- Volume 15, Issue 1, 1982

Six serotypes were found among haemolytic streptococci of Lancefield-group G. Members of these types accounted for about one-third of the strains isolated from human infections and carriers in Nigeria. The type antigens were similar to the M-protein antigens of group-A streptococci in that they were associated with the ability of the streptococci to survive and multiply in fresh human blood unless specific antibody was present. It was also possible to demonstrate in these group-G streptococci a non-type-specific M-associated protein similar to that formed by M-positive strains of group-A streptococci.

The identity and motility of enterococci isolated as urinary pathogens were compared with those of strains from other sources. The majority of isolates from all sources proved to be Streptococcus faecalis or S. faecium but eight of 117 urinary strains and seven of 127 non-urinary strains belonged to a group intermediate between S. faecalis and S. faecium. Of the seven “intermediate” strains from non-urinary sources, four were motile. None of the urinary enterococci was motile. The results do not indicate that urinary enterococci are more likely to be motile than are non-urinary strains.

Intranasal inoculation of mice aged 1-6 days with Mount Elgon bat virus produced an acute brain infection and death of all the mice at 5-7 days after inoculation. Virus multiplied in the olfactory bulbs and spread to the midbrain and then hindbrain, reaching titres of 109-1010 plaque forming units/g of wet tissue. Fatal disease was prevented by administration of virus antibody after infection, which was then restricted to the olfactory bulbs. Antibody was ineffective when infection was established in the midbrain; it reduced infectivity by about 99% in olfactory bulbs but by only a small fraction in midbrain and hindbrain. The findings may reflect differences in virus maturation and spread, and the accessibility of virus antibody to the olfactory bulbs, midbrain and hindbrain.

Many strains of Ureaplasma urealyticum were inactivated, in the presence of complement, by a control antiserum prepared in guinea-pigs against the uninfected culture medium used to grow ureaplasmas. This mycoplasmacidal activity of the control serum, unlike that of the specific antisera prepared against the organisms themselves, was removed by treatment with dithiothreitol or by absorption with the horse-serum component of the medium, suggesting that the activity was due to an antibody of the IgM class acting on horse-serum proteins that had become associated with the surface of the ureaplasmas. The mycoplasmacidal activity in the specific ureaplasma antisera appeared to be due mainly to antibody of the IgG class. A similar complement-dependent mycoplasmacidal antibody to U. urealyticum, apparently active against serum components, was present in normal rabbit sera.

Three recently described methods for quantitative sampling of the bacterial flora of the vagina were evaluated and none proved satisfactory. In a third of the samples, paired swabs showed large differences between the two weights of vaginal secretion collected by this method, and the recovery rate of bacteria deliberately added to test swabs was unsatisfactorily low. A calibrated loop gave a wide variation in the amount of secretion collected, due to variations in density and viscosity of the secretion. When secretion was collected with a calibrated pipette, it was often difficult to expel the collected volume from the pipette for testing. A simple weight-based method was devised in which a loop was used to collect an undefined volume of secretion for weighing in a tube of transport medium before homogenisation and quantitative bacteriological testing. Initial assessment indicates this to be a satisfactory method for quantitative studies of the vaginal bacterial flora.

Alpha haemolysin, produced by Escherichia coli, grown in a chemically defined medium, was purified 19-fold and the endotoxin content reduced 2176-fold by ultrafiltration and glycerol-gradient ultracentrifugation. Immunodiffusion of purified α haemolysin (PH) against antiserum to crude haemolysin (CH) revealed only one precipitation line. PH was cytotoxic in nanogram amounts for mouse-fibro-blast 3T3 cells, and the cytotoxicity exhibited proportional dose-response and time-course kinetics. The cytotoxic and haemolytic activities of PH were neutralised by immunoglobulins to CH. A mutant, produced by treating the haemolytic wild type with mitomycin C, possessed all of the biochemical characteristics of the wild type with the exception that the extracellular products of the mutant were non-haemolytic and noncytotoxic.

Transfer of an Hly plasmid determining production of α haemolysin to a non-haemolytic strain of Escherichia coli increased the virulence of the strain for mice. Injections of non-toxic amounts of α haemolysin, phenylhydrazine, haemoglobin, iron or manganese salts simulated the effect of the Hly plasmid by stimulating bacterial growth. Active or passive immunisation against α haemolysin protected mice on challenge with haemolytic E. coli by inhibiting in-vivo proliferation of the strain. Protection was eliminated by administration of iron salts at the time of challenge. The Hly plasmid probably acts as a virulence factor by enabling haemolytic strains of E. coli to obtain iron for growth from the lysed erythrocytes of infected animals.

Stable small-colony variants of Proteus species were isolated and characterised. They differed from typical organisms in their morphology, biochemical properties and drug resistance. They were found most frequently in culture media of low osmolarity. Their growth rate was depressed at high concentrations of salts, which had only a small effect on typical organisms. This may be important in the routine isolation of Proteus spp. and in testing of disinfectants.

In studies with the adult-rabbit ileal-loop model, antibodies to the lipopolysaccharide somatic-antigen component of Vibrio cholerae gave passive protection against challenge with live V. cholerae. The antisomatic antibodies had no effect on bacterial proliferation and toxin production either in vivo or in vitro; after challenge, antibody-protected and non-protected rabbit ileal loops developed almost identical amounts of cholera toxin and numbers of V. cholerae. The protection could be correlated only with a 10-15-fold reduction in the number of V. cholerae adherent to the mucous membrane of the antibody-protected loops. The amount of cholera toxin in the two sets of loops ranged from 1600 to 3200 units. In contrast, when biologically active cholera toxin was prepared in vitro, the amount required to induce ileal-loop secretion was very large (25 600 units). These findings indicate that toxin production by adherent vibrios on the surface of the mucous membrane is an important factor in the pathogenesis of cholera.

