Influence of water quality and temperature on adhesion of high and low virulence Flavobacterium columnare strains to isolated gill arches

The ability of Flavobacterium columnare ( Flexibacter columnaris ) to attach to the gills of common carp, Cyprinus carpio L., was evaluated using a gill perfusion model. A comparison between a high and a low virulence strain of F. columnare was made and evaluated in comparison to results obtained previously with an in vivo model. The ion composition of the water of the organ bath in which the gills were suspended was varied and the influence on adhesion processes assessed. Experiments were carried out to examine the influence of water quality (i.e. nitrite and organic matter) and temperature on the capacity of the bacteria to adhere. It was found that the high virulence strain adhered more readily than the low virulence strain, as was found during the in vivo experiments. Moreover, it was observed that adhesion of the high virulence strain was enhanced by a number of factors. These were immersion of the gill in bivalent, ion-rich water, the presence of nitrite or organic matter, and high temperatures.     

Efficacy of avermectin B1 given orally against equine intestinal strongyles and Onchocera microfilaria

Three groups of horses and ponies (N = 13, 13 and 12) were treated with ivermectin paste (0.2 mg/kg p.o.), avermectin B1 solution (0.2 mg/kg p.o.), or fenbendazole suspension (10 mg/kg via nasogastric tube). The avermectin B1 was a 1% solution in a propylene glycolglycerol formal base. Faecal strongyle egg counts were performed before, and 14, 28, 42, 56 and 70 d, after treatment. Full-thickness skin biopsies from the neck, pectoral and umbilical regions were examined for Onchocera microfilaria before treatment, and again 14 and 70 d later. Ivermectin therapy produced a significant (P less than 0.01) decrease in mean strongyle egg counts 14, 28, 42 and 56 d after treatment. Avermectin B1 therapy resulted in significant (P less than 0.01) decreases in mean strongyle egg counts 14, 28 and 42 d after treatment. All horses given ivermectin or avermectin B1 had zero strongyle egg counts 14 and 28 d after treatment. Fenbendazole failed to significantly decrease strongyle egg counts. Both ivermectin and avermectin B1 resulted in zero microfilaria counts in all horses 14 d after treatment. On day 70 the percentage decrease in microfilaria counts were 100% and 99.6% respectively. Fenbendazole failed to significantly decrease microfilaria counts. The oral administration of this formulation of avermectin B1 appeared to be highly efficacious against intestinal strongyles and Onchocera microfilaria. The duration of anti-strongyle activity was, however, significantly (P less than 0.01) shorter than that of ivermectin paste.     

Respiratory adenovirus-like infection in a rose-ringed parakeet (Psittacula krameri).

Intranuclear inclusions were observed under light microscopy in the bronchial epithelial cells of a recently purchased female rose-ringed parakeet that died of chlamydiosis. Transmission electron microscopy revealed the presence of numerous particles of adenovirus morphology. A latent adenovirus infection may have become more severe following chlamydiosis and the stress of handling.     

On the origin of bacterial resistance to penicillin: comparison of a beta-lactamase and a penicillin target

Structural data are now available for comparing a penicillin target enzyme, the D-alanyl-D-alanine-peptidase from Streptomyces R61, with a penicillin-hydrolyzing enzyme, the beta-lactamase from Bacillus licheniformis 749/C. Although the two enzymes have distinct catalytic properties and lack relatedness in their overall amino acid sequences except near the active-site serine, the significant similarity found by x-ray crystallography in the spatial arrangement of the elements of secondary structure provides strong support for earlier hypotheses that beta-lactamases arose from penicillin-sensitive D-alanyl-D-alanine-peptidases involved in bacterial wall peptidoglycan metabolism.     

Characterization and purification of the F17 adhesin on the surface of bovine enteropathogenic and septicemic Escherichia coli

The F17 antigen from bovine enterotoxigenic Escherichia coli strain (E coli 25KHO9), which adhered to calf intestinal villi, was isolated. An enterotoxin-negative derivative (25KHO9st) was used for further studies. Using an immunogold-labeling technique, the F17 antigen was characterized as a fimbrial protein. Pure fimbriae with a subunit molecular weight of 20,000 were obtained by homogenization and use of a sucrose gradient. The adhesion of E coli 25KHO9st was mediated by the F17 fimbriae, as both F17 antibodies and F17 protein blocked the adhesion of the strain 25KHO9st. The F17 fimbriae were serologically distinct from K88, K99, F41, and 987P fimbriae and did not agglutinate bovine, ovine, guinea pig, human, or chicken erythrocytes. Peptide fingerprint analysis revealed F17 and F(Y) adhesins to be homologous, if not identical.     

Procedure for PEG treatment of bovine sera used for cell culture in virus diagnosis

A method for PEG treatment of bovine sera to be used for cell cultures is presented. The procedure consists in repeated freezing and thawing cycles of the sera, after PEG precipitation until a clear solution is obtained. The sera, so prepared, are homogeneous in composition and appropriate for cell growth in primary cell cultures and cell lines.