Fatal Septic Shock Caused by Enterotoxigenic Escherichia coli O128 and Rare Polymicrobial Co-Infection with Streptococcus equi Subsp. zooepidemicus, Klebsiella oxytoca and Enterococcus durans in a Patient with Liver Cirrhosis: A Case Report

Escherichia coli, Streptococcus equi subsp. zooepidemicus, Klebsiella oxytoca, and Enterococcus durans are microorganisms capable of causing severe infections, particularly in patients with underlying comorbidities or immune dysfunction. We report a rare clinical case of a 65-year-old man with advanced cardiac and hepatic disease who developed severe diarrheal syndrome followed by septic shock, rapid clinical deterioration, and death. Microbiological examination of autopsy specimens from the intestinal wall and spleen identified Escherichia coli O128 with an enterotoxigenic profile (lt+, st+, eae−), together with Streptococcus equi subsp. zooepidemicus, Klebsiella oxytoca, and Enterococcus durans. Histopathological analysis demonstrated catarrhal enteritis with fibrinous deposits, mucosal edema, vascular congestion, and inflammatory infiltration. Although the microbiological findings were partly derived from autopsy material and postmortem bacterial translocation cannot be completely excluded, the concordance between clinical presentation, laboratory findings, and morphological changes supports the presence of a clinically significant infectious process. To our knowledge, this is the first reported human case of fatal polymicrobial infection involving these four pathogens. The case highlights the potential severity of polymicrobial infections in patients with cirrhosis-associated immune dysfunction and underscores the importance of integrated microbiological and molecular diagnostics for accurate etiological assessment.