- Volume 10, Issue 3, 1977

To investigate the role that the known disaccharidase depression may play in the aetiology of infant gastroenteritis caused by Candida albicans, C. albicans and the rarely pathogenic, Saccharomyces cerevisiae were studied by three different methods. Both types of yeast significantly depressed the lactose-hydrolysis activity of β-galactosidase, and both depressed lactose hydrolysis in the ligated small intestine of infant rabbits, either in intact animals allowed to survive for 10 h, or in a physiological bath for 20 h. The depression of lactose activity was not temperature dependent; living and inactivated yeast preparations produced comparable degrees of depression of enzyme activity. It is concluded that the depression of lactose hydrolysis is not a virulence factor of C. albicans, but contributes to the often observed disaccharide intolerance associated with Candida gastroenteritis in infants.

Colonial type variation of gonococci is well known, but change from type 4 to type 1 is rare except in vivo.

By observing quantitatively subcultures from a new liquid medium it was possible to follow the day-to-day changes in the ratio of colonial types present. The results obtained showed that type 1 colonies could be derived from type 5 inocula even in unsupplemented media. In unsupplemented liquid medium, type 4 inocula did not revert to other types and indeed colonial type 4 appeared to be the final form of the organism before it died out. If, however, iron in the form of ferric citrate was added to the medium, reversion occurred and type 1 colonies rapidly came to predominate.

A method is described of determining the susceptibility of enterobacteria to four amino-glycosides by means of an antibiotic diffusion method. The results are expressed as the minimal inhibitory concentration (MIC) of antibiotic and were compared with those obtained by a method that involved titration in agar plates and the use of a multi-point in-oculator. A statistical analysis showed that the diffusion method gave accurate reproducible results.

The antibiotic can be incorporated into paper disks, paper strips or agar ditches and the calculation converting the measured zones of inhibition to MIC values is easily performed. The appropriate equation is derived from another-obtained from observations on a single strain of known sensitivity-describing the diffusion of the antibiotic from the reservoir.

An assay for the detection of Bruceila abortus is described. IgG from rabbit antisera against live brucellae or brucella extracts was chemically linked to cellulose to form a solid phase reagent capable of binding brucella antigens present in buffer solutions or serum. After washing away any unbound material the presence of bound antigen was revealed by incubation with radioactively-labelled anti-brucella antibodies.

The assay was capable of detecting less than 100 pg brucella antigen in a 20 μg sample. Experiments in which IgG of non-related specificity was used in place of anti-brucella IgG showed that the test was specific. Normal human serum had only a slight inhibitory effect but anti-brucella antibodies were strongly inhibitory if present in the test sample. The extent of this effect and its relationship to antibody titre was investigated in 12 sera from brucellosis patients.

With the API 20 E Enterobacteriaceae system of biochemical testing, a bio type, coded numerically, was determined for each of 574 strains of Escherichia coli isolated from patients with urinary tract infection. The serotypes of the strains were also determined.

Fifty-five different biotypes were identified, two accounting together for 42% of the strains examined and seven others each accounting for between 8.4 and 1.9%. There was little correlation between biotype and serotype.

Fifty pairs of strains were isolated from patients before treatment. In 43 the biotype and serotype of both strains of each pair were the same. In six pairs the biotypes, but not the serotypes, differed, the difference being limited to the results of the tests for lysine decarboxylase. The biotypes of the strains of the remaining pair differed widely although their serotypes were the same.

It is suggested that this method of biotyping offers a simple but accurate way of discriminating between recrudescent urinary tract infection caused by E. coli and that due to reinfection.

During a 3-year period, 771 rectal swabs were taken from abacteriuric school-children. Out of 709 E. coli strains, each isolated from one faecal specimen, 102 were found to be resistant to one or more antibacterial agents, and 607 to be fully sensitive. Another 204 resistant strains were found by selection for antibiotic resistance. The antibiotic-sensitive and the resistant strains were found to be two somewhat different populations, distinguished by a different distribution of O antigen types. Also, the Kl antigen was more common among the sensitive than among the resistant strains. Resistant strains that were not O typable were very seldom haemolytic.

A new technique based upon the inhibition of the peroxidase-labelled antibody staining (PLAS) has been used to type Herpesvirus hominis (HVH) antibodies in four groups of human sera taken from patients with one or both types of HVH infection and in mixtures of different proportions of type 1 and type 2 antisera. The results were compared with those of the microneutralisa-tion (MN) test and the indirect haemagglutination (IHA) inhibition test. The sensitivity and specificity of the three methods were identical for sera containing only one type of HVH antibody. The MN test was slightly more sensitive than the other tests for detecting small amounts of HVH-1 antibody mixed with large amounts of HVH-2 antibody. Nevertheless, the PLAS inhibition technique was far more rapid and it would seem a satisfactory alternative to the IHA inhibition test for HVH antibody typing.

