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Results for “microbial detection”

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At least 181 records · Page 10Linked to original sources

PubMed2004

Assessment of a novel approach to evaluate the outcome of endoscope reprocessing.

OBJECTIVE: To investigate and evaluate the use of a portable luminometer system for detecting contamination following the reprocessing and high-level disinfection of flexible endoscopes. DESIGN: Random sampling of endoscopes spaced at 1- to 2-week intervals following normal use in patients. METHODS: Portable luminometer system testing of 31 endoscopes undergoing reprocessing, 63 stored endoscopes, and 15 reprocessed endoscopes that underwent in-depth microbiological analysis. For testing with the portable luminometer system, samples were collected by swabbing a 100-cm2 shank surface area and the internal tip end orifice. Standardization of portable luminometer system results was performed in vitro by comparison of serial dilutions of known quantities of microorganisms and blood, tested before and after sterilization by autoclave. Microbiological analysis included Gram stain, culture for aerobic bacteria, and gene probes for Mycobacterium tuberculosis, herpes simplex viruses 1 and 2, and Cytomegalovirus. Trichrome and calcofluor white stains were used to detect parasites and fungi. Legionella was detected by stain with fluorescent-labeled monoclonal antibody. SETTING: The gastroendoscopy unit of a Veterans Affairs hospital. RESULTS: The portable luminometer system was capable of detecting microbial and cellular contamination of flexible endoscopes following high-level disinfection and reprocessing. The sensitivity of the assay was sufficient for detecting low-level contamination. CONCLUSIONS: The system provided a rapid microbiological outcome monitor for the cleaning and disinfection process. The system was easy to use and relatively accurate.

Bacteria↗

PubMed2006

Sensor molecules in intestinal innate immunity against bacterial infections.

PURPOSE OF REVIEW: Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain (NOD)-containing proteins are innate immune sensors for microbial signature molecules. This review highlights new insights into the functions of these sensors in intestinal physiology. RECENT FINDINGS: TLRs are membrane bound and survey the extracellular space for microbe-derived molecules, while NOD-containing proteins are cytoplasmic and detect microbial molecules in the cytoplasm. Most microbial sensors recognize components of the bacterial cell wall and its appendages. For example, TLR4 detects lipopolysaccharide in the Gram-negative bacterial cell wall. TLR5 recognizes flagellin, a component of bacterial flagella required for motility. NOD1 recognizes diaminopimelic acid-containing dipeptide or tripeptide motifs in the Gram-positive bacterial cell wall, while NOD2 detects muramyl dipeptide, a ubiquitous cell wall peptidoglycan motif. These sensors are important for host defense against gastrointestinal pathogens. Thus, TLR4 is required for Salmonella eradication, NOD1 contributes to controlling Helicobacter pylori infection, and NOD2 is involved in mucosal defense against Listeria monocytogenes. These sensors also regulate mucosal inflammation independent of pathogen infections. SUMMARY: Toll-like receptors and nucleotide-binding oligomerization domain-containing proteins not only play critical roles in host defense against known gastrointestinal bacterial pathogens, but also contribute to mucosal homeostasis in the apparent absence of such pathogens.

Animals↗

PubMed1976

On methods of detection of extraterrestrial life.

New methods have been developed for detecting microbial growth from the microflora of desert soils. The first is a polarimetric method in which the fall in optical activity due to assimilation of D-glucose is followed. Detectable changes with desert soils were seen in a few hours, and the method can be employed with small amounts of material. The second method is the release of heat from metabolizable substrates as measured by a microcalorimeter. In the presence of glucose a characteristic response from desert soils was found within 24 hours.

Culture Media↗

PubMed2004

Toll-like receptor control of the adaptive immune responses.

Recognition of microbial infection and initiation of host defense responses is controlled by multiple mechanisms. Toll-like receptors (TLRs) have recently emerged as a key component of the innate immune system that detect microbial infection and trigger antimicrobial host defense responses. TLRs activate multiple steps in the inflammatory reactions that help to eliminate the invading pathogens and coordinate systemic defenses. In addition, TLRs control multiple dendritic cell functions and activate signals that are critically involved in the initiation of adaptive immune responses. Recent studies have provided important clues about the mechanisms of TLR-mediated control of adaptive immunity orchestrated by dendritic cell populations in distinct anatomical locations.

Adaptation, Physiological↗

PubMed2005

False-positive alarms for bacterial screening of platelet concentrates with BacT/ALERT new-generation plastic bottles: a multicenter pilot study.

