Reducing risk of infection when obtaining hematocrit and bilirubin determinations: beyond universal precautions.

Obtaining hematocrit and bilirubin determinations is associated with infection risks, including human immunodeficiency virus infection. This study describes two simple procedures to decrease the risk of infection to health care providers while obtaining hematocrit and bilirubin determinations. Using readily available, inexpensive items (nonsterile gauze, a standard file, and plastic holder) and some simple techniques, the risk of infection can be decreased without increasing the time required. We believe these procedures are very reasonable and simple solutions to a common nursery problem.

The sensitivity and specificity of a modified ELISA for the diagnosis of Johne's disease from a field trial in cattle.

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against Mycobacterium paratuberculosis in cattle was evaluated in three herds known to have Johne's disease. Prior to testing, the plasma was absorbed with dried Mycobacterium phlei in order to remove cross-reacting antibody specificities. The sensitivity and specificity of the ELISA were calculated after repeatedly testing 327 cattle in the infected herds. Of these, 53 animals had one or more positive faecal cultures or had post-mortem histopathological evidence of infection. The other 274 had three or more negative faecal culture results, and were regarded as non-infected for the purpose of evaluation of the ELISA. Using these criteria for the presence or absence of infection, the M. phlei-absorbed ELISA under field conditions had a 57% sensitivity and a 98.9% specificity. The sensitivity of the absorbed ELISA depended on the stage of disease of the animal under test. In general, it appeared that animals in the more advanced stages of disease were absorbed ELISA positive, whereas those in the early stages of infection were not detected. These results indicate that the M. phlei-absorbed ELISA has an important role as a test for the diagnosis and control of Johne's disease in cattle.

Trichostrongylus colubriformis: analysis of monoclonal antibody and lectin binding to the larval cuticle.

A monoclonal antibody (VRI 86-1) raised against third stage Trichostrongylus colubriformis preferentially bound to the excretory pore of living exsheathed larvae, with little or no binding to other sites on the parasite surface. A similar binding pattern was observed with fluorescein-labelled wheat germ agglutinin (WGA), although the anterior end of the parasite was also stained. To gain information at the molecular level regarding the parasite components at these sites, the residues recognized by WGA (i.e. N-acetylglucosamine and N-acetylneuraminic acid) were radiolabelled on the surface of living larvae. After homogenization and detergent extraction of the larvae, four dominant bands and a number of minor bands were revealed by SDS-PAGE and fluorography. None of these bands was specifically immunoprecipitated or recognized on a Western blot by VRI 86-1, suggesting that the epitope recognized by this antibody either resides on a different molecule or is destroyed or changed during the radiolabelling procedures. These results provide further evidence that the nematode cuticle is not uniform at the molecular level, and that the excretory pore contains molecules and antigens that may be unique to that site.

Microbial film development in a trickling filter.

The transmission and scanning electron microscopes were employed to visualize the sequence of the biofilm development in the trickling wastewater filter. After the deposit of a small amount of debris upon a hard surface, the bacterial cells attach and develop the matrix on which the biofilm is formed. Protozoa invade the basic layer where they feed on the bacteria. The algae are seeded upon the bacterial matrix and grow so profusely that the bacteria must develop aerial colonies in the competition for food and oxygen. Destruction of the bacteria in the matrix and the weight and hydraulic pressure cause detachment of the biofilm and a new matrix must be developed.