Characterization of the Repair of Injury Induced by Freezing Salmonella anatum1

Abstract

Fast freezing and slow thawing of Salmonella anatum cells suspended in water resulted in injury of more than 90% of the cells that survived the treatment. The injured cells failed to form colonies on the selective medium (xyloselysine-peptone-agar with 0.2% sodium deoxycholate) but did form colonies on a nonselective (xylose-lysine-peptone-agar) plating medium. In Tryptic soy plus 0.3% yeast extract broth or minimal broth, most of the injured cells repaired within 1 to 2 hr at 25 C. Tryptic soy plus yeast extract broth supported repair to a greater extent than minimal broth. Phosphate or citrate at concentrations found in minimal broth supported repair of some cells. MgSO4, when present with inorganic phosphate or citrate or both, increased the extent of repair. The repair process in the presence of phosphate was not prevented by actinomycin D, chloramphenicol, and D-cycloserine, but was prevented by cyanide and 2,4dinitrophenol (only at pH 6). This suggested that the repair process might involve energy metabolism in the form of adenosine triphosphate. The freeze-injured cells were highly sensitive to lysozyme, whereas unfrozen fresh cells were not. In the presence of phosphate or minimal broth this sensitivity was greatly reduced. This suggested that, at least in some of the cells, the injury involved the lipopolysaccharide of the cell wall and adenosine triphosphate synthesis-was required for repair.

SURVIVAL OF THREE SALMONELLA SEROTYPES ON BEEF TRIMMINGS DURING SIMULATED COMMERCIAL FREEZING AND FROZEN STORAGE

“…The survival of bacteria following freezing is dependent on a number of factors intrinsic to the bacterium, including the species and strain (Enkiri and Alford 1971 ; Speck and Ray 1977), the growth phase of the cells (Mackey et al 1980) and the conditions under which the cells grew prior to freezing (Mackey et al 1980). Furthermore, factors related to the freezing medium or food substrate, such as its chemical composition (Woodburn and Strong 1960;Janssen and Busta 1973) temperature of freezing, time of frozen storage and conditions of thawing (Ray et al 1972;Raccach and Juven 1973;Obafemi and Davies 1986;Uljas and Ingham 1999) also play important roles in bacterial survival.…”

“…Pathogenic Salmonella serotypes have been shown to variously result in death, injury and unharmed survival when frozen on different food products (Sorrells et al 1970;Smith 1995;Peplow et al 1999). In particular, factors such as slow thawing and the absence of insulating compounds (such as fat) in different foods generally resulted in high death and injury rates (Ray et al 1972;Raccach and Juven 1973;Mackey and Demck 1982;Sheridan 1996). Rapid freezing and higher cell concentrations, on the other hand, resulted in a high percentage of survival with very little injury to cells (Raccach and Juven 1973).…”

The effect of potassium sorbate on the structural integrity of Alteromonas putrefaciens

“…Damaged cells are known to undergo rapid repair in the presence of metabolizable energy sources (Ray et al 1972) and unless completely inhibited or killed, damaged cells can regenerate LPS within 60 min and resume growth in the presence of inhibitors (Freese & Levin 1978). The presence of broth appears to give the cells some protection against the effect of sorbate, either by allowing rapid repair of sublethally damaged cells, or by components of the broth physically screening the cell, preventing interaction between the outer membrane and the inhibitor.…”

Combined enrichment procedure for the detection of salmonellae in foods

“…Speck(1973b)andWarseck et al (1973) found that substantial repair of stressed coliforms would occur in TSB within 1 to 2 hours. Injured coliforms, when surface plated on trypticose soy agar (TSA), were also able to undergo repair within 1 to 2 h (Speck et al 1975), Cells of S^ anatum NF3, after being frozen by Ray et al (1972), were unable to form colonies when surface plated on XLP agar plus 0.2% sodium deoxycholate.…”

“…Modifications of the techniques of Roy et al (1971a) and Ray et al (1972) were utilized to produce populations of freeze injured salmonellae. (Mayou, 1976) and salmonellae (Galton et al 1968) in the recovery media.…”