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Concordance of bacterial cultures with endotoxin and interleukin-6 in necrotizing enterocolitis.

Concordance between gram-negative enteric and other toxin-producing bacteria in blood and stool culture, endotoxin (lipopolysaccharide), and interleukin-6 (IL-6) was measured in 60 preterm infants (600-1600 g) as a clinical index in neonatal necrotizing enterocolitis (NEC). E. coli, Klebsiella, Enterobacter, and Clostridium spp., identified by routine bacteriology, were each strongly associated with elevated concentrations of endotoxin (P < 0.01) in stool filtrates, with Clostridium spp. most strongly associated with NEC disease. Stool filtrate endotoxin (EU/g) measured by a Limulus amebocyte lysate assay was age dependent. Samples from stage I NEC (61%) and infants with advanced disease (67%) had notably elevated levels of stool endotoxin (> 10 ln EU/g) compared to NEC-negative (47%) samples tested. Plasma and stool IL-6 generally tested at the low, nonmeasurable limit of the ELISA for NEC-negative (88%) and stage I NEC (93%), although a small proportion of samples (25%) from infants with stage II or III NEC had elevated stool concentrations of IL-6. We conclude that identification of toxin-producing organisms and endotoxin elevations in stool filtrates are more useful than circulating levels of endotoxin in plasma in predicting mucosally limited disease in the gastrointestinal tract. The prognostic value of monitoring stool endotoxin in infants with overgrowth of gram-negative bacteria has implications for therapeutic strategies in patients with early and advanced stages of disease. Monitoring inflammatory cytokines (IL-6) in relation to endotoxin values in stool appears of limited clinical value in controlling this devastating disease in preterm neonates.

Endotoxins↗

Cellular activating properties and morphology of membrane-bound and purified meningococcal lipopolysaccharide.

Neisseria meningitidis, the cause of epidemic meningitis and acute lethal sepsis, synthesizes surplus lipopolysaccharides (LPSs) during growth, which are released as outer membrane vesicles (OMV) or "blebs". Meningococcal disease severity is related to plasma LPS levels. We have compared the biological activities of native outer membrane vesicles (nOMV) to those of purified Nm-LPS (Nm-LPS) and LPS-depleted OMV (dOMV) prepared from N. meningitidis. The LPS content of nOMV was determined spectrophotometrically by quantifying KDO and by silver-stained SDS-PAGE gels. The morphology of the preparations was studied by transmission electron microscopy. The Limulus amoebocyte lysate (LAL) assay was used to quantify LPS in the plasma solutions. The preparations were diluted in endotoxin-free heparin plasma to equal amounts of LPS (w/w) in the range 50-5000 pg/ml. The biological reactivity was tested by: (i) a monocyte target-assay (monocyte purity > or =96%); and (ii) a whole blood model, measuring the secretion of TNF-alpha and IL-6 induction of procoagulant activity in monocytes (PCA). In both models, nOMV induced dose-dependent cell responses (TNF-alpha, IL-6, PCA) similar to purified Nm-LPS, whereas dOMV induced minimal responses. However, LAL activity was significantly higher for nOMV than for purified Nm-LPS and dOMV. The cellular responses of purified Nm-LPS and nOMV were reduced (>95%) by a specific anti-CD14-antibody.

Adult↗

Endotoxicity of newly recognized gram negative organism: a collective review.

A comprehensive picture of the in part personal investigations concerning an Endotoxin-like activity associated with some recently recognized Gram negative significant pathogens has been drawn. Suspensions of heat-killed organisms (or endotoxic lipopolysaccharide when available) have been tested using as markers of endotoxicity the Limulus assay and the skin Shwartzman reaction in rabbit. Some general considerations are finally set forth on the possible role of the surface structures in mediating (with other virulence factors) the damage in the host.

Animals↗

[Limulus amebocyte lysate assay for diagnosing intraamniotic infection].

