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

It was observed in a previous study that the growth of Streptococcus mutans strain OMZ 176 on sorbitol was inhibited by xylitol. The aim of the present study was to investigate the mechanisms involved in this inhibition. It was shown that the uptake of 14C-sorbitol was delayed when the cells had been pre-exposed to xylitol, and that the only labelled substance found intracellularly was sorbitol; no further metabolization occurred. This is in contrast with untreated normal cells, where sorbitol is taken up by a specific phosphotransferase system (pts). The 14C-xylitol metabolism of the cells was qualitatively unchanged in the presence of sorbitol; an intracellular accumulation of 14C-xylitol-phosphate (xylitol-P) and 14C-xylulose-phosphate (xylulose-P) was observed. However, a reduced uptake of xylitol was observed in the presence of sorbitol. Xylitol thus appears to change the pathway by which sorbitol is taken up by the cells. An inducible permease may replace the normal sorbitol pts when xylitol is present. No further metabolization of this intracellular sorbitol seemed to occur in the resting cell suspensions. It was furthermore observed that the presence of sorbitol enhanced the inhibitory potential of xylitol. The accumulation of intracellular sorbitol coincided with markedly increased xylulose-P/xylitol-P ratio. It may be speculated that, if xylulose-P were the major inhibitor of the glycolysis instead of xylitol-P, as previously assumed, an increased concentration of xylulose-P induced by sorbitol could explain that sorbitol enhances the inhibition potential of xylitol. It is not evident, however, how intracellular sorbitol could affect the xylulose-P/xylitol-P ratio.

The antibacterial activity of cefotetan, 8 other beta-lactam antibiotics and gentamicin, was tested in vitro on 288 recently isolated bacteria. The activity of cefotetan was generally higher than the 2.generation cephalosporin cefuroxime and lower than the 3.generation cephalosporins tested. In addition, cefotetan was shown to have some antibacterial activity against anaerobic bacteria. Cefotetan is a cephamycin and was found resistant to all 14 plasmid-mediated and 2 chromosomally-mediated beta-lactamases. With its beta-lactamase resistance and antibacterial activity, cefotetan seems to be a "second-generation-like" cephalosporin, almost with 3.generation cephalosporin antibacterial activity against Enterobacteriaceae.

Incorrect diagnosis of species belonging to the family Pasteurellaceae Pohl 1981 is often due to inadequate laboratory identification techniques. Reinvestigations of 56 human isolates of Pasteurellaceae and comparison of the results obtained with those obtained from nine reference strains in 65 different tests allowed classification of 26 strains as P. multocida ssp. multocida, 11 strains as P. multocida ssp. septica, 12 strains as P. canis, 4 strains as P. dagmatis and 1 strain as P. stomatitis. Two strains were tentatively classified with P. haemolytica biogroup 2(T) and the SP-group, respectively. The present investigation also showed that the type strains of P. gallinarum and Haemophilus aphrophilus were phenotypically related. Members of the family Pasteurellacea Pohl 1981 should be considered as potential etiologic agents of any local infection following animal bites or scratches.

A fragment (alpha-13) of Staphylococcal alpha-toxin was compared with intact alpha-toxin as regards biochemical and biological properties, and the resulting information was used for mapping biologically-active regions of alpha-toxin. The alpha-13 fragment had an apparent Mr of 18,500, judged by sodium dodecylsulphate polyacrylamide gel electrophoresis. However, it showed the same relative mobility as alpha-toxin when subjected to gel filtration on Biogel P60, high pressure liquid chromatography or electrophoresis on polyacrylamide gradient gel. The fragment had roughly the same specific hemolytic activity as intact alpha-toxin. In contrast to intact alpha-toxin, the fragment was neither membrane-damaging to mouse adrenocortical (Y 1) tumour cells nor lethal to mice. However, a short treatment of Y 1 cells with the fragment completely blocked intoxication by subsequently-added alpha-toxin. Likewise, the lethal effect of alpha-toxin was inhibited when the fragment was injected prior to the toxin. Thus, the fragment had lost the active region(s) responsible for Y 1 cell intoxication and lethality, while the region(s) for binding to these targets, as well as the region responsible for hemolysis, were retained. On the basis of these findings and previous reports concerning tryptic fragments of alpha-toxin, a hypothetical map of the different biologically-active regions of alpha-toxin was established.

