- Volume 21, Issue 4, 1986

The ELISA technique was shown to be group-specific for the detection of IgM antibodies against coxsackie B viruses, and probably against a wider range of enteroviruses. No evidence was obtained that recent coxsackie B-virus infection predisposes to myocardial infarction.

The ability of several strains of Clostridium difficile to grow and to produce toxins A and B in complex and defined culture media has been studied with special reference to the amino-acid composition of the medium. The production of these toxins varied with the strain used and with the composition of the growth medium. Toxin A production was not inextricably linked to production of toxin B since conditions were found in which only one or other toxin was produced.

To investigate the importance of the normal gut flora in preventing the establishment of Clostridium difficile in vivo we have developed an in-vitro test system based on growth in faecal emulsions. Growth of C. difficile and cytotoxin production are inhibited in faecal emulsions from healthy adults, but not in sterilised emulsions; the importance of viable bacteria in the inhibitory system is evident. Generally, faecal emulsions derived from infants, children and geriatric patients were less inhibitory than those from healthy adults. Those from bottle-fed infants were significantly less inhibitory than those from breast-fed infants. Decreased levels of cytotoxin in the latter group were attributed to the acidic pH of the stools. With the different patient groups studied, faecal samples not inhibitory to C. difficile in vitro were obtained from 21% of patients with antibiotic-associated diarrhoea, 33% of those taking antibiotics but who did not have diarrhoea, 18·7% of those with diarrhoea unassociated with antibiotics, and 79% of those with C. difficile-mediated diarrhoea. In some cases inhibition was due to low faecal pH, as in some infants, and in others to other filterable substances. The degree of inhibition could not be linked to specific volatile fatty acids or enzymes.

A virulent fish strain of Aeromonas hydrophila was inoculated intramuscularly into laboratory mice (B10.G strain). Histological, biochemical and haematological changes during the first 36 h of the infection were measured. Inoculation led to septicaemia, tissue damage, endotoxic shock and death. Histological examination revealed: (1) severe muscle necrosis at the injection site; (2) oedema, haemorrhage and neutrophil infiltration of the lung; and (3) focal parenchymal necrosis in the liver. Significant increases in aspartate aminotransferase, alanine aminotransferase, intestinal bilirubin and blood urea nitrogen were noted in blood and intestinal samples; decreased plasma glucose and haematological changes were also recorded. Ketones, increased protein, glucose, bilirubin and blood were detected in the urine. Endotoxaemia was demonstrated as early as 2 h after inoculation and persisted for more than 36 h. The changes resembled those described for certain other experimental infections in laboratory animals. Our results suggest that endotoxin contributed to the pathogenesis of aeromonas infection in mice.

A soluble haemagglutinin has been identified in cell-free culture supernates of human diarrhoeal isolates of Aeromonas sobria, A. hydrophila and A. caviae. It was oligomeric; a major peak of haemagglutinating activity had an apparent mol. wt of 780000 but there was haemagglutinating activity throughout the mol. wt range <40000— > 106. Human group O, A and B, horse, rabbit, chicken and rat erythrocytes, but not those of sheep and cow, were agglutinated by the soluble haemagglutinin, in contrast to the cell-bound agglutinin. Agglutination was inhibited by fetuin, a complex glycoprotein, but not by simple sugars. The haemagglutinating activity was not affected by 0·5 m NaCl, dithiothreitol or the presence or absence of Ca++. It was unrelated to the haemolytic, enterotoxigenic and proteolytic activities present in cell-free extracts of A. sobria. All A. sobria, 73% of A. hydrophila and 68% of A. caviae strains tested produced this soluble haemagglutinin. A. caviae does not appear to be an enteric pathogen, therefore this soluble haemagglutinin alone is unlikely to be a virulence factor in Aeromonas spp.

Two hundred and eighty-seven coliform bacteria were isolated from 116 rectal swabs or faecal specimens obtained from 113 patients. By means of plasmid analysis and resistance transfer (R-transfer) Escherichia coli was found to differ from other enteric genera in plasmid distribution. Criteria were proposed that enabled in-vivo "R-transfer potential" and in-vivo "R-transfer rate" to be calculated. From each of 22 of the 113 patients numerous coliforms were isolated, of which at least one per patient contained one or more self-transmissible R-plasmids potentially transferable to 43 other coliforms. Evidence indicated that R-plasmid transfer had occurred in vivo on two of the 43 potential occasions. These results are discussed in the context of plasmid ecology in the human host.

The locus responsible for mucoid colony morphology in five independent clinical isolates of Pseudomonas aeruginosa from cystic fibrosis patients have been transferred by means of pM060-mediated conjugation to the genetically characterised strain P. aeruginosa PAO. Genetic mapping has shown that in all five strains the locus is on the chromosome between 89’ and 94’, although it is not possible to say that the same locus is involved in each case. The way is now open for a more detailed genetic analysis of the loci responsible for mucoid colony morphology.

Biochemically inactive, non-motile strains of Escherichia coli of the group formerly known as Alkalescens-Dispar (AD) and of known AD serogroups were analysed for biotype, resistotype, type-1 fimbriation, P fimbriation and haemolysin production. All strains of AD serogroups O1 and O2 examined were P-fimbriate and of closely related bio-resistotypes, suggesting that they may be representatives of two E. coli P-fimbriate clones, members of which have not infrequently been isolated from infected urine.

Passive haemagglutination (PHA) and Staphylococcus aureus protein A-antibody-mediated haemagglutination (SAPA-AMHA) were used to analyse the cross-reactions of rabbit antisera against four stains of Bacteroides fragilis. There was cross-reactivity between all the strains tested but strain-specific reactions were obtained with three strains. Two to 32-fold higher antibody titres were obtained with SAPA-AMHA than with PHA. The antigen concentration required in inhibition assays was up to 32-fold higher for PHA than for SAPA-AMHA. The latter is a simple and superior alternative to PHA for such studies.

A series of 2027 genital tract specimens was cultured for Haemophilus species on non-selective chocolate agar and on a selective medium (Choc-VBCA). The latter gave a significantly higher isolation rate. H. influenzae was isolated from 27 specimens and H. parainfluenzae from 81 specimens by use of the selective medium. The biotype distribution of both species was compared with that of an equal number of isolates from respiratory-tract secretions. H. influenzae biotypes II and IV were found to predominate in genital strains and biotypes II and III in respiratory strains. With H. parainfluenzae, biotype II was most frequent in both sites. Two new biotypes of H. parainfluenzae (VI and VII) are described. The significance of the use of selective media and of biotype distribution are discussed.

Rabbit serum hyperimmune to Leptospira interrogans var icterohaemorrhagiae serovar icterohaemorrhagiae, reference strain RGA was conjugated to the chemiluminescent label ABEI (6-[N-(4-aminobutyl)-N-ethyl amino]-2,3-dihydro-phthalazine-1,4-dione) in the presence of the coupling agent, EDC (1-ethyl-3(3-dimethyl amino-propyl)-carbodiimide HCl). The luminescent conjugate was incubated with homologous and heterologous antigens. The results indicate that chemiluminescence may provide an accurate and rapid method of detecting leptospires in biological fluids.