Mapping sources of contamination of Escherichia coli on beef in the fabrication facility of a commercial beef packing plant

- Surfaces directly or indirectly involved with beef fabrication were examined for E. coli.
- Selected E. coli isolates from various surfaces were genotyped using MLVA.
- Items in the lounge room where workers took break did not contribute to E. coli on beef.
- Conveyor belt was the primary vector for transmission of contamination after sanitation.
- Cutting tables and mesh gloves were important within shift sources of contamination.

The aim of this study was to map sources of Escherichia coli on beef in the fabrication facility of a commercial beef plant. At monthly intervals for 9 months, 11 groups of items were sampled at the start of work and after a period of work (approximately 2.5 h after the commencement of work). These items included: tables, chairs and paper towel dispenser in the lounge room where workers take their breaks and band saw (blade and table), knives and mesh gloves used by individual workers, cutting tables, conveyor belt, cuts and trimmings in the cutting rooms. Coliforms and E. coli were enumerated and selected E. coli isolates were genotyped using multiple-locus variable-number tandem repeat analysis (MLVA). Numbers of both groups of organisms were recovered at a higher frequency and often at higher numbers after working than when work started. A total of 970 E. coli isolates were confirmed, consisting of isolates from conveyor belt (45), cutting tables (1), and meat (96) when work started; and from conveyor belt (191), mesh gloves (319), meat (52), knives (7), band saw table (1), tables (3), and cutting tables (255) after working. MLVA of these isolates revealed 189 genotypes, with an overall ratio of isolates to genotypes of 5.1. A small fraction of genotypes (4.8%), though representing 30% of the total isolates, recurred in the samples collected from ≥3 months. Genotypes recovered from knives, band saw table and tables after working were also found on one or more items in the fabrication facility. Highly clustering genotypes were recovered, particularly from mesh gloves, cutting tables and conveyor belt. Of the isolates from conveyor belt before work, 93.3% were of genotypes that were also found among isolates from conveyor belt, mesh gloves and cutting tables after working. Of the E. coli on meat, 62.2% were shared with mesh gloves, conveyor belt and cutting tables. The findings show that lounge room items were not relevant sources of E. coli on beef, while conveyor belt, cutting tables and mesh gloves all contributed significantly to the contamination.