The value of the Limulus amebocyte lysate assay (LAL) in the diagnosis of intraamniotic infection was determined in amniotic fluid from transabdominal amniocenteses in 51 women in preterm labor with intact membranes. The prevalence of positive amniotic fluid cultures was 21.5% (11/51) in detecting intraamniotic infection. The LAL was positive in 19.6% (10/51), its sensitivity 81.8% (9/11), specificity 97.5% (39/40), positive predictive value 90.0% (9/10), and negative predictive value 95.1% (39/41). Similarly, in detecting women who would fail tocolysis and deliver prematurely, its sensitivity was 27.6% (8/29), specificity 90.9% (20/22), positive predictive value 80% (8/10), and negative predictive value 48.8% (20/41). We conclude that LAL is a simple, rapid and sensitive test for detecting intraamniotic infection in women in preterm labor.

Amniotic Fluid↗

Endotoxin evaluation of eleven lipopolysaccharides by whole blood assay does not always correlate with Limulus amebocyte lysate assay.

More than 90% of all publications on endotoxin were carried out with endotoxins (lipopolysaccharide, LPS) from enterobacteriaceae. We compared the immune stimulatory potency of 11 different LPSs using human whole blood incubations. While the majority of LPSs induced cytokine release equipotently, a 1,000-fold more LPS from Pseudomonas aeruginosa or Vibrio cholerae was still less potent in inducing TNF, IL-1 beta, IL-10 and IFN-gamma though it potently induced nanogram quantities IL-8. All LPSs tested, regardless of the micro-organism, showed Toll-like receptor (TLR)4-dependence, except for the LPSs from P. aeruginosa and V. cholerae, which were both TLR4- and TLR2-dependent. Interestingly, UV-inactivated P. aeruginosa bacteria, although Gram-negative, also showed TLR2- and TLR4-dependence. Re-purification of commercial LPS preparations by phenol re-extraction led to a complete loss of the TLR2 dependency, indicating contamination with lipoproteins. In the Limulus amebocyte lysate assay, often performed to exclude contamination in purified water likely to originate from P. aeruginosa, P. aeruginosa LPS was only 2-fold less potent than LPS from S. abortus equi or the assay standard LPS from E. coli. This results in an overestimation of pyrogenic burden by a factor of 500 in the sample when compared with the biological activity of highly purified P. aeruginosa LPS in human whole blood.

Animals↗

Correlation between presence of viable bacteria and presence of endotoxin in middle-ear effusions.

The presence of endotoxin (detected by the Limulus amebocyte lysate assay) was compared to the presence of viable Haemophilus influenzae and Moraxella catarrhalis (detected by PCR) in 106 middle-ear effusions from pediatric patients with chronic otitis media. Endotoxin was found in 81 of the 106 specimens. Of these 81 specimens, 66 (81.5%) also tested positive for one or both of the gram-negative bacteria H. influenzae and M. catarrhalis. The data suggest that viable gram-negative bacteria, detectable by PCR but often undetectable by culture, may be the source of endotoxin in middle-ear effusions.

Adolescent↗

Sensitivity, specificity, and predictive values of the Limulus lysate assay for detection of exclusion of gonococcal cervicitis.

The Limulus amoebocyte lysate (LAL) assay was evaluated for its ability to detect or exclude gonococcal cervicitis in two groups of women. The first (positive) group consisted of 100 untreated women who were referred to the venereal disease clinic with culture-proven gonococcal cervicitis. The second (negative) group consisted of 50 normal volunteers who were evaluated on two separate occasions. In the first group, Gram stains and repeat cervical cultures were 53 and 93% sensitive, respectively. In the second group, Gram stains and cultures were negative. For the LAL assay, ectocervical mucus was removed with a sponge, and a depyrogenated cotton-tipped swab was then used to collect endocervical specimens. The swab was placed in 1 ml of diluent (1:1 dilution), and serial twofold dilutions were made and tested for endotoxin by the LAL assay. Incubation was carried out at 37 degrees C for 30 min; positive or negative results were indicated by gelation or lack of gelation, respectively. At a dilution of 1:256, sensitivity and specificity of the LAL assay were 57 and 99%, respectively. The positive predictive values ranged from 36.5 to 97.4% for theoretical prevalence rates of 1 to 40%. At a dilution of 1:8, the sensitivity and specificity were 100 and 78%, respectively. At this dilution, the negative predictive value was 100% regardless of the prevalence rate. Thus, these preliminary results show that at the higher dilution, the LAL assay was comparable to Gram stain in diagnostic accuracy of gonococcal cervicitis, and if used as a screening test at the lower dilution, a negative LAL assay would exclude women without gonococcal cervicitis.

