Chlortetracycline residues in the meat of slaughter calves in relation to transmissible microbial resistance to antibiotics

The occurrence of chlortetracycline residues in the meat of slaughter calves in 62% herds under study (the additive of the medicated premix AUREOVIT to feed without observing the withdrawal times) did not influence significantly the Gram-negative resistant and R+ microflora isolated from the same material, in comparison with control herds that were administered no antibiotics. Neither was the spectrum of donors and transferring R plasmids influenced significantly nor the incidence of different resistance determinants. The effect of chlortetracycline addition to feed was negative (at P = 0.05) only in the occurrence of R+ microflora isolated from stable environment where the slaughtered calves had been housed.     

Differenzierung des Pansenepithels des Rindes während der intrauterinen Entwicklung

The prenatal development of the bovine ruminal epithelium was studied with light- and electronmicroscopical techniques. During the period of the nonstratified epithelium a pseudostratified epithelium is found in the dorso-cranial part, whereas the other areas possess a one-layered epithelium, which is, like the pseudostratified epithelium, transformed to a multilayered epithelium from the 7th week onwards. From the 9th week the period of the stratified epithelium starts with the formation of the stratum profundum and stratum superficiale. First signs of keratinization are seen in the superficial cells from 2.3 months onwards. With 4 months fetal cornified cells can be identified, with 5.5 months a single-layered stratum basale is seen on the differentiating papillar connective tissue, and the superficial cells are transformed to balloon-cells. In suprapapillar areas, a stratum spinosum is formed at the prenatal age of 7.5 months. During epitheliogenesis a horizontal and vertical differentiation of the cells can be observed. The first one includes the differentiation of undifferentiated, embryonal cells to the basal cells of the stratum profundum, the latter the development of the basal cells to spinous cells and then to fetal cornified and balloon-cells. The ultrastructural changes during the process of keratinization were especially considered.     

Diagnosis of avian encephalomyelitis

The diagnostic value of laboratory examination methods was assessed in the diagnosis of avian encephalomyelitis in seven to twenty-two days old chickens. Histological examination and immunofluorescent test are expedient methods meeting the requirements for timely application of infection-control measures. The agreement of histological examination with the over-all laboratory examination is 70 to 81% and the agreement of the immunofluorescence test is 76%. Bioassay on chickens followed by a histological examination appears to be the best method, providing results with the highest significance. However, it is lengthy, applicable to the necessary demonstration of a virus or to cases when the histological or immunofluorescence examinations are dubious. With the over-all laboratory evaluation the method shows agreement in 95 to 100% of cases. The diagnostic value of the method of virus isolation in chick embryos is reduced by the fact that intercurrent viruses (adenoviruses, IB and others) may be passaged at the same time.     

Bio-corrosion: A note on fungal solubilization of iron from stainless steels

Cultures of the fungus Penicillium italicum can extract Fe from powdered stainless steels, including highly corrosion-resistant alloys containing 11 to 13 % Ni. Physical contact of fungus with metal is unnecessary, but acidification alone fails to account for the phenomenon. Evidence from other sources suggests that fungal metabolites are involved.     

Physiological properties and classification of strains of Treponema sp. isolated from pigs in poland

Fifty-one treponemas were isolated from pigs. Twenty-three isolates with typical morphology and growth characteristic were beta hemolytic, enteropathogenic, produced indole and with exception of three strains did not ferment fructose. These strains were classified as typical T. hyodysenteriae and were usually isolated from pigs with symptoms of mucohemorrhagic diarrhoea. The seventeen other isolates were weakly beta hemolytic after 48 h incubation, enteropathogenic, 12 out of 17 produced indole, 10 out 17 fermented fructose. These strains were usually isolated from pigs with symptoms of gray-green diarrhoea and classified as T. hyodysenteriae 2 biotype or intermediate type. They may be compared with Treponema sp. isolated by Taylor et al. Eleven non enteropathogenic strains showed typical characteristic for T. innocens. Gas chromatography analysis of the fatty acids production from glucose, showed that all isolated treponemas produced acetate and butyrate. Typical T. hyodysenteriae produced additionally propionate. Strains of T. hyodysenteriae biotype 2 produced propionate or isobutyrate as well.