Antimicrobial and Transconjugants Characteristics of Sul3 Positive Escherichia Coli Isolated from Animals in Nanning, Guangxi Province

Abstract

Background: Sulfonamides is the second most popular antibiotic in many countries, which leads to the widespread emergence of sulfonamides resistance. Sul3 is a late sulfanilamide resistance gene, whose research is relatively little. Result: 46 sul3 positive E. coli strains were separated. A total of 12 ST types were observed, and 1 of those was previously unknown type. The ST350 is the most numerous type. All isolates were multidrug-resistant E. coli, with high antimicrobial rates to penicillin, ceftriaxone sodium, streptomycin, tetracycline, ciprofloxacin, gatifloxacin and chloramphenicol (100%, 73.9%, 82.6%, 100%, 80.4%, 71.7% and 97.8%), and with at least 3 resistance genes in addition to sul3. The plasmids transfered from 3 sul3-positive isolates to C600, the most of which brought 7 antibiotic resistance and increased resistance genes to C600. The transferred sul3 gene and the plasmid that carries it could be stably inherited in the recipient bacteria for at least 20 days. Those plasmids had no effect on the growth of the recipient bacteria, but it would greatly reduce (at least 60 time) the in vitro competitiveness of the strains. Conclusions: In Nanning, these sul3-positive Escherichia coli have strong antimicrobial resistance, and the plasmid carrying sul3 has the ability to transfer multiple resistance genes, so long-term monitoring is necessary. Since the transferred plasmid will greatly reduce the in vitro competitiveness of the strain, we can consider limiting the spread of antimicrobial in this respect.

Advances in coral aggregate concrete and its combination with FRP: A state-of-the-art review

“…Unlike the relatively low compressive strength of CAC, CAC exhibits a tensile strength close to or higher than that of NAC (Li, 2012; Wu et al, 2018). As the surface of coral aggregates is rough and porous, the mechanical interlock between the aggregates and the cement matrix at the interface is enhanced.…”

“…Therefore, the interface transition zone in the hardened cement matrix becomes denser and has less voids (Xu et al, 2019), as shown in Figure 3(b). Consequently, the microhardness in the interface transition zone is significantly higher than that of the coral aggregates itself and the cement matrix, and higher than that of normal aggregate concrete (NAC) (Li, 2012; Zhang, 2012). This feature also influences the long-term strength of CAC, which will be discussed later.…”

Mechanical properties and constitutive model of coral aggregate concrete subjected to dynamic uniaxial and triaxial compression

“…The deviatoric-plane curves adopt an elliptic curve of William-Warnke 46 0 < θ < 60 to describe the intensity envelope, such as Equation (9) shows: where…”

“…[4][5][6] The coral aggregates are mainly composed of CaCO 3 and are characterized by large porosity, high water absorption, and low strength, which makes more water required in the preparation of concrete to meet the requirements of strength and workability, while the aggregate itself is brittle and therefore generally not easy to prepare a higher strength concrete. [7][8][9][10][11][12] The CAC has the characteristics of early strength development fast, which is shown by the 7d compression strength can reach 80% of the 28d. 13,14 The long-term strength of CAC can still maintain a high level and can meet the requirements of engineering, but the main reason why the application of CAC is limited at present is the corrosion caused by adverse effects of chloride ions in seawater and coral aggregate on corrosion of concrete structures.…”

“…There are many studies on the uniaxial compression and tension of CAC, and the results can be directly applied to some relatively simple structural members. 9,[18][19][20][21] However, the stress state of concrete is generally complex not simple uniaxial force conditions in the actual engineering structure, for example, in the concrete-filled steel tube and beam-tocolumn connections are triaxial stresses. Therefore, the research on the mechanical performances of concrete under triaxial stresses is the focus of current structural engineering.…”