Co-culture with Enterobacter cloacae does not Enhance Virus Resistance to Thermal and Chemical Treatments.

Human noroviruses (hNoV) are the primary cause of foodborne disease in the USA. Most studies on inactivation kinetics of hNoV and its surrogates are performed in monoculture, while the microbial ecosystem effect on virus inactivation remains limited. This study investigated the persistence of hNoV surrogates, murine norovirus (MNV) and Tulane virus (TuV), along with Aichi virus (AiV) under thermal and chemical inactivation in association with Gram-negative (Enterobacter cloacae) bacteria. Thermal inactivation of viruses in co-culture with E. cloacae revealed no protective effects of bacteria. At 56 °C, AiV with and without bacteria was completely inactivated by 10 min with decimal reduction values (D-values) of 41 and 43 s, respectively. Similar results were also observed for TuV. Conversely, MNV with bacteria was completely inactivated by 10 min while MNV alone remained stable up to 30 min at 56 °C. Both MNV and TuV were slightly more stable than AiV at 63 °C with TuV detection up to 2 min without bacteria. For chemical inactivation on stainless steel surfaces, viruses alone and in association with bacteria were treated with 1000 ppm sodium hypochlorite. Virus association with bacteria had no significant effect (p > 0.05) on virus resistance to bleach inactivation compared to virus alone. Specifically, exposure to 1000 ppm bleach for 5 min resulted in an average of 3.86, 2.14, and 0.94 log ₁₀ PFU/ml reductions for TuV, MNV, and AiV without bacteria, respectively. Reductions in TuV, MNV, and AiV were 3.50, 1.88, and 0.61 log10 PFU/ml when associated with E. cloacae, respectively.