Acta pathologica et microbiologica Scandinavica. Section B, Microbiology最新文献

All the S. albus, E. coli and P. aeruginosa strains examined reduced nitroblue tetrazolium (NBT) to dark blue formazan. The amount of formazan produced was proportional to the number of bacteria. Under the same growth conditions, an equal number of bacteria of various strains produced different amounts of formazan. However, there were statistically verified differences in the NBT-reduction between the three species examined. The NBT-reduction took place in all phases of growth but was most intense in the early logarithmic phase. NBT was found to be toxic for bacteria, and the different strains had varying sensitivity to that effect. The NBT-reaction was markedly enhanced by phenazine methosulphate (PMS). The blue colour of formazan produced from NBT has an advantage over the red colour from triphenyltetrazolium chloride (TTC) if the reaction occurs in the presence of haemoglobin often present in biological materials. With NBT and PMS, 10(6)--10(7) bacteria are needed to form detectable amounts of formazan. The NBT-reduction by bacteria may be useful for measuring the influence of bactericidal, bacteriostatic or growth-stimulating factors on bacteria.

An investigation of the resistance types in lactose fermenting E. coli is presented. The frequency and sensitivity to beta-lactam antibiotics of different resistance types was investigated. The strains were divided into three groups according to sensitivity to penicillin derivatives. Group 1 contained the ampicillin-carbenicillin sensitive (A-s/Ca-s), group 2 the ampicillin resistant-carbenicillin sensitive (A-r/Ca-s) and group 3 the ampicillin-carbenicillin resistant (A-r/Ca-r). A-s/Ca-r were not observed. One third of the A-r strains were sensitive to carbenicillin. The distribution of resistance types was different in the three groups. Group 1 was dominated by the usual sensitive E. coli. Group 3 contained a very high proportion of multiresistant types. The IC50 against ampicillin, carbenicillin and cephalothin of 55 strains was determined. Group 3 (A-r/Ca-r, 25 strains) was much more ampicillin resistant than group 2 (A-r/Ca-s, 16 strains). Group 2 was less sensitive to carbenicillin than group 1 (A-s/Ca-s, 14 strains). Group 3 did not differ significantly from group 1 with respect to cephalothin sensitivity, while group 2 was much more resistant than the others.

We described recently an improved counter-immunoelectrophoretic method for quantification of tetanus antitoxin. The toxin neutralization test in mice is considered to correlate well with protection in humans. In the present study, the correlation coefficient between the two methods was 0.89. Sera containing more than 7.0 I.U./ml could be quantified directly by counter-immunoelectrophoresis, while sera containing less tetanus antitoxin had to be concentrated prior to quantification. The passive haemagglutination test was also compared with the toxin neutralization test in mice. The correlation coefficient between the two methods was 0.76.

Nine strains of Streptococcus sanguis were examined for competence in genetic transformation with streptomycin resistance (str-r) as marker. Eight strains belonged to serogroup H and one to the newly-described serogroup W. Seven of the strains, one of which was the reference strain NCTC 7868 (strain Challis), were competent with str-r DNA from strain Challis. Strains NCTC 9124 (strain Wicky) and 480 were incompetent. The efficiency of transformation was examined in four different media. Use of Todd Hewitt broth gave frequencies of transformants as high as the more complex media. Addition of serum to the transformation media was not essential for the development of competence. The presence of a competence factor (CF) in the culture filtrate of strain Challis was confirmed. The factor transferred strain Wicky to competence with a great variation in the number of transformants and had no influence on strain 480. On the other hand, this spontaneously incompetent strain became competent after addition of culture filtrate from the competent strain 13b, in contrast to Wicky which now remained incompetent. Thus, it is suggested that several factors are involved in the induction of competence of S. sanguis.

Forty-one strains of Streptococcus sanguis (37 of serogroup H and four of the newly-described serogroup W) were examined semiquantitatively for genetic transformation with streptomycin as marker. The material comprised eight reference laboratory strains and 33 recent isolates. Eighteen strains (16 of serogroup H and two of W) showed spontaneous competence in genetic transformation (without added competence factor, i.e. culture filtrate.). Individual culture filtrates from 19 spontaneously competent and ten incompetent strains were tested for competence-inducing effect on 23 spontaneously incompetent strains. Competence was induced in 16 of the strains, and 20 of the culture filtrates were active. There was considerable variation with respect to the number of recipient strains which were induced to competence by individual filtrates. Furthermore the recipients varied as regards the number of filtrates that were able to induce that particular strain. There was some relationship, but no complete association, between competence, competence-inducing ability and the occurrence of spreading zones around the colonies assumed to correspond generally to fimbriation. Thus, three incompetent strains had an active culture filtrate and one spontaneously competent strain had an inactive filtrate. Most, but not all, strains with spontaneous or inducible competence showed spreading, as did most of the strains from which broadly inducing filtrates could be produced.