Immunoadsorbent chromatography was used for purification of antibodies to E. coli 055 outer membrane proteins. Antibodies to the 33.5 kD and 7.5 kD proteins were eluted when rabbit antisera were applied to an epoxy-activated Sepharose 6B column to which the outer membrane was coupled in the presence of dioxane. ELISA coats prepared with sonicated bacteria showed binding of the eluted antibodies with strains of all of seven different species of the enteric bacilli, but not with other Gram-negative bacilli or cocci, or with Gram-positive cocci; immunoblot analysis of transblots of SDS-PAGE-separated bacteria showed that antibodies to both of the 33.5 kD and 7.5 kD E. coli outer membrane proteins cross-reacted with the enteric bacilli of different species. Both of the anti-33.5 kD and -7.5 kD antibodies were bound by intact E. coli 055 cells, but more efficiently by sonically disrupted or heat-treated bacteria. The results show that affinity-purified anti-OM antibodies were useful for the study of the antigenic relatedness of E. coli OM proteins with proteins of other bacteria.

Endotoxin (lipopolysaccharide, LPS) from an oral strain of Bacteroides intermedius was isolated by phenol extraction and purified by ultracentrifugation and gel filtration. The preparation was essentially free from contaminating nucleic acid and protein. The LPS contained rhamnose, fucose, mannose, glucose, galactose, glucosamine, and an unidentified sugar (approximate molar ratios 9:1:6:3:1:7:2). Neither heptose nor 2-keto-3-deoxyoctonate was detected. The major fatty acids were 3-hydroxy-15-methylhexadecanoic acid and 3-hydroxyhexadecanoic acid. The LPS was homogeneous with regard to molecular size, and its polysaccharide chain appeared short compared to the E. coli 055 LPS which was used as reference. A molecular weight of approximately 7,800 was estimated from gas chromatography data and by gel filtration in the presence of sodium deoxycholate. The B. intermedius LPS demonstrated low potency in the Limulus amoebocyte lysate assay, and in the chick embryo and mouse lethality tests and gave negative response in the local Shwartzman reaction.

A 71-year-old man with a permanent, subcutaneously implanted, intra-cardial pacemaker suffered from prolonged bacteremia with an antibiotic-susceptible group JK diphtheroid rod. He died in spite of the formation of specific serum antibody and parenteral treatment with ampicillin, cephradine and gentamicin. A second multi-resistant, but otherwise similar group JK strain was isolated post-mortem from the aseptically removed pacemaker electrode tip. The susceptible and the multi-resistant strains differed antigenically in crossed immunoelectrophoresis assays, and fatty acid isomer patterns were dissimilar. The theory that a multi-resistant group JK clone emerged by simple mutation in susceptible, indigenous group JK skin flora is rejected. The concept of major structural differences among group JK bacteria, possibly affecting cell-wall permeability, is supported. Crossed immunoelectrophoresis is suggested as a means for strain comparison in epidemiological surveys. Vancomycin is regarded as the antibiotic of choice for the treatment of potentially fatal, deep-seated infections.

Using DNA-DNA-hybridization it could be shown that 52 of 86 clinical isolates of Enterobacter agglomerans were closely related to each other, to the type strain of the species and also to the type strains of Erwinia herbicola and Erwinia milletiae. Most of the strains investigated were of the biogroups 1 and G1 of Ewing & Fife. All strains of the genetically defined group belonged to these two biogroups; none of these isolates fermented dulcitol, and with few exceptions they were also cellobiose, lactose and sorbitol negative.

A test to detect thermostable DNase activity (TDNase test) was evaluated for rapid confirmation of S. aureus bacteraemia, using toluidine blue O DNA agar plates for the testing. A total of 226 blood cultures which grew bacteria were examined. S. aureus was identified in 76 of the cultures. All of the S. aureus isolates showed positive TDNase test after 2 h of incubation of the test plates. The remaining isolates examined, most of them coagulase-negative staphylococci, showed a negative test. The TDNase test enables reliable same-day confirmation of S. aureus bacteraemia.

Population analyses of the susceptibility to ciprofloxacin of eight strains of Pseudomonas aeruginosa, including mucoid strains and strains resistant to aminoglycosides or anti-Pseudomonas beta-lactams, were carried out. All strains were sensitive as judged by the broth-dilution technique, but four strains were found to yield resistant mutants with a frequency of less than 10(-6). Two strains yielded mutants homogeneously sensitive to ciprofloxacin at a level 8-16 times the MIC of the parent strains. Two other strains yielded mutants resistant to different higher concentrations of ciprofloxacin. One of these mutants was examined for production of ciprofloxacin-inactivating enzyme; no enzyme production could be detected. Cross-resistance was found with another quinolone antibiotic, ofloxacin, but not with aminoglycosides or beta-lactam antibiotics.