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Klebsiella oxytocais a gastrointestinal pathobiont with the potential to produce the toxins tilivalline and tilimycin, which cause antibiotic-associated hemorrhagic colitis. Overgrowth of toxigenic K oxytocahas recently been implicated in necrotizing enterocolitis. K oxytocacolonizes 2–9% of healthy adults, however, there is no systematic data on colonization in healthy children. We investigated K oxytocacolonization and its toxigenic properties in healthy infants. We sampled stool of healthy infants and determined K oxytocacolonization using stool culture and PCR (pehX). Toxin in stool was measured with HPLC/high-resolution mass spectrometry. K oxytocaisolates were typed using multi-locus sequence typing (MLST) and K oxytocatoxin PCR (npsA/B). Cytotoxin production of isolates was analyzed by MTT assay. K oxytocawas detected in 30 of 61 infants (49%) using stool culture and in 45 of 61 (73%) using PCR (pehX). Toxin marker PCR (npsA/B) was positive in 66% of stool samples positive for K oxytocaPCR. Stool toxin levels were too low for quantitation but traces of tilivalline were detected. Contrarily, 49% of K oxytocaisolates demonstrated toxicity in the MTT assay. MLST revealed 36 distinct sequence types affiliated with all known K oxytocasequence type clusters (A, B1 and B2). More than 70% of healthy infants were colonized with K oxytoca. Toxin quantities in stool of colonized healthy infants were below detection level, yet half of the isolates produced toxin in vitro demonstrating their pathobiont potential. The high occurrence of toxigenic K oxytocain healthy infants has to be considered for future disease association studies.

The inherent cytotoxicity of aberrantly folded protein aggregates contributes substantially to the pathogenesis of amyloid diseases. It was recently shown that a class of evolutionary conserved proteins, called MOAG-4/SERF, profoundly alter amyloid toxicity via an autonomous but yet unexplained mode. We show that the biological function of human SERF1a originates from its atypical ability to specifically distinguish between amyloid and nonamyloid aggregation. This inherently unstructured protein directly affected the aggregation kinetics of a broad range of amyloidogenic proteins in vitro, while being inactive against nonamyloid aggregation. A representative biophysical analysis of the SERF1a:α-synuclein (aSyn) complex revealed that the amyloid-promoting activity resulted from an early and transient interaction, which was sufficient to provoke a massive increase of soluble aSyn amyloid nucleation templates. Therefore, the autonomous amyloid-modifying activity of SERF1a observed in living organisms relies on a direct and dedicated manipulation of the early stages in the amyloid aggregation pathway.

Burkholderia pseudomalleicauses the severe disease melioidosis. Whole-genome sequencing (WGS)-based typing methods currently offer the highest resolution for molecular investigations of this genetically diverse pathogen.