BACKGROUND: The microbial detection system BacT/ALERT (bioMérieux) is widely used to monitor bacterial contamination of platelet concentrates (PCs). Recently, the manufacturer introduced polycarbonate culture bottles and a modified pH-sensitive liquid emulsion sensor as microbial growth indicator. This reconfigured assay was investigated in a routine setting. STUDY DESIGN AND METHODS: In each of eight transfusion centers, samples from 500 consecutive PCs were monitored for 1 week. For all PCs with a positive BacT/ALERT signal, retained samples and, if available, original PC containers and concomitant red blood cell concentrates were analyzed independently. Initially BacT/ALERT-positive PCs without bacterial identification in any sample were defined as false-positive. BacT/ALERT-positive PCs with bacteria in the first sample only were called potentially positive. PCs with bacteria in the first sample and the same strain in at least one additional sample were accepted as positive. RESULTS: Five PCs (0.13%) were positive, 9 PCs (0.23%) were potentially positive, and 35 PCs (0.9%) were false-positive. The rate of false-positive BacT/ALERT results varied substantially between centers (<0.2%-3.2%). Tracings from false-positive cultures lacked an exponential increase of the signal during incubation. Most of these false-positives were due to malfunctioning cells in various BacT/ALERT incubation units. CONCLUSION: Careful assessment of individual tracings of samples with positive signals helps to identify malfunctioning incubation units. Their early shutdown or replacement minimizes the high rate of unrectifiable product rejects attributed to false-positive alarms and avoids unnecessary concern of doctors and patients after conversion to a reconfigured BacT/ALERT assay.

Bacteria↗

PubMed2006

Time to positivity of blood culture in newborn infants.

The purpose of this study was to evaluate the minimum incubation time required to detect positive blood cultures from newborn infants with sepsis. Data were collected retrospectively on seventy-five positive blood cultures from newborn infants in the neonatal intensive care unit of Songklanagarind Hospital. The BacT/Alert Microbial Detection System had been used to culture the samples. Data were obtained retrospectively from the patients' medical records for positive blood cultures. A computer algorithm in the automated blood culture system determined the time to positivity, which was then evaluated for clinically important definite bacterial pathogens, possible bacterial pathogens, fungi and contaminants. Definite bacterial pathogens accounted for 46% (34/74) of the positive blood culture results, possible bacterial pathogens accounted for 39% (29/74), fungi for 7% (5/74) and contaminants for 8% (6/74). The cultures were positive at 24, 36 and 48 hours of incubation in 70.2%, 91.8% and 95.9% respectively. At 36 hours of incubation, the sensitivity, specificity and negative predictive value were 70.3%, 100% and 93.3%, respectively. All cultures growing clinically significant definite bacterial pathogens were positive by 36 hours of incubations, 88% by 24 hours. The cultures had 100% sensitivity, specificity and negative predictive value at 36 hours of incubation. If definite and possible bacterial pathogens were considered, the time to positivity was 71% at 24 hours, 95% at 36 hours and 97% at 48 hours, respectively. The sensitivity, specificity and negative predictive values were 70.3%, 100%, and 93.3%, respectively. Of cultures growing fungi, 80% were positive by 36 hours and all by 48 hours.

Algorithms↗

PubMed2005

Infection, autoimmunity, and glycolipids: T cells detect microbes through self-recognition.

De Libero et al. (2005) demonstrate in this issue of Immunity that bacterial infection leads to increased synthesis of autologous glycolipids that are recognized by CD1-restricted human T cells, indicating that recognition of inducible self-glycolipids could be a mechanism for microbial detection. This mechanism also may provide a connection between infection and autoimmunity.

Antigens, CD1↗

PubMed1984

Comparative evaluation of three commercial products and counterimmunoelectrophoresis for the detection of antigens in cerebrospinal fluid.

Three commercial products and counterimmunoelectrophoresis were evaluated for their ability to detect microbial antigens of Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae in cerebrospinal fluid from 157 patients suspected of having meningitis. Thirty-four patients were diagnosed as having bacterial meningitis by culture, microscopy, or antigen detection. The overall results showed the following detection percentages; counterimmunoelectrophoresis, 76%; Phadebact CSF, 76%; Directigen, 82%, and Bactigen, 93%. The results with purified antigen revealed that latex agglutination was more sensitive than coagglutination, which in turn was more sensitive than counterimmunoelectrophoresis.

Agglutination Tests↗

PubMed2000

Post-pH effect in oral streptococci.