Animals↗

Endotoxemia: methods of detection and clinical correlates.

As an assay for endotoxin, the Limulus amebocyte lysate assay has several desirable properties: sensitivity, specificity, and potential for adaptation to a quantitative format. Several modifications have been developed to enhance its potential for clinical application. The modifications that allow quantitative measurement of endotoxin and also improve its application to blood samples are described in this review. In fluids other than blood, the detection of endotoxin with the Limulus amebocyte lysate assay can be used as an aid to identify the presence of gram-negative bacteria, and the assay has established utility. With blood, however, there are a range of factors that interfere with the detection of endotoxemia and there are disparate views with respect to the diagnostic and prognostic significance of the test results. In general, the clinical significance of the finding of endotoxemia broadly parallels the frequency and importance of gram-negative sepsis in the patient groups studied and a decline in endotoxin levels accompanies clinical improvement. However, with therapies designed to reduce levels of endotoxin, or to antagonize its effects, it is unclear whether clinical improvement occurs as a consequence of changes in the levels of endotoxemia.

Endotoxins↗

Endotoxin potency in the A549 lung epithelial cell bioassay and the limulus amebocyte lysate assay.

The purpose of this study was to elucidate to what extent the potency of endotoxins measured by the limulus amebocyte lysate (LAL) assay is reflected in the potency in an in vitro assay based on release of interleukin-8 (IL-8) from a lung epithelial cell line, A549. Lipopolysaccharides (LPS) from Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enteritidis and detoxified LPS from E. coli were applied in serial dilutions in the LAL assay and in the A549 bioassay. Also 19 organic dust samples from waste recycling plants were tested. The A549 cells were incubated for 24 h with LPS or dust, and the IL-8 secretion was determined by ELISA. The method for evaluation of the LAL assay showed linearity for the four endotoxins. Using the slope as a measure of the potency factor (PF), LPS from E. coli and S. enteritidis was about four times more potent than that for LPS from K. pneumoniae and P. aeruginosa. In the A549 bioassay each of the different types of endotoxin had characteristic and very different dose-response curves. The potency of the LPS, in the A549 bioassay, ranked as follows K. pneumoniae > P. aeruginosa > E. coli > or = S. enteritidis. The content of endotoxin in the dust samples did not correlate with their potency in the A549 bioassay. The present study indicates a poor correlation between the potency of endotoxin in the LAL assay compared with the A549 bioassay. The lack of correlation when organic dust samples are tested may reflect the fact that these samples contain biological active compounds, which are non-reactive in the LAL-assay but stimulate IL-8 secretion from epithelial cells.

Animals↗

(1-->3)-beta-D-glucan in culture fluid of fungi activates factor G, a limulus coagulation factor.

Two well-known polysaccharides, (1-->3)-beta-D-glucan and mannan, are major structural components of the fungus cell wall. The G test is a direct method to measure (1-->3)-beta-D-glucan using a (1-->3)-beta-D-glucan-sensitive component, factor G, fractionated from the limulus lysate. The concentration of (1-->3)-beta-D-glucan in culture supernatants of Candida albicans increased to 1,390.0 pg/ml at 24 hours. The concentration of mannan also increased parallel with fungal growth. However, after digestion of supernatants with endo-(1-->3)-beta-D-glucanase, the reactivity to factor G disappeared, although titers of antimannan monoclonal antibody-based latex agglutination were unchanged. Our study demonstrated that cell suspensions of both C. albicans and Cryptoccocus neoformans activated the limulus factor G, and that not only the conidia form but also the filamentous form of Aspergillus fumigatus reacted with factor G. Various Candida spp. (C. paraspilosis, C. glabrata, C. tropicalis, C. krusei), Saccharomyces cerevisiae, Rhodotorula rubra, Trichosporon beigelii, and A. fumigatus released soluble (1-->3)-beta-D-glucan into their culture supernatants, but C. neoformans and Cunninghamella bertholletiae showed only a small reaction to the G test during their culture. Our results indicate that the G test is a good method for serodiagnosis of deep mycosis and also as a screening tool for contamination of medical devices, drugs, and experimental materials with (1 --> 3)-beta-D-glucan.

