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

Thin-layer chromatography (TLC) of extracts of cells which had been exposed to 14C-xylitol indicated that xylulose-phosphate is produced by the cells in addition to the previously reported xylitol-phosphate. Resting cell cultures of Streptococcus mutans OMZ 176 pretreated with xylitol were exposed to 14C-glucose and glycolytic metabolites identified by TLC of boiling water extracts of the cells. The developed TLC-sheets showed an accumulation of 14C-hexose-6-phosphates in the xylitol-treated bacteria. This could indicate that a xylitol metabolite, or metabolites, compete with fructose-6-phosphate for the phosphofructokinase, since the glycolysis is inhibited at this step. It was also shown that after accumulation of xylitol-5-phosphate, the bacteria were able to expel xylitol, presumably after and intracellular dephosphorylation of xylitol-5-phosphate; a "futile cycle" is thus present in these cells. Xylitol is taken up and phosphorylated, and at a later step dephosphorylated and expelled. The most important inhibition mechanism was judged to be the competitive inhibition of the glycolysis at the fructose-6-phosphate level.

A virulent strain of Pseudomonas aeruginosa was assayed for adhesion to HEp-2 cells, production of toxin A, and production of elastase, in the presence of sub-inhibitory concentrations of carbenicillin and gentamicin. Both antibiotics, assayed in a concentration of 1:12 of their minimum bactericidal concentration (MBC), inhibited the production of toxin A. Gentamicin at this concentration totally abolished the production of elastase, whereas carbenicillin had little or no effect on this factor. Both antibiotics inhibited the bacterial adhesion, but in different ways. While gentamicin had a strong activity of slow onset, carbenicillin had a transitory activity of rapid onset, with return towards normal values after 90 min incubation.

Minibact, a new system for four-hour identification of Enterobacteriaceae, combined with a computer identification system, was compared with Micro-ID and API 20E in testing 110 strains of Enterobacteriaceae. Minibact gave identification rates of 96.4% at species level and 96.4% at genus level; the corresponding values for Micro-ID were 87.3% and 91.8%, and for API 20E 91.8% and 94.5%. In conclusion, Minibact combined with a computer identification program gave high identification rates fully comparable to those of Micro-ID and API 20E, and the system might be an alternative to conventional identification systems in clinical microbiological departments.

The morphological changes of human blood granulocytes and monocytes caused in vitro by alpha-hemolytic strains of E. coli and bacteria-free culture supernatants of these bacteria were studied by light- and transmission electron microscopy. The following sequence of cellular alterations were observed: Cessation of intracellular cytoplasmic streaming and cellular movements succeeded by extension of cytoplasmic pseudopodia, degranulation and development of cytoplasmic and nuclear edema. Within two hours the leukocytes appeared as empty sacks. Finally, long straight filaments were formed between the cells. The changes induced by alpha-hemolytic bacteria and culture supernatants containing free alpha-hemolysin appeared to be identical. The cytotoxic effect became more pronounced as the numbers of bacteria, the hemolytic activity of growth supernatants or the period of incubation were increased. A beta-hemolytic and a nonhemolytic E. coli strain were not cytotoxic.

The in vitro activity of coumermycin has been compared with those of ampicillin, clindamycin, cloxacillin, doxycycline, erythromycin, netilmicin, penicillin G and vancomycin. A total of 251 clinical isolates of Gram-positive cocci were examined. The minimal inhibitory concentration (MIC) was determined by an agar dilution method. Clindamycin, coumermycin and erythromycin were the most active drugs against Staphylococcus aureus and S. epidermidis on a weight-for-weight basis. All the staphylococcal isolates were inhibited by coumermycin at a concentration of 0.12 mg/l or less. Netilmicin seemed to be somewhat more active against S. epidermidis than against S. aureus. The MICs of vancomycin for the staphylococcal isolates were clustered around 1 mg/l. Streptococcus pneumoniae, S. pyogenes and S. agalactiae were highly susceptible to penicillin G and erythromycin; most isolates were inhibited by 0.03 mg/l or less of either drug. Coumermycin showed poor activity against S. pyogenes, S. agalactiae and enterococci. Most of the S. pneumoniae isolates had also high MICs, although a wide range of sensitivities was found.

The present investigation has been undertaken to illustrate the antibacterial effect on 20 diarrhoea producing enterobacteriaceae of an anti-depressive drug available as femoxetine and its three analogs. It has been shown that the stereo-isomeric trans forms of femoxetine are more than twice as active as the cis forms and inhibited all the strains below 400 microgram/ml (1.2 mM). The two cis compounds only inhibited 11 and 9 of the 20 strains respectively in the investigated area 100 microgram/ml - 800 microgram/ml (0.3 mM - 2.4 mM). Our investigations point out that the bacterial cell has a target for psychopharmacologically active agents. Thus the known psychopharmaca and their stereo-isomeric analogs may represent a pool of potentially new antimicrobial drugs. Furthermore the bacterial model may be useful as a model system in the study of the interaction of neuropharmacological agents and other membrane active compounds with biological membranes.

Interferon production in mouse and human cells induced by paramyxovirus was inhibited by pretreatment of cells with 7.12 dimethylbenz (alpha) anthracene. The inhibition was moderate but reproducible. It was most pronounced in mouse fibroblast cells, somewhat less in the mouse L-929 cell line and in human embryo fibroblast cells. Addition of the microsomal activator systems was necessary in the human system. A possible employment of this phenomenon in testing carcinogenic potential is discussed.

An assessment of the Gram, the Methylene blue, and the Ziehl-Neelsen procedures in diagnosing Pneumocystis carinii has been performed. By using heat and methanol as fixatives and phase-contrast microscopy we found the procedures valuable in detecting the pneumocysts, especially in the Gram staining. The diagnosis should, however, be confirmed by a re-staining with a specific staining, viz. the toluidine blue 0 or the silver impregnation a.m. Gomori-Grocott. It is additionally shown that the staining a.m. Gomori-Grocott is dependent on the density of the preparation.

Aggregates of various mammalian beta 2-microglobulin (beta 2m) homologues were tested in binding experiments with group A streptococcal strains of different M types. The binding patterns obtained were similar, suggesting that evolutionarily conserved parts of the beta 2m molecule are responsible for the interaction with group A streptococci. An N-terminally abnormal beta 2m showed binding characteristics similar to those of normal human beta 2m, indicating that the amino-terminal does not participate in this interaction. Aggregates of human IgG Fab fragments, kappa chains and lambda chains, were also analyzed. Whereas several of the beta 2m-reactive M types did not interact with any of these aggregates, all strains binding aggregated Fab, kappa or lambda, also bound aggregated beta 2m. Strains of M types 4, 12, 23 and 53 bound all the tested proteins; M type 1 bound all but IgG Fab, whereas M types 46, 49 and 53 showed affinity for beta 2m and lambda chains only. In inhibition experiments, unlabelled aggregated beta 2m in excess completely blocked the uptake of radiolabelled aggregated IgG Fab, kappa and lambda chains. Conversely, Fab, kappa and lambda aggregates inhibited the binding of radiolabelled beta 2m aggregates. Our results indicate that the differences in reactivity recorded between beta 2m and IgG Fab, kappa and lambda chains, all structurally related, are quantitative rather than qualitative. Thus, a common binding structure for these aggregated proteins on group A streptococci appears probable.