Livestock-associated methicillin-resistant Staphylococcus aureus (clonal complex 398) causing bacteremia and epidural abscess.

Methicillin-resistant Staphylococcus aureus (MRSA) clonal complex (CC) 398 has spread from pigs to humans, but rarely from person to person. This strain of MRSA has been considered less virulent than others. Livestock-associated MRSA CC398 (LA-MRSA CC398) is particularly known to colonize pig farmers. Recent studies have shown an increasing number of people colonized with LA-MRSA CC398 and invasive infections caused by LA-MRSA CC398. The case of a previously healthy, 61-year-old woman admitted to a Danish regional hospital is reported here. She presented with fever, severe back pain, and bilateral hyperreflexia of patellar and Achilles reflexes. Blood tests revealed leukocytosis and elevated C-reactive protein. Empiric antimicrobial therapy with intravenous piperacillin-tazobactam was initiated, but blood cultures grew MRSA and antimicrobial therapy was changed to intravenous vancomycin. Whole-genome sequencing showed that the MRSA strain belonged to LA-MRSA CC398 spa type t011 and was Panton-Valentine leukocidin-negative. Magnetic resonance imaging revealed an epidural abscess at the level of L1-L4. Surgery was performed and pus from the abscess grew MRSA. The duration of antimicrobial therapy was 12 weeks. This case report describes bacteremia with LA-MRSA CC398 in a previously healthy patient without exposure to livestock or previous admission to a hospital. This highlights the risk of person-to-person transmission of LA-MRSA CC398 and brings into question whether LA-MRSA CC398 may have a greater pathogenic potential than previously assumed.

Determination of the separation efficiencies of a single-stage cryogenic distillation setup to remove krypton out of xenon by using a (83m)Kr tracer method.

The separation of krypton and xenon is of particular importance for the field of direct dark matter search with liquid xenon detectors. The intrinsic contamination of the xenon with radioactive (85)Kr makes a significant background for these kinds of low count-rate experiments and has to be removed beforehand. This can be achieved by cryogenic distillation, a technique widely used in industry, using the different vapor pressures of krypton and xenon. In this paper, we present an investigation on the separation performance of a single stage distillation system using a radioactive (83m)Kr-tracer method. The separation characteristics under different operation conditions are determined for very low concentrations of krypton in xenon at the level of (83m)Kr/Xe = 1.9 ⋅ 10(-15), demonstrating, that cryogenic distillation in this regime is working. The observed separation is in agreement with the expectation from the different volatilities of krypton and xenon. This cryogenic distillation station is the first step on the way to a multi-stage cryogenic distillation column for the next generation of direct dark matter experiment XENON1T.