OBJECTIVES: To study the post-pH effect (PpHE) in 11 strains of oral streptococci belonging to Streptococcus sanguis, S. mitis, S. gordonii, S. mutans and S. sobrinus by using the BacT/Alert microbial detection system. METHODS: The bacterial cultures were exposed to a different pH (3.6, 4.0, 4.6, 5.0, 5.6, 7.0, 7.5, 8.0 and 8.6) for 1 h, and then returned to a neutral medium. The automated BacT/Alert system determined resumed microbial growth by measuring CO2 generation. The PpHE expresses the time difference between resumed growth (after pH shock) and optimal growth (pH 7.0 used as the control). RESULTS: PpHE was found to be minimal for alkaline pH values, and to be strain and species dependent. CONCLUSIONS: The PpHE may be useful as an ecological determinant or as an indicator of the cariogenicity of oral streptococci.

Carbon Dioxide↗

PubMed2005

Quantum dots as fluorescent labels for quantitative detection of Salmonella typhimurium in chicken carcass wash water.

Fluorescent semiconductor quantum dots have recently emerged as a novel and promising class of fluorescent labels for biological detection. In this study, quantum dots were used as fluorescent labels in immunoassays for quantitative detection of foodborne pathogenic bacteria. Salmonella Typhimurium cells were separated from chicken carcass wash water using anti-Salmonella antibody coated magnetic beads and reacted to secondary biotin-labeled anti-Salmonella antibody. Quantum dots coated with streptavidin were added to react with biotin on the secondary antibody. Measurement of the intensity of fluorescence produced by quantum dots provided a quantitative method for microbial detection. A linear relationship between Salmonella Typhimurium cell number (log N) in the samples of chicken carcass wash water and the fluorescence intensity (FI) was found for the cell numbers ranging from 10(3) to 10(7) CFU/ml. The regression model can be expressed as FI = 198.6 Log N - 639.03 with R2 = 0.96. The detection limit of this method was 10(3) CFU/ml.

Animals↗

PubMedDate not supplied

Comparative physiological disposition of some anthraquinone glycosides and aglycones.

The in vitro microbial degradation and the urinary excretion and biliary secretion in rats of two anthraquinone glycosides (sennosides A and B) and four aglycones (sennidins A and B, rhein, and danthron) were studied using a high performance liquid chromatographic system with gradient elution and amperometric detection. Microbial degradation of sennosides A and B occurred almost exclusively in the presence of mice caecum inoculae and was associated with the release of sennidins A and B. Rhein and danthron were indiscriminately metabolized by bacteria sampled from all regions of mice intestine, whereas sennidins lacked stability in biological media. The fraction of the dose administered orally to rats and recovered as aglycones or as glucuronides in bile and urine after 48 hours was five times greater for rhein (15 per cent) and danthron (13.4 per cent) than for sennosides A (1.8 per cent) and B (2.8 per cent) excreted or secreted as sennidins. These results support the concept that anthraquinone glycosides are less likely to enter the systemic circulation and, thus, are able to exert their laxative effect at lower doses than aglycones.

Animals↗

PubMed1998

Reassessment of the incubation time in a controlled clinical comparison of the BacT/Alert aerobic FAN bottle and standard anaerobic bottle used aerobically for the detection of bloodstream infections.

This study assessed the minimum incubation time required to detect bloodstream infections during a controlled clinical comparison of the performance characteristics of the BacT/Alert aerobic FAN bottle and the standard anaerobic bottle used aerobically except on a selective basis. Blood was collected from adults with suspected bloodstream infections and inoculated into each bottle, which was monitored in the BacT/Alert Microbial Detection System. The anaerobic bottle was vented before incubation except when cultures were obtained from patients on the colorectal and gynecologic surgical and emergency services. Statistical analysis was limited to those culture sets in which each bottle was inoculated with > or = 8 mL of blood and bacterial growth was considered to be clinically significant. A total of 682 positive cultures from 243 patients satisfied the inclusion criteria. Significantly more isolates of Staphylococcus aureus (p < 0.001), S. epidermidis (p < 0.001), other coagulase-negative staphylococci (p < 0.001), Enterococcus spp. (p = 0.04), Escherichia coli (p = 0.03), all Enterobacteriaceae (p < 0.001), Pseudomonas aeruginosa (p = 0.001), and Candida spp. (p < 0.001) were detected by the aerobic FAN bottle. Significantly more septic episodes due to S. aureus, S. epidermidis, other coagulase-negative staphylococci, Enterobacteriaceae, P. aeruginosa, and Candida spp. were detected by the aerobic FAN bottle. Significantly more bacterial isolates were detected by the aerobic FAN whether or not antibiotics were being administered at the time of blood culture, whereas there were significantly fewer positive cultures in the vented standard anaerobic bottle when patients were receiving antimicrobial therapy than when they were not. All but 5% of positive cultures were detected within three days. Only six of the cultures requiring four or five days of incubation represented true misses, and only one of these six resulted in a change in therapy which, however, did not affect the patent's outcome.