The OK10 virus complex is known to contain two detectable viruses: a) focue-forming virus OK10V that transforms chick embryo cells, and b) an associated virus OK10AV present in excess that converts the morphology of cultured chick embryo cells. The pathogenesis of OK10 virus infection was studied, using 2--4 day old Brown Leghorn chickens. A group of chickens was sacrificed at weekly intervals, serum samples were taken and tissues were examined for virus. Autopsies of the chicken were performed and gross and microscopic changes were registered. After intraperitoneal injection of 10(4) focus-forming units of OK10 virus, infectious OK10AV was detected after one week in Bursa Fabricius, thymus and liver, and OK10V after two weeks in Bursa Fabricius but in no other organ. Neutralizing serum antibodies developed within three weeks. The first malignant changes, in the mesentery, were detected after three weeks. The infection was lethal in all experiments within 6--8 weeks. In the mesentery, the tumors consisted of large tumour cells with clear cytoplasm, a large nucleus and prominent nucleoli. The origin of these cells could not be established. The cells were surrounded by lymphoid cells. From the tumours, vontinuous cell lines were established which produced both viruses OK10V and OK10AV and had blast-like morphology. After intravenous injection of OK10 virus, tumours could also be found in liver, kidneys and testes. The associated virus OK10AV was injectious for chickens and induced neutralizing serum antibodies. One out of seven chickens died of leukosis after 1 1/2 years. The OK10 virus complex, consisting of a tumour-forming and a weakly oncogenic associated virus, appears to have a multiple oncogenic potential in its rapid oncogenic action in vivo.

The quantitative recovery of E. coli, S. faecalis and B. fragilis from operative abdominal wounds was investigated in pigs in an experimental model suitable for statistical calculations. Wounds were contaminated in groups of ten with different numbers of either a single bacterial species or a mixture of two species. The wound was irrigated with saline 20 minutes after contamination. Significant differences in recovery were found between the bacterial species investigated. Expressed as percentage of the number of bacteria used for contamination, the recovery for a given species was rather low, but it was constant and independent of the degree of contamination. The investigation did not suggest any principle difference in the recovery of anaerobic and aerobic bacteria. The clinical applicability of the method is not yet clarified.

Insertion of a polyethylene catheter into the heart was used for regular establishment of sterile endocarditis in 52 rabbits. The catheter was inserted with the aid of guide wire, and distance marking on the catheter was used to obtain precise positioning, so that the catheter was retained with the curved distal end inside the left ventricle of the heart. The results showed that the catheterization procedure could be carried out with a high degree of accuracy. Uniform localization of the vegetations was obtained, these reaching a suitable size of development in all rabbits after insertion of the catheter for 3 days. Histological examination of the sterile vegetation showed that catheter withdrawal at this time would still permit the regular development of an infection. After withdrawal of the catheter, the sterile vegetations rapidly decreased in size and disappeared almost completely by 10 days. Sterile endocarditis in rabbits induced by a catheter for a period of 3 days proved to be a harmless and self-limiting disease. The model presented seems to be suitable for futher investigations on experimental bacterial endocarditis.

Insertion of a polyethylene catheter in the left side of the heart was used to induce sterile endocarditis in 34 rabbits. Bacterial endocarditis was established by injection of approximately 10(8) Streptococcus faecalis into the blood stream simultaneous with the removal of the catheter which had been in place for 3 days. The course of the bacterial endocarditis was examined by autopsy of rabbits sacrificed at regular intervals after the infection. The results showed that the presence of the catheter was not essential for the induction or maintenance of the infection. Growth of the bacteria took place in the preformed vegetations in the aorta, on the aortic valves and in the left ventricle. However, increases in the size of the vegetations, a high density of bacteria in the vegetations and secondary spreading were found only on the aortic valves. The extracardial manifestations of left-sided S. faecalis endocarditis included constant bacteriaemia, a high frequency of septic kidney infarcts and enlargement of the spleen. This form of experimentally provoked bacterial endocarditis in rabbits provides a good imitation of human subacute endocarditis, and would thus seem to be suitable for further study of the pathophysiology of endocarditis and evaluation of the effect of treatment with antibiotics.

The effect of colchicine on human neutrophil granulocyte chemotaxis, chemokinesis and spontaneous motility was examined, using a modified reversible Boyden chamber. Colchicine was shown to inhibit the attraction of neutrophils to casein and to a bacterial chemotactic factor at concentrations as low as 10(-7) M. Experiments in which the absolute concentrations and the concentration gradients of the chemotactic agent were varied, revealed that colchicine inhibited chemokinesis rather than chemotaxis. The spontaneous motility measured in the absence of chemotactic agents was not inhibited by colchicine. Pre-incubation of the cells with a bacterial chematactic factor did not change the sensitivity of the cells to colchicine. It is concluded that the integrity of microtubule function is not necessary for the ability of the cells to discern a concentration gradient or to react to this with directional locomotion. Thus the inhibitory effect of colchicine on neutrophil granulocyte chemokinesis may not depend on its inhibition of microtubule function. It is suggested that colchicine may block the still unidentified membrane mechanism involved in the translation of the recognition signal into an appropriate locomotory cell response.