1-Undecene from Pseudomonas aeruginosa is an olfactory signal for flight-or-fight response in Caenorhabditis elegans.

Animals possess conserved mechanisms to detect pathogens and to improve survival in their presence by altering their own behavior and physiology. Here, we utilize Caenorhabditis elegans as a model host to ask whether bacterial volatiles constitute microbe-associated molecular patterns. Using gas chromatography-mass spectrometry, we identify six prominent volatiles released by the bacterium Pseudomonas aeruginosa. We show that a specific volatile, 1-undecene, activates nematode odor sensory neurons inducing both flight and fight responses in worms. Using behavioral assays, we show that worms are repelled by 1-undecene and that this aversion response is driven by the detection of this volatile through AWB odor sensory neurons. Furthermore, we find that 1-undecene odor can induce immune effectors specific to P. aeruginosa via AWB neurons and that brief pre-exposure of worms to the odor enhances their survival upon subsequent bacterial infection. These results show that 1-undecene derived from P. aeruginosa serves as a pathogen-associated molecular pattern for the induction of protective responses in C. elegans.

Acute liver failure due to hepatitis A virus presented with Guillain-Barré syndrome and ocular myasthenia gravis.

Hepatitis A is one of the most common causes of acute viral hepatitis in children. Immunological manifestations involving the nervous system are rare with hepatitis A infection. We report a case of a toddler who presented with acute liver failure secondary to hepatitis A infection. The child showed clinical and laboratory improvement initially with conservative management. However, after the initial improvement, she developed acute-onset ptosis along with areflexia. Serological and neurophysiological tests revealed the occurrence of ocular variant Guillain-Barré syndrome and ocular myasthenia gravis, which was only partially responsive to treatment (intravenous immunoglobulin and pyridostigmine). A sudden clinical deterioration was noted after the onset of ptosis. She succumbed on day 40 of hospitalisation due to hospital-acquired infection along with the primary hepatic pathology. This is a rare coincidental presentation of acute viral hepatitis A infection with autoimmune manifestations.