Isolation of OXA-48-like carbapenemase-producing Escherichia coli susceptible to piperacillin/tazobactam in a Japanese patient without a history of travel abroad.

Oxacillinase (OXA)-48-like ß-lactamases are the most common carbapenemases in Enterobacterales in certain regions of the world and are being introduced on a regular basis into regions of non-endemicity. Japan has been characterized by low rates of carbapenemase-producing Enterobacterales, and among them, OXA-48-like carbapenemase-producing isolates are extremely rare. Here we describe a Japanese medical worker, without a history of travel abroad, who was diagnosed as having a community-acquired urinary tract infection, and whose urine sample was found to be positive for OXA-48-like carbapenemase-producing Escherichia coli. None of her close contacts had a history of foreign travel, and the same drug-resistant organism was not observed in other patients who had been hospitalized and undergone environmental culture tests in the same medical institution. This isolate was resistant to penicillins, narrow-spectrum cephalosporins, fluoroquinolones, and cefmetazole, but was susceptible to broad-spectrum cephalosporins, piperacillin/tazobactam, and meropenem and displayed reduced susceptibility to imipenem. The modified carbapenem inactivation test supported carbapenemase production, but inhibitor-based synergistic tests yielded negative results of carbapenemase production. Multiplex polymerase chain reaction revealed the presence of the carbapenemase gene (blaOXA-48) blaTEM and AmpC ß-lactamase gene (blaDHA). Singleplex polymerase chain reaction targeting the blaOXA-48 region amplified a product sequencing to nearly the full length (722 bp) and matching 100% with OXA-48. The present case highlights a new concern regarding OXA-48-like carbapenemase-producing Enterobacterales, which remain challenging to detect for clinical laboratories in regions of non-endemicity, and may already be latent in Japan.

IL-1ß augments H2S-induced increase in intracellular Ca2+ through polysulfides generated from H2S/NO interaction.

H2S has excitatory and inhibitory effects on Ca2+ signals via transient receptor potential ankyrin 1 (TRPA1) and ATP-sensitive K+ channels, respectively. H2S converts intracellularly to polysulfides, which are more potent agonists for TRPA1 than H2S. Under inflammatory conditions, changes in the expression and activity of these H2S target channels and/or the conversion of H2S to polysulfides may modulate H2S effects. Effects of proinflammatory cytokines on H2S-induced Ca2+ signals and polysulfide production in RIN14B cells were examined using fluorescence imaging with fura-2 and SSP4, respectively. Na2S, a H2S donor, induced 1) the inhibition of spontaneous Ca2+ signals, 2) inhibition followed by [Ca2+]i increase, and 3) rapid [Ca2+]i increase without inhibition in 50% (23/46), 22% (10/46), and 17% (8/46) of cells tested, respectively. IL-1ß augmented H2S-induced [Ca2+]i increases, which were inhibited by TRPA1 and voltage-dependent L-type Ca2+ channel blockers. However, IL-1ß treatment did not affect [Ca2+]i increases evoked by a TRPA1 agonist or high concentration of KCl. Na2S increased intracellular polysulfide levels, which were enhanced by IL-1ß treatment. A NOS inhibitor suppressed the increased polysulfide production and [Ca2+]i increase in IL-1ß-treated cells. These results suggest that IL-1ß augments H2S-induced [Ca2+]i increases via the conversion of H2S to polysulfides through NO synthesis, but not via changes in the activity and expression of target channels. Polysulfides may play an important role in the effects of H2S during inflammation.

Bidirectional effects of hydrogen sulfide via ATP-sensitive K(+) channels and transient receptor potential A1 channels in RIN14B cells.

Hydrogen sulfide (H2S) reportedly acts as a gasotransmitter because it mediates various cellular responses through several ion channels including ATP-sensitive K(+) (KATP) channels and transient receptor potential (TRP) A1 channels. H2S can activate both KATP and TRPA1 channels at a similar concentration range. In a single cell expressing both channels, however, it remains unknown what happens when both channels are simultaneously activated by H2S. In this study, we examined the effects of H2S on RIN14B cells that express both KATP and TRPA1 channels. RIN14B cells showed several intracellular Ca(2+) concentration ([Ca(2+)]i) responses to NaHS (300 µM), an H2S donor, i.e., inhibition of spontaneous Ca(2+) oscillations (37%), inhibition followed by [Ca(2+)]i increase (24%), and a rapid increase in [Ca(2+)]i (25%). KATP channel blockers, glibenclamide or tolbutamide, abolished any inhibitory effects of NaHS and enhanced NaHS-mediated [Ca(2+)]i increases, which were inhibited by extracellular Ca(2+) removal, HC030031 (a TRPA1 antagonist), and disulfide bond-reducing agents. NaHS induced 5-hydroxytryptamine (5-HT) release from RIN14B cells, which was also inhibited by TRPA1 antagonists. These results indicate that H2S has both inhibitory and excitatory effects by opening KATP and TRPA1 channels, respectively, in RIN14B cells, suggesting potential bidirectional modulation of secretory functions.