Correction: Fang et al. Study on Dispersion, Adsorption, and Hydration Effects of Polycarboxylate Superplasticizers with Different Side Chain Structures in Reference Cement and Belite Cement. Materials 2023, 16, 4168.

In the original publication [...].

pH-Responsive Polymeric Micelle Dynamic Complexes for Selective Killing of Helicobacter pylori.

Helicobacter pylori, the world's most common chronic infection-causing pathogen, is responsible for causing gastric ulcers, the fourth-leading cause of cancer-related death globally in 2020. In recent years, the effectiveness of the current treatment regimen (two antibiotics and one proton pump inhibitor) has often been plagued with problems such as resistance and the undesired elimination of commensal bacteria. Herein, we report the synthesis of block and random copolycarbonates, functionalized with cationic guanidinium and anionic acetate functional groups, aimed at selectively killing H. pylori in the acidic environment of the stomach, while remaining nontoxic to the commensal bacteria in the gut. The compositions of the polymers were fine-tuned so that the polymers were readily dispersed in water without any difficulty at both pH 3.0 and 7.4. The self-assembly behavior of the polymers at different pH values by dynamic light scattering showed that the random and block copolymers formed stable micelles in a simulated gastric environment (pH 3.0) while aggregated at pH 7.4. Both polymers demonstrated stronger antibacterial activity against H. pylori than the guanidinium-functionalized homopolymer without any acetate functional group at pH 3.0. The block copolymer was significantly more bactericidal at pH 3.0 across the concentrations tested, as compared to the random copolymer, while it did not show significant toxicity toward rat red blood cells (rRBCs) and HK-2 cells or bactericidal effect toward E. coli (a common gut bacterium) and nor caused aggregation of rRBCs at its effective concentration and at physiological pH of 7.4. Additionally, both the block and random copolymers were much more stable against hydrolysis at pH 3.0 than at pH 7.4. This study provides insight into the influence of both polymer architecture and dynamic assembly on the bioactivities of antimicrobial polymers, where the disassembly of coacervates into narrowly dispersed micelles at pH 3 make them potent antimicrobials aided by the protonated carboxylic acid block.

Study on the Effect of Main Chain Molecular Structure on Adsorption, Dispersion, and Hydration of Polycarboxylate Superplasticizers.

Polycarboxylate ether (PCE) with different main chain structures was prepared by aqueous solution free radical polymerization using unsaturated acids containing sulfonic acid groups, acrylamide groups, and carboxyl groups and isoprenyl polyoxyethylene ether (IPEG). The molecular structure was characterized by infrared spectroscopy and gel chromatography, while adsorption, dispersion, and hydration properties were studied using a total organic carbon analyzer, rheometer, and isothermal microcalorimeter, respectively. The results show that the adsorption process of PCE on cement particles is spontaneous physical adsorption. The adsorption forces are mainly electrostatic interaction, and hydrogen bonding. The introduction of sulfonic acid groups and polycarboxylic acid groups reduces the initial adsorption amount of PCE but can accelerate the adsorption rate of PCE on cement and increase the adsorption amount at the adsorption equilibrium. The introduction of acrylamide groups in the PCE main chain is beneficial to the initial dispersion of PCE and can reduce the plastic viscosity of cement slurry. PCE can delay the hydration of cement. The introduction of acrylamide groups and dicarboxylic acid groups in the PCE main chain helps prolong the induction period of cement hydration, while the introduction of sulfonic acid groups is not conducive to its retarding effect.

Study on Dispersion, Adsorption, and Hydration Effects of Polycarboxylate Superplasticizers with Different Side Chain Structures in Reference Cement and Belite Cement.

To investigate the effects of Reference cement (RC) and Belite cement (LC) systems, different molecular structures of polycarboxylate ether (PCE) were prepared through the free radical polymerization reaction and designated as PC-1 and PC-2. The PCE was characterized and tested using a particle charge detector, gel permeation chromatography, a rotational rheometer, a total organic carbon analyzer, and scanning electron microscopy. The results showed that compared to PC-2, PC-1 exhibited higher charge density and better molecular structure extension, with smaller side-chain molecular weight and molecular volume. PC-1 demonstrated enhanced adsorption capacity in cement, improved initial dispersibility of cement slurry, and a reduction in slurry yield stress of more than 27.8%. LC, with its higher C2S content and smaller specific surface area compared to RC, could decrease the formation of flocculated structures, resulting in a reduction in slurry yield stress of over 57.5% and displaying favorable fluidity in cement slurry. PC-1 had a greater retarding effect on the hydration induction period of cement compared to PC-2. RC, which had a higher C3S content, could adsorb more PCE, leading to a greater retarding effect on the hydration induction period compared to LC. LC and PC-2, on the other hand, exhibited inhibition during the hydration acceleration period. The addition of PCE with different structures did not significantly affect the morphology of hydration products in the later stage, which was consistent with the trend of KD variation. This indicates that the analysis of hydration kinetics can better reflect the final hydration morphology.

