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[Use of the toxin-binding inhibition test for estimation of tetanus antitoxin in serum].

The usefulness of the toxin binding inhibition test (ToBI) for the titration of tetanus antibody in human sera was assessed. Sera from 80 healthy people with different vaccination histories that had been previously tested by the in vivo toxin neutralization (TN) test were retested by the ToBI test. The lowest tetanus antibody titre which could be detected by using 0.1 Lf/ml tetanus toxin was 0.01 IU/ml. Comparison between the estimates obtained by the ToBI test and those obtained by the TN test (r = 0.93 and r = 0.7 for titration low titre sera) showed good correlation. No overestimation of antibody content was seen in titrating low titre sera by the ToBI test. It is concluded that the ToBI-test is a reliable alternative to toxin neutralization test in mice.

Adult↗

Neutralizing antibodies to pertussis toxin in whooping cough.

The development and duration of neutralizing antibodies (antitoxin) to pertussis toxin were studied in 38 patients with culture-verified infections due to Bordetella pertussis and one patient with infection due to Bordetella parapertussis. An in vitro neutralization test in microplate culture of Chinese hamster ovary cells was used. An antitoxin response was recorded in 36 patients, the exceptions being two patients treated early with erythromycin (one of whom developed clinical pertussis two years later) and the patient with infection due to B. parapertussis. A long-term follow-up for several months to several years after disease showed maintenance of high antitoxin levels. These results are in accordance with the hypothesis that antibodies to pertussis toxin mediate long-term immunity to whooping cough.

Adult↗

Use of automated sequencing of polymerase chain reaction-generated amplicons to identify three types of cholera toxin subunit B in Vibrio cholerae O1 strains.

Cholera toxin is the principal factor causing the profuse intestinal fluid secretion that is characteristic of cholera. The DNA sequences of the cholera toxin subunit B structural genes from 45 Vibrio cholerae O1 strains isolated in 29 countries over a period of 70 years were determined by automated DNA sequencing of polymerase chain reaction-generated amplicons. Three types of cholera toxin B subunit gene (ctxB) were identified. Genotype 1 was found in strains of classical biotype worldwide and El Tor biotype strains associated with the U.S. Gulf Coast, genotype 2 was found in El Tor biotype strains from Australia, and genotype 3 was found in El Tor biotype strains from the seventh pandemic and the recent Latin American epidemic. All base changes correspond to an amino acid substitution in the B subunit of the cholera toxin. Heterogenicity in the B subunit could have implications for vaccine development and diagnostic tests for cholera toxin and antitoxin. We conclude that this technology provides timely and potentially useful epidemiological information.

Africa↗

Monoclonal antibodies as probes of tetanus toxin structure and function.

Monoclonal antibodies specific for fragment B, fragment C, and light chain of tetanus toxin were prepared by fusion of P3X63Ag8 BALB/c myeloma cells with spleen cells from BALB/c mice immunized with tetanus toxoid or fragment B. Hybridoma colonies were assayed for antibody production by an enzyme-linked immunosorbent assay. Fourteen positive clones were identified, cloned by limiting dilution, and injected intraperitoneally into mice to obtain ascites fluids. Thirteen of the monoclonal antibodies were of the immunoglobulin G1 subclass and one was immunoglobulin G2. Two of the antibodies were directed against sites on fragment C, nine were directed against the light chain, and three were directed against the portion of fragment B which does not comprise the light chain of tetanus toxin. At least one antibody in each group exhibited significant toxin neutralization activity. However, only one of these neutralizing antibodies strongly inhibited the binding of 125I-tetanus toxin to ganglioside-coated plates. These data indicate that interference with receptor recognition is not the only means of neutralizing tetanus toxin. Monoclonal antitoxins as potential therapeutic and prophylactic reagents are discussed.

Animals↗

Diphtheria corneal ulcers.

An adult with cutaneous diphtheria was admitted with bilateral purulent conjunctivitis and a perforated eye with most of the cornea absent due to Corynebacterium diphtheriae. At the time of admission of grayish patch of corneal epithelium was noted in the other eye, and in the next 24 hours there developed a large corneal perforation with dissolution of much of the cornea. Involvement of the external eye in diphtheria is rare but it is usually associated with cutaneous forms of the disease. Cutaneous diphtheria has been prominent in several recent outbreaks in the United States. Prompt recognition, early antibiotic treatment, and neutralization of the toxin with antitoxin are required for successful therapy.

Cephalexin↗

Bacterial death comes full circle: targeting plasmid replication in drug-resistant bacteria.

It is now common for bacterial infections to resist the preferred antibiotic treatment. In particular, hospital-acquired infections that are refractory to multiple antibiotics and ultimately result in death of the patient are prevalent. Many of the bacteria causing these infections have become resistant to antibiotics through the process of lateral gene transfer, with the newly acquired genes encoding a variety of resistance-mediating proteins. These foreign genes often enter the bacteria on plasmids, which are small, circular, extrachromosomal pieces of DNA. This plasmid-encoded resistance has been observed for virtually all classes of antibiotics and in a wide variety of Gram-positive and Gram-negative organisms; many antibiotics are no longer effective due to such plasmid-encoded resistance. The systematic removal of these resistance-mediating plasmids from the bacteria would re-sensitize bacteria to standard antibiotics. As such, plasmids offer novel targets that have heretofore been unexploited clinically. This Perspective details the role of plasmids in multi-drug resistant bacteria, the mechanisms used by plasmids to control their replication, and the potential for small molecules to disrupt plasmid replication and re-sensitize bacteria to antibiotics. An emphasis is placed on plasmid replication that is mediated by small counter-transcript RNAs, and the "plasmid addiction" systems that employ toxins and antitoxins.

Bacteria↗

STAPHYLOCOCCAL ALPHA-HEMOLYSIN: DETECTION ON THE ERYTHROCYTE MEMBRANE BY IMMUNOFLUORESCENCE.

Purified staphylococcal alpha-hemolysin (but not the toxoid) was demonstrated on the surface of rabbit and human erythrocytes by immunofluorescence. This occurred during the period of maximal hemolysis and was a transient event. These findings have been analyzed in relation to previous data on the kinetics of leakage of both small and complex molecular constituents of the erythrocyte.

Animals↗

Serum antibody to Pseudomonas aeruginosa exotoxin measured by a passive hemagglutination assay.

A passive hemagglutination (PHA) assay for antibody to Pseudomonas aeruginosa exotoxin is described which utilizes chromic chloride-treated ovine erythrocytes coated with purified toxin. PHA antitoxin titers correlated well with those obtained by a cytotoxicity neutralization assay (r = 0.91, P less than 0.001), whereas the PHA assay was four to eight times as sensitive. The mean serum PHA titer of 16 patients convalescing from recent pseudomonas infections (log2 = 9.4 +/- 3.9) was significantly higher (P less than 0.001) than that of 17 healthy controls (2,7 +/- 2.6), and fourfold or greater rises were demonstrated in 5 of 7 patients examined sequentially. The lower levels of PHA antibody in sera from 11 of 17 controls suggested the acquisition of antitoxin secondary to asymptomatic infection.

Animals↗