Changes in Heat Resistance and Mechanical Properties of Peroxide Cross-Linking HDPE: Effects of Compounding Cross-Linkers

Due to excellent chemical resistance and impermeability, high-density polyethylene (HDPE) is widely used in petrochemical transportation, product packaging, sports equipment, and marine applications. Yet, with the wide variety of service environments, its mechanical and thermal properties do not meet the demand. In the present study, a compounding cross-linker comprising di-tert-butyl peroxide (DTBP) and triallyl isocyanurate (TAIC) is employed by combining with a two-step preparation process. High-quality cross-linking reactions are achieved for HDPE. In this study, the cross-linking of DTBP is first examined separately. A peak cross-linking degree of 74.7% is achieved, and there is a large improvement in thermal resistance and mechanical properties. Subsequently, the composite cross-linking system of DTBP and TAIC is investigated. The peak cross-linking degree is 82.1% (10% increase compared to DTBP). The peak heat deformation temperature is 80.1 °C (22% increase compared to DTBP). The peak impact strength is 104.73 kJ/m2 (207% increase compared to neat HDPE). The flexural strength is 33.6 MPa (22% increase compared to neat HDPE). The results show that this cross-linking system further improves the cross-linking degree, heat resistance, and mechanical properties of HDPE, indicating its potential application in engineering materials for high performance

Risk Factors for Acquiring Multi-Drug Resistant Klebsiella Pneumoniae At A Tertiary Teaching Hospital in China

Abstract BACKGROUD To analyze the risk factors for acquiring multi-drug resistant Klebsiella pneumoniae (MDR-Kpn). METHODS Data were collected from patients who were admitted into a tertiary teaching hospital in China from January 2018 to October 2020. Sensitive Klebsiella pneumoniae (Kpn) was detected in 82 patients. After a period of treatment, 41 patients were detected with MDR-Kpn, and they were designed as the MDR-Kpn group. Another 41 patients always detected with sensitive Klebsiella pneumoniae were assigned to the sensitive Kpn group. The baseline characteristics and clinical parameters were compared between these two groups. Multivariate logistic regression analysis were conducted to determine the risk factors for acquiring MDR-Kpn. RESULTS The proportion of sex, history of smoking and department distribution had no significant differences between these two groups. However, the patients with chronic pulmonary diseases and neurological disorders were more likely to acquire MDR-Kpn. It also showed longer hospital stay before the first detection of multi-drug resistant Kpn in MDR-Kpn group than the hospital stay before the last detection of sensitive-Kpn in sensitive Kpn group. Additionally, days of hospitalization, ICU stay, days of drainage tube use, times of sputum suction, days of foley catheter use, days of vascular catheter use between the twice detection (it represents the time interval between first detection of sensitive-Kpn to first detection of resistant-Kpn in MDR-Kpn group, and also represents the time interval between first detection of sensitive-Kpn to last detection of sensitive-Kpn in sensitive Kpn group), were higher in MDR-Kpn group. The results showed more categories of antimicrobials in patients of acquiring MDR-Kpn, along with more days of using broad-spectrum cephalosporins, fluoroquinolones and glycylcyclines, compared to non-transition group. Multivariate logistic regression analysis showed that the number of comorbidities, hospital stay before the first detection of multidrug-resistan Kpn (MDR-Kpn group) or last detection of sensitive Kpn (Sensitive group), days of using drainage tube and number of antimicrobial categories between the two detection were independent risk factors of acquiring multidrug-resistance for Kpn. CONCLUSION: The number of comorbidities, the hospital stay, the number of antimicrobial categories, and days of using drainage tube were independent risk factors for acquiring MDR-Kpn.</jats:p

Antibiotic Resistances and Molecular Characteristics of Clostridioides difficile in ICUs in a Teaching Hospital From Central South China

