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Eggshell membrane structure and penetration by Salmonella typhimurium
M E Berrang1, J F Frank, R J Buhr
1United States Department of Agriculture, Agricultural Research Service, Russell Research Center, Athens, Georgia 30604-5677, USA. mberrang@asrr.arsusda.gov
Abstract:
Eggshell membrane was removed from 10 broiler hatching eggs at approximately monthly intervals through the productive life of a commercial flock. A piece of membrane (2 by 2 cm) was used to cover an opening in an apparatus designed to test penetration by Salmonella Typhimurium. The membrane was placed between two chambers as the only means of liquid transfer. The chamber above the membrane was filled with a suspension of Salmonella Typhimurium cells. Sampling of the bottom chamber provided cultural evidence of the penetration by a marker strain of Salmonella Typhimurium. Samples were drawn at 15 min and at 1, 3, 5, 7, 12, 24, and 48 h. Following the cultural penetration experiment, the same pieces of membrane were removed and stained for microscopic examination. Membrane structure was examined with the use of a confocal laser scanning microscope. Each image consisted of a composite of eight 1-microm optical slices showing the fibers making up the outer surface of the membrane. These images were transferred to an image analysis software package that allowed the measurement of the interfiber area. No clear correlation could be made between the average size of all interfiber areas or the total interfiber area measured in the outer 8 microm of the outer membrane and the ability of Salmonella Typhimurium to penetrate the same piece of eggshell membrane.
Insights
Eggshell membrane structure did not correlate with Salmonella Typhimurium penetration. This study examined broiler eggshell membrane integrity and its role in preventing bacterial contamination.
Area of Science:
- Food safety
- Microbiology
- Animal science
Background:
- Eggshell membrane serves as a natural barrier against microbial contamination.
- Understanding its structural properties is crucial for preventing pathogen entry in poultry products.
Purpose of the Study:
- To investigate the relationship between eggshell membrane structure and Salmonella Typhimurium penetration.
- To assess the structural integrity of broiler eggshell membranes over the flock's productive life.
Main Methods:
- Broiler eggshell membranes were collected monthly and tested for Salmonella Typhimurium penetration using a two-chamber apparatus.
- Membrane structure was analyzed using confocal laser scanning microscopy and image analysis software to measure interfiber areas.
- Bacterial penetration was assessed through cultural analysis of samples collected at various time points.
Main Results:
- No significant correlation was found between the measured interfiber areas of the eggshell membrane and the penetration rate of Salmonella Typhimurium.
- Bacterial penetration was detected over a 48-hour period, indicating potential breaches in the membrane barrier.
Conclusions:
- The structural characteristics of the eggshell membrane, specifically interfiber area, do not appear to be a reliable predictor of Salmonella Typhimurium penetration.
- Further research is needed to identify other factors influencing eggshell membrane's barrier function against bacterial pathogens.