Uninoculated Eggs Research Articles

Egg carton and eggshell: is there a possibility of Salmonella cross-contamination?

Producers and consumers associated with small scale backyard egg production tend to reuse egg cartons. Egg cartons are also reused for arts and craft projects, gardening, and organization units for small items. The reuse of egg cartons is primarily driven by economic or ecological reasons. The ability of zoonotic bacteria, such as Salmonella Enteritidis ( SE ), to survive on the eggshell surface and a variety of food packaging materials makes the reuse of egg carton risky. This study was aimed at determining the scope of cross-contamination of SE between eggshell and different egg carton types using 2 experiments. Unwashed eggs from end-of-lay white Leghorn hens were used in the experiments. Two different SE strains were used with 3 independent tubes of inocula from each strain as replicates. In Experiment 1, 216 eggs from each SE strain (72/replicate) were inoculated with 10 μL of SE inoculum (~ 9.95 log cfu/mL), allowed to dry in room temperature, and placed in nonadjacent wells of noninoculated plastic, polystyrene foam, and pulp egg cartons. Egg cartons of each type were then stored either at refrigeration (4 ° C) or room temperature (25 ° C). After 24 h eggs were discarded and the carton-wells were swabbed for SE recovery. In Experiment 2, wells of egg cartons were inoculated with SE and uninoculated eggs were placed in them and stored similar to Experiment 1. A total of 216 wells within the egg cartons were inoculated for each SE strain (72/replicate). Eggshell samples were collected for SE recovery. Only 3 samples were detected positive for SE in Experiment 1 and no effect of carton type, SE strain, or incubation temperature was observed. In Experiment 2, 8 eggshell samples were SE positive – 6 from polystyrene foam and 2 from plastic carton. Statistical difference was observed for pulp versus polystyrene foam only ( P < 0.05). These results indicate that transfer of SE between egg carton and eggshell surface is possible and that the risk of cross-contamination is associated with type of carton material.

Fate of mesophilic aerobic bacteria and Salmonella enterica on the surface of eggs as affected by chicken feces, storage temperature, and relative humidity

We compared the microbiological quality of chicken eggshells obtained from a traditional wholesale market and a modern supermarket. We also determined the survival and growth characteristics of naturally occurring mesophilic aerobic bacteria (MAB) and artificially inoculated Salmonella enterica on eggshells under various environmental conditions (presence of chicken feces, temperature [4, 12, or 25 °C], and relative humidity [RH; 43 or 85%]). The populations of MAB, coliforms, and molds and yeasts on eggshells purchased from a traditional wholesale market were significantly (P ≤ 0.05) higher than those from a modern supermarket. In the second study, when we stored uninoculated eggs under various storage conditions, the population of MAB on eggshells (4.7–4.9 log CFU/egg) remained constant for 21 days, regardless of storage conditions. However, when eggshells were inoculated with S. enterica and stored under the same conditions, populations of the pathogen decreased significantly (P ≤ 0.05) under all tested conditions. Survival of S. enterica increased significantly (P ≤ 0.05) in the presence of feces, at low temperatures, and at low RH. These observations will be of value when predicting the behavior of microorganisms on eggshells and selecting storage conditions that reduce the populations of S. enterica on eggshells during distribution.

Outgrowth of Salmonellae and the Physical Property of Albumen and Vitelline Membrane as Influenced by Egg Storage Conditions

This study was undertaken to determine the influence of storage time and temperature on the volume, weight, and pH of egg albumen, the physical strength of vitelline membrane, and the fate of Salmonella Enteritidis artificially inoculated into egg albumen. A fiber-optic probe was used for inoculation with Salmonella Enteritidis at 102, 104, or 106 cells per egg. Both fresh and inoculated eggs were stored at 4, 10, and 22°C for 6 weeks. Five fresh uninoculated eggs from each storage group were collected each week, and the weight, volume, and pH of the egg albumen were measured. The forces, energies, and degrees of membrane deformation required to rupture the vitelline membranes also were determined from either albumen-free yolks or yolks surrounded by albumen. In separate experiments, five inoculated eggs were evaluated each week for populations of Salmonella Enteritidis. When the eggs were stored at 4°C, the albumen retained significantly more volume and weight and had a relatively lower pH. The vitelline membranes from eggs stored at 4 and 10°C required more force and energy for rupture. Salmonellae flourished at 22°C, even in the albumen with the lowest initial population, 102 cells per egg. Storage at 4 and 10°C inhibited the growth of salmonellae in the albumen of eggs with initial populations of 102, 104, or 106 cells per egg. In eggs with initial Salmonella populations of 106 cells per egg that were stored at 22°C, the populations of reached as high as 1010 cells per egg after 4 weeks of storage. Storage at 4 and perhaps 10°C postponed the aging process of chicken eggs, preserved the antimicrobial agents of the albumen, and maintained the integrity of vitelline membrane. Low-temperature storage therefore had a significant impact on the safety and overall quality of the eggs.

