Specific antibacterial activity of copper alloy touch surfaces in five long-term care facilities for older adults
Introduction
Among the risk factors for patients or residents in healthcare facilities, direct skin contact between two people is the main vector for microbial dissemination. Ensuring good hand hygiene is therefore essential. Inanimate environments are also reported as pathogen reservoirs and sources of cross-contamination. In healthcare environments, touch surfaces are one of the main points of cross-contamination, and their involvement in pathogens' spread has already been demonstrated [1]. Numerous studies have shown that bacteria (e.g., Escherichia coli [[2], [3], [4]], Enterococcus faecalis [5], Staphylococcus aureus [5], Klebsiella pneumoniae [3]), fungi (e.g., Candida albicans [6]) and viruses (e.g., adenovirus [7,8], norovirus [9,10]) can survive for several months on dry inanimate surfaces [1,11].
Metals, especially copper, have been drawing continual interest as natural antimicrobial agents. During direct contact between bacteria and a copper-containing surface, copper ions are massively released from the surface, at first inducing damage to the cell wall [12,13]. Inside the bacterial cytoplasm, copper ions trigger the formation of reactive oxygen species through the Fenton-type reaction and compete with various metal ions such as iron (in iron–sulphur clusters) and zinc for important binding sites on proteins [[14], [15], [16]]. Combined together, these various mechanisms result in rapid bacterial killing. Efficiencies of pure copper and copper alloy surfaces against a wide range of micro-organisms have recently been demonstrated in in vitro tests [[17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33]]. For example, Mehtar et al. [21] demonstrated a 5-log reduction of C. albicans and 8-log reduction of K. pneumoniae within 60 min, a 7-log reduction of Acinetobacter baumannii within 180 min, and an 8-log reduction of meticillin-resistant S. aureus (MRSA) and Pseudomonas aeruginosa within 270 min.
In situ studies have looked for specific types of pathogens on copper and control touch surfaces in healthcare facilities [[34], [35], [36], [37]], while another study has initiated a large screening of environmental bacteria present on high-touch athletic centre surfaces (copper and control) [38]. However, environmental bacterial populations present in long-term care facilities on copper touch surfaces, have never been characterized before. Previously, we showed that copper touch surfaces reduce overall bacterial contaminations in five long-term care facilities [17]. The aim of this current study was to analyse the diversity of the environmental bacterial populations recovered from copper and control surfaces during 18 months and the impact of copper surfaces on these populations.
Section snippets
Long-term care environment
Five long-term care facilities located in Marne (France) had been 50% outfitted with copper alloy door handles (residents' room) and handrails (corridors) (Steriall®, Lebronze Alloys, Suippes, France) at least 18 months before the start of this study. Depending on the structure of each facility, the design was not the same but after random selection of half of the areas, the outfitted rooms were always close to each other and represented blocks (distinct aisle, distinct levels, etc.).
Bacterial population diversity recovered from the long-term care facilities
The different types of colonies grown on TSA plate were identified for each 23 sampling series, representing 429 control surfaces and 428 copper surfaces. A total of 2407 colonies (637 from control and 452 from copper door handles, 745 from control and 573 from copper handrails) were analysed by MALDI-TOF. Successfully identified colonies (62%) belonged to one of the three major clades and were divided into 34 distinct genera: protobacteria (12 genera), actinobacteria (12 genera) and firmicutes
Discussion
Increasing numbers of elderly and immunocompromised people live in long-term care facilities and are particularly vulnerable to infections by pathogens or opportunistic pathogens (skin, urinary tract, respiratory tract infections, pneumonia or gastroenteritis, etc.) [40]. Furthermore, even if a slight decrease in the rate of healthcare-associated infections (HAIs) is observed in long-term care facilities like in hospitals, their threat remains worrying and the prevalence of infected residents
Acknowledgements
The authors would like to warmly thank Dr.F. Velard (EA 4691 BIOS, Reims), Dr. O. Meunier (Service hygiène, Centre Hospitalier, Haguenau), Dr. F. Squinazi (Haut Conseil de la Santé Publique, Paris), Dr. C. Roques (Service de Bactériologie–Hygiène, CHU Toulouse), Dr. L. Brasme (Laboratoire de Bactériologie – Virologie – Hygiène hospitalière, CHU Reims) and Dr. L. Kanagaratnam (Unité d'aide méthodologique, CHU Reims) for their fruitful interactions and discussions, C. Chausson (Laboratoire de
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2021, Materials LettersCitation Excerpt :Stainless steel (SS) coupons of X2CrNi18-09 (AISI 304L) measuring 50 by 7 by 1 mm (814 cm2) were used as control. A0 was used as referent copper alloy in preliminary tests as it has previously been used in the manufacturing of door handles installed in five healthcare facilities [12,13]. Before tests, copper alloy samples were brushed with abrasive pad for one minute, then rinsed with 20 spray of deionized water.