Evaluation of the virulence of enterococcal strains isolated from high touch surfaces in a hospital in Bejaia (Algeria)

Biofilms are key drivers of healthcare-associated infections (HAIs). Recently, the emergence of Enterococcus strains as major contributors to HAIs has been linked to their high antibiotic resistance and biofilm formation capabilities. In this study, we report for the first time the isolation and characterisation of Enterococcus strains (5 E. faecalis, 2 E. faecium and 1 E. hirae), from hospital surfaces in Algeria. We evaluated their biofilm-forming ability under different culture conditions, cytotoxicity on Caco-2/TC7 epithelial cells, antibiotic resistance profiles and the presence of key virulence genes (agg, gelE, vanA, vanB). Results showed that the biofilm formation capacity was enhanced in the presence of sucrose and all strains were slime-positive. They were non-hemolytic but cytotoxic on epithelial cells; 75 % and 62.5 % of the strains harbored the gelE and agg genes respectively. No strain carried vanA and vanB genes. Seven strains were resistant to cefotaxime and penicillin G, and all of them were resistant to ciprofloxacin but sensitive to ofloxacin. Importantly, we evaluated the anti-biofilm efficacy of benzalkonium chloride (BAK) against mature biofilms on stainless steel coupons, complete biofilm removal required BAK >1250 × MIC, highlighting the limitations of standard biocide use. This study provides one of the few comprehensive characterisations of environmental Enterococcus strains, including E. hirae, with a focus on their resistance, virulence and tolerance to biocides. Our findings highlight the importance of contamination control of inanimate surfaces and equipment in hospitals and inefficacy of commonly used biocides against biofilm-embedded cells, posing a threat for HAIs and call for improved disinfection strategies targeting biofilm-embedded bacteria.