Polystyrene, poly-L-lysine and nylon as adsorptive surfaces for the binding of whole cells of Mycobacterium tuberculosis H37 RV to ELISA plates

Attachment of motile bacterial cells to prealigned holed microarrays

Construction of biomotors is an exciting area of scientific research that holds great promise for the development of new technologies with broad potential applications in areas such as the energy industry and medicine. Herein, we demonstrate the fabrication of prealigned microarrays of motile Escherichia coli bacterial cells on SiOx substrates. To prepare these arrays, holed surfaces with a gold layer on the bottom of the holes were utilized. The attachment of bacteria to the holes was achieved via nonspecific interactions using poly-l-lysine hydrobromide (PLL). Our data suggest that a single motile bacterial cell can be selectively attached to an individual hole on a surface and bacterial cell binding can be controlled by altering the pH, with the greatest occupancy occurring at pH 7.8. Cells attached to hole arrays remained motile for at least 4 h. These data indicate that holed surface structures provide a promising footprint for the attachment of motile bacterial cells to form high-density site-specific functional bacterial microarrays.

Bacterial cell microarrays for the detection and characterization of antibodies against surface antigens

Bacterial cell surface antigens interact with the host immune system resulting in the production of antibodies. Detection of antibodies against surface antigens has applications in diagnosis of many bacterial infections, assessment of immune status and epidemiological studies. We developed a microarray platform, for antibody detection, by printing Gram-negative and Gram-positive whole bacterial cells on nitrocellulose coated glass substrates. Antibody binding was detected using fluorophore labeled secondary antibodies. The sensitivity of antibody detection was found to be 0.1 microg/ml. Using bacterial cell microarrays it was also possible to successfully detect antibodies against Francisella tularensis in canine serum samples declared positive for tularemia based on microagglutination antibody titer. Use of bacterial cells as the antigen source in immunoassays has the advantages of simulating in vivo presentation of surface antigens and also eliminating the need for antigen purification. The microarray format gives the added advantage of simultaneous detection of antibodies against multiple bacteria employing only small amounts of samples and reagents.

Methods for fabricating microarrays of motile bacteria

Motile bacterial cell microarrays were fabricated by attaching Escherichia coli K-12 cells onto predesigned 16-mercaptohexadecanoic acid patterned microarrays, which were covalently functionalized with E. coli antibodies or poly-L-lysine. By utilizing 11-mercaptoundecyl-penta(ethylene glycol) or 11-mercapto-1-undecanol as passivating molecules, nonspecific binding of E. coli was significantly reduced. Microcontact printing and dip-pen nanolithography were used to prepare microarrays for bacterial adhesion, which was studied by optical fluorescence and atomic force microscopy. These data indicate that single motile E. coli can be attached to predesigned line or dot features and binding can occur via the cell body or the flagella of bacteria. Adherent bacteria are viable (remain alive and motile after adhesion to patterned surface features) for more than four hours. Individual motile bacterial cells can be placed onto predesigned surface features that are at least 1.3 microm in diameter or larger. The importance of controlling the adhesion of single bacterial cell to a surface is discussed with regard to biomotor design.

Development and clinical application of an immunoassay using intact Helicobacter pylori attached to a solid phase as an antigen

OBJECTIVE

At present, H. pylori homogenates, extracts and recombinant proteins are used as antigens in immunoassays, but significant false positive and negative results are obtained. We attempted to develop an ELISA system using immobilized whole intact H. pylori cells as a solid phase antigen (WIC-ELISA) which specifically recognizes surface antigens.

METHODS

Intact H. pylori cells were immobilized on ELISA plates by centrifugation (150 g for 10 min). HRP-labeled antihuman IgG was used as the second antibody. H. pylori-infections were investigated with WIC-ELISA and a conventional method in which H. pylori-extracts were used as antigen in 117 patients.

RESULTS

WIC-ELISA showed better characteristics than conventional ELISA in regards to sensitivity (98.9 vs. 90.4%), specificity (95.7 vs. 95.7%), positive predictive value (98.9 vs. 98.8%), negative predictive value (95.7 vs. 71.0%) and accuracy (98.3 vs. 91.5%).

CONCLUSIONS

WIC-ELISA is useful for quantification of antibodies against H. pylori surface antigens and as a clinical screening test.

Enzyme linked immunosorbent assay for identification of whole Mycobacterium bovis isolates with the monoclonal antibodies

OBJECTIVE

The development of a test system for identification of Mycobacterium bovis with the use of monoclonal antibodies (Mabs).

DESIGN

BALB/c mice were immunized with whole gamma-radiation-exposed M. bovis strains. The splenocytes of the immunized mice were used for producing hybridomes which generated Mabs specific to M. bovis. The specificity of the Mabs was determined with the ELISA procedure for the whole cells of the 11 mycobacteria of various species fixed in the wells of a microtitre plate. The optimal conditions for performing identification were selected.

RESULTS

Three Mabs specific to M. bovis have been produced which identify various epitopes of the protein with a molecular weight of 31 kD. The ELISA tests with the 2A1 Mab have been conducted for 213 strains of 15 species of mycobacteria. the technique has been shown to be highly specific and reproducible.

CONCLUSION

An ELISA test system with a Mab for identification of M. bovis has been developed.

Evaluation of mouse salivary IgA directed against indigenous oral bacteria

We are developing an ELISA to follow the evolution of specific salivary IgA directed against the indigenous oral bacteria of the BALB/c mouse. To reduce the variability of the IgA levels detected between different mice, we standardized the method used for sampling saliva and the method used for bacterial cell fixation. Incubation of whole bacteria for one hour at 4 degrees C in poly-L-lysine-treated plates followed by glutaraldehyde fixation increased ELISA reactivities by improving cell fixation. Our results also indicate that salivary IgA concentrations in BALB/c mice peak at the age of three months and that biweekly carbachol-stimulated saliva sampling does not significantly affect the amount of salivary IgA detected.