Effect of dry sanitization on dry surface biofilm of Cronobacter sakazakii

Cronobacter sakazakii is an opportunistic foodborne pathogen that affects neonates, and has the ability to produce dry surface biofilm (DSB). However, little is known about its resistance to dry sanitizers. This study aimed to evaluate the efficacy of dry sanitizers compared with sodium hypochlorite (SH) on DSB of C. sakazakii . DSB were formed on stainless steel or polypropylene coupons (10 cm 2 ) using two cycles of hydrated/dry phases at 25 °C: T1 (48/48 h) or T2 (24/120 h). At the DSB endpoint, the coupons were sanitized with 70% ethanol, a commercial product based on isopropyl alcohol (25%) and quaternary ammonium (0.015%), hot air (90±2 °C), UV-C light (254 nm), gaseous ozone (45±2 mg/L), or SH (200 mg/L, pH 6.5). All dry sanitizers showed no significant antimicrobial activity (p > 0.05), with reductions ≤ 0.8 log CFU/cm 2 over a 30-min exposure. In contrast, SH was effective against DSB regardless of the DSB formation protocol, with reductions ≥ 2 and > 5 log CFU/cm 2 after 10 and 30 min, respectively. Interestingly, DSB formed with a shorter hydrated phase and a longer dry phase (T2) had greater sensitivity to SH, but this was not observed with dry sanitizers. CLSM images suggested the presence of VBNC cells, particularly after SH treatment. In conclusion, under the conditions evaluated in the current study, SH exhibited more effective control of C. sakazakii DSB compared to the dry sanitization methods assessed.