Agglutination↗

Characterization of Brucella abortus soluble antigen employed in immunoassay.

A soluble antigen extract of Brucella abortus (BASA) has been prepared by the National Veterinary Services Laboratories and furnished to a number of workers who are examining antibody-mediated and cell-mediated immune responses of cattle infected with B. abortus. Three lots of BASA were examined. There were quantitative but not qualitative differences among lots by content of protein, total carbohydrate, hexose, fatty acid, and 2-keto-3-deoxyoctonic acid. The presence of smooth lipopolysaccharide was demonstrated by the presence of 2-keto-3-deoxyoctonic acid and lipid, by Limulus lysate gelation activity, and by formation of characteristic lipopolysaccharide precipitates in immunoelectrophoresis. A polysaccharide antigen as well as two nonsurface antigens, A2 and C, were also identified. BASA is a satisfactory antigen for use in the enzyme-linked immunosorbent assay since the smooth lipopolysaccharide component bound to polystyrene and functioned in the test. Normal murine spleen cells showed a mitogenic response to BASA similar to that produced by purified smooth lipopolysaccharide. BASA has been used in other laboratories to stimulate peripheral blood leukocytes from cattle infected with B. abortus. Because BASA is a mixture of antigenic components shown to have mitogenic effects in the mouse system, questions on the nature of its stimulatory effect on bovine cells are raised.

Animals↗

Variability in LPS composition, antigenicity and reactogenicity of phase variants of Bordetella pertussis.

Comparison of lipopolysaccharides (LPS) from phase variants of different strains of Bordetella phase variants of different strains of Bordetella pertussis has shown a difference in their composition, antigenicity and reactogenicity. Phase I variants of B. pertussis, with the exception of strain 134, contain a preponderance of LPS I whereas the major component of LPS of phase IV variants is LPS II. Sera raised to LPSs of phase I strains, other than 134, cross-react with each other but not with phase IV LPSs; and similarly all sera raised to phase IV LPSs cross-react with each other and with LPS from 134 phase I. The LPSs of all phase I variants, including that of 134, are approximately ten-fold or more reactive in the limulus amoebocyte lysate assay (LAL) than phase IV LPSs. In the human mononuclear cell pyrogen assay phase IV LPSs also stimulated a lower response than phase I LPSs. The B. pertussis phase I LPSs are 10-times more reactive than Escherichia coli standard endotoxin in the LAL assay but 100-times less reactive than E. coli LPS in the monocyte test for pyrogen. The SDS-PAGE profiles of B. pertussis LPSs are quite different from those of B. parapertussis and B. bronchiseptica strains. B. pertussis LPSs produced a typical lipo-oligosaccharide (LOS) pattern. B. bronchiseptica LPS produced a similar pattern but was antigenically distinct from B. pertussis LPSs I and II. B. parapertussis in contrast produced a ladder pattern typical of smooth type LPS.

Animals↗

Lipid A in Helicobacter pylori.

Free lipid A of Helicobacter pylori was characterized with regard to chemical composition, reactivity with anti-lipid A antibodies, and activity in a Limulus lysate assay. The predominant fatty acids of H. pylori lipid A were 3-OH-18:0, 18:0, 3-OH-16:0, 16:0, and 14:0. Hexosamine was present in amounts similar to those in Campylobacter jejuni or Salmonella typhimurium lipid A. The lipopolysaccharide of H. pylori contained 2-keto-3-deoxyoctonic acid, a common constituent of enterobacterial and C. jejuni lipopolysaccharides. In the enzyme-linked immunosorbent assay, the doses of lipid A required to inhibit anti-lipid A by 50% (EI50 values) by absorption of the immune (rabbit) serum were 7.9, 1.2, and 1.4 micrograms of O-deacylated lipid A's from H. pylori, C. jejuni, and S. typhimurium per ml, respectively. The lower reactivity of H. pylori lipid A compared with those of the other two lipid A preparations (as shown by the higher EI50 value) was underscored by the use of a murine monoclonal anti-lipid A antibody in the inhibition assay. An EI50 value was not obtained at the concentrations tested for H. pylori lipid A; the corresponding figures for C. jejuni and S. typhimurium lipid A's were 13 and 14 micrograms/ml, respectively. No inhibition was obtained with H. pylori lipopolysaccharide, which showed a low-molecular-weight profile on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The activity of H. pylori lipid A in the Limulus assay was approximately 71 and 650 times lower than those of C. jejuni and S. typhimurium lipid A's, respectively. These findings suggest that lipid A is an integral part of the outer cell wall of H. pylori. The lower reactivity of H. pylori lipid A with anti-lipid A antibodies and in the Limulus assay compared with that of C. jejuni or S. typhimurium lipid A may be explained by a different composition of the fatty acids, especially the 3-hydroxy fatty acids, and a possible deviating phosphorylation pattern.