Study on the Effect of Polycarboxylate Ether Molecular Structure on Slurry Dispersion, Adsorption, and Microstructure.

This study synthesized polycarboxylate superplasticizer (PCE) with varying carboxyl densities and main chain degrees of polymerization. The structural parameters of PCE were characterized using gel permeation chromatography and infrared spectroscopy. The study investigated the impact of PCE's diverse microstructures on cement slurry's adsorption, rheology, hydration heat, and kinetics. Microscopy was used to analyze the products' morphology. The findings indicated that an increase in carboxyl density led to an increase in molecular weight and hydrodynamic radius. A carboxyl density of 3.5 resulted in the highest flowability of cement slurry and the most considerable adsorption amount. However, the adsorption effect weakened when the carboxyl density was the highest. Decreasing the main chain degree of polymerization led to a significant reduction in the molecular weight and hydrodynamic radius. A main chain degree of 16.46 resulted in the highest flowability of slurry, and both large and small main chain degrees of polymerization exhibited single-layer adsorption. PCE samples with higher carboxyl density caused the greatest delay in the induction period, whereas PCE-3 promoted the hydration period's acceleration. Hydration kinetics model analysis indicated that PCE-4 yielded needle-shaped hydration products with a small nucleation number in the crystal nucleation and growth stage, while PCE-7's nucleation was most influenced by ion concentration. The addition of PCE improved the hydration degree after three days and facilitated the strength's later development compared to the blank sample.

Effect of the Short-Term Use of Fluoroquinolone and ß-Lactam Antibiotics on Mouse Gut Microbiota.

BACKGROUND: Antibiotics play an important role in the treatment of infectious diseases. However, the overuse of antibiotics increases the spread of drug-resistant bacteria and causes dysbiosis of the intestinal microbiota. Few studies have addressed the longitudinal effects of antibiotics on the microbiome and host immunity. MATERIALS AND METHODS: In this study, the short-term effect of fluoroquinolone (levofloxacin) and ß-lactam antibiotics (meropenem, cefoperazone/sulbactam, and aztreonam) on the gut microbiota of mice was evaluated by 16S rRNA gene sequencing. The susceptibility of Bifidobacterium longum, Lactobacillus lactis, Enterococcus faecium, and Clostridium butyricum to these antimicrobial agents was assessed using the disc diffusion method. RESULTS: Our results showed that 4-day antibiotic exposure significantly reduced the alpha and beta diversity of gut bacteria and increased serum inflammatory cytokines, and these changes persisted long after antibiotic withdrawal and did not return to pre-treatment levels. Nonetheless, the bacterial community composition tended to return to pre-treatment levels after discontinuing treatment. The tested probiotic strains were resistant to aztreonam but were sensitive to meropenem and cefoperazone/sulbactam. CONCLUSION: Short-term antibiotic treatment led to significant changes in the intestinal flora with a tendency to recover. The antibiotics had different effects on the intestinal microbial community and probiotic strains. This study provides guidance for the concomitant use of probiotics and antibiotics, and the results emphasize the importance of using broad-spectrum antibiotics responsibly to prevent the long-term disruption of the native microbiota.

Whole genome analysis reveals new insights into the molecular characteristics of Clostridioides difficile NAP1/BI/027/ST1 clinical isolates in the People's Republic of China.