Live cells and cell-free culture supernates of 50 strains of Aeromonas hydro-phila isolated from diarrhoeic and healthy human faeces, drinking water, sewage, the river Ganges and faeces from domestic animals caused accumulation of fluid in ligated ileal loops of adult rabbits. The amount of fluid produced was comparable to that of a toxigenic strain of Vibrio cholerae. Three of the strains gave positive reactions only after two passages in ileal loops of rabbits. Inocula of about 103 viable cells and 0-25 ml of culture supernate caused fluid accumulation in the loops. The enterotoxic factor was inactivated at 60°C for 20 min. and 65°C for 10 min., was precipitated with ammonium sulphate and was non-dialysable; these results indicate the protein nature of the enterotoxin. An inoculum of 40 µg of crude toxin caused as much fluid accumulation as larger inocula. The only histopathological change in the loops was depletion of mucus from the goblet cells.

Faeces voided by eight species of laboratory or feral rodents were cultured for campylobacters by means of selective methods. Campylobacters were isolated from bank voles and from rats, but not from rabbits, laboratory mice, hamsters, guinea-pigs, field mice or field voles. In routine biochemical tests isolates from bank voles resembled a type of Campylobacter fetus that causes infectious infertility in cattle; isolates from rats resembled Campylobacter coli associated with swine dysentery. Electrophoretograms of acid plus phenol soluble proteins revealed striking differences between isolates from rodents, C. fetus and C. coli. It is concluded that campylobacters are more widespread in rodents than hitherto realised, and that routine methods for differentiating campylobacters do not allow an adequate correlation with pathogenicity or habitat.

Culture filtrates and total water-soluble extracts (TWSE), including ultra-sonication products of Micropolyspora faeni were primarily fractionated by electrophoresis in polyacrylamide gels. Other separations included chromato-graphy with Con A-Separose and human immunoglobulins from sera that contained precipitins to farmer’s lung hay (FLH) antigen coupled to Sepharose 4B by the cyanogen-bromide method. Fractions were tested for their effects on the lung by the intranasal inoculation of non-immunised mice and of mice immunised with TWSE in Freund’s complete adjuvant to give precipitin-negative and precipitin-positive groups. Particulate antigens of M. faeni did not induce respiratory disease in non-immunised mice, but TWSE produced negligible, sporadic lesions. Precipitin-positive mice developed symptoms of extrinsic allergic alveolitis when challenged with particulate antigens consisting of living or dead spores and mycelium of M. faeni or with TWSE. Elements of both Type III (Arthus) and Type IV (cell-mediated) hypersensitivities were identified histologically. The allergenicity of spores and mycelium was almost nullified by de-fatting, and activity was retained solely in a serologically inert ethanol-ether extract. Fractionation of soluble antigens produced immuno-logically-acti ve extracts, only some of which induced clinical disease. Alveolitis-inducing glycoprotein antigens obtained from Con A-Sepharose by desorption with α-methyl-D-glucopyranoside precipitated in the C region on immuno-electrophoresis. A disease-provoking group of antigens precipitating in the A region was isolated by electrophoresis in agar after primary fractionation in polyacrylamide gel. Antigens desorbed both by 3.0m acetic acid and 6.0m guanidine-HCl from immunoadsorbent columns also precipitated in the A region, but only those desorbed by guanidine-HCl induced alveolitis.

Most fractions inducing disease in precipitin-positive mice also did so in precipitin-negative, immunised animals. The formation of large hyper-sensitivity granulomata, indicative of the occurrence of a Type IV cell-mediated response, followed the introduction of bentonite particles coated with reactive fractions into the lung. Mean diameters of the granulomata did not correlate directly with the degree of alveolitis induced by the fractions. Skin reactions were bimodal and showed early Type III and late Type IV histology.

Gonococci in pus appear in specific clusters in which they are surrounded by organelles and granules derived from the host cells in which they multiplied. These clusters have been named infectious units because (1) the cocci multiply within them, (2) the whole complex makes contact with epithelial cells, (3) the cocci in the units are not recognised by polymorphs as long as the coating of granules is dense enough, and (4) the cocci are probably protected against humoral defence mechanisms. During multiplication of bacteria in infectious units, soluble antigenic material is probably produced. No morphological evidence of multiplication of gonococci outside infectious units was observed in pus from patients with gonorrhoea. Attempts to reproduce typical infectious units in animal models have so far failed.

The identity of the surrounding granular coating was established morphologically and with appropriate sera labelled with 125 I and horseradish peroxidase. It is proposed that the mechanism of gonococcal pathogenicity is primarily based on the internal disorganisation of the regulatory mechanism of human macrophages. A sequence of events in the infection is discussed.

The anatomical changes observed in subcutaneously implanted plastic chambers in guinea-pigs infected with gonococci may be attributable to partial interference with the internal regulation of phagocytes. The effect of drugs on bacterial counts in the chamber cavity was studied. Under the influence of colchicine the number of colony-forming units increased 100 times within 8 h; vinblastine was without effect. Neither of these drugs had any effect on the growth of gonococci in vitro. In studies by immune electron microscopy with sera from patients with gonococcal septicaemia, IgG was shown to react strongly with the gonococcal surface, free endotoxin, ring structures (pits) liberated from the lipopolysaccharide backbone and with unspecified soluble antigenic material. The detection of pilar antibodies in these sera was rare.