# Evolution of copper coupons resistance in Enterobacteriaceae strains isolated from high-contact surfaces in hospital

## TL;DR

This study shows that copper surfaces can kill bacteria but may also lead to the development of antibiotic-resistant strains over time.

## Contribution

The study demonstrates rapid acquisition of copper resistance and its link to reduced antibiotic sensitivity in hospital bacteria.

## Key findings

- Copper coupons killed Serratia odorifera in 3 hours and Escherichia coli in 6 hours.
- 83.33% of Enterobacteriaceae strains acquired copper resistance within three days.
- Copper-resistant bacteria showed reduced antibiotic sensitivity, especially to beta-lactams and chloramphenicol.

## Abstract

Metallic copper alloys have gained attention recently as a cutting-edge antibacterial weapon for areas where surface hygiene is crucial. The present study aimed to assess copper coupons (99% Cu) for their potential to decrease the viability of various Enterobacteriaceae strains from inanimate hospital surfaces.

This in vitro-experimental study was conducted at the Microbiology Laboratory, Faculty of Natural and Life Sciences and Earth and Universe Sciences, University of Guelma, and Khodja Ahmed Public Hospital Establishment, Algeria, for a period of six months from January to May 2022. A total of 85 samples were collected from patient room door handles and bed rails at the government hospital in Guelma State, from which 12 enterobacterial isolates were obtained. These isolates were evaluated for susceptibility to copper and polyvinyl chloride (PVC) coupons using plate counts to determine bacterial viability after 72 hours of incubation at 37°C or room temperature (25°C). Antibiotic sensitivity testing was then carried out using a modified Kirby-Bauer disc diffusion method. Copper coupons’ ability to either select for or create antibiotic resistance is also determined.

Copper showed a bactericidal effect after three hours for Serratia odorifera and six hours for Escherichia coli. Whereas it was shown that within three days of selection, 83.33% of Enterobacteriaceae strains are capable of rapidly acquiring Cu resistance. Indeed, the increase in temperature reduced the effects of Cu (p<0.05; Student’s t-test). Antimicrobial susceptibility testing revealed that the copper-resistant bacteria were less sensitive than their predecessors. Citrobacter freundii strains showed the highest incidence of multidrug resistance. The most significant findings included widespread resistance to beta-lactams (100%-75%) and chloramphenicol (66.67%).

These results suggest that prolonged copper usage may contribute to the development of antibiotic resistance, which could have significant ramifications.