Effect of Chlorine, Sodium Chloride, Trisodium Phosphate, and Ultraviolet Radiation on the Reduction of Yersinia enterocolitica and Mesophilic Aerobic Bacteria from Eggshell Surface

Eggshell sanitizing practices are necessary to improve microbiological safety of fresh hen eggs and their products. In this work, the effects of 100 mg/liter free chlorine (chl), 3% sodium chloride (NaCl), 1, 5, and 12% trisodium phosphate (TSP) in wash solutions, and UVR (ultraviolet radiation; 4,573 μW/cm2) were studied at different times on uninoculated and Yersinia enterocolitica-inoculated eggs. On uninoculated eggs, the best results were obtained with 100 mg/liter chlorine and UV exposure for >25 min, with reductions of 1.28 and 1.60 log cycles, respectively, compared to the average bacterial count (4.55 log CFU/egg) on the control (untreated eggs). On Y. enterocolitica-inoculated eggs, highest reductions of the average bacterial count (7.35 log CFU/egg) were obtained with 5 and 12% TSP and 100 mg/liter chl. The decrease obtained with 12% TSP (3.74-log reduction) was significantly higher (P < 0.05) than those obtained with the remaining treatments. Y. enterocolitica was more resistant to UVR than the eggshell natural mesophilic aerobic microflora, except when low inoculum (4.39 log CFU/egg) was assayed. Changes in eggshell microstructure were measured by the blue lake staining method. The presence of Yersinia and Salmonella in eggshell natural flora was also investigated.

Effect of Salmonella in young chicks on competitive exclusion treatment

The potential of Salmonella contamination in hatching cabinets to 1) generate seeder chicks and 2) interfere with the efficacy of competitive exclusion (CE) treatments was investigated in six experiments. Hatchery-generated seeder: chicks were produced by hatching in the same hatcher with inoculated eggs (immersed in a 1.0 x 10(5) cfu/mL suspension of Salmonella typhimurium or inoculated with 10(5) to 10(6) cells on the air cell membrane). Salmonella spread through the hatching cabinet to chicks hatching from uninoculated eggs in adjacent trays. In two experiments, Salmonella was isolated from 31 and 100% of the chick rinses after the birds were held in groups for 3 d in isolation units. When these hatchery-generated seeder chicks were stocked in floor pens at a 1:10 ratio with uncontaminated contact chicks, the pen environment became contaminated to the extent that greater than 50% of the contact chicks became contaminated. In two experiments with only one to three inoculated eggs per 200 egg hatching cabinet, 98% of uninoculated chicks were intestinally colonized with Salmonella after the birds were held 1 wk in isolation cabinets. This hatchery-acquired Salmonella substantially reduced the effectiveness of subsequent CE treatments to prevent Salmonella colonization of the young chicks. These studies demonstrate that control of Salmonella in hatching cabinets is critically important for control of Salmonella in broilers.

Destruction of Salmonella enteritidis by High pH and Rapid Chilling During Simulated Commercial Egg Processing

Shell eggs were inoculated with a double mutant of Salmonella enteritidis (resistant to both nalidixic acid and streptomycin) by dipping the eggs into a sterile poultry fecal slurry inoculated with this organism. The inoculated eggs were washed with either pH 9 or pH 11 washwater at 37.7°C using a small-scale commercial egg washer. Both washed and unwashed eggs were subjected to either rapid or slow chilling. Both internal contents and external surfaces of eggs were examined immediately after: 1) inoculation; 2) washing; and 3) chilling and 30 days storage at 7.2°C. Washwater pH had a significant effect on the survival of S. enteritidis on the surface of the eggs (p <0.001). Significant cross-contamination occurred between inoculated and uninoculated eggs washed at pH 9; 75% of the uninoculated eggs became S. enteritidis -positive on their surface. No cross-contamination occurred at pH 11 between inoculated and uninoculated eggs, and only 8.3% of inoculated eggs were still surface-positive for S. enteritidis. Slow chilling increased the survival of S. enteritidis on the surface of the eggs (p < 0.01) and appeared to permit penetration of S. enteritidis into eggs washed at pH 9.

Vaccination Response of Parentally Immune Chicks after Yolk-Sac Inoculation of the Embryo with Inactivated Newcastle Disease Virus

Eggs from hens immune to Newcastle disease virus (NDV) were inoculated into the yolk sac with formalin-inactivated F strain NDV on the ninth day of incubation. Chicks hatched from these eggs had lower levels of parentally acquired NDV antibodies than chicks from uninoculated eggs. Chicks from inoculated eggs showed a better serological response to intranasal vaccination at five days old with live F strain NDV than did chicks from uninoculated eggs.

A Simplified Technique for the Serum-Neutralization Test in Infectious Bronchitis

The classic serum-neutralization test for Infectious Bronchitis (IB), as described by Cunningham (1), Fabricant (2), Hofstad (3), and others, consists of comparing the infective titer of a reference egg-adapted virus with the infective titers of different mixtures of the same virus and the serum to be tested. This difference is expressed in logs;, and is significant only when above 2. Two series of embryonated eggs are necessary, one for the live virus and the other one for each serum-virus mixture, each series including six dilutions (10-1 to 10-6). Four or more embryos are inoculated with each dilution, and six uninoculated eggs are kept as controls. In addition to the series of eggs for titration and control with an accurately titrated virus, when only 3 dilutions are used, 12 eggs are necessary for each serum tested. This method is expensive and time-consuming. We describe below a simplified technique that, in one year of use, has been accurate enough for zootiological surveys.

Cytological hepatitis specimens in embryonated eggs.

SummarySerums from 10 acute cases of infectious hepatitis were inoculated into the allantoic cavity of embryonated eggs. The allantoic fluids from these eggs contained numbers of histiocytes far in excess of the limits detected in uninoculated eggs, and in eggs inoculated with heat-inactivated serums and with icteric serums from cases of obstructive jaundice. This histiocyte promoting factor could not be demonstrated in serums from convalescent patients. No bacteria could be associated with this cellular response. Histiocyte counts engendered through inoculations with acute IH serums were returned to normal limits by gamma globulin, by serums experimentally produced in chickens, and by serums from 3 IH-convalescent patients.