Diagnosis Of Endotoxemia Research Articles

Diagnosis of Endotoxemia with Gram-Negative Bacteremia Is Bacterial Species Dependent: a Meta-Analysis of Clinical Studies

Endotoxemia is undetectable for up to 60% of cases of bacteremia caused by gram-negative (GN) species, a discordance attributed to the limitations of the Limulus assay for endotoxemia. The lipid A structure of the endotoxin molecule is critical for the sensing of GN bacteria by the host immune system although not so for sensing by the Limulus assay. The lipid A structure of commensal Enterobacteriaceae is hexa-acyl, whereas non-Enterobacteriaceae have a broader range of structures. By using a previously published classification of lipid A structures (R. S. Munford, Infect. Immun. 76:454-465, 2008), the association of endotoxemia with bacteremia caused by GN organisms is reexamined for 580 GN bacteremic patients from 46 studies. Endotoxemia was less commonly detected for cases of bacteremia caused by Salmonella enterica serovar Typhi (four studies; 15 of 55 cases of bacteremia [27%]) than for cases of bacteremia caused by Neisseria meningitidis (five studies; 69 of 84 cases [82%]) and Pseudomonas pseudomallei (one study; 38 of 41 cases [93%]) among studies restricted to those with specified cases of bacteremia caused by GN organisms. Among 23 unrestricted studies, endotoxemia was less commonly detected for cases of bacteremia with a commensal member of the Enterobacteriaceae (104 of 240 cases [43%]) than with non-Enterobacteriaceae (59 of 100 cases [59%]) (summary odds ratio, 0.53 [90% confidence interval, 0.33 to 0.85]). This finding is consistent across all the unrestricted studies, even including studies with seemingly contrary results for endotoxemia diagnosis among cases of bacteremia caused by GN bacteria overall. Surprisingly, with bacteremia caused by commensal Enterobacteriaceae, the diagnosis of endotoxemia appears to be unrelated to the Limulus assay sensitivity. Across these 45 studies, the association of endotoxemia with GN bacteremia is variable but consistent for different types of GN bacteremia.

Immunohistochemical Staining for Endotoxin Using Horseshoe Crab Factor C in Fecal Peritonitis

The object of the present study was to apply a new immunohistochemical staining method to the in vivo determination of endotoxin localization. The immunohistochemical staining method requires factor C (an initiation factor in the Limulus clotting system which is mediated by endotoxin) as a specific ligand of endotoxin, and a newly developed murine monoclonal antibody to factor C. The blood endotoxin level and endotoxin localization in the rat were determined before and at 6, 12 and 24 h after intraperitoneal injection of 0.25 g/kg of fresh rat feces. The greatest blood endotoxin level was achieved at 12 h after the injection, and uptake of endotoxin was evident in Kupffer cells in the liver at 24 h after the injection. There has been no report on determining endotoxin localization in cases of endotoxemia attributed to fecal peritonitis. This new immunohistochemical staining method for determining endotoxin localization will contribute to the histopathological diagnosis of endotoxemia in humans.

Limulus amebocyte lysate (LAL) detection of endotoxin in human blood

Limulus amebocyte lysate (LAL) has been applied to the detection of endotoxin in human serum, plasma and blood since the early 1970s. Although the diagnostic potential of LAL for endotoxemia was recognized immediately, the assay's modest sensitivity and specificity (for Gram-negative sepsis/bacteremia) were perceived as limiting the clinical usefulness of LAL. In an attempt to overcome these drawbacks, many studies have been conducted since the initial work by Levin and his colleagues. Numerous attempts have been made to improve the sensitivity of the assay by changing the formulation of the LAL and assay methodology. The original gel-clot method has for the most part been replaced with turbidimetric or chromogenic methods. The amount of endotoxin detectable within a 1 h incubation period has gone from the nanogram to the picogram range. Since blood (plasma) components interfere with the test, various methods to remove inhibition and/or enhancement have been developed. The chloroform extraction technique of Levin and co-workers has been replaced with acid extraction or with dilution and heating. Partitioning of endotoxin in blood may also influence the assay (recovery). Many recent investigators use platelet-rich plasma instead of ordinary plasma, while a few studies have used whole blood. Even with all the improvements, the specificity and related diagnostic usefulness of the LAL assay for Gram-negative sepsis remain an obstacle for regulatory acceptance. This may have more to do with our understanding of the septic process than with the ability of LAL to detect endotoxin. Although a recent study indicates that the type of Gram-negative bacteremia may be a critical determinant for clinical utility of the LAL test, the presence of endotoxin is not highly predictive of Gram-negative sepsis and vice versa. However, with the potential availability of anti-endotoxin therapy, the diagnosis of endotoxemia, with or without bacteremia, may be extremely important for timely and effective treatment modalities. It is concluded that the LAL test and accompanying sample preparation has evolved into a clinically useful test for the detection of circulating endotoxins and even its modest predictability for sepsis may have some clinical utility.

Bacterial Endotoxemia and Reproductive Effects in Ruminants

Gram-negative bacterial infections are fairly common in domestic ruminants. They can cause an endotoxemia with a variety of systemic signs, including fever, leukopenia, and ruminal stasis. Reproductive effects of endotoxemia include alterations in the estrous cycle and inability to maintain pregnancy. Diagnosis of endotoxemia is based largely on clinical evaluation. Confirming the diagnosis of endotoxin-induced reproductive alterations also is complicated by the lag period between clinical signs and abortion or infertility.

A field test for endotoxin in the horse

Summary Equine endotoxemia was diagnosed with a new rapid test for endotoxin in whole blood (Etox-Dx, KenVet, Ashland, OH). Test results of 66 horses referred to an equine clinic were compared to clinical diagnosis of endotoxemia. Samples from 55 horses examined for colic in the field were tested. The test was compared to a whole blood Limulus amebocyte lysate assay. Between 82% and 95%, of endotoxin (gram-negative bacterial lipopolysaccharide, LPS) in equine blood was found to be associated with formed elements and removed by separating serum or plasma. Detecting endotoxin in whole blood accurately assessed its presence or absence. Overall agreement between endotoxemia diagnosis by clinical signs and assay was 29%. Clinical diagnosis and test result agreed in 77% of endotoxic cases. With cases clinically diagnosed as negative for endotoxin, 67% were positive with the test. Overall, positive endotoxin test results were obtained with 74% of hospitalized cases compared to a 45% positive rate cases in the field. These data suggest that the test provides direct diagnosis of endotoxemia that may be of particular value in horses without clinical symptoms of endotoxemia.

Redistribution of Intraorgan Blood Flow in Acute, Hyperdynamic Porcine Endotoxemia

In a standardized porcine model of acute, hyperdynamic endotoxemia the distribution of intraorgan blood flow within heart, kidney and brain was analyzed. Twelve pigs received either short-term (23 min) or long-term (205 min) continuous intravenous infusion of endotoxin (Salmonella abortus equi). A high cardiac output/low peripheral resistance state was maintained throughout the 3.5 h observation period. Total organ blood flow in heart, kidney and brain remained high; however, already small amounts of endotoxin provoked a significant redistribution of intraorgan blood flow within the left ventricle and the kidney. These characteristic alterations were absent in a control group of 5 animals subjected to the same protocol, but receiving 0.9% saline instead of endotoxin. Deterioration of respiratory function developed exclusively after continuous intravenous endotoxin infusion over 205 min, indicating incipient organ failure. Using electron microscopy, endothelial cells swelling and entrapment of blood cells in capillaries of the midmyocardium as well as severe ultrastructural damage in the kidney could be demonstrated already after 90 min of endotoxemia in two additional animals. It is concluded that already in the initial phase of acute endotoxemia, in the presence of high cardiac output and high global organ blood flow microcirculatory deterioration and organ failure develops. As small amounts of endotoxin are capable of inducing these alterations, earliest possible diagnosis of endotoxemia should be achieved in critically ill patients.

Diagnosis of endotoxemia and fungemia by Endospecy test and Toxicolor test

Diagnosis of endotoxemia and fungemia by Endospecy test and Toxicolor test

Endotoxemia and Endotoxemia Diagnostics

After the study of a group of severely burned patients with septicemia the authors reached the conclusion that the diagnosis of endotoxemia should be based on the following criteria: clinical condition, laboratory results and autopsy findings. Clinical findings can be subdivided into anamnestic data (such as age, liver function etc.) and direct clinical observation (taking into account states of stress and some specific surgical procedures). The most significant laboratory findings in the investigated group of patients were hypoxy, metabolic acidosis, lowered platelet count and positive Limulus test. Autopsy findings corresponded to findings in septicemia and shock. The authors also discuss the significance of activated lymphocyte accumulation in the liver following endotoxin administration in animals.

Clinical Forms of Endotoxemia in Burns

Two groups of patients in whom endotoxemia was suspected were studied with respect to the laboratory data, clinical picture and autopsy findings. The first group showed the signs of gram-negative septicemia (age range 3 to 54 years with burns of 25 to 80% TBSA) and the second group (age range 20 to 76 years with burns not greater than 20% TBSA) showed an unexpected deterioration of the patient's condition. In 15 patients we established the diagnosis of endotoxemia on positive Limulus test as well as on other laboratory examinations and on the clinical signs. Five different forms of endotoxemia were distinguished varying in the evoking circumstance, clinical manifestation and pathological findings at autopsy: (1) the so called laboratory form--all survived; (2) the pulmonary form displaying the most brief and fulminant course--all died; (3) the form of disseminated intravascular coagulopathy; (4) the form of endotoxic shock due to administration of antibiotics; (5) the form of endotoxic shock as terminal stage of protracted gram-negative septicemia--the fatal outcome was inevitable in all cases. The authors stress the importance of minding and preventing all circumstances that might provoke the endotoxic (septic) shock.

Lack of Clinical Usefulness of the Limulus Test in the Diagnosis of Endotoxemia

Studies of the clinical value of the limulus amebocyte lysate test for the detection of endotoxemia are inconsistent. In an attempt to define the value of this test, a total of 237 plasma samples from 111 patients were tested for endotoxin with seven different lysate preparations. A total of 48 plasma samples yielded a positive test with one or more of the seven preparations. Two of eight samples positive with all seven preparations were from ambulatory patients. A significant positive correlation of the test with bacteremia, neutrophilia and elevated serum alkaline phosphatase was found. Only three of the 48 positive tests occurred by four hours of incubation, and only 12 were associated with positive blood cultures (eight contained gram-negative bacteria). The test now available has no clinical usefulness in the detection of endotoxemia or gram-negative septicemia.