EFFICACY OF SELECTED MEDIA FOR RECOVERY OF ESCHERICHIA-COLI O157-H7 FROM FROZEN CHICKEN MEAT CONTAINING SODIUM-CHLORIDE, SODIUM LACTATE OR POLYPHOSPHATE

The viability of Escherichia coli O157:H7 in frozen chicken meat (CMI containing sodium chloride (NaCl), sodium lactate, or polyphosphate over an 18 month period was determined. Additionally, several recovery media were evaluated. Ground CM (10 g) was inoculated (10(6) cfu g(-1)) with E. coli O157:H7, then held at -20 degrees C. Surviving cells were enumerated monthly using a nonselective medium, tryptic soy agar (TSA). After 11 months, seven additional recovery media were also used to evaluate the ability to recover freeze/NaCl-injured cells. In all treatments, the initial population decreased (P < 0.05) during storage. In CM with no additives, E. coli O157:H7 decreased by 0.6 log(10) cfu g(-1) in 18 months. Addition of NaCl and sodium lactate resulted in reductions (P < 0.05) ranging from 1.4-2.4 log(10) cfu g(-1) over the same period. Addition of polyphosphate did not affect recovery (P < 0.05). Recovery of E. coli O157:H7 was least (P < 0.05) from CM containing 8% NaCl, and recovery was least efficient CP < 0.05) on selective media (i.e. MacConkey sorbitol agar, MSA). The addition of Mg2+ to MSA did not enhance recovery. Highest recoveries (P < 0.05) occurred on TSA, TSA plus 1% pyruvic acid and phenol red sorbitol agar (PRSA). E. coli O157:H7 survived (greater than or equal to 18 months) well in frozen poultry, and selective media such as MSA were inadequate for recovering freeze/NaCl-injured cells.