Immunogical study of anti-beta-lactamase antibodies by acidimetric methods

Development of a sensitive and specific enzyme-linked immunosorbent assay for detecting and quantifying CMY-2 and SHV beta-lactamases

Polyclonal rabbit antibodies against SHV-1 and CMY-2 beta-lactamases were produced and characterized, and enzyme-linked immunosorbent assays (ELISAs) were developed. Immunoblots revealed that the anti-SHV-1 antibody recognized SHV-1 but did not recognize TEM-1, K-1, OXA-1, or any AmpC beta-lactamase tested. The anti-CMY-2 antibody detected Escherichia coli CMY-2, Enterobacter cloacae P99, Klebsiella pneumoniae ACT-1, and the AmpC beta-lactamases of Enterobacter aerogenes, Morganella morganii, and Citrobacter freundii. No cross-reactivity of the anti-CMY-2 antibody was seen against laboratory strains of E. coli possessing TEM-1, SHV-1, K-1, or OXA-1 beta-lactamases. Operating conditions for performing ELISAs were optimized. Both anti-CMY-2 and anti-SHV-1 antibodies detected picogram quantities of purified protein in ELISAs. The reactivity of the anti-CMY-2 antibody was tested against a number of AmpC beta-lactamases by assaying known quantities of purified enzymes in ELISAs (AmpC beta-lactamases of M. morganii, C. freundii, E. coli, and E. cloacae). As the homology to CMY-2 beta-lactamase decreased, the minimum level needed for detection increased (e.g., 94% homology recognized at 1 ng/ml and 71% homology recognized at 10 ng/ml). The ELISAs were used to assay unknown clinical isolates for AmpC and SHV beta-lactamases, and the results were confirmed with PCR amplification of bla(AmpC) and bla(SHV) genes. Overall, we found that our ELISAs were at least 95% sensitive and specific for detecting SHV and AmpC beta-lactamases. The ELISA format can facilitate the identification of AmpC and SHV beta-lactamases and can be used to quantify relative amounts of beta-lactamase enzymes in clinical and laboratory isolates.

Monoclonal antibodies to TEM-1 plasmid-mediated beta-lactamase

At least 28 plasmid-mediated beta-lactamases have been described in gram-negative bacteria. To assess the relationship among these enzymes, we produced and characterized 28 murine monoclonal antibodies to the TEM-1 plasmid-mediated beta-lactamase. Radial immunodiffusion identified 3 monoclonal antibodies as immunoglobulin M (IgM), 18 as subclass IgG1, 2 as IgG2a, and 5 as IgG2b. Using a newly described enzyme immunoassay, cross-reactivity of 16 of these monoclonal antibodies was tested against 24 plasmid-determined beta-lactamases. The 16 monoclonal antibodies cross-reacted with TEM-2 and TLE-1 and, to a certain extent, SHV-1. Different levels of cross-reactivity were also observed with OXA-3 (11 of 16), OXA-7 (8 of 16), OXA-1 (2 of 16), OXA-6 (2 of 16), and AER-1 (2 of 16). Six monoclonal antibodies demonstrated partial neutralization of beta-lactamase activity. This study suggests that common epitopes are shared by nine biochemically distinct plasmid-mediated beta-lactamases. On the basis of cross-reactivities with these monoclonal antibodies, we identified four epitopes on TEM-1, TEM-2, TLE-1, and SHV-1 beta-lactamases.

Monoclonal antibodies against species-specific cephalosporinase of Pseudomonas aeruginosa

Ten hybridomas which produced monoclonal antibodies against species-specific cephalosporinase of Pseudomonas aeruginosa were constructed by somatic cell fusion of SP-2/0 myeloma cells with spleen cells from hyperimmunized BALB/c mice and intraperitoneally injected into mice. Monoclonal antibodies were partially purified from ascites fluids. All ten antibodies thus prepared were IgG immunoglobulins. In a solid-phase immunoassay the antibodies gave positive reactions which could be prevented by the presence of free cephalosporinase. When the antibodies were precipitated with anti-(mouse IgG), the cephalosporinase activity was co-precipitated. Also, these antibodies were co-eluted with cephalosporinase activity in gel filtration. Nine of the monoclonal antibody preparations elevated the cephalosporinase activity by about 6-40% and only one inhibited it by about 50%. All the monoclonal antibodies were highly specific to P. aeruginosa cephalosporinase and showed no cross-reaction with nine cephalosporinases and four penicillinases of other gram-negative bacteria.

Characterization of eight beta-lactamases of Gram-negative bacteria

Eight kinds of beta-lactamases produced by gram-negative bacteria were characterized by the following properties: molecular weight, isoelectric point, pH optimum, molecular activity, immunochemical reactivity, and kinetic parameters with respect to twelve kinds of common beta-lactam antibiotics. These beta-lactamases included two types of penicillinases mediated by R plasmids and six kinds of species-specific cephalosporinases. To determine a reliable value of the kinetic parameter, Km, we introduced a continuous and acidimetric assay method of beta-lactamase activity with a pH stat.

Enzymatic and immunological characterization of a new cephalosporinase from Enterobacter aerogenes

A hospital strain of Enterobacter aerogenes (MULB 250) isolated from a urinary tract infection was found to be cephalosporin and ampicillin resistant and carbenicillin susceptible. The beta-lactamase produced by this strain was extracted and purified by means of affinity chromatography, using a cephalosporin C-bound Sepharose 4B column. The purified enzyme was tested for hydrolysis of penicillin and various cephalosporins. The K(m) value is 11.8 muM for benzyl penicillin and 130 muM for cephalosporin C. The isoelectric point of the enzyme is 9.3, and its molecular weight is 29,500 +/- 1,000. Rabbit antiserum obtained against this MULB 250 beta-lactamase showed no cross-reaction with other penicillinases or cephalosporinases in neutralization tests. Comparisons of results obtained with other beta-lactamases, particularly from Enterobacter cloacae P99, indicate that the Enterobacter MULB 250 enzyme presents a typical cephalosporinase profile. As far as we know, this type of enzyme is relatively rare.

[Immobilized antibodies: a possible technic for the epidemiological study of antibiotic resistant bacteria]

An antibody specific to a cephalosporinase responsible for the resistance of bacteria to cephalosporines has been immobilized on agarose beads by the iminocarbonate method. The resin thus obtained has been studied at a biospecific point of view. Its high thermostability is also demonstrated. This biospecific resin allows the performance of epidemiologic experiments of bacteria resistant to beta lactamines.