a battery of different antigens (metacestode, cyst fluid, and protoscoleces-derived native E. multilocularis and E. granulosus antigens, affinity purified Em2G11 antigen, antigen B, recombinant Em II/3–10 antigen). Two different reaction patterns were recorded. In the two pigs with the small lesions, pronounced reactions against all crude antigens with peaks 3–5 months p.i. and clearly elevated levels until the end of the experiment were noted. In all other pigs, antibody reactions remained low in all cases. In conclusion, we demonstrated two types of E. multilocularis metacestode development in pigs with distinct immunological response patterns.     

Evaluation of multiple immune parameters after vaccination with modified live or killed bovine viral diarrhea virus vaccines

The development of immunity to vaccine antigen was examined using three prime/boost strategies and the progression of immune activities was evaluated over the course of 8 weeks. Calves were vaccinated and multiple immune parameters were evaluated using several methods to assess humoral or cellular immunity from the same samples in parallel. The three vaccination protocols used were a killed vaccine followed by a killed boost (killed/killed), MLV vaccine and boost (MLV/MLV), or a MLV vaccine and killed boost (MLV/killed). All the vaccines used included modified live IBR/PI3 viruses to make the bystander context as similar as possible. The Singer strain of BVDV was used as the source antigen in the killed vaccine, and the NADL strain of BVDV was used in the MLV vaccine. Controls received a vaccine containing only MLV IBR/PI3. The assessment panel measured SN titers, as well as lymphocyte proliferation, cytokine mRNA expression, intracellular cytokine production, and released IFN-gamma after in vitro stimulation with three strains of BVDV virus. MLV/MLV and MLV/killed groups developed significant SN titers to the type 1 BVDV virus strains, Singer and NADL, and low crossover titers were also seen to the type 2 strain, 890 over the evaluation period. These two groups showed significant proliferation in response to the NADL virus as compared to controls. Multiple immune assessments were conducted simultaneously to attempt to provide a broader, more in depth evaluation of immune response to these BVDV vaccination protocols. We observed that the correlation among most of the assays conducted were weak; the correlation between SN titers and cellular proliferation assays demonstrated a moderate correlation.