Peracetic Acid Induced Viable but Non-Culturable Salmonella in Poultry Meat

Introduction: Some bacteria tolerate harmful environmental insults by entering the viable but non-culturable (VBNC) state. The VBNC cells lose the ability to grow in routine culture media yet maintain their metabolic activity as well as the ability to cause diseases. This phenomenon, described in over 60 different pathogenic species, poses a significant risk to public health as it renders the bacteria not only resistant to chemical interventions but impairs their growth on diagnostic culture media.  

Purpose: The goal of this study was to examine the ability of commercial food disinfectants to induce the VBNC state in foodborne pathogens such as Salmonella.

Methods: A laboratory-based spray model was developed and was used to test Salmonella enterica bearing chicken parts sprayed with either peracetic acid (PAA) or 1, 3-Dibromo-5, 5-dimethylhydantoin (DBDMH). Salmonella recovered from the test samples were enumerated based on traditional culturing methods coupled with a direct viability assessment via LIVE/DEAD fluorescent dyes.

Results: Our results demonstrate the presence of over 1 log of Salmonella population that failed to grow on the agar media in response to PAA treatment (P < 0.00), while no VBNC population was detected in either the DBDMH-treated or un-treated control samples (P > 0.05). A detailed description of our spray protocol, experimental reproducibility and statistical analysis of the results are also provided.

Significance: Both PAA and DBDMH are widely used meat processing aids with the former being considered as one of the most effective disinfectants in the industry. The formation of the VBNC state in Salmonella after treatment with PAA poses a significant concern to public food safety as it may lead to underestimation of Salmonella occurrences in food samples.