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1.
A 24 h screen to detect viable salmonellas in faeces was developed by studying growth dynamics of salmonellas and competing flora in combinations of enrichment media and artificially-inoculated pig faeces. Muller-Kauffmann tetrathionate (MK) broth, incubated overnight at 42°C, maintained the lowest ratio of salmonella: competing flora and identified all inoculated samples. A 4 h postenrichment in M broth plus novobiocin reduced the number of false-positive results in subsequent ELISAs. Adjusting the negative cut-off values and incubation time of the chromogenic substrate from that recommended in the ELISA instructions reduced the rate of false-positive results further and allowed the detection of 103 salmonellas per ml in the presence of up to 107 ml−1 aerobic-competing cells. Suspension of faeces diluted 1 in 2 and 1 in 5, rather than 1 in 10 in MK broth did not necessitate further adjustments to the ELISA baseline values. The proposed screen protocol is an overnight incubation of faeces suspended 1 in 10 in MK broth, a 1 in 100 subculture into M broth plus 10 μg ml−1 novobiocin (MbN) for 4 h, steam inactivation of MbN cultures and testing by ELISA, and can detect three salmonella cells per g faeces. 相似文献
2.
H. J. Beckers J. V. D. Heide U. Fenigsen-Narucka R. Peters 《Journal of applied microbiology》1987,62(2):97-104
Studies have been carried out in which growth patterns of a Salmonella sp. and competing micro-organisms, especially other Enterobacteriaceae, were followed during pre-enrichment in buffered peptone water (BPw) and subsequent selective enrichment in tetrathionate broth (TBB). Pre-enrichment cultures were inoculated with minced meat and three reference samples containing nalidixic acid-resistant salmonellas. Irrespective of their initial numbers in BPw, Enterobacteriaceae increased to 108 /ml or more. During incubation in TBB at 43C, numbers of lactose-positive Enterobacteriaceae decreased in most enrichments which resulted in a positive salmonella isolation, but remained constant in the majority of those that did not. Levels of lactose-negative Enterobacteriaceae did not decrease in most salmonella-positive tests, but did so in half of the salmonella-negative ones. In the salmonella-positive tests the numbers of salmonellas had increased to 103 –107 /ml in BPw and after transfer to TBB slowly reached 104 /ml or more. In all cases the numbers of salmonellas exceeded those of the competing flora on brilliant green agar (BGA). In the salmonella-negative tests the numbers of salmonellas had increased less in BPw and decreased in most of the TBB enrichments. In none of these negative tests did the numbers of salmonellas exceed those of the competing flora on BGA. Escherichia coli dominated in most of the salmonella-negative tests. The results suggest more influence of lactose-positive than lactose-negative Enterobacteriaceae on the detection of salmonellas. The effect of competing microorganisms seems to depend not only upon their initial numbers, but also upon the types that can interact with salmonellas during selective enrichment. 相似文献
3.
T. Fujisawa K. Namba K. Hirayama W.K. Lee T. Mitsuoka 《Journal of applied microbiology》1995,78(5):481-486
Two selective media, novobiocin-colistin agar (NCA) and colistin-crystal violet agar (CCA), were developed for isolating clostridia from human and animal faeces. The basal medium was modified Eggerth-Gagnon agar. The NCA medium contains novobiocin (8 μg ml-1 ) and colistin (8 μg ml-1 ) and the CCA medium contains colistin (10 μg ml-1 ) and crystal violet (10 μg ml-1 ). Nine faecal specimens were cultured. Clostridia isolated on these media were similar to those on non-selective media, and higher than those isolated after heat treatment. However, more clostridial species were isolated on the new selective media compared with the non-selective medium. These selective agars were particularly useful for enumerating and isolating clostridia from human faeces. 相似文献
4.
Evaluation of the Vitek Immunodiagnostic Assay System (VIDAS) for the detection of Salmonella in foods 总被引:1,自引:0,他引:1
C. de W. Blackburn L.M. Curtis L. Humpheson S.B. Petitt 《Letters in applied microbiology》1994,19(1):32-36
A Salmonella Assay using the Vitek Immunodiagnostic Assay System (VIDAS) was compared with a conventional cultural method (CCM) for the detection of salmonellas in 141 samples of artificially and naturally contaminated foods. There was an overall agreement of 92.9% between the methods. The productivity of the VIDAS Salmonella Assay (VSA) was not improved using an alternative enrichment protocol for the detection of Salmonella in 12 raw meat samples.