Clostridioides (C.) difficile is a major healthcare-associated pathogen inducing infectious diarrhea. Approximately 25–33% of patients with antibiotic-associated diarrhea (AAD) and 90% of patients with pseudomembranous enteritis are caused by C. difficile infection (CDI). Stool samples were collected from hospitalized adults with presumptive AAD in four nonneonatal intensive care units (ICUs). Diagnosis of CDI was based on both clinical symptoms and laboratory results. The stool specimens were transferred onto CDIF (C. difficile agar), and C. difficile was finally confirmed by the latex agglutination test. Toxin-producing genes tcdA (A), tcdB (B), and cdt (CDT) were detected by PCR, and all isolates were performed multilocus sequence typing analysis. The antibiotic susceptibility of C. difficile isolates was assessed by the agar dilution method. A total of 184 C. difficile were isolated from 857 specimens in our study, the isolation rate of C. difficile was 21.5% (184/857). The 184 C. difficile were isolated from 179 patients, among these 115 patients were toxin-positive, giving the incidence of CDI being 58.0/10,000 patient days in the four ICUs. Among these 115 toxin-positive C. difficile isolates, 100 (87.0%) isolates produced two toxins (A+B+CDT-), three (2.6%) isolates were A+B+ with binary toxin-producing (A+B+CDT+), and 12 (10.4%) isolates only produced one toxin (A-B+CDT-). A total of 27 sequencing types (STs) were obtained. The most prevalent was ST3 (34 isolates), followed by ST39 (27 isolates), ST54 (19 isolates), ST26 (16 isolates), ST35 (15 isolates), and ST2 (13 isolates). All the ST26 isolates were nontoxigenic. Meanwhile, five STs were newly discovered. Although multidrug resistance was present in ≥50% of these C. difficile isolates, all of them were susceptible to tigecycline, fidaxomicin, metronidazole, and vancomycin. In conclusion, C. difficile isolates producing two toxins (A+B+CDT-) were dominant in our hospital. The most prevalent was ST3, and all ST26 isolates were NTCD. Although multidrug resistance was present in ≥50% of the C. difficile isolates, metronidazole, tigecycline, fidaxomicin, and vancomycin were still effective treatments for CDI in our hospital.</jats:p

Is It an Outbreak of Health Care-Associated Infection? An Investigation of Binocular Conjunctival Congestion After Laparoscopic Cholecystectomy Was Traced to Chitosan Derivatives

BackgroundFrom May 6 to May 23, 2019, 24 (80.00%) patients who underwent laparoscopic cholecystectomy (LC) developed binocular conjunctival congestion within 4–8 h after their operation in the day ward of a teaching hospital.MethodsNosocomial infection prevention and control staff undertook procedural and environmental investigations, performed a case-control retrospective study (including 24 cases and 48 controls), and reviewed all lot numbers of biological material products to investigate the suspected outbreak of health care-associated infection.FindingsInitially, an outbreak of health care-associated infection caused by bacteria was hypothesized. We first suspected the membranes that covered patients' eyes were cut using non-sterile scissors and thus contaminated, but they failed to yield bacteria. In addition, both corneal and conjunctival fluorescein staining results were negative in case-patients and isolated bacteria were ubiquitous in the environment or common skin commensals or normal flora of conjunctiva from 218 samples from day surgery and the day ward. Hence, we considered a non-infectious factor as the most likely cause of the binocular conjunctival congestion. Then, we found that case-patients were more likely than LC surgery patients without binocular conjunctival congestion to be exposed to biological materials in a retrospective case-control study. When we reviewed lot numbers, duration of use, and the number of patients who received four biological material products during LC in the day ward, we found that the BLK1821 lot of a modified chitosan medical membrance (the main ingredient is chitosan, a linear cationic polysaccharide) was used concurrently to when the case aggregation appeared. Finally, we surmised there was a correlation between this product and the outbreak of binocular conjunctival congestion. Relapse of the pseudo-outbreak has not been observed since stopping usage of the product for 6 months.ConclusionA cluster of binocular non-infectious conjunctival congestion diagnosed after LC proved to be a pseudo-outbreak. We should pay more attention to adverse events caused by biomaterials in hospitals.</jats:sec