Enhanced resistance to Listeria monocytogenes in mice injected with either whole cells or fractions of the aerobic corynebacterium, Corynebacterium catarrhalis

Resistance of mice to Listeria monocytogenes was shown to be enhanced by pretreatment with either intact or delipidated whole cells of a new species of aerobic corynebacteria, designated as Corynebacterium catarrhalis, as well as with fractions isolated therefrom. Both whole cells and a particulate fraction (CBAp40) proved to be effective when given intravenously, whereas a water-soluble fraction (CBA-LS) was not. In contrast, CBA-LS, as well as CBAp40 and whole cells were found to be effective when given subcutaneously as far as they had previously been adsorbed onto a gel of either calcium phosphate or aluminum hydroxide. Furthermore, pretreatment of mice with either of the mineral gels in the absence of the products failed to confer protection on them to the challenge with L. monocytogenes. It is suggested that C. catarrhalis or products derived therefrom could be used as agents for enhancing resistance to infections of immuno-compromised individuals.     

Isolation of a plasmid from “canine” Staphylococcus epidermidis mediating constitutive resistance to macrolides and lincosamides

A small plasmid of 2.5 kB mediating constitutive resistance to macrolide-lincosamide-(ML)antibiotics could be detected in a “canine” Staphylococcus epidermidis-culture. This plasmid, designated as pSES 1, was identified by interspecies protoplast transformation into Staphylococcus aureus RN 4220. A detailed restriction map of pSES 1 could be constructed using the restriction endonucleases Acc I, Bcl I, Cfo I, Cla I, Hind III, Hinf I, Mbo I, Sst I and Taq I. This map allowed structural comparisons of pSES 1 with plasmids from “human” Staphylococcus- and Bacillus-species, also mediating macrolide-lincosamide resistance (ML^R). On the basis of its restriction map, pSES 1 proved to be similar to the plasmids pNE 131 from “human” S. epidermidis, pE 194 from “human” S. aureus and pIM 13 from B. subtilis.     

Specific binding of bovine, ovine, caprine and equine IgG subclasses to defined types of immunoglobulin receptors in gram-positive cocci

One hundred and twenty bacterial strains were tested for non-immune binding of radiolabelled bovine, ovine, caprine and equine immunoglobulins. Bacteria possessing previously defined IgG receptors interacted in a well defined manner with purified IgG subclass immunoglobulins. Human group C and G streptococci carrying IgG receptors type III were capable of binding all IgG subclasses in the four mammalian species studied. Protein A-containing staphylococci demonstrated a restricted specificity with binding of bovine IgG1, ovine IgG1, caprine IgG1 and IgG2 as well as equine IgG(ab). Group A streptococci which can bind human IgG did not show specific reactivity. A new type of binding unrelated to the regular Fc-mediated binding was observed with equine IgG(T).The differences in specificity for IgG subclasses suggest that structures with binding capacity to streptococcal type III Fc receptors are different from staphylococcal protein A reactive sites. Inhibition experiments performed with purified immunoglobulins showed that individual IgG subclasses differed greatly in their inhibiting capacity reflecting differences in avidity.The high avidity and the broad, unrestricted immunoglobulin G reactivity of streptococcal IgG receptor type III indicate that human group C and G streptococci may provide a valuable tool for solid phase absorption of immunoglobulins from several mammalian species.     

Escherichia coli EAST1 toxin toxicity of variants 17-2 and O 42

EAST1 (EnteroAggregative heat-Stable Toxin 1) is a 4.1 kDa toxin that was first detected in the enteroaggregative Escherichia coli (EAEC) strain 17-2 (O3:H2) isolated from the stools of a Chilean child with diarrhoea. Accordingly, EAST1 is thought to play a role in the pathogenicity of EAEC. The goal of this study was to obtain purified biologically active forms of two EAST1 variants (17-2 and O 42). Purified toxin samples were treated with protein disulfide isomerase (PDI) to ascertain the integrity of the disulfide bridges. Since EAST1 is often compared to STa (heat-Stable Toxin a), both purified EAST1 variants were tested for biological activity using the suckling mouse assay, the reference test for STa. A positive gut to body (G/B) weight ratio was not observed for any of the EAST1 preparations tested, although STa was active. Exposure of the purified toxins to T84 cell monolayers, an epithelial cell line derived from a human colon carcinoma, in modified Ussing flux chambers resulted in a rapidly attained and prolonged increase in short circuit current, a sensitive measure of net ion transport. Responses to 17-2 and O 42 variants were comparable in magnitude and inhibitable by bumetanide and DASU-02, indicating net anion secretion. The results demonstrate that EAST1 toxin stimulates anion secretion by T84 cell monolayers and it is sustained for the duration of toxin exposure.     

Developing a double-antigen sandwich ELISA for effective detection of human hepatitis B core antibody

A new double-antigen sandwich ELISA for detecting antibody against the human hepatitis B core antigen (anti-HBc) was developed, with recombinant HBc (rHBcAg) immobilized on the solid phase of the plate and a HRP–rHBcAg conjugation for detection. The rHBcAg was expressed in Escherichia coli and purified by a monoclonal antibody (against HBcAg) specific affinity chromatography. This sandwich ELISA could give a semi-quantitative measurement of anti-HBc concentration in the specimen and was 32–256-folds more sensitive than the competitive ELISA. Total of 942 clinical serum samples were tested in parallel by the sandwich ELISA and the commercially competitive ELISA kit. Overall agreement of 98.4% (927 of 942 cases) was obtained. Ten of 15 (67%) discordant specimens reactive by the sandwich assay but negative by the competitive ELISA resulted from the increased sensitivity of the sandwich assay, as other hepatitis B markers present indicated previously or currently being exposed to HBV.     

IS1245 RFLP-based genotyping study of Mycobacterium avium subsp. hominissuis isolates from pigs and humans

Mycobacterium avium subsp. hominissuis, ubiquitous environmental mycobacterium, is an opportunistic pathogen that is regularly isolated from pigs and humans in Slovenia. Genetic diversity of 114 isolates from pigs (n = 57) and humans (n = 57), identified by means of bacteriology, DNA–RNA hybridization techniques, IS901 PCR and IS1245 PCR, was investigated in this study, using IS1245 restriction fragment length polymorphism (RFLP) analysis.Identical IS1245 RFLP profiles were found in isolates from pigs, isolates from humans and isolates from both origins. The proportion of clustered isolates varied as it depended on the similarity level (100% and 75%) chosen for the cluster limits. Using IS1245 RFLP, it was possible to detect monoclonal, polyclonal and recent infections and to monitor the genetic variability of the strains from individual patients.Our findings indicate the environment as the source of infection for both pigs and humans. The questions about the possibility of intra- and inter-species transmission of infection remain to be answered.