Background: The epidemic new strain NAP1/BI/027/ST-1 of Clostridioides difficile (C. difficile) causes more severe coliti and a higher mortality rate than historical strains. However, C. difficile NAP1/BI/027/ST-1 (C. difficile RT027) infections have been rarely reported in Asia, particularly in China. Purpose: The objective of this study was to strengthen the understanding of the molecular characterizations of C. difficile RT027 in China. Patients and methods: Two C. difficile NAP1/BI/027/ST-1 were detected from two patients, and no additional isolates were found. Whole genome sequencing (WGS) was used to characterize two C. difficile RT027 isolates and control strain CD6 (from Hong Kong), and comparative genomic analysis was performed to compare genomic differences between seven isolates from Mainland China, CD6, and 10 isolates from North America and Europe. Results: The comparative genomic analysis revealed that isolates obtained from Mainlan China were outside of the two epidemic lineages, FQR1 and FQR2, and might have decreased virulence and transmissibility for outbreak. Furthermore, unique SNP mutations were detected in isolates obtained from Mainland China, which may affect the biological function of C. difficile. Conclusion: We speculate that C. difficile RT027 isolates in Mainland China may have different features, compared to those in North America and Europe.

Longitudinal investigation of carriage rates and genotypes of toxigenic Clostridium difficile in hepatic cirrhosis patients.

Toxigenic Clostridium difficile (C. difficile) carriers represent an important source in the transmission of C. difficile infection (CDI) during hospitalisation, but its prevalence and mode in patients with hepatic cirrhosis are not well established. We investigated longitudinal changes in carriage rates and strain types of toxigenic C. difficile from admission to discharge among hepatic cirrhosis patients. Toxigenic C. difficile was detected in 104 (19.8%) of 526 hepatic cirrhosis patients on admission, and the carriage status changed in a portion of patients during hospitalisation. Approximately 56% (58/104) of patients lost the colonisation during their hospital stay. Among the remaining 48 patients who remained positive for toxigenic C. difficile, the numbers of patients who were positive at one, two, three and four isolations were 10 (55.6%), three (16.7%), two (11.1%) and three (16.7%), respectively. Twenty-eight patients retained a particular monophyletic strain at multiple isolations. The genotype most frequently identified was the same as that frequently identified in symptomatic CDI patients. A total of 25% (26/104) of patients were diagnosed with CDI during their hospital stay. Conclusions: Colonisation with toxigenic C. difficile strains occurs frequently in cirrhosis patients and is a risk factor for CDI.

Effect of Side Chain Length on Polycarboxylate Superplasticizer in Aqueous Solution: A Computational Study.

Molecular dynamics simulations were carried out to study the conformations of polycarboxylate ether (PCE) superplasticizers with different side chain lengths in aqueous solution. For four types of PCE molecules-PCE1, PCE2, PCE3, and PCE4-the steric hindrance between the PCE molecules increased with increasing side chain length. The side chain length not only affects water mobility but also affects the distribution of water molecules in the system. Simulation results indicate that water molecules were trapped by the PCE molecules, reducing the diffusion properties. PCE molecules with long side chains have more water molecules probability around the main chain and fewer water molecules probability near the side chain. Microscopic-level knowledge of the interaction between superplasticizer and water molecules facilitates understanding of the performance of superplasticizers in cement systems.

High prevalence of KPC-2-producing hypervirulent Klebsiella pneumoniae causing meningitis in Eastern China.

BACKGROUND: Klebsiella pneumoniae has been the leading causative pathogen for adult bacterial meningitis in several Asian countries. The clinical and microbiological characteristics of K. pneumoniae meningitis in mainland China are still unknown. MATERIALS AND METHODS: The clinical data of patients with K. pneumoniae meningitis from January 2011 to July 2017 in a tertiary hospital were retrospectively evaluated. The isolates were tested for antibiotic-resistance genes, virulence-associated genes, and molecular subtypes. Hyper-virulent K. pneumoniae (hvKP) was defined as the presence of pLVPK-like virulence plasmid. RESULTS: During the study period, a total of 48 patients with meningitis caused by K. pneumoniae were identified, accounting for 21.2% (48/226) of Gram-negative bacilli meningitis. Of the 44 available isolates, 65.9% (29/44) were carbapenem resistant, and all except one har-bored bla KPC-2. K64 was the most common serotype (n=13), followed by K47 (n=11) and K1 (n=5). The pLVPK-related genetic loci were found in about half of isolates (iutA: 56.8%, iucA: 56.8%, rmpA2:50.0%, rmpA: 43.2%, and iroN: 40.9%). Twenty-two strains carrying pLVPK-derived virulence plasmid were defined as hvKP. Notably, the coexistence of bla KPC-2-encoding plasmid and the pLVPK-derived virulence plasmid was detected in 15 strains (34.1%, 15/44), suggesting K. pneumoniae carbapenemase-2 (KPC-2)-producing hvKP. The proportion of KPC-2-producing hvKP by year increased remarkably from 0% (2011) to 71.4% (2017). Of the 15 KPC-2-producing hvKP strains, 80.0% (12/15) were assigned to sequence type 11 and 2 strains (13.3%) belonged to clonal complex 23. Most of the patients infected with KPC-2-producing hvKP had preceding postneurosurgical state (93.3%, 14/15) and severe pneumonia (73.3%, 11/15). All the cases (100%, 15/15) had fatal outcome. CONCLUSION: The high prevalence and mortality of K. pneumoniae, especially KPC-2-producing hvKP meningitis, in China should be of concern. The implementation of epidemiological surveillance and identification of an effective clinical treatment are paramount.

Tribological properties of attapulgite/La2O3 nanocomposite as lubricant additive for a steel/steel contact.

Attapulgite is a layered silicate with good friction-reduction and self-repairing properties. In order to further improve its tribological properties, the present work mainly focuses on the preparation of attapulgite/La2O3 nanocomposite and study on its tribological behaviors. The tribological properties of mineral lubricating oil (150SN) containing attapulgite/La2O3 nanocomposite were investigated through an Optimal SRV-IV oscillating friction and wear tester. The rubbing surfaces and generated tribofilms were characterized by SEM, EDS, XPS and nanoindentation. Results indicated that the friction-reducing ability and antiwear property of the oil were both remarkably improved by attapulgite/La2O3 nanocomposite. A tribofilm mainly composed of Fe, Fe3C, FeO, Fe2O3, FeOOH, SiO, SiO2 and organic compound was formed on the rubbing surface under the lubrication of oil with attapulgite/La2O3 nanocomposite. The tribofilm possess excellent self-lubricating ability and mechanical properties, which is responsible for the reduction of friction and wear.

Molecular epidemiology and antimicrobial susceptibility of Clostridium difficile isolated from hospitals during a 4-year period in China.

OBJECTIVE: The aim of this study was to perform molecular characterization for and determine the antimicrobial susceptibility profiles of Clostridium difficile collected from hospitals during a 4-year period (2009-2013) in China. METHODS: Strains of toxigenic C. difficile were isolated from patients with diarrhoea, and this was followed by typing using multilocus sequence typing (MLST) and testing for susceptibility to 10 antimicrobials by using the E-test. The mechanisms of resistance to moxifloxacin, erythromycin, clindamycin and tetracycline were investigated by PCR. RESULTS: A total of 405 non-duplicate toxigenic C. difficile isolates were identified, while 31 sequence types (STs) were identified. A predominant type, ST-54, accounted for 20.2 % of the STs, followed by ST-35 (16.3 %) and ST-37 (13.6 %). We found that 6.2 % of the isolates were binary toxin genes-positive, and 83.7 % of these belonged to ST-5. All of the isolates demonstrated 100 % susceptibility to first-line Clostridium difficile infection (CDI) therapies (i.e. metronidazole and vancomycin), while the resistance rates varied for the other antibiotics tested. Two hundred and ninety three (72.3 %) isolates were susceptible to moxifloxacin. All 112 moxifloxacin-resistant isolates had mutations resulting in an amino acid substitution in gryA and/or gyrB. The ermB gene was detected in 86.7 % (241/278) of the erythromycin- and clindamycin-resistant isolates, while the tetM gene was present in 97.1 % (85/87) of the tetracycline-resistant isolates. CONCLUSION: MLST typing revealed a wide variety of STs causing CDI, while ST-54 was the most common ST. All of the isolates were susceptible to metronidazole and vancomycin, while the resistance rates varied for the other antibiotics tested. There were no changes in the trends for the STs and antibiotic susceptibility profiles over 4 years.

Hospital-acquired Clostridium difficile infection in Mainland China: A seven-year (2009-2016) retrospective study in a large university hospital.

Clostridium difficile infection (CDI) is associated with risk for severe disease and high mortality. Little is known about the extent of hospital-acquired CDI in Mainland China. In this study, we aimed to investigate the annual CDI incidence, bacterial genotypes, risk factors for severe CDI and survival over a 7-year period. A total of 307 hospital-acquired CDI patients were enrolled, and 70.7% of these cases were male. CDI incidence was 3.4 per 10,000 admissions. Thirty-three different sequence types (STs) were identified, among which ST-54 (18.2%), ST-35 (16.6%) and ST-37 (12.1%) were the most prevalent. During the follow-up period, 66 (21.5%) patients developed severe CDI and 32 (10.4%) patients died in 30 days. Multivariate analysis revealed that bloodstream infection, pulmonary infection and C-reactive protein were significantly associated with severe CDI. After adjustment for potential confounders, old age, bloodstream infection, fever, mechanical ventilation, connective tissue disease, macrolide use and hypoalbuminaemia were independently associated with 30-day mortality in patients with CDI. The CDI prevalence has been low and stable in our center, and STs of Clostridium difficile were different from dominant STs in Western countries. Our data emphasize the need of continued education and surveillance of CDI to reduce the CDI burden in China.

Characterization of a novel metallo-ß-lactamases fold hydrolase from Pelagibacterium halotolerans, a marine halotolerant bacterium isolated from East China Sea.

In this study, a novel metallo-ß-lactamases fold hydrolase PH-1 was identified from Pelagibacterium halotolerans B2(T). This novel member of the family Hyphomicrobiaceae was isolated from the East China Sea. In silico analysis demonstrated that PH-1 and its relative homologues cluster in a unique branch and constitute a new subgroup among MBLs. PH-1 was cloned and overexpressed in Escherichia coli BL21 in a soluble form. SDS-PAGE, MALDI-TOF/TOF-MS, and size-exclusion chromatography analysis demonstrated that the PH-1 was a monomer with molecular weight of about 29 kDa. Substrate specificity study showed PH-1 preferred penicillin type ß-lactams and exhibited maximum activity toward penicillin-G. Additionally, our experiments also revealed that PH-1 was a halotolerant enzyme since it is active under 4 M NaCl. The enzyme activity of PH-1 was negatively affected by 1 mM Mn(2+) and EDTA. These observations lay a foundation for further study of MBLs from marine bacterium.

Clostridium difficile carriage in healthy pregnant women in China.

Infection with Clostridium difficile has been shown to have particularly poor outcomes for pregnant women, including an increased risk of death. The purpose of this study was to investigate the prevalence, genotypic distribution, and characterization of C. difficile strains isolated from pregnant women without diarrhea in China. As part of this study, 3.7% (37 out of 1009) of samples acquired from pregnant females tested positive for C. difficile. Of these positive samples, 27.0% (10) were toxigenic isolates containing both toxin A and toxin B genes (A+B+), 13.5% (5) of the variant strains contained the toxin B gene (A-B+) only, while the rest were non-toxigenic isolates (59.5%, 22 isolates). Among the non-pregnant women without diarrhea tested, 1.4% (9 of 651) contained toxigenic isolates (all of which were A+B+). Sixteen different sequence types (STs) were isolated during the course of this study. ST-37 (ribotype 017) and ST-54 (ribotype 012) were the most frequent toxigenic types observed in pregnant women. All strains showed susceptibility to the antibiotics metronidazole and vancomycin. The resistance rates of toxigenic C. difficile strains isolated from pregnant females to clindamycin, erythromycin, moxifloxacin, levofloxacin, and rifampicin were 20%, 46.7%, 13.6%, 46.7% and 13.3%, respectively. There was no significant difference between resistance rates of toxigenic and non-toxigenic strains with respect to their susceptibility to these antibiotics. However, when compared with the same data from non-pregnant women, toxigenic strains from pregnant women showed lower resistance rates to clindamycin (P < 0.05).

Emergence of Raoultella ornithinolytica coproducing IMP-4 and KPC-2 carbapenemases in China.

We report here the emergence of seven IMP-4-producing Raoultella ornithinolytica isolates obtained from one patient. All isolates carried the blaIMP-4 carbapenemase gene, five isolates also carried blaSHV-12, four contained blaTEM-1, and one contained blaOXA-1. Notably, the R. ornithinolytica isolate Ro25724 also expressed Klebsiella pneumoniae carbapenemase (KPC)-2. The blaKPC-2 gene was located on a Tn3-Tn4401 integration structure on a plasmid of ∼450 kb. This is the first description of the coexistence of blaKPC-2 and blaIMP-4 from the genus Raoultella.