摘要:

A rapid and inexpensive method for the measurement of copy number of small plasmids, ranging from 8.7 to 13 kb, in under 1 ml of liquid culture is described. The method involves whole cell lysis, electrophoretic separation of plasmid and chromosomal DNA followed by relative densitometric measurement of each, to give an estimation of the plasmid copies per chromosome. Results can be obtained in under 8 h and the method proved to be reproducible, fast and ideal for processing large numbers of samples from batch or continuous culture.

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1986.tb01561.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

A scheme for speciating and biotyping enterococcal isolates from chickens is described. All tests are performed using solid media inoculated with a multipoint inoculator and can be done in conjunction with an antibiotic sensitivity test in which the agents are also incorporated into agar.

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1986.tb01562.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Organisms ofEscherichia coliattached to glass beads in a model attachment system were more resistant to acid than were unattached organisms and this applied to cultures exposed to either pH 2·5 or 3·5. Attached organisms of both Col‐and Col V, I‐K94+strains showed the effect but with prolonged exposure to pH 2·5, the attached Col V+organisms appeared more resistant than the attached Col‐ones, possibly because they formed a thicker surface layer. It is proposed that the increased resistance of attached organisms to pH 2·5 might allow the survival, in gastric acid, of organisms attached to food particles. This would be more significant for the Col V+strains because the plasmid enhances enterobacterial attachment properties. The increased resistance of attached organisms to pH 3·5 might be significant for survival of particle‐ or surface‐bound organisms in the acidic environment of the phagocyte especially since lactate (which occurs in phagocytes) enhanced the effect of expo

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1986.tb01563.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Mycotoxin production by various toxigenic fungi, growing on a bread analogue, was investigated at various water activities (aw) and pH combinations. Citrinin, ochratoxin A and sterigmatocystin could be detected at aw>0·80, while patulin was only observed at aw= 0·95. These results show that some toxins may be produced at lower water activities than have been reported on synthetic media and suggest that, where possible, natural substrates should be used to investigate factors affect‐ing mycotoxin production in foodstu

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1986.tb01564.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The storage and survival of 97 species (276 strains) of bacteria at – 70° to – 80°C was investigated. Each strain was subcultured at regular intervals over a period of 6–40 months in order to check its viability. All strains were viable after the latest subculture except strains ofNeisseria gonorrhoeaewhich proved non‐viable when tested after 12 months. The method proved most useful for storing stock cultures which required frequent and regular

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1986.tb01565.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

When tested in phosphate buffer at pH 7·0, strains ofStaphylococcus aureusisolated from turkeys immediately after commercial slaughter were reduced in viability by at least 10000‐fold following exposure to 1 mg/1 of free available chlorine for 2 min at 20°C. In contrast, corresponding isolates from samples taken later in the process, and apparently derived from strains capable of colonizing processing equipment (‘endemic’ strains), were reduced onlyca100‐fold; some of these strains survived treatment with 2 mg/1 of free chlorine, when tested under the same conditions. The greater resistance of ‘endemic’ strains to chlorine may contribute to their persistence in the pro

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1986.tb01566.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1986.tb01567.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY