Piotr Osuch

Antibiotic resistance, ability to form biofilm and susceptibility to copper alloys of selected staphylococcal strains isolated from touch surfaces in Polish hospital wards

BackgroundDespite the employment of sanitary regimes, contact transmission of the aetiological agents of hospital infections is still exceedingly common. The issue of microbe transmission becomes particularly important when facing multidrug-resistant microorganisms such as methicillin-resistant staphylococci. In the case of deficiencies in cleaning and disinfection procedures, hospital equipment made of copper alloys can play an important role, complementing traditional hospital hygiene procedures.The objective of this study was to characterize staphylococcal strains isolated from touch surfaces in Polish hospital wards in terms of their drug resistance, ability to form biofilm and susceptibility to antimicrobial activity of copper alloys.MethodsThe materials for the study were 95 staphylococcal strains isolated from touch surfaces in 13 different hospital wards from Małopolska province (the south of Poland). Phenotypic and genotypic antibiotic resistance were checked for erythromycin, clindamycin, gentamycin, ciprofloxacin, trimethoprim/sulfamethoxazole and mupirocin. Biofilm formation ability for the tested strains was checked with the use of culture on Congo red agar. Susceptibility to copper, tin bronze, brass and new silver was tested using a modification of the Japanese standard.ResultsOver 67% of the analysed staphylococcal strains were methicillin-resistant (MR). Four strains were resistant to all of the tested antibiotics, and 14 were resistant to all except mupirocin. Strains classified as MR had significantly increased resistance to the remaining antibiotic groups. About one-third of the analysed strains revealed biofilm-forming ability. Among the majority of species, biofilm-forming and non-biofilm-forming strains were distributed evenly; in the case of S. haemolyticus only, negative strains accounted for 92.8%. Susceptibility to copper alloys was different between strains and rather lower than in the case of the SA strain selected for comparison.ConclusionsCoagulase-negative staphylococci, the most commonly isolated in Polish hospital wards, should not be neglected as an infection risk factor due their high antibiotic resistance. Our experiments confirmed that touch surfaces made of copper alloys may play an important role in eliminating bacteria from the hospital environment.

Impact of the Direct Ageing Procedure on the Age Hardening Response of Al-Mg-Si 6101 Alloy

Al-Mg-Si alloys are used not only as construction material, but also as a material for electrical conductors. For this application, it is crucial for the alloy to achieve a balance between strength and electrical properties. This is achieved in practice by a combination of strain and precipitation hardening. The current paper focuses on a heat treatment procedure in which the EN AW 6101 alloy is cooled by a flowing air stream from the solutionizing temperature down to the artificial ageing temperature. The proposed procedure, unlike the common heat treatment leading to the T6 temper, allowed for the precipitation of the coarser β” phase with the presence of relatively wide precipitate-free zones. The age hardening response was investigated by Brinell hardness measurements, eddy current testing and microstructural observations using transmission electron microscopy (TEM). The applied heat treatment resulted in slightly lower strength (compared to the T6 temper), but improved electrical performance of the alloy.

Antimicrobial Properties of Selected Copper Alloys on Staphylococcus aureus and Escherichia coli in Different Simulations of Environmental Conditions: With vs. without Organic Contamination

Background: Hospital equipment made from copper alloys can play an important role in complementing traditional methods of disinfection. Aims of the study: The aim of this study was to assess the dynamics of the antimicrobial properties of selected copper alloys in different simulations of environmental conditions (with organic contamination vs. without organic contamination), and to test alternatives to the currently used testing methods. Materials and Methods: A modification of Japanese standard JIS Z 2801 as well as Staphylococcus aureus (SA) and Escherichia coli (EC) suspended in NaCl vs. tryptic soy broth (TSB) were used in tests performed on seven commonly used copper alloys, copper, and stainless steel. Results: A much faster reduction of the bacterial suspension was observed for the inoculum prepared in NaCl than in TSB. A faster reduction for EC than for SA was observed in the inoculum prepared in NaCl. The opposite results were found for the inoculum based on TSB. A significant correlation between the copper concentration in the copper alloys and the time and degree of bacterial suspension reduction was only observed in the case of EC. Conclusions: This study confirmed the antimicrobial properties of copper alloys, and additionally showed that Staphylococcus aureus was more resistant than Escherichia coli in the variant of the experiment without organic contamination. However, even for SA, a total reduction of the bacterial inoculum’s density took no longer than 2 h. Under conditions simulating organic contamination, all of the tested alloys were shown to have bactericidal or bacteriostatic properties, which was contrary to the results from stainless steel.

A Study of the Influence of Strain Hardening and Precipitation Hardening Sequence on Mechanical Properties of AlMgSi Conductor Alloys

Precipitation-hardenable AlMgSi alloys grade 6101 of 0.5% Mg and 0.5% Si contents, are used for the construction of homogenous wires in overhead power lines. The dominating group of alloys with increased electrical conductivity is the AlMgSi alloy group, these are HC, EHC and EEHC type materials with tensile strength at approximately 300 MPa and electrical conductivity lower than conventional wires (56,5 – 54,3 %IACS). The study presents the results of the research of AlMgSi wires heat treatment in compliance with the PN-EN 50183 standard. The shaping of heat treatable AlMgSi alloy rods and wires properties is possible through an appropriate sequence of a precipitation hardening (during ageing) and strain hardening (during drawing processes). This paper is a comprehensive analysis of the technologies for the production of wires from AlMgSi alloys.

Analysis of the Antimicrobial Copper Alloys Registered by the Environmental Protection Agency

The paper raises the issue of antimicrobial copper and its alloys constituting a promising solution for the constantly increasing problem of dangerous hospital-acquired infections. The major aim of the presented work is a precise analysis of antimicrobial copper alloys approved by The Environmental Protection Agency (EPA) in accordance with the Unified Numbering System, taking into account their European and international equivalent symbols as well – CEN and ISO, respectively. The analysis focuses mostly on the copper alloy types which the EPA list is composed of, their prices as well as materials and technological properties.

The Effect of Homogenization and Interrupted Rolling on Microstructure and Properties of Zn-Cu-Ti Rolled Sheets

Due to specific application of the Zn-Cu-Ti alloy rolled sheets as a roofing material, ready-made sheets has to meet some specific requirements of bendability at relatively low temperatures, as low as 5°C. In the current paper it was shown that susceptibility of the Zn-Cu-Ti sheets to low temperature bending, is closely related to degree of its dynamic recrystallization during rolling process. The paper discusses effect of different technological routes on the microstructure, mechanical properties and in particular the low temperature performance of Zn-Cu-Ti rolled sheets. The experimental results shows that the homogenization of Zn-Cu-Ti casted strips at the pre-rolling stage can play important role in recrystallization of the sheets during rolling. The current work is part of research on designing new technological route.

Microstructure and Properties of Al-Mg-Si Wire-Rod Subjected to Continuous Heat Treatment

Among multiple applications 6XXX-series aluminum alloys are widely used as electrical conductor for overhead power lines. For that application Al-Mg-Si alloys are produced mainly in the form of wire rod in the continuous casting and rolling lines (CCR). There is many technological routes possible to transform the Al-Mg-Si wire-rod into precipitation hardened, ready to use Al-Mg-Si wires. One of these routes involves using the heat of continuous casting and rolling process to artificial ageing of wire-rod, which is motivated by ecological premise. In the current paper the results of continuous heat treatment of the wire-rod within the CCR line (involving quenching of the alloy to artificial ageing temperature) on the microstructure and properties has been examined. It was shown the structure of wire rod formed in such process is very irregular. TEM investigations has shown that many heterogeneous particles are present and the arrangement of the β main hardening phase is very inhomogeneous with wide precipitate free zones occurred. However this type of microstructure has a positive effect on electrical properties of the material in question, which is important taking into consideration application of the alloy.

Effect of Precipitation Hardening on the Structure and Properties of Al-Mg-Si Conductor Alloys in Different Technological Routes

The Al-Mg-Si alloys, due to their unique combination of lightweight, mechanical and electrical properties and excellent corrosion resistance, are used as a material for the production of overhead power conductors, commonly known as AAAC (All Aluminium Alloy Conductor). Wires intended for conductor manufacturing are obtained from the wire rod produced by a continuous casting and rolling line (CCR, e.g., Continuus-Properzi). The Al-Mg-Si wire rod can be processed into ready-made wires by different technological routes, which mainly consist of different combinations of strain hardening as well as precipitation hardening of wire rod or wires. In Europe the conventional technological route comprises solution heat treatment of wire rod coils (heated at temperatures over ~500 °C, followed by quenching into water), then natural ageing of wire rod at ambient temperature for a couple of days, next wire drawing, and finally artificial ageing.This paper discusses results of investigations on developing an alternative technological route. In this process heat from the continuous casting and rolling process by Continuus-Properzi is used for heat treatment of the wire rod. The new technological route allows the abandonment of the high temperature heat treatment as well as natural ageing of the wire rod, making the production process less energy consuming, cheaper and faster than the conventional one. The current paper presents research results identifying the structure of materials from different Al-Mg-Si wires production process routes. It also focuses on electrical and mechanical properties.

A Study of the Influence of Strain Hardening and Precipitation Hardening Sequence on Development of Mechanical Properties of AlMgSi Conductor Alloys

The paper focuses on 6xxx series AlMgSi conductor alloys. Such alloys are used for manufacturing of conductors for power transmission. Since the most current standards define as many as seven types of wires with various mechanical and electrical specifications, the existing philosophy of AlMgSi wires manufacturing technology for electrical applications has to be revised. Strength specifications of precipitation hardened AlMgSi alloys may be enhanced by strain and by precipitation hardening. Therefore from the scientific point of view identification seems to be relevant of the impact of the sequence of these mechanisms on development of final wire properties. In particular, this paper tries to answer the following question: Does the sequence of hardening mechanisms affect the development of mechanical properties of AlMgSi alloy wires The paper presents results of a study of the impact of artificial ageing parameters of 6201 grade AlMgSi alloy wires on their final properties. The study results are presented and discussed in two parts. The first part addresses the impact of artificial aging temperature and duration on the strength properties of AlMgSi (grade 6201) alloy wire rod. The second part is focused on hardening development in the process of drawing of a AlMgSi wire made of the same alloy grade, subjected to different thermal treatments, the parameters of which have been selected based on analysis of the results of the first, wire-rod related, part of the study.

Analysis of the Technology for Manufacturing Heat-Treatable AlMgSi Alloy Wire Rod, in Terms of Physical Phenomena that Affect the Structure and Properties

Precipitation hardening AlMgSi alloys are widely used not only as constructional material, but also a very attractive material for the manufacturing of conductors for overhead power lines. These alloys, with a mass density typical of aluminum and with relatively low resistivity, reach twice the level of mechanical properties, compared to aluminum. Semi-finished product in the manufacturing of overhead conductors is wire rod produced by the technology of the continuous casting and rolling (CCR), for example Continuus-Properzi. The entire complex of wire rod required properties (electrical, tensile, rheological, fatigue) are obtained through proper selection of the quantities of alloying elements (Si, Mg) and structure modifier (Fe, Ti) as well as the right combination of type and sequence of thermo-mechanical treatments and technological process parameters. The article discusses the physical background of opportunities to controlling the wire rod properties, taking into consideration all elements of technology for continuous casting and rolling and also thermo-mechanical treatments. In particular, article contains the presentation and analysis of investigations results identifying the structure, electrical properties and hardness of materials from particular stages of the process, refer to physical phenomena affecting the properties of the material during CCR process including the final product intended for the manufacture of wires.