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 0157:H7 in frozen chicken meat (CMI containing sodium chloride (NaCl), sodium lactate, or polyphosphate ov er an 18 month period was determined. Additionally, several recovery m edia were evaluated. Ground CM (10 g) was inoculated (10(6) cfu g(-1)) with E. coli 0157:H7, then held at -20 degrees C. Surviving cells wer e enumerated monthly using a nonselective medium, tryptic soy agar (TS A). After 11 months, seven additional recovery media were also used to evaluate the ability to recover freeze/NaCl-injured cells. In all tre atments, the initial population decreased (P < 0.05) during storage. I n CM with no additives, E. coli 0157:H7 decreased by 0.6 log(10) cfu g (-1) in 18 months. Addition of NaCl and sodium lactate resulted in red uctions (P < 0.05) ranging from 1.4-2.4 log(10) cfu g(-1) over the sam e period. Addition of polyphosphate did not affect recovery (P < 0.05) . Recovery of E. coli 0157:H7 was least (P < 0.05) from CM containing 8% NaCl, and recovery was least efficient CP < 0.05) on selective medi a (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 0157:H7 survived (greater than or equal to 18 months) well in frozen p oultry, and selective media such as MSA were inadequate for recovering freeze/NaCl-injured cells.