Acta microbiologica Hungarica最新文献

Human tonsillar lymphocytes separated on nylon wool and rat macrophages showed different sensitivity to deoxycholate (DOC) treatment at a low (0.24 mM, 0.01%) concentration for 3 h. The T cell-enriched fraction was stimulated more readily by PHA whereas the B-cell enriched fraction lost its adherence and a decrease of chromium binding capacity was observed after the detergent treatment. Rat peritoneal macrophages under the same conditions lost their chromium label and lysozyme content, whereas their adherence and phagocytic capacity decreased dramatically without affecting their binding capacity. Higher sensitivity to the detergent was observed in peritoneal macrophages compared to tonsillar lymphocytes when various DOC concentrations were used. These findings proved that this low concentration DOC treatment, at least in macrophages, touched mainly the adhesive proteins and the dynamics of the membrane and not its receptor-associated properties.

The role of flagella in the colonization of the intestine by Campylobacter jejuni was investigated by challenging infant mice with two flagellated strains and their nonflagellated variants. The intestinal tracts of infant mice were regularly colonized with motile strains, but not by nonmotile variants. Colonization of mice with motile C. jejuni occurred with as few as 1000 bacteria per mouse.

The Manhattan strain of canine adenovirus type 2 (CAV 2) was examined. Restriction endonuclease analysis and blot hybridization experiments revealed the heterogeneity of the viral DNA. At least 9 unequally expanded species of the viral genome have been recognized. This diversity is caused by different enlargements in the right inverted terminal repeat (ITR) of the virus. The differences between the individual enlargements were shown to be the different multiples of 150 base pairs. Relatedness of CAV 2 DNA to the DNA of bovine adenovirus type 2 (BAV 2) and human adenovirus type 2 (HAV 2) has also been observed during DNA hybridization experiments.

Human T cell Lymphotropic Virus-I (HTLV-I) carrying human T cell line MT4 is highly sensitive to Human Immunodeficiency Virus-1 (HIV-1). After HIV-1 infection cell clusters characteristic of intact MT4 rapidly disintegrate, syncytia appear and the cells die. Surviving MT4 cells were subcultured following HIV-1 infection of high multiplicity. We succeeded to establish an MT4 cell line continuously producing infective HIV (MT4/HIV-1). The original and the HIV-1 infected MT4 cells were morphologically similar. The MT4/HIV-1 cells proved to be nearly 100% positive in indirect immunofluorescence assay using the serum of an HIV-1 antibody positive individual. OKT4 surface antigen could not be demonstrated on MT4/HIV-1 cells. On electron microscopic pictures typical and atypical virus particles could be seen near the surface of the cell membrane. The persistently produced virus particles were infective for H9 and MT4 cells. The antigenic structure of the virus produced by MT4 cells was similar to that produced by H9 cells.

During the Tenth International Symposium on Listeriosis (Pécs, Hungary, 1988) the Working Party on Culture Media of IUMS-ICFMH suggested comparative examination of nine enrichment broths and nine solid selective media. On the basis of this proposal the following media were studied: LiCl-phenylethanol-moxalactam agar (LPM), polymyxin-acriflavine-LiCl-ceftazidime-aesculin-mannitol agar (PALCAM) No. 1 (home made) and No. 2 (Merck), acriflavine-ceftazidime agar (AC), Oxford agar, tripaflavine-nalidixic acid serum agar (TNSA) and Forray's agar. The study was performed as described in "Testing methods for use in quality assurance of culture media". Oxford agar proved to be the best medium. LPM, AC and Forray's agars were somewhat more inhibitory than Oxford medium. In productivity TNSA and PALCAM media were weakest but the latter one was more selective. When 43 sausage samples were enriched in UVM broths and subcultured on the above mentioned media the number of positive samples was the same on Oxford, LPM, AC and TNSA agars but it was lower on PALCAM agar No. 1. When 103 milk samples were subcultured on TNSA and PALCAM agar No. 2, the number of positive samples was the same.

In food hygiene the differentiation of Escherichia coli and coliforms as index resp. indicator organisms is very important as a basis for the assessment of good manufacturing practice (gmp). Using a fluorogenic (MUG) and chromogenic (X-gal) substrate the laborious methods have become more simple and reliable. A new German DIN standard method (10.183, part 3) was used as a base to examine 200 soft cheese samples for coliforms and Escherichia coli comparing different media, parameters and incubation times. It could be shown that an incubation of 48 h is absolutely necessary for E. coli and coliforms in both media, that X-gal is a quicker and more sensitive parameter for total coliforms than gas production and that the combination of fluorescence and indole is slightly superior to fluorescence and gas for the identification of E. coli. To sum up, the new fluorescence principle, integrated in new standard methods will be an excellent tool to simplify the differentiation of E. coli and coliforms in food hygiene. Additionally, X-gal as a chromogenic substrate for all coliforms, including E. coli, may be integrated in further standard methods.

For rapid identification of Escherichia coli, we evaluated Fluorocult MacConkey Agar, Fluorocult Laurylsulfate Broth and Bactident E. coli, which are incorporating fluorogenic substrate, MUG (4-methylumbeliferyl-beta-D-Glucuronide) that specifically reacts with E. coli. To assess the specificity and sensitivity of Fluorocult MacConkey Agar and Laurylsulfate Broth, beta-D-glucuronidase; beta-GUR activities of 264 strains from urine including 72 of E. coli were investigated. For both media, sensitivity was 92% and specificity was 100%. When there was 10(8) c.f.u./ml of E. coli in urine specimen, incubation times required for positive fluorescence by Fluorocult MacConkey Agar, Laurylsulfate Broth, and Bactident E. coli were 8 h, 4 h and 15 min, respectively. Influence of drugs in urine to fluorescence reaction was not observed.

BDG is an inducible enzyme that is encoded by the uidA gene in Escherichia coli. Genetic sequences of this gene are present in most if not all E. coli strains regardless of the BDG phenotype. Expression of BDG activity can be influenced by lactose-induced catabolite repression or genetic mutations. Salmonella, Shigella and Yersinia strains frequently exhibit positive BDG reaction. BDG activity of strains belonging to genus Edwardsiella, Serratia, Yersinia, Vibrio, Erwinia, Alcaligenes, Acinetobacter, Moraxella, Plesiomonas, Achromobacter, Flavobacterium, Chromobacterium and Pasteurella awaits examination.

An artificial monoflora of Escherichia coli in mice, as well as their autochtonous E. coli, exhibited enhanced resistance to streptomycin, chloramphenicol, sodium hypochlorite and silver nitrate. The level of resistance of the monoflora, which was 10-32 times higher than the in vitro determined Minimal Bactericidal Dose (MBCD), reached its maximum on the 7th-9th day after implantation. This latency is a requirement for the stabilization of the monoflora. Formaldehyde and carbenicillin were equally effective in the planktonic and in the biofilm mode of growth. In the case of carbenicillin the pieces of mouse colon contained about 60% of the dose used for exposure, in contrast to the 3% rate of streptomycin, showing the excellent penetrating ability of carbenicillin into the intestinal biofilm.