- Volume 11, Issue 2, 1978

A bovine enterovirus (serotype VG-5-27) was grown in BHK 21 cells and purified using gel filtration and sedimentation procedures. Infective particles sedimented at 165s and the empty capsids or procapsids at 75s. Proteins extracted from each type of component were separated by polyacrylamide-gel electrophoresis. The infective component yielded four polypeptides of molecular weight 34,000, 28,000, 26,000 and 9,000 and were present in molar ratios of 1:1:1:0.5, respectively. Three polypeptides were extracted from the procapsid. These have molecular weights 37,000, 34,000 and 26,000 and were present in molar ratios of 1:1:1, respectively. We interpret these results as indicating that the small polypeptide of the virus particle may have a specific location in the virus in relation to the three major structural proteins.

Evidence is presented that a lethal toxin is produced by P. aeruginosa growing in the burned skin of experimental mice. After injection of approximately 100 P. aeruginosa cells into the burned skin there was a rapid proliferation of organisms at the site of inoculation. When the organisms in the burned skin tissue reached a critical concentration, there was generalised toxaemia with subsequent mortality; the process was not reversible at this stage, even by reducing substantially the numbers of infecting organisms. However, when the reduction was accompanied by administration of rabbit serum prepared against filter-sterilised extracts of infected burned tissues, approximately 40 % of the animals survived for at least 96 h. The data suggests that the antiserum afforded protection by inactivating a toxin produced by the organisms growing in the infected burned tissues rather than by further reducing the numbers of infecting organisms.

A series of 71 spontaneous temperature-sensitive mutants of vesicular stomatitis virus (type indiana) have been isolated in chick embryo cells (Flamand, 1970). In addition, 175 induced mutants have been isolated from a different wild-type strain propagated in BHK 21 cells (Pringle 1970b). These mutants have been classified into complementation groups independently.

Reciprocal complementation experiments are now described which establish the genetic homologies of these mutants. The results obtained in the two systems are in good agreement, despite differences in experimental procedure, restrictive temperature, wild-type strain and host cell. It can be concluded that complementation groups I–IV in the Glasgow classification correspond to the groups represented by ts 4, ts 52, ts 23 and ts 100 in the Orsay system. Mutant ts 45 (Orsay) belongs to a fifth group not represented among the Glasgow mutants.

Forty-four strains of non-haemolytic streptococci, from a variety of sites,. that required C02 for aerobic growth were identified as Streptococcus milled. Of these strains, 40 (90%) possessed the Lancefield group-F antigen, the remainder being non-groupable with antisera to the group antigens A, C, F andG.

On staining adenovirus-infected cells with phenanthrenequinone and with copper phthalocyanin-neutral red, characteristic structures in the form of rings and rosettes were observed. These structures could also be visualized by phase-contrast microscopy and by fluorescent antibody staining with adenovirus P antiserum. The cytochemical staining could be blocked by pre-treatment of the fixed cells with benzil, and the result suggested that the rings and rosettes were the sites of accumulation of arginine-rich basic proteins.

The adhesion of a bovine and a human isolate of Escherichia coli to epithelial cells from the teat and lactiferous sinuses of the udder was examined. Adhesion was detected with bacterial suspensions that produced mannose-sensitive agglutination of guinea-pig red cells. Adhesion to epithelial cells could be inhibited by mannose and the degree of adhesion occurring with a suspension correlated with its haemagglutinating activity. This demonstrated that fimbriae were responsible for the adhesion. The observation that whole milk inhibited attachment of E. coli to cells in vitro indicates that such attachment may not occur in vivo in the lactating cow.

Temperature-sensitive mutants of adenovirus type 5 have been isolated from virus stocks mutagenized by nitrous acid, hydroxylamine and 5-bromodeoxyuridine. The frequency of such mutants in the surviving fractions of nitrous acid and hydroxylamine-treated stocks was 8.4 and 9.6%, respectively, while it was around 0.55% in stocks of virus grown in 5-bromodeoxyuridine. Most of the mutants tested so far appear to be relatively stable and show little evidence of excessive leakiness or back mutation, and will be suitable for genetic analysis. Preliminary experiments show good complementation between four of these mutants, and they have been assigned to four complementation groups.

The effects of 5-day courses of orally administered cephalexin, clindamycin and erythromycin on the Gram-negative, aerobic faecal flora of healthy adults were examined. The concentration of cephalexin reached in the intestine was high enough to cause the emergence of resistant Gram-negative bacteria; organisms belonging to the genera Enterobacter, Citrobacter and Pseudomonas increased to easily detectable levels. The faecal concentration of erythromycin was high and caused a severe reduction of the coliform flora. Clindamycin administration resulted in a considerable increase in the coliform count; the increase in the proportion of klebsiellae was especially marked.

The molecular weight of the influenza virus genome was estimated by sucrose density-gradient centrifugation, analytical centrifugation and polyacrylamide gel electrophoresis. The results indicated that the virus contained at least six species of RNA of total molecular weight approximately 3.9×106.

