Enteric bacteriophages as potential fecal indicators in ground beef and poultry meat

Recovery efficiencies of enteric bacteriophages (F+ RNA coliphages, somatic coliphages, and Salmonella phages) as alternative fecal indicators were determined from ground beef and chicken breast meat using amino acid eluants (glycine and threonine) and a complex eluant (3% beef extract). Levels of F+ RNA coliphages (MS2, GA, Qbeta, FI, and SP), the somatic coliphage phiX174, and three environmental isolates of Salmonella phages (isolated from raw sewage) were assayed using three respective hosts: Escherichia coli Famp, E. coli C, and Salmonella Typhimurium. When 8% polyethylene glycol and 0.1 M NaCl were used to precipitate bacteriophages eluted with five different eluants, the highest recoveries of the three phage groups were with 0.5 M threonine and 0.25 M glycine-threonine. The average recoveries of F+ RNA coliphages, somatic coliphages, and the Salmonella phages from ground beef and chicken meat were 100, 69, and 65%, respectively, with threonine (0.5 M, pH 9.0) as the eluate. Of eight market food samples tested, F+ RNA coliphages were detected in five (63%) and somatic coliphages were detected in seven (88%). The overall detection sensitivity of the method was 3 PFU/100 g of ground beef or chicken meat. Levels of bacteriophages and bacterial indicators on chicken carcass surfaces were determined at identified critical control points at a poultry plant. Through the processing steps of evisceration, washing, and chilling, the levels of F+ RNA coliphages and fecal coliforms were reduced by 1.6 and 1.9 log10 PFU or CFU/100 g, respectively. F+ RNA coliphages and perhaps other enteric bacteriophages may be effective candidate indicators for monitoring the microbiological quality of meat, poultry, and perhaps other foods during processing. The bacteriophage concentration method developed provides a simple, rapid, and practical tool for the evaluation of fecal contamination levels in ground beef and processed chicken meat.