Testing disinfectants for efficacy.

Testing under laboratory conditions is undoubtedly useful in assessing the activity of disinfectants. However, such testing must be regarded as no more than a preliminary to field trials. This not only indicates the unreliability of laboratory tests, but also poses the wider problem of how any laboratory evaluation can be correlated with the field requirements. Many attempts have therefore been made to devise tests which are suitable to evaluate the in-use requirements of disinfection (e.g. on farms). The aim of these techniques is to record the end-point of a disinfection procedure on the surfaces in animal houses. In view of the need to standardise testing conditions in the field, the author provides details of the optimum time and place for taking samples under field conditions. Samples for culture media should be taken from the floor when dry. The various techniques (i.e. swabbing, agar cylinder, agar carrier, 'ready-to-use' set) should provide information on the end-point of the disinfection. The desired end-points is approximately one viable bacterium per cm2 of surface area. The technique used should demonstrate whether the disinfection has been effective.

Immunization of day-old chickens against Newcastle disease.

The avirulent Newcastle disease virus strain designated NDV-6/10, selected by B. Lomniczi at the Veterinary Medical Research Institute, Hungarian Academy of Sciences, is completely safe for day-old chickens by aerosol vaccination. Aerosol immunization using the Hungarian-made MASTERDROP generator (particle size: maximum 7 microns) caused no vaccination reactions among 206,000 chickens with different maternal antibody levels. Other vaccines given simultaneously did not significantly affect the protection elicited against Newcastle disease (ND). Almost 100% and 90% of the aerosolized chickens survived subcutaneous challenge with 10(6) LD50 NDV at 30 and 50 days old, respectively. A single immunization is sufficient for broilers; however, parent flocks should be revaccinated at 7 so 8 weeks old.

Growth inhibition of Escherichia coli by nitrate reductase.

The metabolite of a not nearer identified Pseudomonas strain inhibited or inactivated Escherichia coli in presence of nitrate.

Investigation of survival time of some poultry mycoplasmas.

Glucose-fermenting poultry mycoplasmas (Mycoplasma [M.] gallisepticum, M. pullorum, M. gallinaceum, M. gallopavonis) were tested in 2 experiments for their survival time at 20 degrees C and 37 degrees C on 18 different materials used on farms and in hatcheries. All mycoplasmas survived up to 16 days in egg yolk at both temperatures. On other materials, like egg shell, egg white, paper trails, feather, and others mycoplasmas generally survived 2 to 16 days at 20 degrees C. M. gallinaceum and M. gallopavonis proved more resistant to the environment than M. gallisepticum and M. pullorum.

Differential stain for mycobacteria that does not require heat.

A stain of 0.1% toluidine blue in a 1.0% aqueous solution of triethylene glycol followed by decolorization with acid-alcohol resulted in mycobacteria retaining the stain (violet), whereas non-acid-fast bacteria were decolorized.

Resistance to symptomatic insulin reactions after fasting.

This study was carried out to determine if, in fasting, an adaptation to utilization of ketones could prevent cerebral dysfunction during periods of acute, insulin-induced glucopenia. In the course of standard insulin tolerance tests (0.1-0.2 U/kg), nine obese subjects manifested frank hypoglycemic reactions resulting in an increase in urinary catecholamine excretion from 61 to 113 mug/24 hr (P < 0.01). After fasting 2 months, administration of weight-adjusted doses of insulin produced identical maximum insulin concentrations and disappearance curves. However, no insulin reactions nor significant rises in catecholamine excretion occurred despite equal extent and rate of glucose fall. Glucose concentrations as low as 0.5 mmoles/liter (9 mg/100 ml) failed to precipitate hypoglycemic reactions. During the postfast insulin tolerance tests, mean plasma 2-hydroxybutyrate (beta-OHB) decreased from 8.02 to 6.69 mmoles/liter (P < 0.01). In another five fasting subjects tested, the A-V difference for beta-OHB across brain increased progressively from 0.21 to 0.70 mmoles/liter whereas across the forearm no consistent uptake could be demonstrated. Simultaneously, the A-V difference across the brain for glucose decreased from 0.24 to 0.07 mmoles/liter of plasma. In addition to insulin-induced suppression of hepatic ketogenesis, the augmented cerebral ketone uptake during insulin hypoglycemia contributes to the net fall in plasma beta-OHB. Ketoacids, extracted by the fast-adapted brain, supplant glucose as a metabolic substrate preventing overt hypoglycemic reactions during acute glucopenia.