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

Research on the Shear Behaviour of Composite Shear Connectors

In order to make full use of the advantages of welded stud and perfobond rib shear connectors, a new type of composite shear connector is proposed. Studs are welded to the perforated steel plate of the PBL connectors. Six specimens were designed and tested to investigate the shear behaviour of the composite connectors. The effects of the hole number, welded stud number, and end-bearing modes on the shear behaviour of the composite connectors were discussed. In addition, the composite connectors were compared with the conventional welded stud and perfobond rib connectors to analyse the difference in shear performance. The composite connectors’ shear behaviours are significantly better than those of welded stud connectors and PBL connectors. The experimental results show that increasing the number of welded studs and perforated holes and end-bearing concrete can significantly improve the shear performance of composite connectors. Secondly, a finite element model was established considering the nonlinearity of the structure and was validated based on the experimental results. Finally, the effects of reinforcement diameter, welded stud diameter, and concrete strength on the shear performance of composite connectors were analysed. The shear resistance increases as the penetrating rebar diameter, welded stud diameter, and concrete strength increase. Moreover, the overall damage level of the concrete can be significantly affected

Research on the Shear Behaviour of Composite Shear Connectors

In order to make full use of the advantages of welded stud and perfobond rib shear connectors, a new type of composite shear connector is proposed. Studs are welded to the perforated steel plate of the PBL connectors. Six specimens were designed and tested to investigate the shear behaviour of the composite connectors. The effects of the hole number, welded stud number, and end-bearing modes on the shear behaviour of the composite connectors were discussed. In addition, the composite connectors were compared with the conventional welded stud and perfobond rib connectors to analyse the difference in shear performance. The composite connectors’ shear behaviours are significantly better than those of welded stud connectors and PBL connectors. The experimental results show that increasing the number of welded studs and perforated holes and end-bearing concrete can significantly improve the shear performance of composite connectors. Secondly, a finite element model was established considering the nonlinearity of the structure and was validated based on the experimental results. Finally, the effects of reinforcement diameter, welded stud diameter, and concrete strength on the shear performance of composite connectors were analysed. The shear resistance increases as the penetrating rebar diameter, welded stud diameter, and concrete strength increase. Moreover, the overall damage level of the concrete can be significantly affected

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

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

Novel plasmid-mediated tet(X5) gene conferring resistance to tigecycline, eravacycline, and omadacycline in a clinical Acinetobacter baumannii Isolate

A novel, plasmid-mediated, high-level tigecycline resistance tet(X) gene variant, tet(X5), was detected in a clinical Acinetobacter baumannii isolate from China in 2017. Tet(X5) shows 84.5% and 90.5% amino acid identity to Tet(X3) and Tet(X4), respectively, with similar binding sites and a comparable affinity for tetracyclines. The tet(X5)-containing plasmid could only be transferred to A. baumannii via electrotransformation. This report follows the recent study describing the identification of tet(X3) and tet(X4)