- Volume 9, Issue 4, 1976

Twenty of 28 calves, 10-12 weeks of age when given intravenous injections of the galactan from Mycoplasma mycoides subsp. mycoides, showed transient apnoea, increased pulmonary arterial and decreased systemic arterial blood pressures, and increased packed-cell volume. Necropsy revealed haemorrhages associated with alveolar ducts and vessel walls, areas of pulmonary oedema, usually associated with the haemorrhages, dilated airways and, in some, capillary thrombosis. Animals that had shown changes in blood pressure and respiration in response to a dose of galactan did not react to a second dose an hour later. One goat tested died, four lambs were mildly affected and a cat and several rats and guinea-pigs did not respond.

It is suggested that the galactan released biogenic amines that produced the effects listed. Immunological mechanisms were discounted on the grounds that only a small amount of antigenic material was injected at the time the reaction occurred, and neither serological nor skin tests produced any evidence of prior sensitisation to the galactan or a similar substance.

A relationship between reactivity to the galactan and susceptibility to the natural disease has been suggested. This, together with the pulmonary oedema found in galactan-treated calves and in natural lesions of contagious bovine pleuropneumonia (CBPP), and the possibility that contraction of blood vessels could be an initiating cause of thrombosis indicates the role that galactan may play in the pathogenesis of CBPP.

Patients undergoing dental extractions were non-randomly allocated to three groups, one of which received no antibiotic, one benzylpenicillin followed by oral penicillin for 5 days, and the third intramuscular lincomycin followed by oral clindamycin. Dental extraction was performed at the beginning of the course of chemotherapy. Streptococci were isolated from the extracted teeth, from blood cultures collected before and immediately after dental extraction, and from sutures removed from the gums 5-7 days after the operation. The species of these organisms was determined, and their susceptibilities to penicillin, clindamycin, cephaloridine, erythromycin and tetracycline were assessed.

The majority of streptococci isolated from teeth belonged to the species Streptococcus sanguis, S. mitior, S. mutans and S. milleri. Occasional isolates of each of these organisms collected before the antibiotic could take effect were resistant to penicillin.

Three of these species, but not S. mutans, were the commonest streptococci to be isolated from the blood after dental extraction. Penicillin completely suppressed dental bacteriaemia under the conditions of our investigation, and lincomycin reduced the incidence by about 60 per cent.

The commonest streptococci from sutures were also S. sanguis, S. mitior, S. mutans and S. milleri; S. faecalis was also isolated, but only in patients who had received antibiotics. Among the non-faecalis organisms, penicillin resistance was significantly more frequent among isolates from patients given penicillin than from patients not given this antibiotic, and clindamycin resistance was significantly more frequent among isolates from patients given lincomycin and clindamycin than from patients not given these antibiotics.

Factors that may determine the variable resistance of urinary strains of Escherichia coli to the bactericidal activity of normal human serum have been analysed. No statistically significant difference was found in the amount of lipopolysaccharide (LPS) that could be extracted from serum-sensitive and serum-resistant strains by either the phenol-water or warm-saline techniques. The ratio of LPS O-side-chain sugars to core sugars was not found to be significantly greater in serum-resistant than in serum-sensitive strains. A sugar resembling D-glycero-D-mannoheptose was found in LPS from some of the strains; in one case the sugar was shown to be associated with the O-side-chain moiety. Lipopolysaccharides from all but two of the strains contained the E. coli Rl core structure.

No consistent difference was observed between serum-sensitive and serum-resistant strains in either the amount of acidic polysaccharide extracted or its red-cell agglutination-inhibiting activity; nor was a clear relationship found between sensitivity to serum and sensitivity to R-specific bacteriophages.

It is concluded that no one mechanism of serum resistance explains the response to serum of the E. coli strains examined in this study.

The effect on the faecal flora of adding wheat fibre to a controlled diet in four healthy volunteers for a 3-week period has been observed. No change in the concentration of the bacteria in the bacterial groups counted was found, although there was a slight increase in total output associated with increased faecal weight. The predominant organisms in all subjects were nonsporing anaerobes, but the dominant species in each subject was different and was unaffected by changing the diet. Similarly, the concentration of faecal β-glucuronidase detected in two subjects was unaltered and the concentration of clostridia able to dehydrogenate the steroid nucleus found in one subject was unaltered.

It is suggested that the faecal microflora is not primarily controlled by the presence of undigested food residues in the large bowel.