Animals↗

Endotoxin-mediated activation of cytokine production in human PBMCs by collagenase and Ficoll.

Endotoxin-induced early inflammatory reactions may inhibit the function and survival of isolated cells or cell aggregates after transplantation. By the chromogenic Limulus amebocyte lysate assay we found rather high but variable endotoxin concentrations in the chemicals used for islet isolation, i.e. collagenase and Ficoll. Liberase, a special collagenase preparation from Boehringer, was nearly endotoxin-free. Correlating to the endotoxin content, collagenase and Ficoll had the capacity to induce interleukin-1beta release from human peripheral blood mononuclear cells. Because collagenase and density gradient media are needed in most cell isolation procedures from solid organs, each lot of these chemicals should be tested for endotoxin contamination. In pancreatic islet transplantation, the use of endotoxin-free chemicals may diminish early local inflammatory reactions at the graft site and thereby reduce the number of islets needed for successful islet transplantation.

Collagenases↗

Three Rs potential in the development and quality control of pharmaceuticals.

The intention of a pharmaceutical company is to develop new, efficient products quick and with a minimum of costs. Compared to in vitro methods, animal experiments in general consume much more time and resources (costs as well as time to the market) than in vitro methods. Therefore, the use of whole animal models depends primarily on the judgement of their efficacy in the screening process, but the willingness to incorporate in vitro methods in general is high and is furthered by new developments such as high-throughput screening. Nevertheless, in vitro tests might be politically promoted by increasing their costs (quality controls, requested housing conditions) and duration (time to start of an experiment, sequential performance). Which models are favoured by industry to include them in a screening process: They have to be based on our most recent understanding of the respective disease, well characterised to allow interpretation of results and require only limited development time. All these aspects argue in favour of collaboration between industry and academia, where our understanding of pathophysiology is generated and mechanism based models are developed and characterised. However, technology transfer towards industry represents a bottle-neck for industrial use of these new in vitro models. New platforms to promote this transfer should be developed in order to bring together developer and user of novel in vitro systems and promote demonstration projects. Financing of such collaborations is not the key problem (the development of a single drug makes up to 500 million $) but the dilemma of publication of results: The development advantage compared to competitors depends on the exclusive use of novel models. The protection of intellectual property rights and the public interest in spreading alternatives to animal experiments must be balanced, e.g. by delayed but indispensable publication or advantages for companies employing alternatives in the regulatory approval process for a new drug. Quality control of therapeutic drugs (except hormones and blood products) represents a minor field of animal consumption with the exception of pyrogenicity testing. Despite considerable progress due to the introduction of the Limulus assay which represents the most successful in vitro alternative in use so far. However, some limitations of this in vitro test might be overcome in the near future by the currently validated human whole blood assay. During the last few years considerable progress has been made in the replacement (and deletion) of animal tests required for the potency and safety testing of hormones. This has been made possible by biotechnical production methods, by better-defined products, and because physico-chemical methods can be used for the potency testing of these products. In general, the better defined a drug is, the easier chemical, physical or in vitro techniques can be used for batch control. Control authorities should therefore urge the use of highly standardised components.

Animal Testing Alternatives↗

Endotoxin and nanobacteria in polycystic kidney disease.

