Correlation Between Microbial Toxin Levels and Biochemical Markers of Organ Damage in ICU Patients

Critically ill patients admitted to ICUs are at high risk of severe infections that may progress to sepsis and multi-organ dysfunction. Microbial toxins, such as endotoxins from Gram-negative bacteria and exotoxins from Gram-positive organisms, play a major role in the pathogenesis of systemic inflammation and tissue injury. While biochemical markers are routinely used to monitor organ function, their direct relationship with microbial toxin levels in ICU patients is not well established.

To determine the correlation between circulating microbial toxin levels and biochemical indicators of organ damage in ICU patients with microbiologically confirmed infections.

A prospective observational study was conducted over 18 months in a tertiary care hospital ICU. A total of 120 adult patients (≥18 years) with confirmed bacterial or fungal infections were enrolled. Plasma endotoxin concentrations were measured using the limulus amebocyte lysate (LAL) chromogenic assay, with each sample analyzed in duplicate to ensure reproducibility. Intra- and inter-assay variability was maintained below 10% as per the manufacturer's specifications, and polymyxin B inhibition was used in selected samples to confirm assay specificity. Gram-positive exotoxins were quantified using an enzyme-linked immunosorbent assay (ELISA), also performed in duplicate with appropriate positive and negative controls. Biochemical parameters included serum creatinine, alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), high-sensitivity troponin I, and total bilirubin. Organ dysfunction severity was evaluated using the Sequential Organ Failure Assessment (SOFA) scores. Data normality was assessed by the Shapiro-Wilk test, with Pearson's correlation applied to normally distributed variables (creatinine, ALT, AST, hs-TnI) and Spearman's correlation to skewed variables (bilirubin, LDH, endotoxin, exotoxin).

The study cohort had a mean age of 54.8±13.2 years, with a male-to-female ratio of 1.4:1. Gram-negative organisms were identified in 68 patients (56.7%), Gram-positive in 38 (31.7%), and mixed infections in 14 (11.6%). Median endotoxin levels were significantly higher in Gram-negative infections compared to Gram-positive (Mann-Whitney U test, p<0.001). Endotoxin concentrations correlated strongly with serum creatinine (r=0.64, 95%CI: 0.48-0.75, p<0.001), total bilirubin (r=0.59, 95%CI: 0.42-0.72, p<0.001), and SOFA scores (r=0.71, 95%CI: 0.57-0.81, p<0.001). Exotoxin levels demonstrated significant correlations with LDH (r=0.55, 95%CI: 0.31-0.72) and high-sensitivity troponin I (r=0.48, 95%CI: 0.22-0.67, p=0.004). Patients with septic shock (n=42) exhibited markedly elevated toxin levels, deranged biochemical parameters, prolonged ICU stays (median: 12 days, IQR: 9-16), and mortality rates exceeding 50%. In multivariate logistic regression adjusting for SOFA scores and comorbidities, both endotoxin (OR=2.18) and exotoxin levels (OR=1.74) remained significant independent predictors of mortality and organ dysfunction severity.

Microbial toxin burden demonstrates a strong association with biochemical evidence of organ injury and disease severity in ICU patients. Combined toxin-biomarker profiling may have prognostic value for identifying high-risk patients, but its clinical application requires validation through larger multicentre studies with serial sampling before widespread adoption.