The in-vitro adhesion of Vibrio cholerae to intestinal mucous membrane was studied in isolated adult-rabbit ileal loops. Antisomatic antiserum against V. cholerae Inaba could inhibit adhesion of three different strains of V. cholerae Inaba but had no effect on the adhesion of two different strains of enterotoxigenic NAG vibrios. The antiserum’s bacterial agglutinin titre was 320, its anti-Inaba lipopolysac-charide (LPS) titre was 16 000 and its anti-flagellar antibody titre was 3200. Conversely, anti-live V. cholerae Inaba antiserum absorbed with boiled cells of Inaba and devoid of antisomatic antibody, could not inhibit adhesion of the same three strains of V. cholerae Inaba. This antiserum had no anti-LPS or bacterial agglutinin activity, but its anti-flagellar antibody titre was 32 000. Thus, ability to inhibit adhesion of V. cholerae could be correlated only with antisomatic (anti-LPS) antibody activity. Antisomatic antiserum had no activity against ‘adhesin’, a V. cholerae surface antigen described by Freter. Conversely anti-live V. cholerae antiserum absorbed with boiled cells showed anti-adhesin activity even at a dilution of 1 in 200. LPS preparations from V. cholerae strain 569B Inaba could inhibit adhesion of two different Inaba strains to the intestinal mucous membrane. It is concluded that the somatic antigen plays a major role in the adhesion of V. cholerae to the intestinal mucous membrane.

Herpesvirus hominis type 1 (HSV-1) was isolated from fallopian-tube biopsies of two women who were using an intra-uterine contraceptive device; the strains were isolated on different dates and at different hospitals. Both the isolates were shown to be HSV-1 by restriction-enzyme analysis, polypeptide profiles and indirect immunofluorescence; the two isolates could not be distinguished by these tests, but the tests distinguished them from HSV-1 strain 71-15 and HSV-2 strain 333. The viruses were again isolated from samples of fallopiantube tissue stored in liquid nitrogen, and their polypeptide and restriction-enzyme profiles were the same as those of the initial isolates. Virus was not isolated from fallopian-tube samples obtained from other IUD patients undergoing surgery at the same two hospitals at the same time.

The fimbrial haemagglutinin (F-HA) of Bordetella pertussis grown on solid medium was extracted with 1m sodium acetate for 72 h at 20°C, and partially purified by Sephacryl S-300 gel chromatography. A pooled fraction with fimbrial haemagglutinating activity was shown to contain fimbriae of the expected morphology by electron microscopy. Chemical and biological assays showed that the F-HA fraction contained some heat-labile agglutinogen and lipopolysaccharide but no measurable lymphocytosis-promoting factor or heat-labile toxin. The F-HA fraction used as antigen in an enzyme-linked immunosorbent assay (ELISA) permitted the detection of antibodies in convalescent serum from a patient with whooping cough. The impurities, heat-labile agglutinogens and lipopolysaccharide, did not contribute to the ELISA activity. The method for preparation of the F-HA antigen is simple, reproducible and gives a high yield.

Antibody responses in human sera against Bordetella pertussis during natural infection were investigated by a microplate enzyme-linked immunosorbent assay (ELISA) with a purified fimbrial haemagglutinin preparation as antigen. Significant rises of specific IgG, IgM and IgA were demonstrated in paired sera. A secondary type of antibody response was found in most children and adults. In children, the type of response correlated with previous vaccination status; there was a primary response in unvaccinated children. A survey of antibodies in the general population showed low IgG titres in a small proportion of sera from the youngest healthy children. The titres and the number of individuals with measurable antibodies increased with age. In a limited study of the effect of vaccination, significant rises of titres were demonstrated after vaccination. The ELISA test was specific for antibodies against B. pertussis except that the test also seemed to measure antibody to B. parapertussis. A comparison between ELISA and the complement-fixation test showed a good correlation between the tests only in sera from children 1-12 years old.

The preliminary characterisation of an unusual gram-negative bacillus isolated from genital ulcers in Swaziland is reported. Like Haemophilus ducreyi, it is an oxidase positive, nitrate-reductase-positive gram-negative rod that forms streptobacillary chains in some circumstances; it was therefore called the “ducreyi-like bacterium” (DLB). Distinguishing features of DLB are production of α-haemolysis on horse-blood agar, stimulation of growth by a microaerophilic atmosphere and by a factor produced by Staphylococcus aureus, a strongly positive porphyrin test, and a remarkable ability to undergo autolysis. DLB has a guanine + cytosine value of c. 50 mole% but it cannot be classified, even at the genus level, until more taxonomic data are obtained.

The virulence of 17 isolates of Bordetella bronchiseptica from 13 pig herds was compared by intranasal infection of gnotobiotic piglets and LD50 tests on mice. Of 59 piglets given 8.1-10.5 log10 colony-forming units (cfu) of isolates from two herds with atrophic rhinitis (AR isolates) or isolates from six unaffected herds (non-AR isolates), 16 died of acute pneumonia; the survivors developed non-progressive turbinate hypoplasia and chronic pneumonia. Infection of 11 piglets with c. 3.0 log10 cfu of three AR isolates or three non-AR isolates caused turbinate hypoplasia, but only slight pneumonia and no deaths. There were no significant differences between the virulence of AR and non-AR isolates in piglets. In LD50 tests in mice, there were no significant differences between the results from six AR isolates and six non-AR isolates, or from toxin prepared from two AR isolates and one non-AR isolate. It was concluded that the virulence of AR and non-AR isolates was fairly uniform, and that other factors must be responsible for the occurrence of progressive lesions of atrophic rhinitis in some but not all infected herds.