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At least 325 records · Page 18Linked to original sources
PubMed2000

Microbial testing methods for detection of residual cleaning agents and disinfectants-prevention of ATP bioluminescence measurement errors in the food industry.

The ATP luminescence measurement is based on the presence of an enzymatic reaction and may significantly be affected by cleaning agents and disinfectants. In addition, disinfectants can also reduce the activity of the luciferase enzyme and also act as ATP-releasing agents. The agents disrupt the cell walls but preserve ATP in measurable form, and therefore correlation with culture methods can be poor. Therefore, if a rapid method is used to detect ATP, a control must be used for reliable results. The possible effect of disinfectants can be eliminated with a rapid test to minimize sources of error. In the present study a microbiological residue testing method that is nonspecific for residues was developed. The effects of a total of 38 commercial cleaning agents and disinfectants of various types were assessed using two microbiological methods, the Vibrio fischeri photobacteria test and Micrococcus luteus inhibition zone technique. The results show that the V. fischeri photobacteria test is very sensitive. This test can therefore be used for testing cleaning agent residues on surfaces in very small amounts. A small study was also carried out in a food factory to show applicability in processing facilities. The study showed, that a need for this type of method exists in food processing.

Adenosine Triphosphate↗
PubMed1985

[Vi antigen and microbial adhesion factors. The detection of adhesins in commercial Vi antigen preparations].

Enterobacterial Vi-antigen inhibit the Escherichia coli-induced agglutination of red blood cells of guinea pigs and other animals, which indicates that Vi-antigen contains the admixture of adhesion associated with type I pili. The amount of adhesion contained in Vi-antigen can be determined from the degree to which its hemagglutination-inhibiting effect is manifested.

Adhesins, Escherichia coli↗
PubMed1994

Novel automated microbial screening of platelet concentrates.

The recovery of bacteria and the speed of detection of microbial growth in platelet concentrates (PC) were studied, comparing a novel automated blood culture system (BacT/Alert) with two traditional methods. Full-scale experiments were performed with a total of 33 units of PC (average content 320 x 10(9) platelets per unit) obtained from pooled buffy coats. Six strains known as possible PC contaminants were tested: S. epidermidis, S. aureus, P. aeruginosa, B. cereus, E. aerogenes, and S. sanguis. Using an inoculum of 50-98 bacteria/ml, bacterial contamination was detected in all of 11 PCs on 132 sampling occasions. With a small inoculum (0.3-9 bacteria/ml), the bacterial contamination was detected in all PCs in which abundant growth appeared, but failed to be detected in some instances where the bacterial content was very small. All of 11 uninoculated PC controls were negative. With the automated method the time for detection of a culture-positive PC was 6-16 h, clearly shorter than with the two manual-visual systems. The new system provides a rapid, reliable, and labour-saving method for screening of bacterial contamination in PCs. This would increase safety particularly if the present 5-day shelf life were extended.

Bacillus cereus↗
PubMed2003

PCR-denaturing gradient gel electrophoresis and two feces antigen tests for detection of Helicobacter pylori in mice.

PCR-denaturing Gradient Gel Electrophoresis (PCR-DGGE), a method suitable for the detection of microbial species in complex ecosystems, was evaluated for the detection and identification of Helicobacter spp. in feces and stomach tissue of mice. Two commercially available stool antigen tests for clinical diagnostics in humans were also evaluated in the C57Bl/6 mouse model of H. pylori infection. PCR-DGGE detected only Helicobacter ganmani in feces from H. pylori-infected as well as control animals, whereas in stomach specimens it demonstrated the presence of H. pylori in challenged and H. ganmani in control animals. Hence, the method detected DNA only of the predominant Helicobacter spp., which was also shown in cell dilution experiments. The Amplified IDEIA Hp StAR feces antigen test detected H. pylori in feces from all infected animals and generated no false-positive results, whereas the Premier Platinum HpSA-test also detected H. pylori in all infected animals but generated false-positive or equivocal results in 50% of the control animals. Premier Platinum HpSA, as opposed to Hp StAR, cross-reacted with non-pylori Helicobacter spp. in vitro.

Animals↗
PubMed1987

Molecular diagnosis of infectious diseases by nucleic acid hybridization.

