Formation, Transmission, and Dynamic Evolution of a Multidrug-Resistant Chromosomally Integrated Plasmid in Salmonella Spp.

IncHI2 plasmids, possessing high flexibility and genetic plasticity, play a vital role in the acquisition and transmission of resistance determinants. Polymorphic mobile genetic elements (MGEs) generated by a chromosomally integrated IncHI2 plasmid in an individual Salmonella isolate have not yet been detected, and the mechanisms of the formation, excision, and dynamic evolution of a multidrug-resistant chromosomally integrated plasmid (MRCP) have remained obscure. Herein, we identified a 260-kb bla CTX-M-55-qnrS1-bearing IncHI2 plasmid within a Salmonella Muenster strain. Plenty of heterogeneous MGEs (new Escherichia coli chromosomally integrated plasmid or circular plasmids with different profiles) were yielded when this MRCP was conjugated into E. coli J53 with a transfer frequency of 10-4-10-5 transconjugants per donor. A bioinformatic analysis indicated that replicative transposition and homologous recombination of IS26 elements were particularly active, and the truncated Tn1721 also played a vital role in the formation of MRCP offspring. More importantly, when released from the chromosome, MRCP could capture and co-transfer adjacent chromosomal segments to form larger plasmid progeny than itself. Stability and growth kinetics assays showed that the biological characteristics of MRCP progeny were differentiated. This study provides an insight into a flexible existence of MRCP. The conversion between vertical and horizontal transmission endowed MRCP with genetic stability as a chromosomal coding structure and transferability as extra-chromosomal elements. This alternation may accelerate the acquisition and persistence of antibiotic resistance of clinical pathogens and enhance their ability to respond to adverse environments, which poses a great challenge to the traditional antibiotic treatment.

[Effects of acorus tatarinowii Schott and alpha asarone on free radicals and nNOS/NO in hippocampus of rats with fatigue movement].

OBJECTIVE: To study the effects of acorus tatarinowii Schott and its active ingredient-alpha-asarone on learning and memory, free radical metabolism and nNOS/NO signal in hippocampus of rats with fatigue movement. METHODS: Eighty SD male rats were randomly divided into eight groups: control group(A), exercise group(B), exercise + alpha-asarone low, middle and high dose treatment group (C, D, E), exercise + acorus tatarinowii Schott low, middle and high dose treatment group (F, G, H),with ten rats in each group. The rats in group C, D and E were administered with alpha-asarone at the doses of 0.10, 0.50 and 1.00 mg.kg-1.WT-1 by ig. The rats in group F, G and H were administered with the extracts of Acorus tatarinowii Schott of at the doses of 0.12, 1.20 and 4.80 g.kg-1.WT-1 by ig. Learning and memory of rats were tested by the method of water maze experiment, and the activities of SOD and NOS, the contents of MDA were detected by the biochemical methods, and the expression levels of nNOS protein in hippocampus of rats were tested by the method of Western blot in at the end of the experiment. RESULTS: The escape latency and MDA content in hippocampus of rats in groups E and H were lower than those in groups B, C, D, F and G and the numbers of Plateau crossing, SOD and NOS activities and the expression levels of nNOS protein in hippocampus of rats were higher than those in groups B, C, D, F and G(P＜0.01). The activities of SOD in hippocampus of rats in groups A, E and H were A＞E＞H, whereas the contents of MDA were opposite (P＜0.01); the activities of NOS and the expression levels of nNOS protein in hippocampus of group E were lower than those of groups A and H (P＜0.01 or P＜0.05), but there was no significant difference between groups A and H (P＞0.05). There were no significant difference in escape latency and numbers of crossing platform among groups A, E and H (P＞0.05). CONCLUSION: Acorus tatarinowii Schott and alpha-asarone can significantly improve learning and memory of rats with fatigue movement. The mechanism is related to reclaiming the imbalance of free radical metabolism and up-regulating nNOS/NO signal in hippocampus of the rats.

Emergence of ciprofloxacin heteroresistance in foodborne Salmonella enterica serovar Agona.

BACKGROUND: Bacterial heteroresistance has been increasingly identified as an important phenomenon for many antibiotic/bacterium combinations. OBJECTIVES: To investigate ciprofloxacin heteroresistance in Salmonella and characterize mechanisms contributing to ciprofloxacin heteroresistance. METHODS: Ciprofloxacin-heteroresistant Salmonella were identified by population analysis profiling (PAP). Target mutations and the presence of PMQR genes were detected using PCR and sequencing. Expression of acrB, acrF and qnrS was conducted by quantitative RT-PCR. Competition ability and virulence were also compared using pyrosequencing, blue/white screening, adhesion and invasion assays and a Galleria model. Two subpopulations were whole-genome sequenced using Oxford Nanopore and Illumina platforms. RESULTS: PAP identified one Salmonella from food that yielded a subpopulation demonstrating heteroresistance to ciprofloxacin at a low frequency (10-9 to 10-7). WGS and PFGE analyses confirmed that the two subpopulations were isogenic, with six SNPs and two small deletions distinguishing the resistant from the susceptible. Both subpopulations possessed a T57S substitution in ParC and carried qnrS. The resistant subpopulation was distinguished by overexpression of acrB and acrF, a deletion within rsxC and altered expression of soxS. The resistant population had a competitive advantage against the parental population when grown in the presence of bile salts but was attenuated in the adhesion and invasion of human intestinal cells. CONCLUSIONS: We determined that heteroresistance resulted from a combination of mutations in fluoroquinolone target genes and overexpression of efflux pumps associated with a deletion in rsxC. This study warns that ciprofloxacin heteroresistance exists in Salmonella in the food chain and highlights the necessity for careful interpretation of antibiotic susceptibility.

[The role and mechanism of leucyl-tRNA synthetase in the regulation of protein synthesis in aging skeletal muscle].

The imbalance of protein metabolism is the major cause of skeletal muscle atrophy, and the decrease of protein synthesis directly leads to the occurrence and development of age-related sarcopenia. The canonical role of leucyl-tRNA synthetase (LeuRS) is ligating leucine to the cognate tRNA, and thus it plays a central role in genetic coding. With the further studies of LeuRS in recent years, LeuRS has been found to control protein homeostasis in aging skeletal muscle via its non-canonical role. In this paper, we reviewed the structure and biological features of aminoacyl-tRNA synthetase and LeuRS, and summarized the recent advances in studies on the effects of LeuRS in regulating aging skeletal muscle protein synthesis as an intracellular leucine sensor. Moreover, we also analyzed the potential role of LeuRS in activation of mammalian target of rapamycin complex 1 (mTORC1) signaling transduction pathway in response to anabolic stimuli such as exercise and amino acids ingestion. This paper may provide some new ideas for the prevention, diagnosis and treatment of age-related sarcopenia.

[Effects of Acorus tatarinowii Schott and its active component -5- hydroxymethylfurfural on ERK/CREB signal in hippocampus of exercise-induced fatigue rats].

OBJECTIVE: To investigate the effects of Acorus tatarinowii Schott and its active component 5- hydroxymethyl furfural (HMF) on learning and memory and ERK/CREB signal in hippocampus of rats with exercise-induced fatigue. METHODS: SD rats were randomly divided into normal group (A), exercise group (B), exercise + HMF low, middle and high dose treatment group (C, D, E), exercise + acorus tatarinowii Schott low, middle and high dose treatment group (F, G, H), with ten rats in each group. The rats in group C, D and E were treated with HMF at the doses of 0.10, 1.00 and 3.00 mg. kg-1 by ig. The rats in group F, G and H were treated with the extracts of Acorus tatarinowii Schott at the doses of 0.12, 1.20 and 4.80 g. kg-1 by ig. Learning and memory of rats were tested by the method of water maze experiment, and the expression levels of p-ERK1/2 and p-CREB protein in hippocampus of rats were tested by the method of Western blot in the end of the experiment. RESULTS: The escape latencies of E and H groups were lower than those of groups B, C, D, F and G; and the numbers of plateau crossing were more than those of groups B, C, D, F and G and the expression levels of p-ERK1/2, p-CREB protein were higher than those of groups B, C, D, F and G , respectively(P ＜ 0.01). There was no significant difference in the above indexes among groups A, E and H(P＞0.05) except that the expression levels of p-ERK2 protein in group E were lower than those in group A and H (P＜0.05). CONCLUSION: Acorus tatarinowii and its active component- HMF can improve the learning and memory of rats with exercise-induced fatigue, and the mechanism is related to the up-regulation of ERK / CREB signal in hippocampus of rats with exercise-induced fatigue.

The Emergence of Chromosomally Located bla CTX-M-55 in Salmonella From Foodborne Animals in China.

The emergence and increase in prevalence of resistance to cephalosporins amongst isolates of Salmonella from food animals imposes a public health threat. The aim of the present study was to investigate the prevalence and characteristics of CTX-M-producing Salmonella isolates from raw meat and food animals. 27 of 152 (17.76%) Salmonella isolates were ESBL-positive including 21/70 (30%) from food animals and 6/82 (7.32%) from raw meat. CTX-M-55 was the most prevalent ESBL type observed (12/27, 44.44%). 7 of 12 CTX-M-55-positive Salmonella isolates were Salmonella Indiana, 2 were Salmonella Typhimurium, 2 were Salmonella Chester, and the remaining isolate was not typeable. Eight CTX-M-55-positive Salmonella isolates were highly resistant to fluoroquinolones (MICCIP = 64 ug/mL) and co-harbored aac(6')-Ib-cr and oqxAB. Most of the CTX-M-55 positive isolates (11/12) carried bla CTX-M-55 genes on the chromosome, with the remaining isolate carrying this gene on a transferable 280 kb IncHI2 plasmid. A chromosomal bla CTX-M-55 gene from one isolate transferred onto a 250 kb IncHI2 plasmid which was subsequently conjugated into recipient strain J53. PFGE and MLST profiles showed a wide range of strain types were carrying bla CTX-M-55. Our study demonstrates the emergence and prevalence of foodborne Salmonella harboring a chromosomally located bla CTX-M-55 in China. The co-existence of PMQR genes with bla CTX-M-55 in Salmonella isolates suggests co-selection and dissemination of resistance to both fluoroquinolones and cephalosporins in Salmonella via the food chain in China represents a public health concern.

Fire-Safe Polyesters Enabled by End-Group Capturing Chemistry.

Upon heating, polyesters decompose to small molecules and release flammable volatiles and toxic gases, primarily through chain scission of their ester linkages, and therefore exhibit poor fire-safety properties, thus restricting their applications. Reported herein is an end-group-capturing effect of (bis)oxazoline groups, generated from the thermal rearrangement of the N-(2-hydroxyphenyl)phthalimide (HPI) moiety which was incorporated into the polyester chain by copolymerization. These copolyesters, as a result, exhibit high efficiency in retarding decomposition by capturing the decomposed products, particularly for the carbonyl-terminated fragments, thus increasing the fire-safety properties, such as self-extinguishing, anti-dripping, and inhibiting heat release and smoke production. The successful application of this method in both semi-aromatic and aliphatic polyesters provide promising perspectives to designing versatile fire-safe polymers.

(E)-Methyl N'-(2-furylmethyl-ene)-hydrazinecarboxyl-ate.

The title compound, C(7)H(8)N(2)O(3), crystallizes with two independent but essentially identical mol-ecules in the asymmetric unit. Each mol-ecule adopts a trans configuration with respect to the C=N bond. The hydrazinecarboxyl-ate group is twisted from the furan ring by 7.78 (13)° in one mol-ecule and by 7.01 (17)° in the other. In the crystal structure, mol-ecules are linked into chains running along [010] by bifurcated N-H⋯(N,O) and N-H⋯O hydrogen bonds. In addition, weak C-H⋯O inter-actions and an O⋯C short contact [2.896 (3) Å] are observed.

(E)-Methyl N'-(3,4-dimethoxy-benzyl-idene)hydrazinecarboxyl-ate.

The title compound, C(11)H(14)N(2)O(4), crystallizes with two independent but essentially identical mol-ecules in the asymmetric unit. Each mol-ecule adopts a trans configuration with respect to the C=N bond. Mol-ecules are linked into a one-dimensional network by inter- and intra-molecular N-H⋯O and C-H⋯O hydrogen bonds.

(E)-Ethyl N'-(3,4-dimethoxy-benzyl-idene)hydrazinecarboxyl-ate monohydrate.

In the title compound, C(12)H(16)N(2)O(4)·H(2)O, the mol-ecular skeleton of the hydrazinecarboxyl-ate is nearly planar [within 0.053 (3) Å]. In the crystal, chains propagating along the c axis arise, composed of alternating hydrazinecarboxyl-ate mol-ecules and crystalline water, which inter-act via N-H⋯O and O-H⋯O hydrogen bonds.