Shredded cabbage was inoculated with Listeria monocytogenes Scott A cells and stored in normal air or a modified (70% carbon dioxide and 30% nitrogen) atmosphere at 5 and 25°C. Under the normal atmosphere at 25°C, colony counts increased by 2 logs within 2 d of storage but then decreased to undetectable levels within 6 d of storage. In the modified atmosphere at 25°C, numbers also decreased to undetectable levels within 6 d, but with a less marked initial increase and a decline that was more rapid than in the unmodified atmosphere. In the cold (5°C), the counts increased gradually, but only by about 1 log, in both atmospheres. In the normal atmosphere at 5°C, however, colony counts decreased sharply after 13 d of storage. Reductions in colony counts coincided with decreases in cabbage pH and development of spoilage. The increased level of carbon dioxide was ineffective in controlling L. monocytogenes at 5°C. At 25°C cabbage spoilage was rapid and colony counts declined under both atmospheres of storage.

Spore suspensions of Bacillus stearothermophilus (ATCC 7953, 10149, 12980), Bacillus subtilis (ATCC 6633), Bacillus subtilis var. niger (ATCC 9372), Bacillus pumilus (ATCC 27142, and a wild strain) and Bacillus cereus (ATCC 11778) were heated (20 min at 121°C for thermophiles, and 2.5–20 min at 100°C, 105°C, or 107°C for mesophiles) in 1 ml sealed ampoules. Surviving spores were recovered by a 5-tube most probable number (MPN) procedure with soybean casein digest (SCD) or fluid thioglycollate (FTH) broths containing variable concentrations of solids. Numbers of heated thermophilic spores (ATCC 7953) recovered with SCD broths were approximately 1.5 log MPN/ml higher at the 100% broth solids concentration than numbers recovered with FTH broth. Increasing the solids of SCD broth to twice the recommended amount (200%) reduced recovery of heated thermophilic spores compared to regular (100%) strength broth. Recovery of heated thermophilic spores with SCD or FTH broths was higher (P < 0.05) when their content of solids was reduced to as low as 0.391% compared to regular concentrations (100%). Broths with concentrations of solids at 10% of the manufacturer's recommended levels resulted in maximum recovery of heated thermophilic spores. In contrast, reduction of solids in SCD broth to 10% did not (P > 0.05) influence recovery of heated mesophilic spores compared to SCD broth with regular concentration of solids. Broths with reduced as well as regular concentrations of solids were equally effective in recovering unheated spores. These results should be useful in future modifications of methodology for sterility testing.