The sensitivity and specificity of the VSA was assessed using pure cultures of salmonellas and non-salmonellas. The detection limit was 1.8 times 106 salmonellas ml-1 in M-broth and some Citrobacter freundii strains gave false-positive results.
Using an immunomagnetic separation (IMS) technique and an abbreviated cultural enrichment, the VSA results could be obtained a day earlier than the standard VSA method. 相似文献
The sensitivity and specificity of the VSA was assessed using pure cultures of salmonellas and non-salmonellas. The detection limit was 1.8 times 10
Using an immunomagnetic separation (IMS) technique and an abbreviated cultural enrichment, the VSA results could be obtained a day earlier than the standard VSA method. 相似文献
5.
A polymerase chain reaction (PCR) assay based on the 16S rRNA gene and an improved DNA extraction procedure were developed for the direct detection and differentiation of Campylobacter upsaliensis and C. helveticus in seeded human faeces. The PCR assay was compared with culture detection by a membrane filter (MF) technique and on selective agar (SA) containing 8 mg l−1 cefoperazone. Both MF culture and the PCR assay detected 105 colony-forming units (cfu) g−1 faeces. Selective agar culture of some strains could detect as few as 103 cfu g−1 faeces. However, some strains were susceptible to cefoperazone and either failed to grow or were detected only with reduced sensitivity in the presence of the antibiotic. Detection by MF and SA both required 48–96 h incubation in a microaerobic atmosphere and did not specifically identify the isolate. By contrast, the PCR assay could be completed within 8 h and accurately identified the two phenotypically similar species, C. upsaliensis and C. helveticus. 相似文献
6.
A. P. WALKER 《Journal of applied microbiology》1981,51(3):405-408
A strain of Pseudomonas aeruginosa having colonies that resemble those of salmonellas on brilliant green agar is almost totally inhibited by the addition of 1.0 mg/ml of sulphacetamide to the medium. Low numbers of Ps. aeruginosa grew equally well on brilliant green and nutrient agar, but 106 –107 organisms were needed before any growth appeared on the medium containing sulphacetamide. During 12 months of routine use of the sulphacetamide medium, involving almost 3000 plates, Ps. aeruginosa has been isolated as a contaminant only once. Forty-seven salmonella serotypes were grown on the sulphacetamide brilliant green agar in the same period. 相似文献
7.
I. D. Ogden 《Letters in applied microbiology》1990,11(4):193-196
The effect of air on the conductance response of salmonellas in three selective media was investigated. When assays were carried out aerobically, the time to observe a presumptive positive in all media was reduced and the conductance change was larger than in assays done under microaerophilic conditions. Low (102 /ml) numbers of pre-enriched salmonellas were detected only under aerobic conditions. 相似文献
8.
The selective media PALCAM and L-PALCAMY were evaluated for their potential ability to detect Listeria monocytogenes in faeces. Recovery on PALCAM was almost total, and similar at 30°C and 35°C with or without CO2 incubation. Warm enrichment in L-PALCAMY was necessary in order to detect low numbers (<102 /ml faeces). Faeces in excess of 0.25 ml/10 ml L-PALCAMY was inhibitory. The results point to L-PALCAMY and PALCAM as an epidemiological tool. 相似文献
9.
A method for detecting 101 -102 cells of phytopathogenic bacteria ( Pseudomonas syringae pv. tomato and Xanthomonas campestris pv. vesicatoria ) in either tomato or pepper seed was developed. The method is based on the enrichment of the compatible pathogen inside a detached leaf of its host when placed on a water agar medium. It was found to be superior to the diagnostic growth media method commonly used and to permit the detection of the pathogens in symptomless plants. 相似文献
10.
Experimental enzyme-linked amperometric immunosensors for the detection of salmonellas in foods 总被引:1,自引:1,他引:0
Two enzyme-linked amperometric immunosensors specific for salmonellas were developed as rapid methods for quantifying and detecting these organisms in pure cultures and foods. Both used alkaline phosphatase as the enzyme reporter molecule but one system used phenyl phosphate as the substrate followed by the electrochemical detection of phenol at a polarized platinum electrode. The other system incorporated an enzyme amplification step and relied on the electrochemical detection of a reduced mediator, ferrocyanide. Both assays were rapid (4 h) and specific and generated salmonella-dependent signals above 104 cfu/ml (phenyl phosphate system) or 105 cfu/ml (enzyme amplified system) in pure cultures and samples of several foods, although the results with beef samples showed considerable variation. Both systems were able to detect low (1–5 cfu/g or /ml) numbers of salmonellas in foods after non-selective (18 h) and selective (22 h) enrichment steps but four samples, out of 147, gave false positive results. False positive results were eliminated by reducing the enrichment steps to 6 h and 18 h respectively (90 samples). 相似文献
11.