Diagnostic microbiology has traditionally relied on the cultivation of an infecting agent in an in vitro system. However, the limitations of these methods have led to the development of alternative, molecular techniques which can detect specific microbial proteins or nucleic acids directly in body fluids. One such method, nucleic acid hybridization, has many attractive features including the potential for high sensitivity and specificity, the detection of a chemically stable analyte and the use of uniform reagents. Nucleic acid hybridization reactions have been used to detect a variety of microbial pathogens in assay formats using extracted nucleic acids or tissue sections. However, wider application of these techniques is limited by the fact that current methods employ radioisotopically labelled probes and cumbersome assay procedures. Solutions to these problems have been sought by the development of non-radioactive hybridization techniques which utilize enzymatic detection methods and by the development of rapid hybridization assays performed in solution. Further improvements in labelling techniques, assay formats and enzymatic detection methods should allow for the wider application of nucleic acid hybridization reactions in diagnostic microbiology.

Communicable Diseases↗
PubMed2004

Evaluating putative chimeric sequences from PCR-amplified products.

MOTIVATION: PCR amplification of highly homologous genes from complex DNA mixtures is known to generate a significant proportion of chimeric sequences. Ribosomal RNA genes are used for microbial species detection and identification in natural environments, and current assessments of microbial diversity are based on these sequences. Thus, chimeric sequences could lead to the discovery of non-existent microbial species and false diversity estimates. METHODS: In essence, our only source of information to decide if a sequence is chimeric or not is to compare it with known, non-chimeric sequences. Putative chimeric sequences were analyzed from sequence fragments of selected length (referred to as words) by comparing nucleotides at corresponding positions. Distances for each word between reference sequences (closely related to the tested sequence) were compared to the differences introduced by the tested sequence. The proposed strategy considers the actual variability existing in different regions throughout the analyzed sequences. The result is an efficient strategy for the evaluation of putative chimeric sequences. AVAILABILITY: A program computing the above procedure, Chimera and Cross-Over Detection and Evaluation (Ccode), is available at http://www.irnase.csic.es/users/jmgrau/index.html and http://www.rtphc.csic.es/download.html.

Algorithms↗
PubMed1988

The clinical value of gas-liquid chromatography in the detection of intra-amniotic microbial invasion.

Short-chain organic acids are byproducts of bacterial metabolism, and their detection by gas-liquid chromatography (GLC) in amniotic fluid has been proposed as a rapid, sensitive, and specific method for the diagnosis of infection. This study was conducted to determine whether GLC analysis of amniotic fluid would be helpful in a population of women in whom the Gram stain examination was negative. Amniotic fluid was retrieved by transabdominal amniocentesis from three groups of patients. Group 1 (negative control) contained 14 women with term pregnancies without clinical and microbiologic evidence of infection of the amniotic cavity; group 2 (positive control) included 17 women with a positive Gram stain examination and culture of amniotic fluid; group 3 (study group) comprised 25 women at risk for intra-amniotic infection who had a negative Gram stain of amniotic fluid. None of the patients in group 1 and 16 of 17 patients (94.1%) in group 2 had pathologic short-chain organic acids in the amniotic fluid. Seven of the 25 patients in group 3 had a positive amniotic fluid culture and only two had an abnormal GLC pattern. Of the remaining 18 patients with negative amniotic fluid cultures, eight had abnormal GLC results. In group 3, the sensitivity of GLC was 28.5% and the specificity was 55.5%. Gas-liquid chromatographic analysis of amniotic fluid has limited clinical value in the prediction of amniotic fluid culture when the Gram stain examination is negative.

Amniocentesis↗
PubMedDate not supplied

Comparative study between culture media employed in sterility test.

The sterility test aims at the contact of a product with a culture medium, as a way of detecting the possible presence of viable microorganisms in products which have been submitted to a sterilization process and/or to aseptic processing. Since the official introduction of the methodology, in 1932, several culture media have been proposed and adopted, in a constant attempt to offer conditions which support the growth of as many contaminants as possible. This work aimed at a comparative evaluation of the efficiency of microbial contaminants detection in the different types of culture media employed in sterility tests. The study led to the conclusion that the culture media recommended by the pharmacopoeia compendia, soybean casein digest and fluid thioglycollate, present the best results in microorganisms detection. Besides, the microbial strains, as well as microbial suspension density, recommended by the main pharmacopoeias to verify culture media growth promoting capacity, have also proved suitable for use.

