- Volume 26, Issue 4, 1988

An athymic rat strain lacking functional T cells was used to assess the role of cell-mediated immunity (CMI) in host defence against renal infection. CMI was ruled out as a relevant host defence component, but when cyclosporin A (CsA) was administered to athymic animals, renal infection was exacerbated. CsA is thought to affect T lymphocyte function and, in the absence of a target cell, cellular defences in the athymic animal were not expected to be compromised by CsA. An effect on non-cellular defence mechanisms was therefore considered but our studies did not support this explanation–rather they indicated a depression of either cellular defences or of a specific cellular component. The present experiments have provided additional information on the relationship between CsA administration and the depression of host defence mechanisms but further studies will be necessary to identify the components affected.

Death rates have been determined for staphylococcal strains dried on cotton blanket material and stored at room temperature in the dark and in the light. Methicillin-resistant Staphylococcus aureus (MRSA) strains that produced a golden pigment and had a wide distribution within the hospital survived for longer periods than MRSA strains that produced little pigment and had a restricted local distribution. Death rates of methicillin-sensitive strains of S. aureus at day 7 were similar to those of the general epidemic MRSA strains, and there was no significant difference between the death rates at day 7 of the local epidemic MRSA strains and the coagulase-negative strains.

A dot-blot hybridisation assay for the detection of Campylobacter pylori was used to compare a 32P-labelled probe with two biotinylated probes and a sulphonated probe. The minimum amount of pure C. pylori DNA that could be detected by the 32P-labelled probe was 100 pg, which corresponded to 5 × 104 bacteria. A biotin-labelled DNA (biotin-DNA) probe together with the BluGeneTM detection system produced by Bethesda Research Laboratories (BRL), and a sulphonated probe and Chemiprobe detection system (Orgenics) gave similar levels of sensitivity; nylon membranes could be used with both these non-radioactive detection systems. However, a photobiotin-labelled DNA (photobiotin-DNA) probe and detection system produced by Biotechnology Research Enterprises S.A. (BRESA) gave optimum results only with nitrocellulose membranes, and was quantitatively 100 times less sensitive than the other types of probe. The detection systems for the biotin-DNA and photobiotin-DNA probes produced non-specific reactions with crude bacterial blots of heterologous organisms; these non-specific reactions could be removed by treating the dot blots with proteinase K, but not by treatment with RNAase. The sulphonated probe and detection system did not give any reaction with heterologous organism blots.

An association of the heat-labile antigens detected by the Lior serotyping scheme with ability to protect infant mice against gastrointestinal colonisation with Campylobacter jejuni has been established. Overall, 39 (57%) of 68 infant mice challenged with a heterologous strain of the same Lior serotype as the vaccine strain were protected, compared with 40 (85%) of 47 infants protected against a homologous challenge. In contrast, none of the infant mice challenged with a strain carrying the same heat-stable antigens (i.e., of the same Penner serotype as the vaccine strain) were protected.

A clinical isolate of Pseudomonas cepacia from a cystic fibrosis patient was examined for its ability to produce extracellular toxic material. The organism was grown to stationary phase in a defined medium and toxic material was isolated by ultrafiltration, ion-exchange chromatography on DEAE-Sephacel and gel-filtration chromatography on Sepharose 4B. It consisted of a surface carbohydrate antigen, lipopolysaccharide and protein, and had an LD50 (when injected intraperitoneally into mice) of 395 ±20 μg. The toxicity appeared to be associated with the lipopolysaccharide portion of the complex, because boiling for 15 min and exposure to proteolytic enzymes had no effect on toxicity. However, saponification destroyed the toxicity of the compound. Studies employing radial immunodiffusion with the sera of mice infected with this organism demonstrated production of the complex in vivo at levels approaching those sufficient to produce death. When sublethal amounts of this complex were placed in the lungs of specific-pathogen-free rats, the lung pathology observed after 12, 24, 36 and 48 h was extensive. However, antibody generated in rabbits against this material could protect mice against the complex, as well as against challenge by the homologous organism. These data indicate that extracellular toxic material produced by P. cepacia may be responsible for the lethality and lung tissue destruction normally associated with an active pneumonia caused by this organism.

Liver xanthine oxidase (XOD) and superoxide dismutase (SOD) activities were compared in mice during Salmonella typhimurium and Pseudomonas aeruginosa infections. We observed that XOD activity rose but SOD activity fell for the first 11 days after infection with smooth type S. typhimurium, coinciding with the period of bacterial growth in the liver. Rough type S. typhimurium did not establish an infection and mice inoculated with this strain showed no variation in enzyme activities. P. aeruginosa infection was mild but stimulated both XOD and SOD activities.

The substrates inositol, rhamnose, d-tartrate and m-tartrate used in fermentation tests with 338 cultures of Salmonella paratyphi B differentiated strains in some phage types to give information that could be used in epidemiological investigations. Xylose in Bitter’s medium, the fifth substrate by which 13 of a potential 32 biotypes were identified, differentiated few cultures with the negative character. The possession of a specific type of outer-membrane protein receptor for colicin M or bacteriophage ES18 and the particular type of ribosomal ribonucleic acid present, defined three groups among the phage-typed and biotyped cultures. The possibility that the serotype S. paratyphi B contains clones of different phylogenetic origin and the consequent implications for nomenclature are discussed.

The faecal microbial flora of two patients with food-related irritable bowel syndrome was examined while they were on a diet excluding symptom-provoking foods, and then on a diet including such a food. The patients reacted differently to the challenge diet but some changes in faecal output, flora and short chain fatty acid content were seen.

The addition of Congo red, Trypan blue or haemin to the growth medium allowed the differentiation of phase-I and variant strains of Bordetella pertussis. Phase-I strains produced red (CR+), blue or dark brown colonies on a modified cyclodextrin solid medium containing Congo red, Trypan blue or haemin, respectively, whereas variant (Vir− and phase IV) strains grew as pale (CR−) colonies. Spontaneous CR− variants were isolated and characterised and had a phenotype like that of Vir− or phenotypically modulated, C-mode strains in that they did not produce the haemolysin, haemagglutinin(s), histamine-sensitising factor (pertussis toxin), heat-labile toxin and two major envelope polypeptides associated with phase-I strains. Two such variants had reduced virulence for mice. CR+ strains, when grown on a high nicotinic acid medium to induce modulation, gave CR− colonies. Thus the CR+ phenotype is a characteristic of phase-I B. pertussis and its expression appears to be controlled in a manner similar to that of other phase I-related factors. CR− variants of B. parapertussis and B. bronchiseptica were also deficient in these factors. Four isolates of B. avium were CR−.

In-vitro culture of Haemophilus somnus in liquid or solid media supplemented with bovine blood or serum resulted in non-immune binding of immunoglobulin (Ig) by the organism. This binding was independent of the antigen-combining site of the Ig molecule, since binding of an IgG preparation specific for the hapten dinitrophenol was unaffected by the presence of the homologous antigen. Quantitative comparison of the binding of Ig fragments Fab and Fc demonstrated that the non-immune binding occurred in the Fc region of bovine IgG. The isotypes of Ig that became bound to H. somnus included both bovine IgG subclasses (IgG1 and IgG2), which were bound equally, and bovine IgM.