Cytotoxic and Pathogenic Properties of Klebsiella oxytoca Isolated from Laboratory Animals

Abstract

Klebsiella oxytoca is an opportunistic pathogen implicated in various clinical diseases in animals and humans. Studies suggest that in humans K. oxytoca exerts its pathogenicity in part through a cytotoxin. However, cytotoxin production in animal isolates of K. oxytoca and its pathogenic properties have not been characterized. Furthermore, neither the identity of the toxin nor a complete repertoire of genes involved in K. oxytoca pathogenesis have been fully elucidated. Here, we showed that several animal isolates of K. oxytoca, including the clinical isolates, produced secreted products in bacterial culture supernatant that display cytotoxicity on HEp-2 and HeLa cells, indicating the ability to produce cytotoxin. Cytotoxin production appears to be regulated by the environment, and soy based product was found to have a strong toxin induction property. The toxin was identified, by liquid chromatography-mass spectrometry and NMR spectroscopy, as low molecular weight heat labile benzodiazepine, tilivalline, previously shown to cause cytotoxicity in several cell lines, including mouse L1210 leukemic cells. Genome sequencing and analyses of a cytotoxin positive K. oxytoca strain isolated from an abscess of a mouse, identified genes previously shown to promote pathogenesis in other enteric bacterial pathogens including ecotin, several genes encoding for type IV and type VI secretion systems, and proteins that show sequence similarity to known bacterial toxins including cholera toxin. To our knowledge, these results demonstrate for the first time, that animal isolates of K. oxytoca, produces a cytotoxin, and that cytotoxin production is under strict environmental regulation. We also confirmed tilivalline as the cytotoxin present in animal K. oxytoca strains. These findings, along with the discovery of a repertoire of genes with virulence potential, provide important insights into the pathogenesis of K. oxytoca. As a novel diagnostic tool, tilivalline may serve as a biomarker for K oxytoca-induced cytotoxicity in humans and animals through detection in various samples from food to diseased samples using LC-MS/MS. Induction of K. oxytoca cytotoxin by consumption of soy may be in part involved in the pathogenesis of gastrointestinal disease.

Non-traumatic subdural hematoma secondary to septic brain embolism: A rare cause of unexpected death in a drug addict suffering from undiagnosed bacterial endocarditis

“…Klebsiella oxytoca is a gram-negative bacterium belonging to the Enterobacteriacae family. It is considered an opportunistic pathogen [20]. Polymicrobial endocarditis, as found in our case, occurs mainly in IVDAs [21] and is associated with an especially high mortality rate [17].…”

Natural products as mediators of disease

“…For example, Klebsiella- mediated, antibiotic-associated hemorrhagic colitis has been linked to the NRP tilivalline (22) . 224, 225 Tilivalline was first isolated from Klebsiella oxytoca in the early 1980s and was shown to have toxicity against mouse leukemia L1210 cells. 226, 227 More recently, the pathological symptoms of tilivalline-mediated damage in the colon were more pronounced in animals treated with antibiotics and infected with K. oxytoca as compared to control animals.…”

“…Tilivalline has been shown to induce caspase-3-dependent apoptosis in cultured human epithelial cells, which has also been observed in the pathology of antibiotic-associated hemorrhagic colitis. 224, 225 …”

Identification of Klebsiella pneumoniae Carbapenemase-producing Klebsiella oxytoca in Clinical Isolates in Tehran Hospitals, Iran by Chromogenic Medium and Molecular Methods

“…KPC-producing K. oxytoca isolates are rarely reported [18]. K. oxytoca is an opportunistic pathogen and is now identified and introduced as an important clinical pathogen that is associated with nosocomial infections in hospitalized patients, including children, newborns, and individuals with immune deficiency [19]. A few studies have reported the identification of the KPC gene in K. oxytoca strains in some countries such as Austria [18], Brazil [20], and Venezuela [21].…”