Adult↗

PubMed2006

Involvement of Toll-like receptor 5 in the recognition of flagellated bacteria.

Toll-like receptors (TLRs) are key components of the immune system that detect microbial infection and trigger antimicrobial host defense responses. TLR5 is a sensor for monomeric flagellin, which is a component of bacterial flagella known to be a virulence factor. In this study we generated TLR5-deficient mice and investigated the role of TLR5 signaling in the detection of flagellin and antibacterial immune responses to Salmonella typhimurium and Pseudomonas aeruginosa. We found that TLR5 is essential for the recognition of bacterial flagellin both in vivo and ex vivo. TLR5 contribution to antibacterial host response to i.p. infection with S. typhimurium or intranasal administration of P. aeruginosa may be masked by TLR4 or other sensing mechanisms. By using radiation bone marrow chimera, we showed that upon i.p. injection of flagellin immune responses are mediated by lymphoid cells, whereas resident cells are required for the initiation of response upon intranasal flagellin administration. These results suggest that flagellin recognition in different organs is mediated by distinct TLR5-expressing cells and provide insights into the cooperation of the TLR5 and TLR4 signaling pathways used by the innate immune system in the recognition of bacterial pathogens.

Animals↗

PubMed2004

Microbial monitoring of spacecraft and associated environments.

Rapid microbial monitoring technologies are invaluable in assessing contamination of spacecraft and associated environments. Universal and widespread elements of microbial structure and chemistry are logical targets for assessing microbial burden. Several biomarkers such as ATP, LPS, and DNA (ribosomal or spore-specific), were targeted to quantify either total bioburden or specific types of microbial contamination. The findings of these assays were compared with conventional, culture-dependent methods. This review evaluates the applicability and efficacy of some of these methods in monitoring the microbial burden of spacecraft and associated environments. Samples were collected from the surfaces of spacecraft, from surfaces of assembly facilities, and from drinking water reservoirs aboard the International Space Station (ISS). Culture-dependent techniques found species of Bacillus to be dominant on these surfaces. In contrast, rapid, culture-independent techniques revealed the presence of many Gram-positive and Gram-negative microorganisms, as well as actinomycetes and fungi. These included both cultivable and noncultivable microbes, findings further confirmed by DNA-based microbial detection techniques. Although the ISS drinking water was devoid of cultivable microbes, molecular-based techniques retrieved DNA sequences of numerous opportunistic pathogens. Each of the methods tested in this study has its advantages, and by coupling two or more of these techniques even more reliable information as to microbial burden is rapidly obtained.

Adenosine Triphosphate↗

PubMed2003

Spectral imaging detection and counting of microbial cells in marine sediment.

Semiautomated detection and counting techniques for microbial cells in soil and marine sediment using microscopic-spectral-imaging analysis were developed. Microbial cells in microscopic fields were selectively detected from other fluorescent particles by their fluorescent spectrum, based on the spectral shift between the conjunction and nonconjunction of DNA fluorochrome (SYBR Green II) with nucleic acids. Using this technique, microbial cells could be easily detected in soil and 30-cm deep sediment samples from Tokyo Bay, both of which contain particles other than microbial cells. Total cell density was semiautomatically estimated at 1-6 x 10(9) cells cm(-3) of sediment sampled at different depths in Tokyo Bay, which corresponded to 65-106% (mean 88%) of visual direct counting. This technique may be useful for detecting microbial cells in soil and sediment samples from the deeper subsurface environment.

Bacteria↗

PubMed2005

Comparing recovering efficiency of immunomagnetic separation and centrifugation of mycobacteria in metalworking fluids.

