Growth of Shiga toxin-producing Escherichia coli (STEC) and impacts of chilling and post-inoculation storage on STEC attachment to beef surfaces

Effectiveness of a Commercial Lactic Acid Bacteria Intervention Applied to Inhibit Shiga Toxin-Producing Escherichia coli on Refrigerated Vacuum-Aged Beef

“…Finally, no effort to differentially count surviving STEC from intervention-treated or control strip loins during the experiment was attempted, disallowing authors from determining whether some members of the STEC inoculum were inhibited to greater or lesser extents than other inoculum members. While Kirsch et al [26] reported differing morphological characteristics of STEC strains identical to those used herein on selective/differential media, it was noted that STEC isolates not bearing good isolation were frequently subject to misidentification on selective/differential plating medium surfaces. The enumeration of total surviving STEC from the inoculum would be expected to primarily yield counts of STEC isolates most tolerant to the antimicrobial intervention, though quantification of any differences in inhibition on individual STEC isolates was therefore precluded.…”

“…B. Luchansky, Ph.D. (US Department of Agriculture-Agricultural Research Service, Wyndmoor, PA, USA) (Table 1). Culture revival and maintenance procedures were completed according to previous methods [26]. Working cultures of isolates were prepared by transferring a loopful of culture from tryptic soy agar (TSA; Becton, Dickinson and Co., Sparks, MD, USA) slants into 10 ml sterile tryptic soy broth (TSB) and incubating statically at 35°C for 18–24 h. Each isolate was individually subcultured by inoculating a 50 ml volume of sterile TSB supplemented with 0.1% (w/v) rifampicin (Sigma-Aldrich, St. Louis, MO, USA) with one loopful of fresh culture and incubating statically at 35°C for 18–24 h. Immediately prior to use, a cocktail of STEC isolates was prepared by transferring 50 ml of each culture into a calibrated misting bottle (previously sanitized by immersion in 70% ethanol for 5 min followed by triplicate flushing with sterile distilled water).…”

“…Colonies were enumerated following incubation at 35°C for 18–24 h. Inoculum preparation procedures were completed to provide nondiffering counts of each of the eight E. coli isolates by mixing equivalent volumes into the inoculation bottle and thoroughly mixing isolates together prior to application. Isolates were prepared for inoculation according to methods previously published by Kirsch et al [26], who reported that STEC isolates identical to those used in the current study were able to achieve non-statistically differing counts following 24 h incubation at 35°C in a nutritious medium. Rif R organisms used in the current study were previously compared to antibiotic-sensitive parents for tolerance to common food safety interventions including heating, lactic acid exposure, and high pressure, with no statistically significant differences in survivors between parents and mutants [27].…”

Application of Surfactant Micelle-Entrapped Eugenol for Prevention of Growth of the Shiga Toxin-Producing Escherichia coli in Ground Beef

“…On the day of experiment initiation, 1000 g of thawed beef trimmings were inoculated with a three-strain mixture of STEC and sealed in a sterile plastic bag. The STEC mixture was produced by blending equivalent volumes of overnight cultures of revived STEC isolates ( Section 2.1 ) according to previously published methods [ 22 ]. Inoculated trimmings were hand-massaged for 1 min in order to distribute inoculum over trimming surfaces, after which beef was left undisturbed in a biological safety cabinet at ambient conditions for 30 min to allow inoculum attachment.…”

Genome-wide Screens Reveal Escherichia Coli Genes Required for Growth of T1-like Phage LL5 and rV5-like Phage LL12

“…Phage LL5 was unable to form plaques on any of the tested STEC strains, and phage LL12 exhibited EOPs of close to 1 on STEC strains with serotypes O157:H7, O145:NM, O121:H19, O146 and O121:H19, demonstrating a relatively broad host range among STEC serotypes for this phage (Table 1). a Sources of these isolates are described in [44] b LPS core types information obtained from [45] 3…”