摘要:

ABSTRACTA membrane filtration‐immunostaining technique was developed for detection and direct enumeration of enterotoxigenic Clostridium perfringens in beef. The procedure combined a microcolony technique with an indirect alkaline phosphatase conjugated antibody visualization system. Precooked ground beef samples containing enterotoxigenic C. perfringens cells were diluted in phosphate buffered saline containing 0.1% Tween 80 and filtered through a 0.45 μm cellulose nitrate filter. The membranes were placed onto the surface of solid Duncan and Strong medium and incubated anaerobically for 4–18 h at 37C. The membranes were sequentially overlaid with C. perfringens anti‐enterotoxin and an alkaline phosphatase conjugated antibody resulting in a chromogenic reaction that enabled detection and enumeration. The membrane immunostaining technique proved to be sensitive enough to detect as low as 2 CFU/g of enterotoxigenic C. perfr

ISSN:1060-3999    

DOI:10.1111/j.1745-4581.1995.tb00093.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTMultiple primer sets were combined with the polymerase chain reaction (PCR) and examined for use in the amplification of toxin gene fragments from four Clostridium botulinum types (A, B, E, and F). Vegetative cells obtained from overnight cultures were used directly in the PCR analyses without purification of chromosomal DNA. Gene fragments were amplified from the different botulinal toxin genes that code for types A, B, E and F toxins using a single PCR protocol. Toxin gene fragments were amplified from types B and F toxigenic organisms using the PCR and specific primer sets for these types in a single PCR tube. Type A and E toxin genes were also examined using type A and E specific primers in a separate PCR tube. The PCR‐amplified products were separated by electrophoresis on agarose gels containing ethidium bromide. The identity of the PCR products were confirmed by DNA hybridization using type specific probes. We conclude that this method is useful for the rapid and direct identification of toxigenic botulinal organisms that code for the toxin types A, B, E, or

ISSN:1060-3999    

DOI:10.1111/j.1745-4581.1995.tb00094.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTMembrane fractions obtained from Escherichia coli, Gluconobacter oxydans, and Acetobacter xylinum significantly stimulated rapid growth of Listeria monocytogenes (strains 101, 103, and Scott A) under atmospheric conditions of the OmniSpec Bioactivity System. L. monocytogenes demonstrated a shorter lag phase and faster growth compared to culture systems without the membrane fractions as determined by shorter color detection times, the durations of time for a significant color change to occur. The growth stimulating effect increased as the concentrations of membrane fractions increased. The use of membrane fractions to recover facultative Listeria spp. also lowered the detection limit of the method to<10 cells/ml by increasing small cell numbers to the detectable level (107cells/m) faster under aerobic conditions. The application of membrane fractions with the OmniSpec Bioactivity System shortened the detection time for the bacteria by 0.5–10 h, depending on the specific membrane and initial cell concentrations, compared to the conventional OmniSpec method. This method is very useful as a tool for studying food microbiology. Membrane fractions produced in our laboratory effectively dissipated oxygen in Fraser broth and had growth‐enhancing activities comparable to that of commercial Oxyras

ISSN:1060-3999    

DOI:10.1111/j.1745-4581.1995.tb00095.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTA competitive enzyme immunoassay using a murine monoclonal antibody M105 directed against a genus‐specific epitope in the Salmonella lipopolysaccharide was used to identify over 200 strains of Salmonella submitted to the National Laboratory for Enteric Pathogens. The immunoassay rapidly identified 208 strains of Salmonella representative of subspecies I, II, IIIa, IIIb, IV, and V, including 89 different serotypes from 26 O serogroups. The competitive enzyme immunoassay did not give positive results with 3 strains of Citrobacter freundii and 4 strains of Escherichia coli which were submitted to our laboratory as suspect Salmonell

ISSN:1060-3999    

DOI:10.1111/j.1745-4581.1995.tb00096.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTThis report presents information on the effects of five current enrichment procedures including trypticase soy broth, phosphate buffered saline, peptone enriched phosphate buffered saline, phosphate buffered saline with sorbitol and bile salts and MacConkey broth on the stability of virulence plasmid in Yersinia enterocolitica. Virulence assays using crytal violet binding, low calcium response, Congo red uptake, hydrophobicity by latex particle agglutination, and autoagglutination as well as plasmid DNA analysis showed that Y. enterocolitica did not lose the virulence plasmid during isolation at 28C and the cells remained virulent. Moreover, postenrichment treatment with alkali to reduce competing microflora, when used in conjunction with these five enrichment techniques, did not cause the loss of the virulence plasmid, thus providing a way to selectively isolate this pathogen.

ISSN:1060-3999    

DOI:10.1111/j.1745-4581.1995.tb00097.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTA semi‐automated colorimetric method to measure aminopeptidase activity using reflectance colorimetry is described. p‐Nitroanilide derivatives of 12 amino acids were used to detect aminopeptidase activity in phosphate buffer and milk. Enzyme activity, in phosphate buffer, determined using spectrophotometry and colorimetry, was linearly correlated (R2= 0.991), indicating colorimetry can be used in place of spectrophotometry to measure aminopeptidase activity. Aminopeptidase activity determined colorimetrically in buffer was linearly correlated (R2= 0.981) with activity in milk, indicating colorimetry can be used to detect enzyme activity in turbid solutions such as milk and dairy products. Optimum substrate concentration differed for milk and phosphate buffer. Assays in milk required higher concentrations of chromogenic substrates (0.8–1.0 mM), than did assays in phosphate buffer (0.3–0.5 mM). The assay was more repeatable in milk (average coefficient of variation = 3.6%) than in buffer (average coefficient of variation = 14.0%). Aminopeptidase activity of cell free extracts from Lactobacillus helveticus CNRZ32 were used to demonstrate the use of the assay. Enzyme profiles of this strain were similar in milk and in phosphate buffer. High activity was detected with p‐nitroanilide derivatives of arginine, lysine, leucine, alanine, and m

ISSN:1060-3999    

DOI:10.1111/j.1745-4581.1995.tb00098.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTAlcohol‐flaming to sterilize meat cutting knives is a common practice when microbiologically sampling meat surfaces. Often knives will be wiped with paper towels and repeatedly dipped for a short period in alcohol followed immediately by flaming. This investigation addressed the effectiveness of alcohol and alcohol‐flaming for sterilization of cutting knives. Additionally, the effect of high levels of residual meat particles in alcohol used for repeated dipping on sterilization was determined. Stainless steel knives were used to slice ground beef, wiped with a towel, submerged in alcohol for 2 s to 1 h, and flamed (wiping only and alcohol dipping only serving as control samples). Knives were microbiologically evaluated by placing into tubes of standard plate count (SPC) agar or Brain Heart Infusion (BHI) broth. Slight microbial growth was observed for agar and broth tubes from knives dipped into alcohol fór 2 s receiving no flaming. Agar tubes from knives dipped for 2 s to 1 h receiving flaming indicated no growth. The more sensitive broth assay indicated microbial growth in virtually all tubes, however, viable cell counts from these tubes demonstrated very low levels of contamination (1–4 CFU/cm2). Thus, the use of alcohol dipping with or without flaming provided effective microbial destruction on the knives. Knives repeatedly dipped into alcohol containing high levels of residual meat particles and flamed indicated that the alcohol remains an effective means of decontaminating knife surfaces even during prolonged

ISSN:1060-3999    

DOI:10.1111/j.1745-4581.1995.tb00099.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:1060-3999    

DOI:10.1111/j.1745-4581.1995.tb00091.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY