Streptococcus sputorum, a novel member of Streptococcus with multidrug resistance, exhibits cytotoxicity

We describe the genomic and phenotypic characteristics of a novel member of Streptococcus with multidrug resistance (MDR) isolated from hospital samples. Strains SP218 and SP219 were identified as a novel Streptococcus, S. sputorum, using whole-genome sequencing and biochemical tests. Average nucleotide identity values of strains SP218 and SP219 with S. pseudopneumoniae IS7493 and S. pneumoniae ST556 were 94.3% and 93.3%, respectively. Genome-to-genome distance values of strains SP218 and SP219 with S. pseudopneumoniae IS7493 and S. pneumoniae ST556 were 56.70% (54–59.5%) and 56.40% (52.8–59.9%), respectively. The biochemical test results distinguished these strains from S. pseudopneumoniae and S. pneumoniae, particularly hydrolysis of equine urate and utilization of ribose to produce acid. These isolates were resistant to six major classes of antibiotics, which correlated with horizontal gene transfer and mutation. Notably, strain SP219 exhibited cytotoxicity against human lung epithelial cell line A549. Our results indicate the pathogenic potential of S. sputorum, and provide valuable insights into mitis group of streptococci.National Natural Science Foundation of Chin

Epidemiological characteristics of blaNDM-1 in Enterobacteriaceae and the Acinetobacter calcoaceticus-Acinetobacter baumannii complex in China from 2011 to 2012.

The study aimed to investigate the prevalence and epidemiological characteristics of blaNDM-1 (encoding New Delhi metallo-β-lactamase 1) in Enterobacteriaceae and the Acinetobacter calcoaceticus-Acinetobacter baumannii complex (ABC) in China from July 2011 to June 2012.PCR was used to screen for the presence of blaNDM-1 in all organisms studied. For blaNDM-1-positive strains, 16S rRNA analysis and Analytical Profile Index (API) strips were used to identify the bacterial genus and species. The ABCs were reconfirmed by PCR detection of blaOXA-51-like. Antibiotic susceptibilities of the bacteria were assessed by determining minimum inhibitory concentration (MIC) of them using two-fold agar dilution test, as recommended by the Clinical and Laboratory Standards Institute (CLSI). Molecular typing was performed using pulsed-field gel electrophoresis (PFGE). S1 nuclease-pulsed-field gel electrophoresis (S1-PFGE) and Southern blot hybridization were conducted to ascertain the gene location of blaNDM-1. Conjugation experiments were conducted to determine the transmission of blaNDM-1-positive strains.Among 2,170 Enterobacteriaceae and 600 ABCs, seven Enterobacteriaceae strains and two A. calcoaceticus isolates from five different cities carried the blaNDM-1 gene. The seven Enterobacteriaceae strains comprised four Klebsiella pneumoniae, one Enterobacter cloacae, one Enterobacter aerogen and one Citrobacter freundii. All seven were non-susceptible to imipenem, meropenem or ertapenem. Two A. calcoaceticus species were resistant to imipenem and meropenem. Three K. pneumoniae showed the same PFGE profiles. The blaNDM-1 genes of eight strains were localized on plasmids, while one was chromosomal.Compared with previous reports, the numbers and species containing the blaNDM-1 in Enterobacteriaceae have significantly increased in China. Most of them are able to disseminate the gene, which is cause for concern. Consecutive surveillance should be implemented and should also focus on the dissemination of blaNDM-1 among gram-negative clinical isolates

Numerical Simulation of Critical Production Pressure Drop of Injection and Production Wells in Gas Storage Based on Gas-Solid Coupling

The periodic injection-production process of natural gas in underground gas storage make the rock bear alternating load under the gas-solid coupling. The alternating load changes the physical properties of rock, and then influence the critical production pressure drop of injection-production wells in gas storage. In the case of gas-solid coupling, the decisive factors affecting the alternating load are the number of injection-production cycles and the injection-production differential pressure. Therefore, a discrete element numerical simulation model is established to simulate the gas-solid coupling process of gas storage wells under different injection-production cycle and differential pressure. The influence mechanism of injection-production cycle and differential pressure on particle cementation and primary crack is analyzed microscopically and also the influence law of injection-production cycle and differential pressure on rock mechanical properties is analyzed from the macroscopic. Finally, the influence law of injection-production cycle and differential pressure on the critical production pressure drop of injection-production wells due to gas-solid coupling can be obtained. The results show that under the influence of gas-solid coupling, the number of bonded contact cracks and micro cracks in the model increase gradually, both the elastic modulus ratio and the cohesion ratio decrease gradually with the increase of injection-production cycle and the higher the injection-production differential pressure, the greater the decline range. Then, with the injection-production cycle increasing the Poisson’s ratio increases gradually and the higher the injection-production differential pressure, the greater the increase range. Finally, the internal friction angle ratio increases greatly in the initial stage, after that decreases and then shows a linear increase. According to the influence law, the relationship model between the critical production pressure drop of injection-production wells in gas storage and the injection-production cycle and differential pressure under the gas-solid coupling will be established, which is used for the dynamic prediction of the critical production pressure drop of injection-production wells in the whole life cycle of gas storage

Numerical Simulation of Critical Production Pressure Drop of Injection and Production Wells in Gas Storage Based on Gas-Solid Coupling

The periodic injection-production process of natural gas in underground gas storage make the rock bear alternating load under the gas-solid coupling. The alternating load changes the physical properties of rock, and then influence the critical production pressure drop of injection-production wells in gas storage. In the case of gas-solid coupling, the decisive factors affecting the alternating load are the number of injection-production cycles and the injection-production differential pressure. Therefore, a discrete element numerical simulation model is established to simulate the gas-solid coupling process of gas storage wells under different injection-production cycle and differential pressure. The influence mechanism of injection-production cycle and differential pressure on particle cementation and primary crack is analyzed microscopically and also the influence law of injection-production cycle and differential pressure on rock mechanical properties is analyzed from the macroscopic. Finally, the influence law of injection-production cycle and differential pressure on the critical production pressure drop of injection-production wells due to gas-solid coupling can be obtained. The results show that under the influence of gas-solid coupling, the number of bonded contact cracks and micro cracks in the model increase gradually, both the elastic modulus ratio and the cohesion ratio decrease gradually with the increase of injection-production cycle and the higher the injection-production differential pressure, the greater the decline range. Then, with the injection-production cycle increasing the Poisson’s ratio increases gradually and the higher the injection-production differential pressure, the greater the increase range. Finally, the internal friction angle ratio increases greatly in the initial stage, after that decreases and then shows a linear increase. According to the influence law, the relationship model between the critical production pressure drop of injection-production wells in gas storage and the injection-production cycle and differential pressure under the gas-solid coupling will be established, which is used for the dynamic prediction of the critical production pressure drop of injection-production wells in the whole life cycle of gas storage

Engineering the Biosynthesis of Caffeic Acid in Saccharomyces cerevisiae with Heterologous Enzyme Combinations

Engineering the biosynthesis of plant-derived natural products in microbes presents several challenges, especially when the expression and activation of the plant cytochrome P450 enzyme is required. By recruiting two enzymes—HpaB and HpaC—from several bacteria, we constructed functional 4-hydroxyphenylacetate 3-hydroxylase (4HPA3H) in Saccharomyces cerevisiae to take on a role similar to that of the plant-derived cytochrome P450 enzyme and produce caffeic acid. Along with a common tyrosine ammonia lyase (TAL), the different combinations of HpaB and HpaC presented varied capabilities in producing the target product, caffeic acid, from the substrate, L-tyrosine. The highest production of caffeic acid was obtained with the enzyme combination of HpaB from Pseudomonas aeruginosa and HpaC from Salmonella enterica, which yielded up to (289.4 ± 4.6) mg·L−1 in shake-flask cultivation. The compatibility of heterologous enzymes within a yeast chassis was effectively improved, as the caffeic acid production was increased by 40 times from the initial yield. Six key amino acid residues around the flavin adenine dinucleotide (FAD) binding domain in HpaB from Pseudomonas aeruginosa were differentiate from those other HpaBs, and might play critical roles in affecting enzyme activity. We have thus established an effective approach to construct a highly efficient yeast system to synthesize non-native hydroxylated phenylpropanoids. Keywords: Saccharomyces cerevisiae, Caffeic acid, Heterologous enzyme, Cytochrome P450, Synthetic biolog

Streptococcus sputorum, a Novel Member of Streptococcus with Multidrug Resistance, Exhibits Cytotoxicity

We describe the genomic and phenotypic characteristics of a novel member of Streptococcus with multidrug resistance (MDR) isolated from hospital samples. Strains SP218 and SP219 were identified as a novel Streptococcus, S. sputorum, using whole-genome sequencing and biochemical tests. Average nucleotide identity values of strains SP218 and SP219 with S. pseudopneumoniae IS7493 and S. pneumoniae ST556 were 94.3% and 93.3%, respectively. Genome-to-genome distance values of strains SP218 and SP219 with S. pseudopneumoniae IS7493 and S. pneumoniae ST556 were 56.70% (54–59.5%) and 56.40% (52.8–59.9%), respectively. The biochemical test results distinguished these strains from S. pseudopneumoniae and S. pneumoniae, particularly hydrolysis of equine urate and utilization of ribose to produce acid. These isolates were resistant to six major classes of antibiotics, which correlated with horizontal gene transfer and mutation. Notably, strain SP219 exhibited cytotoxicity against human lung epithelial cell line A549. Our results indicate the pathogenic potential of S. sputorum, and provide valuable insights into mitis group of streptococci

Epidemiological characteristics of nine <i>bla</i>_NDM-1-positive bacteria.

<p>Epidemiological characteristics of nine <i>bla</i>_NDM-1-positive bacteria.</p

PFGE profiles of <i>Salmonella</i> serotype <i>Braenderup</i> strain (H9812), and four <i>K. pneumoniae</i> and two <i>A. calcoaceticus</i> isolates.

<p>(A) PFGE profiles of H9812 and four <i>K. pneumoniae</i> isolates. Lane 1: <i>Salmonella</i> serotype <i>Braenderup</i> strain (H9812), as the marker. Lane 2∼5: four <i>K. pneumoniae</i> isolates (M186, M187, M194, U091, respectively). (B) PFGE profiles of H9812 and two <i>A. calcoaceticus</i> isolates. Lane 1: <i>Salmonella</i> serotype <i>Braenderup</i> strain (H9812), as the marker. Lane 2∼3: two <i>A. calcoaceticus</i> isolates, G113 and X231, respectively.</p

Cfr-mediated linezolid-resistance among methicillin-resistant coagulase-negative staphylococci from infections of humans.

Four methicillin-resistant coagulase-negative staphylococci (MRCoNS), one Staphylococcus haemolyticus and three Staphylococcus cohnii, from infections of humans collected via the Ministry of Health National Antimicrobial Resistance Surveillance Net (Mohnarin) program in China were identified as linezolid-resistant. These four isolates were negative for the 23S rRNA mutations, but positive for the gene cfr. Mutations in the gene for the ribosomal protein L3, which resulted in the amino acid exchanges Gly152Asp and Tyr158Phe, were identified in S. haemolyticus 09D279 and S. cohnii NDM113, respectively. In each isolate, the cfr gene was located on a plasmid of ca. 35.4 kb, as shown by S1 nuclease pulsed-field gel electrophoresis and Southern blotting experiments. This plasmid was indistinguishable from the previously described plasmid pSS-02 by its size, restriction pattern, and a sequenced 14-kb cfr-carrying segment. Plasmid pSS-02 was originally identified in staphylococci isolated from pigs. This is the first time that a cfr-carrying plasmid has been detected in MRCoNS obtained from intensive care patients in China. Based on the similarities to the cfr-carrying plasmid pSS-02 from porcine coagulase-negative staphylococci, a transmission of this cfr-carrying plasmid between staphylococci from pigs and humans appears to be likely

Result of S1-PFGE and Southern blot hybridization.

<p>(A) The left dark background figure shows the results of S1-PFGE, while the right light background shows the Southern blot hybridization. M: Low Range PFG Marker. Lane 1∼6: <i>A. calcoaceticus</i> G113, <i>K. pneumoniae</i> M186, <i>K. pneumoniae</i> M187, <i>K. pneumoniae</i> M194, <i>K. pneumoniae</i> U091 and <i>Citrobacter freundii</i> X122, respectively. (B) The left dark background figure shows the results of S1-PFGE, while the right light background shows the Southern blot hybridization. M: Low Range PFG Marker. Lane 1∼3: <i>Enterobacter cloacae</i> Q297, <i>Enterobacter aerogenes</i> Q442 and <i>A. calcoaceticus</i> X231, respectively.</p