The accurate detection and enumeration of Mycobacterium immunogenum in metalworking fluids (MWFs) is imperative from an occupational health and industrial fluids management perspective. We report here a comparison of immunomagnetic separation (IMS) coupled to flow-cytometric enumeration, with traditional centrifugation techniques for mycobacteria in a semisynthetic MWF. This immunolabeling involves the coating of laboratory-synthesized nanometer-scale magnetic particles with protein A, to conjugate a primary antibody (Ab), specific to Mycobacterium spp. By using magnetic separation and flow-cytometric quantification, this approach enabled much higher recovery efficiency and fluorescent light intensities in comparison to the widely applied centrifugation technique. This IMS technique increased the cell recovery efficiency by one order of magnitude, and improved the fluorescence intensity of the secondary Ab conjugate by 2-fold, as compared with traditional techniques. By employing nanometer-scale magnetic particles, IMS was found to be compatible with flow cytometry (FCM), thereby increasing cell detection and enumeration speed by up to two orders of magnitude over microscopic techniques. Moreover, the use of primary Ab conjugated magnetic nanoparticles showed better correlation between epifluorescent microscopy counts and FCM analysis than that achieved using traditional centrifugation techniques. The results strongly support the applicability of the flow-cytometric IMS for microbial detection in complex matrices.

Centrifugation↗

PubMed1998

Use of an antimicrobial removal device in endophthalmitis cultures.

PURPOSE: This study sought to determine whether the use of an antimicrobial removal device (ARD) to process intraocular fluids increases microbial detection compared with conventional cultures. METHODS: The authors retrospectively reviewed all cases of endophthalmitis submitted to their laboratory from January 1982 through December 1996. Aqueous or vitreous specimens or both that were cultured on conventional media (blood agar, chocolate agar, anaerobic blood agar, and thiol broth) and by ARD processing were included in the study. Specimens were inoculated into tubes with ARD for 5 to 10 minutes. The fluid was then withdrawn and cultured using conventional media; thioglycolate broth was added to the tube containing the resin beads. The conventional and ARD-processed cultures were incubated at 35 degrees C for at least 7 days. RESULTS: Of the 338 endophthalmitis cultures processed using both conventional cultures and a parallel ARD, 166 (49.1%) yielded positive microbial growth on one or more media. Of the 166 culture-confirmed cases, 127 (76.5%) were positive in both the ARD-processed and direct cultures, 17 (10.2%) were positive by conventional culture only, and 22 (13.3%) were positive by the ARD-processed sample alone (P = 0.52). The spectrum of microorganisms was similar among all culture groups. The detection of coagulase-negative staphylococci and micrococci by ARD alone was slightly better than detection by conventional culture only (P = 0.06). Of 93 positive cultures from 179 patients in whom prior antibiotic use was documented, 75 (80.6%) were positive by both methods, 8 (8.6%) by conventional cultures only, and 10 (10.8%) only by the ARD-processed specimen (P = 0.81). CONCLUSION: Use of an antimicrobial removal device does not significantly increase the microbial yield of endophthalmitis cultures compared with conventional culture techniques, whether or not antimicrobial therapy is being used.

Anti-Bacterial Agents↗

PubMed1997

Diagnostic value of CD45RO expression on circulating T lymphocytes of fetuses and newborn infants with pre-, peri- or early post-natal infections.

We examined the expression of the CD45RO antigen, which characterizes the antigen primed/memory phenotype of T lymphocytes, as a marker for congenital infection in blood samples of newborns and fetuses. CD45RO expression on T cells was determined by triple-colour fluorescence flow cytometry. In total 537 blood samples of newborns and infants up to an age of 3 months and 89 fetal blood samples from gestational weeks 19-31 were analysed. Of the newborns and infants, 74 had a clinically, serologically and/or antigenically evident infection, and four of the fetuses had a confirmed intra-uterine infection. In 35 infants with acute predominantly bacterial infections such as sepsis or pneumonia, 17 (48.6%) had elevated CD45RO(bright) expression. In 39 infants with proven pre-, peri- or early post-natal infections with toxoplasmosis, cytomegalovirus (CMV), rubella, herpes simplex virus (HSV) or human herpes virus type 6 (HHV6), 25 (64.1%) exhibited enhanced CD45RO(bright) expression. Three of four fetuses with confirmed intra-uterine infection (three with CMV, one with parvovirus B19) exhibited elevated CD45RO(bright) expression. The specificity of the CD45RO assay for detecting microbial infections was 94.6% for newborns and infants up to 3 months and 90.6% for fetuses. It is concluded that elevated numbers of CD45RO(bright) T cells in infants up to 3 months of age strongly suggest an infection. However, the sensitivity of the CD45RO assay is not sufficient to enable the test to be used as a general marker for prescreening infants to detect pre-, peri- or early post-natally acquired infections.

Bacterial Infections↗