Environmental testing for Salmonella Enteritidis is required for U.S. shell egg producers with > 3,000 hens on a farm. The egg producer assumes all costs for the mandatory testing. According to the FDA Egg Rule, either manure scraper or drag swabs can be collected according to published guidelines and requirements. The current study was undertaken to determine the efficacy of Salmonella detection in single, two, and four swab pools of either manure scraper or drag swabs. Resistant isolates of Salmonella Enteritidis (1000 ppm streptomycin; SE), Heidelberg (200 ppm nalidixic acid (NA); SH), Typhimurium (200 ppm NA; ST), and Kentucky (200 ppm NA; SK) were utilized. Low (approximately 8.4 CFU) and high (approximately 84 CFU) dose inocula were introduced onto a single swab within a pool. A single flock of each conventional cage (manure scraper swabs) and cage-free barn (drag swabs) were monitored throughout the study at the ages required under the FDA Egg Rule. The greatest and most consistent recovery of inoculum was found in single swab samples. For low dose inocula, it was difficult to recover isolates from single manure scraper swabs (57.9 – 29.2 %) and decreased as more swabs were added to the pool. Recovery of isolates in manure scraper swabs was greater for high dose inoculum, though SH exhibited difficulty competing with naturally occurring flora. One and two swab pools of drag swabs had similar rates of recovery at both low and high dose SE, SH, and ST. When SE and SK were combined in an inoculum, SE was recovered at a much higher rate than SK for all types of swabs and doses of inocula. Pooling of two drag swabs allowed for similar detection of low and high dose Salmonella tested in the current study, but the pooling of manure scraper swabs decreased detection of low dose Salmonella .
The effects of two egg holding temperatures (15.5 and 26.7°C) and three wash-water temperatures (15.5, 32.2, and 48.9°C) on internal and external shell surface bacterial counts were tested by using a commercial-type egg-processing unit. Two experiments consisting of five trials, each of which included 360 eggs per treatment for a total of 2,160 per trial, were conducted during two seasons (summer and winter) for a total of 10 replicates per experiment. During the performance of each replicate, counts from tryptic soy agar (TSA) and MacConkey agar (MAC) were obtained from 10 egg samples which were collected prior to processing (prewash), immediately after washing (postwash), and after as-day cooling period at 7.2°C (postcool). No growth was observed on MAC plates in either experiment, indicating that fewer than 100 counts were detected. No significant differences ( P > 0.05) were observed in the prewash, postwash, or postcool internal shell counts of eggs held at l5.5°C compared to internal counts of shells of eggs held at 26.7°C. Likewise, no significant differences ( P > 0.05) were observed in the prewash, postwash, or postcool internal shell counts obtained from eggs washed in l5.5°C water compared with internal shell counts obtained from eggs washed in water at 32.2 or 48.9°C. On the basis of our data, spray washing eggs in l5.5°C water does not appear to increase internal shell bacterial counts. Because warm or hot wash water increases egg temperatures markedly, a reexamination of cold-water processing procedures may be in order.
Research was initiated to evaluate the effects on egg quality and microbial counts of rapidly cooling eggs by using cryogenic gases. Four trials were conducted utilizing a 2 × 2 factorial design with cryogenic cooling and Pseudomonas inoculation as the main variables. The 1440 eggs used in each trial were evaluated for cracked shells, Haugh units, and albumen pH. Cryogenically cooled treatment groups were successfully cooled from 37°C to 7°C in significantly less time than in a traditionally cooled pallet. The Haugh unit values obtained from traditionally cooled eggs were significantly (P > .001) lower than those from cryogenically cooled eggs. There was no significant difference in the albumen pH of the two groups. Internal and external bacterial counts revealed significantly fewer bacteria in the interior of cryogenically cooled eggs than in the interior of traditionally cooled eggs. However, after a 30-day storage period at 7°C, no difference was found in external and internal bacterial contamination rates. The results of this trial suggest that rapid cooling with cryogenic gases could be used in conjunction with current commercial egg processing to cool eggs prior to packaging. The successful commercial application of this procedure would reduce egg temperatures as well as the likelihood of Salmonella enteritidis growth in or on eggs. Thus, consumers would be provided with safer commercially processed shell eggs. In addition, the Haugh unit data indicate that rapid cooling with cryogenic gases enhances the quality of commercially processed shell eggs.