The faecal flora of 29 healthy infants and young children was compared with that of 49 children of similar age and socio-ecomonic status with acute gastroenteritis. In the healthy children the most common organisms in the faeces were bifidobacteria, veillonellae, enterobacteria and enterococci with anaerobes outnumbering aerobes. Most members of the normal faecal flora were present in the diarrhoeal stools, but anaerobes were significantly reduced in number and enterobacteria were significantly increased, thereby altering the ratio of anaerobes to aerobes. The alterations in the flora were not related to the nature of the aetiological agent or to the severity of the diarrhoea. The changes appeared to be a direct result of the altered colonic environment produced by the diarrhoeal state. In 13 of the 28 patients from whom bacterial pathogens were isolated, the pathogens were the predominant faecal organisms.

The virulence of a protease-producing strain of Pseudomonas aeruginosa was compared with that of mutants that had lost the ability to produce proteases and other extracellular enzymes. Lethal infections were produced by inoculating mice intraperitoneally with bacteria in mucin, or by inoculating mice intraperitoneally or intravenously with bacteria 4 days after treatment with cyclophosphamide, 200 mg per kg body weight. No significant difference in virulence between the wild-type parent strain and some of its protease-deficient mutants was found. Histopathological examination of different organs in the cyclophosphamide-treated and infected mice showed striking fatty infiltration and focal necrosis of liver, multiple necrotic foci in the spleen and haemorrhagic cystitis with necrosis. The cystitis was produced by cyclophosphamide alone but was aggravated by the infection. In conclusion, no correlation between the production of protease in broth culture and the ability to produce lethal septicaemia in mice was found, and extracellular proteases probably did not contribute to the virulence of P. aeruginosa. However, the histopathological changes in the liver suggested a role for exotoxin A in systemic infections.

When plant cells die as a result of virus infection, the activity of oxidases, particularly polyphenoloxidases and peroxidases, is altered (Martin, 1958; Farkas, Kiraly & Solymosy, 1960; Farkas et al. 1964). The in vitro activity of these two enzyme groups in extracts of infected leaves kept at 20° shows changes that are correlated with the time of appearance and number of local lesions. With most virus/host combinations, the oxidase concentration is merely increased (Van Kammen & Brouwer, 1964; Novacky & Hampton, 1968; Cabanne, Scalla & Martin, 1968), with some there is a change in the relative amount of different isozymes (Bates & Chant, 1970), and with others there is possibly the appearance of new peroxidases (Farkas & Stahmann, 1966) or of a new phenolase (John & Weintraub, 1967). Different workers have interpreted these facts to explain the formation of necrosis and virus localization in different ways (Farkas et al. 1960; Parish, Zaitlin & Siegel, 1965; Suseno & Hampton, 1966).

Firm agar media containing 3-6% agar-three times the concentration of agar in routine media-inhibited the swarming of 167 strains of Proteus mirabilis and 14 strains of Proteus vulgaris incubated in air. The swarming of P. mirabilis was also prevented by firm agar when incubation was anaerobic, provided that a negative pressure of 600-650 mm of mercury was generated in the removal of air from jars before admitting hydrogen for the palladium-catalysed removal of residua] traces of oxygen. When a negative pressure of only 300 mm of mercury was generated there was a tendency for colonies of P. mirabilis to develop outgrowths after incubation for 2 days. Firm agar inhibited the swarming of Clostridium tetani and Clostridium septicum.

As judged by a viable-count method, firm agar medium permitted the growth of maximal numbers of colonies for all organisms tested except Clostridium chauwei; the organisms included Clostridium oedematiens, Haemophilus influenzae, Neisseria gonorrhoeae, Streptococcus pneumoniae and Streptococcus pyogenes.

Precautions necessary for the preparation of firm agar media are defined. Colonies of a number of bacterial species on firm agar are described and illustrated. Firm agar media, being applicable to all bacteria with swarming colonies and practically non-inhibitory to other bacteria, are recommended for the isolation of bacteria from clinical specimens that may contain swarmers.

Non-fermenting, catalase-positive Gram-negative bacilli that grow on nutrient agar are often isolated in clinical laboratories. We have applied biochemical techniques appropriate to a typical clinical microbiology laboratory, and for the most part described in Cowan and Steel’s Manual for the identification of medical bacteria (Cowan, 1974), to 428 clinical isolates and have evolved a scheme for their identification. Organisms were subdivided into groups on the basis of three tests, namely the glucose oxidation-fermentation test and tests for oxidase activity and motility. A choice was then made among other tests to produce indentification tables, containing only the most useful tests, for the various groups. The most complicated table has only 16 tests.

This simple system identified 96-5 % of the 428 organisms, as well as many subsequent isolates of the more common organisms.

Culture supernates of Escherichia coli from diarrhoea patients were tested in dog jejunal loops for thermostable (ST) and thermolabile (LT) enterotoxins. Pre-treatment with choleragenoid blocked LT but not ST. Glucose was found to reduce fluid accumulation induced by both types of enterotoxin. The findings confirm and extend previous evidence of similarities between cholera toxin and E. coli LT and differences between it and E. coli ST.