Characterization of a Tigecycline-Resistant and blaCTX-M-Bearing Klebsiella pneumoniae Strain from a Peacock in a Chinese Zoo.

In Chinese zoos, there are usually specially designed bird parks, similar to petting zoos, that allow children and adults to interact with diverse birds. However, such behaviors present a risk for the transmission of zoonotic pathogens. Recently, we isolated eight strains of Klebsiella pneumoniae and identified two blaCTX-M-positive strains from 110 birds, including parrots, peacocks, and ostriches, using anal or nasal swabs in a bird park of a zoo in China. There, K. pneumoniae LYS105A was obtained from a diseased peacock with chronic respiratory diseases by a nasal swab, which harbored the blaCTX-M-3 gene and exhibited resistance to amoxicillin, cefotaxime, gentamicin, oxytetracycline, doxycycline, tigecycline, florfenicol, and enrofloxacin. According to an analysis by whole-genome sequencing, K. pneumoniae LYS105A belongs to serotype ST859 (sequence type 859)-K19 (capsular serotype 19) and contains two plasmids, of which pLYS105A-2 can be transferred by electrotransformation and harbors numerous resistance genes such as blaCTX-M-3, aac(6')-Ib-cr5, and qnrB91. The above-mentioned genes are located in a novel mobile composite transposon, Tn7131, which makes horizontal transfer more flexible. Although no known genes were identified in the chromosome, a significant increase in SoxS upregulated the expression levels of phoPQ, acrEF-tolC, and oqxAB, which contributed to strain LYS105A acquiring resistance to tigecycline (MIC = 4 mg/L) and intermediate resistance to colistin (MIC = 2 mg/L). Altogether, our findings show that bird parks in zoos may act as important vehicles for the spread of multidrug-resistant bacteria from birds to humans and vice versa. IMPORTANCE A multidrug-resistant ST859-K19 K. pneumoniae strain, LYS105A, was obtained from a diseased peacock in a Chinese zoo. In addition, multiple resistance genes such as blaCTX-M-3, aac(6')-Ib-cr5, and qnrB91 were located in a novel composite transposon, Tn7131, of a mobile plasmid, implying that most of the resistance genes in strain LYS105A can be moved easily via horizontal gene transfer. Meanwhile, an increase in SoxS can further positively regulate the expression of phoPQ, acrEF-tolC, and oqxAB, which is the key factor for strain LYS105A to develop resistance to tigecycline and colistin. Taken together, these findings enrich our understanding of the horizontal cross-species spread of drug resistance genes, which will help us curb the development of bacterial resistance.

Genomic characteristics of mcr-1 and blaCTX-M-type in a single multidrug-resistant Escherichia coli ST93 from chicken in China.

This study was undertaken to discern the transmission characteristics of mcr-1 and blaCTX-M-type in one multidrug-resistant Escherichia coli LWY24 from chicken in China. The genetic profiles of LWY24 isolate were determined by conjugation, S1-pulsed-field gel electrophoresis, southern blot hybridization, and whole genome sequencing analysis. Meanwhile, co-transfer of plasmids in LWY24 isolate was screened by dual conjugation assays. The LWY24 isolate was identified as ST93, and harbored 3 conjugative plasmids, pLWY24J-3 (blaCTX-M-55-bearing IncFⅡ), pLWY24J-mcr-1 (mcr-1-carrying IncI2), and pLWY24J-4 (non-resistance-conferring IncI1), and one nonconjugative plasmid pLWY24 (blaCTX-M-14-containing IncHI2/IncHI2A). Numerous resistance genes, insertion sequences (especially IS26), and transposons were found in the 4 plasmids, suggesting that horizontal transmission have occurred by plasmid mating, homologous recombination, and transpositions. Under the selection pressure of cefotaxime and colistin or cefotaxime alone, the mcr-1-bearing plasmid and the blaCTX-M-55-harboring plasmid could be co-transferred at a similar frequency, with 8.00 × 10-4 or 9.00 × 10-4 transconjugants per donor cell, respectively. The specific shufflon region in mcr-1-encoding plasmid could generate up to 6 diverse PilV structures, which may further accelerate the horizontal transfer of plasmid. In conclusion, the transmission characteristics of mcr-1 and blaCTX-M-type in LWY24 isolate could due to clonal spread of ST93, selective pressure of cefotaxime, IS26-mediate homologous recombination and transposition, and the specific shufflon region.

Characterization of mitochondrial dynamics and subcellular localization of ROS reveal that HsfA2 alleviates oxidative damage caused by heat stress in Arabidopsis.

Heat shock transcription factor A2 (HsfA2) participates in multiple stress responses. To provide new insights into the role of HsfA2 in the heat stress (HS) response, in vivo production and localization of reactive oxygen species (ROS) and mitochondrial dynamics were investigated during the onset of cell death induced by an HS (40 degrees C, 10 min) applied after a 2 d recovery at 24 degrees C following a conditioning treatment at 37 degrees C for 1 h. In response to the HS, generated ROS were significantly higher in hsfA2 than in wild-type (WT) protoplasts and did not return to the baseline level when compared with WT protoplasts. The uncontrolled ROS in hsfA2 protoplasts localized not only to mitochondria but also to chloroplasts. Microscopic observations also revealed that, prior to cell death, hsfA2 protoplasts underwent more severe alterations in mitochondrial dynamics than WT protoplasts, including mitochondrial swelling, transmembrane potential loss, and the cessation of mitochondrial movement. The lower cell viability in hsfA2 than in WT protoplasts suggested that--combined with the findings that antioxidants only partially blocked ROS generation and arrested cell death in hsfA2 protoplasts relative to WT protoplasts--ROS participated in HS-induced cell death. Also the disruption of HsfA2 resulted in more severe oxidative stress and more cell death which, together with the more severe alterations in mitochondrial dynamics, could be complemented by introducing a WT copy of HsfA2. These results represent the first subcellular evidence that HsfA2 protects plants against HS-induced oxidative damage, organelle dysfunction, and subsequent cell death.