Bacteria↗
PubMedDate not supplied

Enzyme immunoassays for the detection of infectious antigens in body fluids: current limitations and future prospects.

Enzyme immunoassays are attaining increased usage for the direct detection of microbial antigens in body fluids. Advantages of enzyme immunoassays include a high degree of sensitivity resulting from the inherent magnification of the enzyme-substrate reaction and the use of objective end points without the need for radioactivity. Enzyme immunoassays have been developed for the reliable detection of several important microbial antigens in body fluids, including antigens of rotavirus, hepatitis B virus, and Haemophilus influenzae type b. However, standard enzyme immunoassay techniques are not sufficiently sensitive for the measurement of some antigens from other viruses, bacteria, and parasites in concentrations that commonly occur in body fluids during the course of infectious diseases. This review examines some of the limitations of currently available enzyme immunoassay technology and discusses approaches to increasing the sensitivity and specificity of enzyme immunoassay systems. Methods for improving these assay systems include the use of monoclonal antibodies, improved methods of enzyme-immunoreactant conjugation, more sensitive substrate systems, improved methods of antigen-antibody access, and the direct measurement of microbial enzymes. The use of such techniques should lead to the development of efficient enzyme immunoassay systems for the direct detection of a wide range of bacterial, viral, and parasitic infections.

Absorption↗
PubMed2000

A bioelectrode for penicillin detection based on gluten-membrane-entrapped microbial cells.

A bioelectrode for penicillin detection was established using gluten membrane in which cells of Escherichia coli harbouring the plasmid pUC18 coding for penicillinase synthesis were entrapped. For the entrapment preparation, lyophilized cells were mixed with gluten solution during the formation of gel, and the resultant gel was hardened by the addition of oxidized starch. The immobilization procedure employed an inexpensive base material and avoided the use of purified enzyme. When the membrane with a thickness of 30 microm and a cell content of 33% (w/w) was used, the steady response of the bioelectrode to increasing concentrations of penicillin G buffered with 0.025 M phosphate was linear over the range of 1-16 mM. The response time was less than 3 min. Decreasing the cell content decreased the steady response due to a decline in enzymic activity. The treatment of lyophilized cells with ultrasonication or chemically with either N-cetyl-N,N,N-trimethylammonium bromide or guanidine hydrochloride rendered cells permeabilized and exposed the periplasmic enzyme to penicillin. The response time became shorter, but a serious decline in steady responses was observed because of the loss of enzyme activity during the cell permeabilization. The microbial electrode also showed different responses to penicillin G solution, depending on the pH and buffer concentration.

Buffers↗
PubMed1984

A rapid chemical spot test for the detection of lactic acid as an indicator of microbial spoilage in preserved foods.

A rapid method for the detection of lactic acid in preserved foods has been developed, based upon a chemical spot test which does not require solvent extraction or derivatisation of the lactic acid in the sample. The test can be completed within 5 min and was shown to confirm microbial spoilage detected by cultural techniques in a range of preserved foods. In addition the test was able to indicate microbial spoilage in samples where cultural techniques failed because the spoilage organisms were dead. The test may not be appropriate for products which have a naturally high lactic acid content.

Food Analysis↗
PubMed2003

Reagentless detection of microorganisms by intrinsic fluorescence.

Quick and accurate detection of microbial contamination is accomplished by a unique combination of leading-edge technologies described in this and the accompanying paper. In this contribution, a hand-held prototype instrument is described which is capable of statistically sampling the environment for microbial contamination and determining cell viability. The technology is sensitive enough to detect very low levels ( approximately 20 cells/cm(2) or cm(3)) of microbes in seconds.

Bacteria↗
PubMedDate not supplied

Rapid methods for the immunodiagnosis of infectious diseases: recent developments.

Current techniques for rapid diagnosis of microbial infections by direct detection of the microbial agent are compared. The techniques include enzyme immunoassay (EIA) tests, immunofluorescence, latex agglutination assays, and nucleic acid hybridization procedures. It is concluded that, for the near future, the preferred methods for rapid diagnosis will be by (1) EIA tests utilizing monoclonal antibodies and improved enzyme detection systems, and (2) improved latex agglutination procedures for certain antigens. Nucleic acid hybridization techniques, as currently performed, will need to be substantially improved to become the methods of choice.

Bacterial Infections↗