Resistance of pathogenic bacteria on the surface of stainless steel depending on attachment form and efficacy of chemical sanitizers.

Various bacteria including food spoilage bacteria and pathogens can form biofilms on different food processing surfaces, leading to potential food contamination or spoilage. Therefore, the survival of foodborne pathogens (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, Staphylococcus aureus, Cronobacter sakazakii) in different forms (adhered cells, biofilm producing in TSB, biofilm producing at RH 100%) on the surface of stainless steel and stored at various relative humidities (RH 23%, 43%, 68%, 85%, and 100%) at room temperature for 5 days was investigated in this study. Additionally, the efficacy of chemical sanitizers (chlorine-based and alcohol-based commercial sanitizers) on inhibiting various types of biofilms of E. coli O157:H7 and S. aureus on the surface of stainless steel was investigated. The number of pathogens on the surface of stainless steel in TSB stored at 25°C for 7 days or RH 100% at 25°C for 7 days was significantly increased and resulted in the increase of 3 log(10) CFU/coupon after 1 day, and these levels were maintained for 7 days. When stainless steel coupons were stored at 25°C for 5 days, the number of pathogens on the surface of stainless steel was significantly reduced after storage at RH 23%, 43%, 68%, and 85%, but not at 100%. When the bacteria formed biofilms on the surface of stainless steel in TSB after 6 days, the results were similar to those of the attached form. However, levels of S. aureus and C. sakazakii biofilms were more slowly reduced after storage at RH 23%, 43%, 68%, and 85% for 5 days than were those of the other pathogens. Formation of biofilms stored at RH 100% for 5 days displayed the highest levels of resistance to inactivation. Treatment with the alcohol sanitizer was very effective at inactivating attached pathogens or biofilms on the surface of stainless steel. Reduction levels of alcohol sanitizer treatment ranged from 1.91 to 4.77 log and from 4.35 to 5.35 log CFU/coupon in E. coli O157:H7 and S. aureus, respectively. From these results, the survival of pathogens contaminating the surfaces of food processing substrates such as stainless steel varied depending on RH and attachment form. Also, alcohol-based sanitizers can be used as a potential method to remove microbial contamination on the surfaces of utensils, cooking equipment, and other related substrates regardless of the microbial attached form.