Antigenic specificity of Escherichia coli alkaline phosphatase studied with monoclonal antibodies: immunological characterization of E. coli and Shigella strains

Alkaline phosphatase capture test for the rapid identification of Escherichia coli and Shigella species based on a specific monoclonal antibody

A specific monoclonal antibody for Escherichia coli and Shigella sp. alkaline phosphatase was used in an immunocapture assay and allowed identification of E. coli either in culture isolates or directly in clinical specimens. The assay was easy and required only four steps: (i) alkaline phosphatase was released within 10 min by using a gentle lysis procedure, (ii) cell lysates were transferred to antibody-coated tubes for 45 min, (iii) p-nitrophenyl phosphate substrate was added, and (iv) alkaline phosphatase activity was detected in a microsample spectrophotometer at 410 nm. This immunocapture assay was highly specific: only one false-positive reaction was observed with a Klebsiella pneumoniae lysate among the 205 non-E. coli strains tested. The assay was sensitive, detecting 10(7) CFU/ml from culture isolates or 10(5) CFU/ml from urine specimens which had first been grown in phosphate-limiting medium for 2 h. At these bacterial concentrations, the percentages of detected E. coli were high: 91% for blood cultures, 95.4% for culture isolates, and 96.8% for urine specimens.

Isolation and characterization of monoclonal antibodies against alkaline phosphatase of Pseudomonas aeruginosa

Monoclonal antibodies against the alkaline phosphatase of Pseudomonas aeruginosa were produced from spleen cells of BALB/c mice primed with purified alkaline phosphatase of P. aeruginosa ATCC 10145 and SP20/Ag-14 myeloma cells. The eight stable clones established produced antibodies that reacted by enzyme-linked immunosorbent and indirect immunofluorescence assays with all bacterial strains of P. aeruginosa, including the 17 serotypes and two nontypable strains. Three of the clones cross-reacted only with some Pseudomonas species of the rRNA homology group I defined by N. J. Palleroni (in N. R. Krieg and J. G. Holt, ed., Bergey's Manual of Systematic Bacteriology, 8th ed., p. 140-218, 1984). The other clones also interacted with other species, including Pseudomonas acidovorans and Xanthomonas maltophilia. Because other species of the genera Aeromonas and Acinetobacter and species of the family Enterobacteriaceae were not detected by these monoclonal antibodies, the antibodies could be used as reagents for routine detection of P. aeruginosa in clinical specimens. Interactions of the antibodies with other Pseudomonas species such as P. fluorescens and P. stutzeri are not important, since these species are susceptible to the same antipseudomonal agents.

Immunological comparison of major outer membrane proteins from different strains of Escherichia coli

Rabbits were immunized with either the native trimer or the denatured monomer of OmpF porin of Escherichia coli. The specificity of the two antisera was checked by two different techniques. In liquid immunorecognition assays, the antisera detected the presence of common antigenic determinants at the surface of the monomer and trimer forms. A high response was observed between the two antisera and the native form of OmpF. Although cross-reactivity between the antiserum directed against the OmpF monomer and a denatured form of PhoE was obtained, this denatured porin was weakly recognized by the antiserum specific to the native protein. In immunoblotting experiments, though antiserum directed against the native porin detected the two forms of OmpF, antiserum specific to the monomer recognized only the denatured protein. These two antisera were used to check the immunological relationships of E. coli strains isolated from various contaminated waters. Proteins from several wild strains were compared to the immunoblotting patterns of E. coli reference strains. Porins from the majority of these wild strains were immunorelated to porins of the ML30 strain. In two strains, porins were related to the OmpC/OmpF of the K12 strain, and one strain contained a porin identical to the OmpF of the B strain. Thus, an immunological approach using polyclonal antibodies directed against a major outer membrane protein appears to be fruitful for an accurate classification of various E. coli strains. Moreover, the ecological habitat of a strain can also be investigated by this analysis.