Carvacrol efficacy in reducing microbial biofilms on stainless steel and in limiting re-growth of injured cells
2018
Campana, Raffaella | Baffone, Wally
Microorganisms organized in biofilm have demonstrated a decreasing susceptibility to classical disinfectants and the search of new active compounds, such as the natural ones, is still a challenge for the researchers. In this study, the effect of carvacrol against biofilms of Escherichia coli O157:H7 ATCC 35150, Staphylococcus aureus ATCC 43387, Pseudomonas aeruginosa ATCC 9027, Enterococcus faecalis ATCC 29212 and Candida albicans ATCC 14053 developed on stainless steel coupons for 4 days at room temperature was assessed. After 30 s, 5 and 15 min of treatment with carvacrol 1%, the number of viable cells was quantified by plate count agar and the effect of carvacrol on microorganisms was observed in epifluorescence after orange acridine staining. In addition, carvacrol treated coupons were re-incubated for another 24 h at room temperature to determine the re-growth of the injured cells. Carvacrol induced a logarithmic reduction equal to or greater than 3 against all the tested biofilms and the epifluorescence observation revealed mostly green cells, indicating microorganisms with no active RNA transcription, contrarily to the active red ones observed in the controls. The treatment for 15 min was able to inhibit the re-growth of E. coli O157:H7, S. aureus and P. aeruginosa and to reduce the growth of E. faecalis and C. albicans.Since in food processing environments new strategies to overcome bacterial persistence are necessary, carvacrol showed to possess anti-biofilm activity against all the tested microorganisms and to drastically reduce the re-growth of the injured cells after antimicrobial treatment.
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