BACKGROUND: Microbes have been suspected as provocateurs of polycystic kidney disease (PKD), but attempts to isolate viable organisms have failed. Bacterial endotoxin is the most often reported microbial product found in PKD fluids. We assessed potential microbial origins of endotoxin in cyst fluids from 13 PKD patients and urines of PKD and control individuals. METHODS: Fluids were probed for endotoxin and nanobacteria, a new bacterium, by the differential Limulus Amebocyte Lysate assay (dLAL), genus-specific antilipopolysaccharide (LPS) antibodies, monoclonal antibodies to nanobacteria, and hyperimmune serum to Bartonella henselae (HS-Bh). Selected specimens were also assessed by transmission electron microscopy (TEM) and nanobacterial culture methods. RESULTS: LPS or its antigenic metabolites were found in more than 75% of cyst fluids tested. Nanobacteria were cultured from 11 of 13 PKD kidneys, visualized in 8 of 8 kidneys by TEM, and immunodetected in all 13 PKD kidneys. By immunodetection, nanobacterial antigens were found in urine from 7 of 7 PKD males, 1 of 7 PKD females, 3 of 10 normal males, and 1 of 10 normal females. "Nanobacterium sanguineum" was dLAL positive and cross-reactive with antichlamydial LPS and HS-Bh. Some cyst fluids were also positive for LPS antigens from Escherichia coli, Bacteroides fragilis and/or Chlamydia, and HS-Bh, as were liver cyst fluids from one patient. Tetracycline and citrate inhibited nanobacterial growth in vitro. CONCLUSION: Nanobacteria or its antigens were present in PKD kidney, liver, and urine. The identification of candidate microbial pathogens is the first step in ascertaining their contribution, if any, to human disease.

Adult↗

A new kinetic single-stage Limulus amoebocyte lysate method for the detection of endotoxin in water and plasma.

A convenient kinetic chromogenic Limulus amoebocyte lysate (LAL) method, based on components originally intended for a two-stage end-point method, has been developed. The components (LAL and chromogenic substrate) can be pooled and subsequently used in a single-stage kinetic procedure adapted to microplates. With the help of a kinetic software, it is possible to measure over the three log range 0.005-12 EU/ml in one test run--a range considerably wider than the range of the end-point procedure. A good linearity of the log-log standard curve, reflected by coefficients of regression between 0.997 and 1.0, is shown as well as a high-resolution (> 700 s) between the negative control and the lowest standard point. Moreover a good precision (C.V. < 10%) is obtained in both water and plasma, showing the usefulness of the method in different applications. Finally, a strong correlation (r = 0.95-0.99) to other LAL methods is demonstrated.

Endotoxins↗

Is the limulus amebocyte lysate the sole predictor of septic episodes in major thermal injuries?

Septic episodes in thermal injuries are usually hallmarked by a series of physiologic parameters that include tachypnea, prolonged paralytic ileus, hyperthermia or hypothermia, altered mental status, thrombocytopenia, leukocytosis or unexplained leukopenia, acidosis, and hyperglycemia. Recent studies with polycystic kidney disease have clearly indicated that the limulus amebocyte lysate (LAL) assays were predictive of fungal infections in this patient population. Because both bacteria and fungi produce lipopolysaccharide that can be identified with the LAL assay, we randomly assayed sequential sera of 45 patients with major thermal injuries for positivity in the LAL assay, with use of the QCL-1000 kit (BioWhittaker, Walkersville, Md). The average burn size of this patient population was 63.43% total body surface area. The average age of the patient was 6.2 years. The sex distribution included 30 males and 15 females. The infectious agents included gram-positive cocci and gram-negative rods, and 14 patients had concomitant fungal infections. Eighty-five percent of the patients tested were positive for endotoxin, with levels ranging from < 0.1 EU/mL to > 1.0 EU/mL. The predominant organism isolated before or on the date the serum was drawn was Pseudomonas aeruginosa (51%), followed by Klebsiella pneumoniae (15%). The remaining 34% were a variety of Enterobacteriaceae. Of the 14 patients who yielded a fungus, 3 had negative LAL assays. Two patients with an elevated LAL grew only Staphylococcus epidermidis in the bloodstream and the wounds. These data clearly indicate that the LAL assay cannot be relied on as the sole predictor of septic episodes; however, it can be an adjunctive test to confirm sepsis when the other parameters have been considered.

Adolescent↗