The effects of staphylococcal products as chemo-attractants for human blood neutrophils and monocytes and as inhibitors of locomotion of these cells were studied with bacterial cells, culture nitrates and isoelectrically focused fractions from culture filtrates of nine strains of Staphylococcus aureus. Little direct chemotactic activity of staphylococcal products for neutrophils was observed, although a chloroform-soluble extract of the whole organisms contained such activity. The major chemotactic effect of staphylococci for neutrophils was indirect, i.e., generated when the organisms or their products were incubated with plasma, perhaps due to activation of complement. In contrast, direct chemotactic activity for monocytes was found in a large number of staphylococcal fractions. Staphylococci also produced inhibitors of locomotion of both neutrophils and monocytes. Isoelectric focusing showed more fractions inhibitory for neutrophils than for monocytes. Some of the inhibitors could be identified. Staphylococcal α-toxin inhibited migration of both neutrophils and monocytes. Sphingomyelinase C (β toxin) inhibited migration of monocytes but not of neutrophils. Leucocidin-rich strains were strongly active as inhibitors of neutrophil locomotion but less so as inhibitors of monocyte locomotion.

Leucocyte-egested material was harvested after the quantitative in-vitro phagocytosis of Neisseria meningitidis by rabbit or mouse polymorphonuclear leucocytes. The egested material was injected subcutaneously into rabbits and followed 24 h later with an intravenous injection of what would by itself have been a non-lethal quantity of meningococcal endotoxin, or with an equivalent dose of endotoxin in the form of meningococcal cell-wall blebs. Of 32 rabbits treated in this manner, 12 developed disseminated intravascular coagulation and six of these 12 had renal cortical necrosis. The remainder exhibited less severe lesions resembling those of endotoxaemia. Rabbits were not sensitised to meningococcal endotoxin when materials egested from leucocytes containing Staphylococcus epidermidis were used. A description of the pathological findings in the rabbits is presented.

A genotypically non-fimbriate (Fim−) strain of Salmonella typhimurium and a genotypically fimbriate (Fim+) strain derived from it by spontaneous mutation were compared for pathogenicity in mice. The two strains caused similar numbers of infections and deaths in groups of mice challenged by intraperitoneal inoculation, and nearly similar numbers in groups challenged by inoculation on to the conjunctiva, but the Fim+ strain caused many more infections (plus 26%) and deaths (plus 40%) than the Fim− strain when the inoculation was by mouth.

Faecal cultures were made at intervals up to 120 days in the mice surviving after oral or conjunctival challenge and S. typhimurium was isolated more commonly from the animals challenged with the Fim+ strain (906 isolations from 384 animals infected out of 877 challenged) than from those challenged with the Fim− strain (614 isolations from 341 animals infected out of 877 challenged). The greater opportunity for faecal dissemination enjoyed by Fim+ bacteria may account for the preponderance of Fim+ over Fim− strains of S. typhimurium found in mammalian sources.

A serotyping scheme for Clostridium welchii (C. perfringens) type A employing 57 antisera has been used to investigate the epidemiology of 153 food-poisoning outbreaks and 32 cases of gas gangrene and other clinical infections. Respectively 65% and 59% of the isolates were typable, and in 55% of the food-poisoning outbreaks the causative serotypes were established. Isolation and reporting methods that would render the typing scheme of even greater epidemiological value are described.

The type-specific antigen was shown to reside in the capsule and to be lost from strains that had become rough. Development of roughness and its prevention are described.

A great range of antisera and an internationally acceptable serotyping scheme is expected after integration of this set with those developed independently in America and Japan.

The immunogenicity of Leptospira interrogans serotype canicola suspensions inactivated by various degrees of heat exposure was examined in hamsters. No differences between leptospires killed at 50°C and at 98°C were shown. After exposure to 121°C, suspensions retained their ability to protect against lethal infections but lost their ability to prevent leptospiruria. Tests with vaccines inactivated at or below 98°C showed that the doses required for complete protection varied with the interval between vaccination and challenge. Larger doses were required to prevent the development of leptospiruria than to prevent death.

Two main mechanisms of concentric ring formation in cultures of Proteus species are described. One of these is the classically accepted method, wherein rings are produced as the advance of the swarm stops and recommences. In the other, the ring is produced as a fold inside the colony. These are considered to be extremes of a spectrum of growth types, the common feature being that rings are formed by piling-up of growth, and this process is not always directly correlated with morphological change in the individual bacteria, or with cessation of advance of the swarm. The validity of the presently accepted theories of ring formation and swarming in general are thus called into question.

A micromethod of kaolin extraction of non-specific inhibitors from serum is described for the rubella Hi-antibody test. It has proved to be as reliable as, and technically easier to perform than, the conventional macromethod.