Understanding the interactions and effects of environmental biofilms on SARS-CoV-2 viability on contact surfaces.

AIMS: To investigate the role of multispecies drain biofilms in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infectivity and persistence on contact surfaces used in meat processing plants.

METHODS AND SESULTS: Environmental drain biofilms from pork (n = 12) and beef (n = 22) processing plants were grown with and without SARS-CoV-2 on stainless steel (S.S.), polyvinyl chloride (PVC), tile, and galvanized steel (G.S.) at 7°C for 5 days. Biofilm biomass, viral RNA persistence, and viral infectivity were quantified and compared with controls. Surface type significantly influenced viral RNA persistence with PVC, tile, and particularly G.S. supporting increased SARS-CoV-2 RNA persistence relative to virus controls (P < .001), while S.S. consistently showed reduced viral RNA persistence (P < .01). Plaque assays demonstrated that SARS-CoV-2 remained viable on all surfaces after 5 days. Beef drain biofilms on tile and G.S. exhibited two to four-fold higher infectivity than corresponding virus controls (P < .001), while infectivity was reduced in pork drain biofilms on PVC and tile. Viral RNA persistence and infectivity were not consistently correlated, indicating that detection of viral RNA within biofilm matrices does not necessarily reflect infectious virus. SARS-CoV-2 exposure also altered biofilm development in a surface and origin-dependent manner, increasing biomass of pork drain biofilms on PVC and tile (>2-fold; P < .01) while reducing growth of beef drain biofilms on S.S. and G.S. (0.9-1.8 log reductions; P < .01).

CONCLUSIONS

Drain biofilms may act as transient reservoirs for SARS-CoV-2, with viral persistence governed by the combined effects of surface properties, biofilm structure, and microbial origin.