- Volume 8, Issue 3, 1975

Several in vitro reactions between a strain of M. hominis (no. 4195) and homologous antiserum have been delineated and compared. One complement-dependent and four complement-independent activities of antibody have been studied. The complement-dependent activity was mycoplasmacidal and was inhibited by the presence of arginine in the test medium. The complement-independent antibody-mediated reactions were not mycoplasmacidal and were four in number: (a) agglutination, which was manifested in buffered saline after incubation for 24–48 h at 36°C, and in which the end-points were dependent upon the concentration of antigen; (b) metabolic inhibition, in which antiserum added to liquid growth medium produced slowing of the rate at which the pH rises during growth; (c) agglutination during growth, which occurred in liquid growth medium after the addition of antiserum and coincided with, but generally preceded, metabolic inhibition; and (d) inhibition of multiplication in which high concentrations of antiserum led to inhibition of multiplication or metabolic activity, with persistence of viable mycoplasmas, under otherwise favourable conditions of growth. The end-points for each of the above methods of detecting antibody are not identical.

An in-vitro test that demonstrates adhesion of K88-positive Escherichia coli to brush borders prepared from the small intestine of the pig is described. K88-positive E. coli adhered to the brush borders from some pigs (“positive” pigs) but not others (“negative” pigs). The sires of the pigs tested could be placed into two groups, namely, those that sired only “positive” piglets, and those that sired a mixture of “positive” and “negative” piglets. The incidence of the two phenotypes in litters indicated that “positive” and “negative” piglets arose as a result of simple Mendelian inheritance. It is suggested that “negative” pigs could be bred and that they might have a natural resistance to neonatal infection with K88-positive E. coli.

Electron-microscope studies are reported in which gonococci grown in cultures are compared with those present in urethral exudates. Whereas naturally occurring cells presented a smooth appearance with parallel cell layers, cultured cells were rough and their surface layers appeared to be disorganised. Three different types of pili were observed in cultures; the most common type seemed to be a product of unfavourable growth conditions. The number of piliate cells in pus was variable but always much lower than the number of non-piliate cells found. A study of free endotoxin present in cultures was made and its fine structure is described.

Further observations suggest that although the majority of gonococci are killed after phagocytosis, others survive and multiply—giving rise to clusters of gonococci within remnants of phagocytes. It is suggested that these coated clusters are infectious units.

We have postulated that bacteria able to dehydrogenate the bile-acid nucleus are important in the aetiology of cancer of the colon. In this paper we report on screening for the ability to carry out two such reactions. The relevant enzymes are produced by a high proportion of strains of Clostridium para-putrificum, C. tertium and C. indolis, and by small numbers of strains in other clostridial species, but not by organisms of the other genera tested. Strains able to dehydrogenate the bile-acid nucleus represent a high proportion of the lecithinase-negative clostridia isolated from faeces of people living in Britain but a low proportion of those from people living in Uganda or Hong Kong.

Production of β-lactamase by 15 strains of Haemophilus influenzae has been investigated. All the strains produce a constitutive β-lactamase, which readily hydrolyses penicillin G, ampicillin, and cephaloridine. The β-lactamase produced by these strains is indistinguishable from the type-IIIa enzyme commonly found in strains of Escherichia coli. The β-lactamase gene has been transferred from the enzyme-producing strains of Haemophilus to strains of H. parainfluenzae and a strain of E. coli.

A simple method is described for testing milk specimens from nursing mothers for the presence of RNA-dependent DNA-polymerase activity.

Positive results were obtained in five of 137 women (3.6%) without a family history of breast cancer, and in six of 31 women (19.3 %) with a family history of breast cancer.

A technique for measuring glucose utilisation by mycoplasmas, in which the disappear-ance of glucose is monitored by the glucose-oxidase method, is proposed as an alternative to the pH method. For maximum reliability the number of organisms in the test suspension must exceed a critical minimum value. Differences in efficiency of glucose utilisation were demonstrated between species of Mycoplasma and Acholeplasma.

In a 4-year study, 22 strains of group-F streptococci were isolated from children and puerperal women. All were isolated in mixed culture but were associated with sepsis or other pathological conditions. It appears that this organism may be an opportunistic pathogen and that its habitats include the gastrointestinal tract and the vagina as well as the throat.