S.T. Aspinall D.R.A. Wareing P.G. Hayward D.N. Hutchinson 《Journal of applied microbiology》1996,80(6):645-650
The newly developed CAT campylobacter selective medium employing the blood-free charcoal-based agar containing cefoperazone (8 mg I−1 ), amphotericin (10 mg I−1 ) and teicoplanin (4 mg I−1 ) was compared with the membrane filtration culture technique for isolation of Campylobacter spp. including Camp. upsaliensis. Nine hundred and fifty human, 275 dog and 65 cat faeces (in which modified CCDA medium was also compared) were tested. In addition, the recovery of Camp. upsaliensis from pure cultures and from spiked human faeces was examined after membrane filtration. A 50-fold reduction in recovery after filtration using the 0·65 μm filters and a 150-fold reduction using the 0·45 μm filters was found. Recovery of Camp. upsaliensis from spiked faeces was considerably improved using the CAT medium compared with filtration, especially with the lower concentration of organisms (approx. 104 cfu ml−1 ). Campylobacter upsaliensis was recovered from 91 specimens of animal faeces, with CCDA recovering 26 isolates (29%), CAT recovering 76 isolates (84%) and membrane filtration (0·65 μm) recovering 82 isolates (90%). CAT selective agar was found to be a suitable medium for the isolation of thermophilic campylobacters including Camp. upsaliensis from faecal samples. 相似文献
12.
Effect of rigidity of gel medium on benzyladenine-induced adventitious bud formation and vitrification in vitro in Picea abies 总被引:3,自引:0,他引:3
Observations on the effects of different degrees of rigidity of both an agar (Tayio) and a non-agar (Gelrite) gel on the uptake of radiolabelled N6 -benzyladenine (14 C-BA) were also extended to mode of application and positioning of the explant. Regression analysis showed a highly significant inverse correlation between 14 C-BA accumulation and degree of gel stiffness. Significantly greater numbers of adventitious buds per explant were induced at low to medium levels of rigidity (2.5–10 g Tayio 1−1 , 1–5 g Gelrite 1−1 ); this advantage was almost completely nullified at the lower levels (2.5 and 5.0 g Tayio 1−1 , 1 and 1.5 g Gelrite 1−1 ) as a result of the high incidence of vitrification. In addition to turgor distension, vitrified buds displayed cellular damage. Explants with their cotyledons flattened onto the agar surface accumulated less 14 C-BA after 96 h than upright explants, but produced greater numbers of adventitious buds, pseudobuds and phylloids. It was suggested that BA was taken up only by "target" cells, presumably the differentiating subsidiary cells of those stomatal complexes in surface contact with the medium. Pulse treatments of relatively short durations (2 h) with optimal concentrations of BA (ca 125 μ M ), followed by subculturing on hormone-free media gelled with 10 g agar 1−1 , produced a satisfactory balance between yield and competence of adventitiously-induced buds. 相似文献
13.
Yersinia enterocolitica -resembling organisms were found at levels of 107 /g on a high pH (pH ≧ 6·0) vacuum-packaged beef striploin held for 6 weeks at 0·2°C, but did not exceed 105 /g on normal pH (pH < 6·0) striploins held for 10 weeks. Gram negative bacteria that produced H2 S on peptone iron agar were isolated from high pH vacuum packed striploins. These organisms were identified as Alteromonas putrefaciens . They attained levels of about 107 /g in 6 weeks at 0–2°C, at which time greening of the fat surface and 'drip'had occurred. On meat of normal pH, counts of A. putrefaciens were less than 104 /g after 6 weeks and no greening was evident. 相似文献
14.
Sulphate-reducing bacteria (SRB) were found in all of 200 bovine faeces examined. The number of SRB in bovine faeces ranged from 5 times 102 to 6 times 108 bacteria g-1 . Of 50 isolates identified, all were assigned to the genus Desulfovibrio . 相似文献
15.
