Monoclonal antibodies for Streptomyces lividans and their use for immunomagnetic capture of spores from soil

Development of a method for the detection of waterborne microsporidia

Microsporidia are obligate intracellular pathogens capable of infecting humans. There is credible evidence to suggest that microsporidial infections may be transmitted through consumption of spores in contaminated water; however, methods to detect this pathogen have not been standardized and microsporidia occurrence studies have not been conducted. Concentration of spores by continuous flow centrifugation (CFC), purification using immunomagnetic separation (IMS), and detection by either microscopy or real-time polymerase chain reaction (PCR) were evaluated for detection of Encephalitozoon intestinalis spores in seeded water samples. Recovery efficiency of CFC using microscopic detection ranged from 38.7-75.5% in filtered tap water. Using an indirect IMS method, 78.8-90.2% of seeded spores were recovered in ultrapure water (18 M Omega); however, the lack of a specific monoclonal antibody and the presence of other particulates interfered with the IMS assay in some turbid samples. Despite low recovery efficiencies and the detectable presence of PCR inhibitors in each of the samples, a combination of CFC concentration, indirect IMS, and real-time PCR produced a positive test result in six of ten natural water samples (turbidity 0.1-28.9 NTU) at a seeding level of 50 spores/L.

Immunomagnetic recovery of Mycobacterium bovis from naturally infected environmental samples

AIMS

To adapt an immunomagnetic capture (IMC) technique to concentrate and cultivate Mycobacterium bovis from environmental samples including soil, faeces and urine.

METHODS AND RESULTS

Cells of Myco. bovis BCG and wild-type Myco. bovis were successfully isolated and cultured from seeded and naturally infected materials respectively. The IMC cell recovery estimated by colony forming units (CFUs) counts ranged from 0.10% to 0.16% for spiked media, and 0.15-0.36% for naturally infected soil and faeces. Recovery estimated by cell counts calculated using semi-quantitative PCR ranged from 80.3% to 88.6% for spiked and 84.1-88.2% for naturally infected material. The differences in the recovery rates estimated by CFUs compared with pixel intensity is likely to be due to clustering of cells on culture plates, thereby underestimating the true cell count.

CONCLUSIONS

The IMC techniques can be applied to isolate viable wild type Myco. bovis from naturally contaminated environmental samples.

SIGNIFICANCE AND IMPACT OF STUDY

Cultivation of Myco. bovis from environmental samples using traditional methods is extremely problematic. Here, we demonstrate a novel development of IMC techniques that will greatly facilitate the study of the organism in situ in order to assess its epidemiological importance in bovine tuberculosis persistence.

Rapid detection and high-resolution discrimination of the genus Streptomyces based on 16S-23S rDNA spacer region and denaturing gradient gel electrophoresis

As the leading source of antibiotics, Streptomyces species are the subject of widespread investigation. Many approaches have been tried to aid in the classification of Streptomyces isolates to the genus, species, and strain levels. Genetic methods are more rapid and convenient than classification methods based on phenotypic characteristics, but a method that is universal in detecting all Streptomyces yet selective in detecting only Streptomyces is needed. The highly conserved nature of the 16S rRNA gene (16S rDNA) combined with the need to discriminate between closely related strains results in analyses of ribosomal intergenic spacer (RIS) regions being more productive than analyses of 16S rRNA genes. PCR primers were designed to amplify the RIS region as well as a sufficient length of the 16S rRNA gene to enable phylogenetic analyses of Streptomyces. Improved selectivity and specificity for the amplification of RIS sequences from Streptomyces with environmental samples was demonstrated. The use of RIS-PCR and denaturing gradient gel electrophoresis (DGGE) was shown to be a convenient means to obtain unique genetic "fingerprints" of Streptomyces cultures allowing them to be accurately identified at species, and even strain classification levels. These RIS-PCR and DGGE approaches show potential for the rapid characterization of environmental Streptomyces populations.

The use of affinity adsorbents in expanded bed adsorption

The potential for the use of affinity ligands in expanded bed adsorption (EBA) procedures is reviewed. The use of affinity ligands in EBA may improve its use in direct recovery operations, as the enhanced selectivity of the adsorbent permits selective capture of the target from complex feedstocks and high degrees of purification. The properties of ligands suitable for use in EBA processes are identified and illustrated with examples. In addition to its use in the recovery of soluble products, such as proteins and nucleic acids, from particulate feedstocks, EBA can also be used to recover particulate entities, such as cells and packaged DNA (viruses and phages), from feedstocks. Affinity ligands coupled to appropriate chosen support materials will be required for such processes in order to achieve the necessary selectivity for the required particulate entity. The latter point is illustrated by the use of proteinaceous ligands immobilized to perfluorocarbon emulsions to achieve separations of microbial cells.

Development of an immunomagnetic method for selective isolation of Actinobacillus pleuropneumoniae serotype 1 from tonsils

An immunomagnetic separation technique (IMS) for the selective isolation of Actinobacillus pleuropneumoniae serotype 1 was developed. Superparamagnetic polystyrene beads (immunomagnetic beads [IMBs]) were coated with purified rabbit immunoglobulin G specific for A. pleuropneumoniae serotype 1. The antibody concentration, the number of IMBs, the incubation time, and the temperature of incubation influenced the recovery of the target bacteria. The sensitivity of the IMS technique was 1,000-fold higher than that of direct culture. When tonsils from animals from infected herds were tested, significantly more positive tonsils were detected by the IMS technique (68%) than by the standard procedures (22%). The method represents an innovative and highly sensitive approach for the isolation of A. pleuropneumoniae from carrier animals.

Development of an immunomagnetic assay system for rapid detection of bacteria and leukocytes in body fluids

Immunomagnetic (IM) separation and concentration of specific target ligands or particles, such as bacteria or leukocytes, from complex mixtures, such as bone marrow, blood and other body fluids, is now a widely accepted technique. IM methodologies require high affinity antibodies or other receptors, but are potentially as effective as density gradient separations. Thus, a computer-controlled first-generation immunomagnetic assay system (IMAS) biodetector is being developed for clinical diagnostics. This system is fully automated and affords the advantage of rapid flow-through capture of all types of magnetic beads (MBs) and obviates operator contact with body fluid samples during the collection and analysis phases. In the present work, biotinylated capture antibodies were bound to streptavidin-coated MBs for capture of E. coli O157:H7, T cells and T cell subsets. Samples were automatically vortex mixed with antibody-coated MBs, stained with an acridine dye or fluorescent antibody and collected in a specially designed flow cell containing multiple steel pins, which concentrate external magnetic field lines. IM complexes were rapidly (within minutes), separated from their media in the magnetic field. Magnetically captured particles were automatically rinsed in the flow cell to remove unwanted materials and detection was achieved via a flow-through fluorimeter. Samples can be subsequently captured on a microbiological filter for microscopic visualization and image analysis. Preliminary results demonstrate that rapid detection of target bacteria and leukocytes at low concentrations in body fluids is possible with a total assay time under 1 h. This IM technology has many other potential clinical, industrial and environmental monitoring applications.

Affinity adsorption of Saccharomyces cerevisiae on concanavalin A perflurocarbon emulsions

Perfluorocarbon affinity emulsions have been generated by immobilizing concanavalin A onto the surface of triazine-activated perfluorocarbon droplets. Immobilized concanavalin A densities of 0.1, 0.7 and 2.1 mg/ml were obtained by varying the concentration of cyanuric chloride used for activation. The affinity emulsions were found to adsorb Saccharomyces cerevisiae cells from solution with adsorption capacities of 1 x 10(9) cells, 4.6 x 10(9) and 6 x 10(9) cell/ml, respectively. Optimal conditions for the elution of bound cells were obtained by studying inhibition curves of concanavalin A-mannan precipitation using simple sugars. Methyl alpha-D-mannopyranoside showed the greatest inhibitory power with 50 per cent inhibition displayed at a concentration of 0.05 mM. Experiments carried out examining the concentrations of methyl alpha-D-mannopyranoside necessary to dissociate a concanavalin A-mannan precipitate demonstrated that at least a seven-fold higher concentration of methyl alpha-D-mannopyranoside was required for dissociation than that required for inhibition of its formation. The efficiency of elution of bound yeast cells was found to be dependent on the concentration of methyl alpha-D-mannopyranoside used, the time of elution and the immobilized ligand density. Thus, 100 per cent elution was obtained with a concanavalin A affinity emulsion (0.1 mg/ml) by incubation with 500 mM methyl alpha-D-mannopyranoside for 1 h.