AUTHOR=Koti Kavitha , Rodas-Gonzalez Argenis , Nadon Celine , McAllister Tim , Yang Xianqin , Narváez-Bravo Claudia 

TITLE=Evaluating disinfectant efficacy on mixed biofilms comprising Shiga toxigenic Escherichia coli, lactic acid bacteria, and spoilage microorganisms

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1360645

DOI=10.3389/fmicb.2024.1360645

ISSN=1664-302X

ABSTRACT=<p>This study aimed to investigate the impact of temperature and the presence of other microorganisms on the susceptibility of STEC to biocides. Mature biofilms were formed at both 10°C and 25°C. An inoculum of planktonic bacteria comprising 10<sup>6</sup> CFU/mL of spoilage bacteria and 10<sup>3</sup> CFU/mL of a single <italic>E. coli</italic> strain (O157, O111, O103, and O12) was used to form mixed biofilms. The following bacterial combinations were tested: T1: <italic>Carnobacterium piscicola</italic> + <italic>Lactobacillus bulgaricus</italic> + STEC, T2: <italic>Comamonas koreensis</italic> + <italic>Raoultella terrigena</italic> + STEC, and T3: <italic>Pseudomonas aeruginosa</italic> + <italic>C. koreensis</italic> + STEC. Tested biocides included quaternary ammonium compounds (Quats), sodium hypochlorite (Shypo), sodium hydroxide (SHyd), hydrogen peroxide (HyP), and BioDestroy®-organic peroxyacetic acid (PAA). Biocides were applied to 6-day-old biofilms. Minimum Bactericidal Concentrations (MBC) and Biofilm Eradication Concentrations (BEC) were determined. Planktonic cells and single-species biofilms exhibited greater susceptibility to sanitizers (<italic>p</italic> &lt; 0.0001). <italic>Lactobacillus</italic> and <italic>Carnobacterium</italic> were more susceptible than the rest of the tested bacteria (p &lt; 0.0001). Single species biofilms formed by <italic>E. coli</italic> O111, O121, O157, and O45 showed resistance (100%) to Shypo sanitizer (200 ppm) at 25°C. From the most effective to the least effective, sanitizer performance on single-species biofilms was PAA &gt; Quats &gt; HyP &gt; SHyd &gt; Shypo. In multi-species biofilms, spoilage bacteria within T1, T2, and T3 biofilms showed elevated resistance to SHyd (30%), followed by quats (23.25%), HyP (15.41%), SHypo (9.70%), and BioDestroy® (3.42%; <italic>p</italic> &lt; 0.0001). Within T1, T2, and T3, the combined STEC strains exhibited superior survival to Quats (23.91%), followed by HyP (19.57%), SHypo (18.12%), SHyd (16.67%), and BioDestroy® (4.35%; <italic>p</italic> &lt; 0.0001). O157:H7-R508 strains were less tolerant to Quats and Shypo when combined with T2 and T3 (<italic>p</italic> &lt; 0.0001). O157:H7 and O103:H2 strains in mixed biofilms T1, T2, and T3 exhibited higher biocide resistance than the weak biofilm former, O145:H2 (<italic>p</italic> &lt; 0.0001). The study shows that STEC within multi-species biofilms’ are more tolerant to disinfectants.</p>