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P2-10 Comparison of Sensitivity of Shiga Toxin-producing Escherichia coli Serotypes Inoculated on Beef Trimmings to Various Chemical Decontamination Treatments

Tuesday, July 24, 2012
Exhibit Hall (Rhode Island Convention Center)
Ifigenia Geornaras, Colorado State University, Fort Collins, CO
Hua Yang, Roka Bioscience, San Diego, CA
Stavros Manios, Colorado State University, Fort Collins, CO
Nikolaos Andritsos, Colorado State University, Fort Collins, CO
Keith Belk, Colorado State University, Fort Collins, CO
Dale Woerner, Colorado State University, Fort Collins, CO
John Sofos, Colorado State University, Fort Collins, CO
Introduction: There are numerous reports on the efficacy of various chemical decontamination treatments for beef trimmings; however, in most of these studies Escherichia coli O157:H7 was the target pathogen. Data are, thus, needed on whether these antimicrobial interventions are also effective against other pathogens of recent concern in fresh beef, such as non-O157 Shiga toxin-producing E. coli (nSTEC).

Purpose: Six chemical decontamination treatments for beef trimmings were evaluated for their effects against E. coli O157:H7 and six nSTEC serotypes.

Methods: Trimmings (10 cm length × 5 cm width × 1 cm thickness; approximately 100 g) fabricated from fresh beef chuck rolls were separately inoculated (3-4 log CFU/cm2) with 4-strain mixtures of rifampicin-resistant nSTEC serotypes O26, O45, O103, O111, O121 and O145, or rifampicin-resistant E. coli O157:H7. Inoculated trimmings were immersed for 30 s (or 5 s for SYNTRx 3300) in solutions (150 ml) of acidified sodium chlorite (0.1%, pH 2.5), peroxyacetic acid (0.02%, pH 3.8), sodium metasilicate (4%, pH 12.5), Bromitize® Plus (225 ppm active bromine, pH 6.6), SYNTRx 3300 (pH 1.0), or AFTEC 3000 (pH 1.2). Counts of the nSTEC serotypes, on untreated and treated samples, were statistically compared with counts of E. coli O157:H7. The antimicrobials were evaluated (two repetitions per antimicrobial with three samples per repetition) independently; therefore, no comparisons were made between the chemical treatments.

Results: All decontamination treatments evaluated against E. coli O157:H7 were generally equally (P ≥ 0.05) effective against all six tested nSTEC serotypes. Irrespective of pathogen inoculum, treatment of beef trimmings with acidified sodium chlorite, peroxyacetic acid or sodium metasilicate reduced (P < 0.05) initial counts (3.1-3.9 log CFU/cm2) by 0.7-1.0, 0.6-1.0 and 1.3-1.5 log CFU/cm2, respectively. The remaining three antimicrobials reduced pathogen counts by 0.1-0.4 log CFU/cm2, depending on treatment.

Significance: The findings indicated that chemical interventions used against E. coli O157:H7 on beef trimmings should be at least equally effective against nSTEC.

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