Rotation reversal of a ratchet gear powered by active particles.

Rotation of a gear powered by active particles is numerically investigated in a circular chamber. Due to the nonequilibrium properties of active particles, net gear rotation is achieved in a bath composed of self-propelling particles. Our setup can convert the random motion of active particles into the directional rotation of the ratchet gear. The direction of rotation is determined by the asymmetry of the gear and the persistence length (the ratio of the self-propulsion speed to the rotation diffusion coefficient) of active particles. Remarkably, the direction of rotation for large persistence length is opposite to the direction of rotation for small persistence length. Therefore, for a given asymmetric gear, we can observe the rotation reversal when tuning the system parameters (e.g., the self-propulsion speed, the rotation diffusion coefficient, and the packing fraction of active particles). Our findings are relevant to the experimental pursuit of rectifying random motion to directional motion in active matter.

Clonal Spread of 16S rRNA Methyltransferase-Producing Klebsiella pneumoniae ST37 with High Prevalence of ESBLs from Companion Animals in China.

We screened 30 Klebsiella pneumoniae isolates from dogs and cats at a single animal hospital in Guangdong Province, China. Among them, 12 K. pneumoniae strains possessed high-level resistance to amikacin and gentamicin and these were screened for 16S rRNA methyltransferase (16S-RMTase) genes. And then the genes positive isolates were detected for ESBLs (extended spectrum ß-lactamases) and analyzed by pulsed-field gel electrophoresis, multilocus sequence typing, PCR-based replicon typing and plasmid analysis. The genetic profiles of rmtB were also determined by PCR mapping. The twelve 16S-RMTase gene-positive isolates were rmtB (11/30) and armA (2/30) with one isolate carrying both genes. Extended spectrum ß-lactamases genes were represented by blaCTX-M-55 (9/12), blaCTX-M-27 (2/12) and blaCTX-M-14 (1/12). The twelve 16S-RMTase containing strains were grouped into five clonal patterns and ST37 was the most prevalent sequence type. Ten rmtB-bearing plasmids conjugated successfully and all belonged to IncN and IncF (F33:A-:B-) incompatibility groups. Nine of the transconjugants carried a 97 kb plasmid and the other harbored both ∼60 and ∼200 kb plasmids. rmtB and blaCTX-M-55 were present on the same plasmid and indicated the co-transfer of these two genes, with the rmtB gene showing highly relevant relationships with IS26 and Tn3. Our findings suggested a high prevalence of 16S-RMTase genes in K. pneumonia ST37 from dogs and cats. Additional studies are needed to trace the evolutionary path of this type of resistance among the K. pneumonia isolates, and to determine whether they have been transferred to humans.