Viable but non-culturable salmonellas in soil 总被引:4,自引:1,他引:3
P.E. Turpin K.A. Maycroft C.L. Rowlands E.M.H. Wellington 《Journal of applied microbiology》1993,74(4):421-427
P.E. TURPIN, K.A. MAYCROFT, C.L. ROWLANDS AND E.M.H. WELLINGTON. 1993. An enzyme-linked immunosorbent assay (ELISA) and a microwell fluorescent antibody (FA) direct count method have been developed for the monitoring of salmonellas in soil. Both methods have a minimum detection level of ca 106 cells per gram of soil. The FA direct count method gave a linear recovery for the inoculum range 106 –109 cells per gram of soil. When monitored by plate counts the survival of salmonellas was greater in a sterile than in a non-sterile soil. Evidence was found for the production of viable but non-culturable salmonellas in non-sterile soil; plate counts dropped rapidly with time, but FA direct counts and ELISA remained level. The salmonella cells became progressively smaller and rounder with time. Dead salmonella cells introduced into soil rapidly disappeared. 相似文献
16.
Abstract An examination of samples obtained from a commercial fish smoker, using seawater agar with incubation at 4°, 15° and 37°C for up to 28 days, revealed the presence of large bacterial populations in smoked fish. However, initially only low bacterial numbers, i.e., 2 × 103 /g, were present in the muscle of fresh, whole haddock ( Melanogrammus aeglefinus ). With filleting, there was a sudden increase in numbers to 9.2 × 105 /g. Yet immediately after smoking, the bacterial populations decreased (5 × 105 /g), followed by a gradual increase with storage (e.g., 2 × 106 /g after 24 h). Representative colonies were presumptively identified as Acinetobacter, Alcaligenes , coryneforms, Pseudomonas and Vibrio spp. 相似文献
17.
M. MAREKOVÁ, V. KMET' AND P. JAVORSKÝ. 1996. The transformation and subsequent regeneration of ruminal strain Streptococcus bovis AO24/85 protoplasts by plasmid DNA was studied. The best stabilizer for regeneration of protoplasted cells was 5% sucrose in the regeneration medium and in the agar plates. Optimal concentration of polyethylene glycol 6000 in the transformation medium was 25% for both plasmids tested. Addition of Ca2+ and Mg2+ ions (2.5 mmol l-1 ) to the transformation medium increased the proportion of regenerated cells. Transformation frequencies were 3 times 103 transformants per μg of pNZ12 and 2.4 times 102 per μg of pJK108, respectively. 相似文献
18.
The polymerase chain reaction (PCR) has the potential to detect low levels of the human pathogen Escherichia coli O157 : H7 in bovine faeces. To improve the utility of PCR for this application, several methods for preparing template DNA from bovine faeces, both directly and after non-selective enrichment, were tested. These were boiling, enzyme treatment, enzyme treatment plus phenol-chloroform extraction, and enzyme treatment plus phenol-chloroform extraction plus Geneclean® purification. Of these, the boiling method was the most consistent and had a sensitivity of approximately 3 cfu g−1 faeces, with an assay time of less than 32 h. The boiling method was also combined with immunomagnetic separation (IMS) to detect E. coli O157 : H7 in less than 8 h, but with a sensitivity of approximately 103 cfu g−1 faeces. These methods can be used to prepare template for PCR screening of bovine faeces using any appropriate PCR primers. 相似文献
19.
The lactoperoxidase system (LPS), a natural bactericidal system in milk, was investigated for its activity against salmonellas in vivo and in vitro. In acidified raw milk, in which the LPS was supplemented with an exogenous supply of H2 O2 , the numbers of salmonellas decreased rapidly. Different salmonella serotypes were affected to the same extent; rough strains, however, were more susceptible than smooth strains. When calves were fed on fresh milk, containing the LPS, and challenged with Salmonella typhimurium in doses of either 109 or 1010 , the clinical findings and salmonella excretion patterns were similar to those of control calves fed on heated milk. It was concluded that further studies, perhaps in the field, are necessary to evaluate LPS as a possible non-antibiotic system to control salmonellosis. 相似文献
20.
D.CHOI, R.S.W. TSANG AND M.H. NG. 1992. A sandwich capture ELISA based on a murine monoclonal antibody against a genus-specific epitope in the outer core region of the Salmonella lipopolysaccharide is described for the detection of different common serotypes of salmonellas. Four h broth cultures of seven standard and 24 wild strains of salmonellas were all detected by the capture ELISA while overnight broth cultures of 21 non-salmonella standard strains were all negative. The capture ELISA detected 1 ng/ml of Ra lipopolysaccharide, 106 /ml of a smooth wild strain of Salm. typhimurium , and 1120 cells of Salm. heidelberg after enrichment culture for 4 h. 相似文献