摘要:

Methods for the microbiological analysis of drinking water must be able to detectEscherichia colithat may be injured by treatment. The Colilert method, which simulaneously detects total coliforms andE. coliin water samples by the observation of direct colour changes produced by defined substrates in the media, was found to be equivalent to the reference EC MUG method in its ability to recover low numbers (<4/100 ml) of oxidant‐stressedE. col

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1991.tb00620.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

A sodium hydroxide extract from cacao husk inhibited the cytopathic effect of human immunodeficiency virus type 1 (HIV‐1) against HTLV‐1‐transformed T‐cell lines MT‐2 and MT‐4. It also inhibited syncytium formation between HIV‐infected and uninfected lymphoblastoid T‐cell line, MOLT‐4. The anti‐HIV activity was concentrated by membrane filter fractionation to a fraction with molecular weight of 100–300 KDa. Anti‐HIV activity of the extract was attributable to interference with the virus adsorption, rather than to inhibition of the virus repli

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1991.tb00621.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

A one‐day procedure for enumeratingSalmonellain milk powder is described. Milk powder suspension was treated with a mixture of trypsin and Tween 80, then centrifuged to give a sediment of microbial cells that was plated on the xylose lysine desoxycholate agar for the direct enumeration ofSalmonella.Known populations (1–200 cfu/25 g of sample) of salmonellas inoculated into milk powder suspensions were recovered with almost 100% efficiency in each of 152 trials of the method, covering 17 different seroty

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1991.tb00622.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Urease‐negative variants ofHelicobacter mustelaewere isolated after spontaneous loss of activity during sub‐culture. The whole‐cell protein patterns showed that the loss of urease activity was linked to the absence of two polypeptides of 29·1 and 65·4 kDa. Restriction endonuclease analysis of chromosomal DNA indicated no substantial differences between the urease negative and positive variants. It is likely that a change in the expression of the gene for urease was responsible for these obser

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1991.tb00623.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Flavobacteriumsp. ATCC 27551 is prototrophic, streptomycin‐resistant and contains plasmid DNA. Two strains of thisFlavobacteriumsp. with altered growth requirements and antibiotic sensitivity have been isolated. Unlike the parental strain, both isolates are sensitive to the antibiotic streptomycin. Isolate YE requires yeast extract supplementation of the medium and contains no plasmid DNA. Isolate AHC contains plasmid DNA and requires aspartic acid, histidine and cysteine for growt

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1991.tb00624.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

PCR was used to develop a method to detectEscherichia coliin surface water and soft cheese, which does not require cultivation of bacteria. DNA sequences from thema/B operon ofE.coli were amplified to specifically detect this bacterium. Samples of surface water and soft cheese naturally contaminated withE. colifrom less than 100 cells per g up to several times 105cells per g were analysed by both the classical culture method and the PCR assay. Comparable results were obtained with both methods. Soft cheese samples artificially contaminated with various levels of enterotoxigenicE. coliwere analysed with a second PCR test specific for the heat‐labile enterotoxin type I (LTI) ofE. coli.The detection limit was about 1000 bacteria per g of soft cheese. In addition, two soft cheese samples naturally contaminated with 2 times 105and 6 times 105E. coliper g as determined by the culture method were analysed by LTI‐PCR and found to contain low levels of enterotoxigenicE. c

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1991.tb00625.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

In a membrane filter method for the enumeration ofEscherichia coliin water samples, the James' indole reagent has several advantages over the commonly used diaminobenzaldehyde (DAB) reagent. Results with James' reagent were easier to read because the red colour of positive colonies was more intensive and developed within a few minutes without exposure to UV light. DAB‐coloured colonies were pale pink with a diffuse pink zone surrounding the colonies after 30 min of exposure to UV‐source radiation. Incorporation of 4‐methylumbelliferyl‐β‐D‐glucuronide (MUG) into the selective medium to detectE. coliby means ofβ‐glucuronidase‐activity gave discouraging results. Fluorescence was difficult to read on membrane filters incubated on this medium and 14% ofE. colistrains wereβ‐gl

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1991.tb00626.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Saxitoxin was coupled to horseradish peroxidase via a novel adaptation of the periodate reaction. Based on polyclonal antibodies against saxitoxin, this conjugate was used for the development of two formats of direct enzyme immunoassay (EIA)–a microtitration enzyme‐linked immunosorbent assay (ELISA) and a test strip EIA. The detection of saxitoxin without instrumentation by visual evaluation of the test strip EIA is described. The detection limits for saxitoxin were 7 pg/ml (0·35 pg/assay) in the ELISA and 200 pg/ml in the test strip EIA using visual evaluation. Employing a simple procedure of sample preparation, both ELISA and test strip EIA were applied to the analysis of shellfish. The detection limits for saxitoxin in shellfish tissue of the ELISA and the test strip assay were 3 and 4 ng/g, respecti

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1991.tb00627.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

A simple and rapid method for the transfer of plasmids between the Gram‐positive speciesLactococcus lactisandEscherichia coliwithout the need for plasmid preparation is described. The donor strain was subjected to an electroporation pulse which released plasmid DNA into the suspending buffer which was then centrifuged to remove cells and debris. The supernatant was mixed with the recipient strain and subjected to a second electroportion pulse, resulting in the transfer of plasmid from donor to recipient. In cases where a high transformation efficiency is not required, such as the transfer of a cloned construct fromE. colitoLactococcusorvice versa, this method has the advantages of convenience and rapidit

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1991.tb00628.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Lactobacillus reuteriLA 6, isolated from infant faeces, produced an antimicrobial agent active againstLactobacillus acidophilusJCM 2125,Lactobacillus delbrueckiisubsp.bulgaricusJCM 1002 andLactobacillus delbrueckiisubsp.lactisJCM 1148 and JCM 1248. The agent was sensitive to proteolytic enzymes and retained activity after heating at 100°C for 20 min. This agent was a bacteriocin and has been designated as reutericin 6. Reutericin 6 exceeds 200 kDa as determined by ultrafiltration studies. Activity against sensitive cells was both bacteriocidal and bacteriolytic

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1991.tb00629.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY