Presence of endotoxemia and its relationship to liver dysfunction in patients with typhoid fever

Prognostic value of endotoxemia in patients with Gram-negative bacteremia is bacterial species dependent

The prognostic impact of endotoxemia detection in sepsis is unclear. Endotoxemia is detectable in <70% of patients with Gram-negative (GN) bacteremias. Mortality proportion data were available from 27 published studies of patients with GN bacteremia in various settings. Among ten studies restricted to specific types of GN bacteremia, endotoxemia was associated with significantly increased mortality risk for Neisseria meningitidis (4 studies; 138 bacteremias; OR 26.0; 95% CI, 1.6-321) but not for Salmonella enterica serovar Typhi (3 studies; 36 bacteremias; OR 0.89; 95% CI, 0.01-74.1). For 17 unrestricted studies (319 GN bacteremic patients), endotoxemia was associated with an increased mortality risk with non-Escherichia coli Enterobacteriaceae such as Klebsiella and Enterobacter species (97 bacteremias; OR 3.7; 95% CI, 1.3-10.3). By contrast, E. coli (144 bacteremias; OR 0.78; 95% CI, 0.36-1.7), and non-Enterobacteriaceae species such as Pseudomonas species (78 bacteremias; OR 1.7; 95% CI, 0.7-4.6) had no increased mortality risk. That endotoxemia detection is predictive of mortality among patients bacteremic with non-E. coli Enterobacteriaceae but not E. coli is surprising given the presumed commonality of the hexa-acyl lipid A structure among Enterobacteriaceae species.

Endotoxemia and mortality prediction in ICU and other settings: underlying risk and co-detection of gram negative bacteremia are confounders

INTRODUCTION

The interdependence between endotoxemia, gram negative (GN) bacteremia and mortality has been extensively studied. Underlying patient risk and GN bacteremia types are possible confounders of the relationship.

METHODS

Published studies with ≥ 10 patients in either ICU or non-ICU settings, endotoxemia detection by limulus assay, reporting mortality proportions and ≥ 1 GN bacteremia were included. Summary odds ratios (OR) for mortality were derived across all studies by meta-analysis for the following contrasts: sub-groups with either endotoxemia (group three), GN bacteremia (group two) or both (group one) each versus the group with neither detected (group four; reference group). The mortality proportion for group four is the proxy measure of study level risk within L'Abbé plots.

RESULTS

Thirty-five studies were found. Among nine studies in an ICU setting, the OR for mortality was borderline (OR <2) or non-significantly increased for groups two (GN bacteremia alone) and three (endotoxemia alone) and patient group one (GN bacteremia and endotoxemia co-detected) each versus patient group four (neither endotoxemia nor GN bacteremia detected). The ORs were markedly higher for group one versus group four (OR 6.9; 95% confidence interval (CI), 4.4 -to 11.0 when derived from non-ICU studies. The distributions of Pseudomonas aeruginosa and Escherichia coli bacteremias among groups one versus two are significantly unequal.

CONCLUSIONS

The co-detection of GN bacteremia and endotoxemia is predictive of increased mortality risk versus the detection of neither but only in studies undertaken in a non-ICU setting. Variation in GN bacteremia species types and underlying risk are likely unrecognized confounders in the individual studies.

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.

Concordance of endotoxemia with gram-negative bacteremia. A meta-analysis using receiver operating characteristic curves

OBJECTIVE

To apply meta-analysis to compare the concordance between the results of 2 types of limulus amebocyte lysate (LAL) assay, gelation (GLAL) and chromogenic (CLAL), with the detection of gram-negative bacteremia in patients with suspected bacteremia.

DESIGN

Meta-analysis using receiver operating characteristic-based analytical method.

DATA SOURCES

MEDLINE literature search and manual reviews of article bibliographies together with direct approaches to authors of potentially eligible studies.

STUDY SELECTION

The studies that were selected had all included at least 10 patients, of whom at least 2 patients were diagnosed with gram-negative bacteremia, and all had data available for extraction into a contingency table format.

RESULTS

Fifty-six studies (28 GLAL and 28 CLAL studies) met the inclusion criteria. Studies were stratified by type of test (GLAL vs CLAL). Each analysis was repeated with smaller studies excluded. There was no difference between the 2 types of LAL assays. Among the CLAL studies, there was no difference between studies that did versus those that did not use the sepsis syndrome criteria as a basis for patient inclusion. Among 45 studies for which data on the proportion of non-Enterobacteriaceae were available, there was a trend toward higher concordance as this proportion increased.

CONCLUSIONS

The concordance between the LAL test and the detection of gram-negative bacteremia in patients with suspected bacteremia is no higher with the CLAL assay than with the original GLAL version. However, the concordance is higher among studies with a higher proportion of non-Enterobacteriaceae among the gram-negative bacteremia isolates.

Salmonella hepatitis

Typhoid fever is often associated with abnormal liver biochemical tests, but severe hepatic involvement with a clinical feature of acute hepatitis is a rare complication. There have been more than 150 cases of salmonella hepatitis reported from both developed and developing countries. The documented incidence varies widely from less than 1% to 26% patients with enteric fever. The possible associated factors for development of salmonella hepatitis are virulence of the organisms, delayed treatment and poor general health of the patients. The pathogenesis of severe hepatic involvement in salmonella infection may be multifactorial and includes endotoxin, local inflammatory and/or host immune reactions. Clinical jaundice in salmonella hepatitis usually occurs within the first 2 weeks of the febrile illness. Hepatomegaly and moderate elevation of transaminase levels are common findings. Extreme hepatic dysfunction with hepatic encephalopathy is a rare coexisting complication in salmonella hepatitis. A positive culture for salmonella from blood or stool is essential to differentiate salmonella hepatitis from other causes of acute hepatitis. Hepatic pathology is characterized by the presence of typhoid nodules with marked hyperplasia of reticuloendothelial cells. The prognosis is usually good as salmonella hepatitis responds well to a specific antibiotic therapy and juandice resolves with clinical improvement. The clinical course can be severe with a mortality rate as high as 20%, particularly with delayed treatment or in patients with other complications of salmonella infection. As enteric fever is a common infection, the recognition of salmonella hepatitis is of clinical importance.

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.

Concordance of endotoxemia with gram-negative bacteremia in patients with gram-negative sepsis: a meta-analysis

The Limulus amebocyte lysate (LAL) assay is a sensitive method for detecting endotoxin. Using gram-negative (GN) bacteremia as the basis for comparison, concordance with endotoxemia in 45 studies could be expressed as an odds ratio. Calculation of summary odds ratios by the Mantel-Haenszel-Peto method indicated that the concordance of the results was no higher by the chromogenic LAL assay than by the gelation version, and the sensitivity was improved by only 11% (62 versus 51%). Endotoxemia was detected in 77 (68%) of 114 patients with bacteremia caused by an organism that was not a member of the family Enterobacteriaceae, whereas endotoxemia was detected in only 120 (45%) of 269 patients with bacteremia caused by a member of the family Enterobacteriaceae or an anaerobe (P < 0.001). This difference was also apparent for patients with GN bacteremia for whom a fatal outcome had been recorded. The prevalence of GN bacteremia in the tested population and the type of etiological agent are critical and previously unrecognized variables which affect the interpretation of the LAL test in patients with suspected sepsis.

Ataxia in patients infected with Salmonella typhi phage type D2: clinical, biochemical and immunohistochemical studies

Reversible cerebellar dysfunction has been described in association with typhoid fever by a number of authors. Ataxia and tremors are relatively common manifestations of typhoid fever in Papua New Guinea. A series of 14 patients with typhoid fever and ataxia was compared with non-ataxic typhoid patients. Hyponatraemia and hypoalbuminaemia were common in both groups and more severe in the ataxic group. Hypotension was also more common in the ataxic group. These features may reflect more severe disease. All isolates of Salmonella typhi, from both ataxic and non-ataxic patients, were phage type D2 which is endemic around Port Moresby. Tests for autoantibodies cross-reacting with cerebellar tissue were negative. It is possible that cerebellar dysfunction in typhoid fever is more common in association with phage type D2.

Typhoid fever associated with adult respiratory distress syndrome

Adult respiratory distress syndrome (ARDS) is rarely reported in association with typhoid fever despite the fact that sepsis is a common manifestation and endotoxemia has been described in this multisystem condition. We describe the course of a patient with ARDS and typhoid fever. With conventional treatment of the lung injury and with specific antimicrobial therapy, the patient survived. Recent consensus definitions of sepsis and ARDS simplified reporting of this case. Clinicians caring for individuals from or recent visitors to developing countries should be aware of the association of typhoid fever, sepsis, and ARDS.