The Role of the External Structure of Chicken Eggs in Resisting Bacterial Penetration

In this article, we will discuss the role of three eggshell models in resisting bacterial penetration. The internal membrane was found to be the most important barrier, followed by the shell. The outer membrane acted as the least effective barrier. Genetic selection, Cuticle thickness, and the number of pores were also considered. The results of this study show the importance of the external structure of chicken eggs in resisting bacterial penetration.

Cuticle Thickness

A study has been conducted to evaluate the role of cuticle thickness in bacterial penetration of chicken eggs. This study shows that cuticle thickness is important in resisting bacterial penetration. It has many advantages. For example, it is simple and cost-effective. Moreover, it can be applied to hatchery systems and commercial egg grading.

Further, it can be used to predict cuticle quality in different egg species. According to research by professional authors from Essay Writing Help Pro, a cuticle thickness of one millimeter decreases the risk of bacterial penetration of eggs.

The presence of cuticle proteins decreases the chances of bacterial penetration of eggs. A cuticle has several properties that make it a good barrier to bacteria, reducing bacterial adherence and promoting the safety of table eggs.

In addition to a thick cuticle, the internal composition of an eggshell determines the probability of bacterial penetration. Its quality and porosity play a major role in this resistance. Furthermore, washing eggs could damage the cuticle. Moreover, the eggshell’s thickness varies between different breeds and ages. The thickest Dwarf layer eggs had the lowest bacterial penetration ratio.

Number of Pores

The number of eggshell pores affects bacterial penetration in chicken eggs. Pores can pass through a thin layer of eggshell without being able to penetrate an eggshell of a higher quality. Thicker layers of shell have more internal pores and therefore, it takes more time for bacteria to enter a thin layer of eggshell. Bacterial penetration rates vary depending on the type of microflora.

Eggshells from different species show different levels of bacterial penetration. Pigeon and budgerigar eggs lack the cuticle layer on their eggshells, exposing the eggshell pores to bacteria

. In addition, albricias bird eggs have fewer eggshell pores than chicken eggs. Using a scanning electron microscope, researchers identified differences between eggshell thickness and cuticle opacity. The eggs with higher cuticle opacity had a lower E. coli penetration rate.

During the eggshell’s passage through the oviduct, a layer of mineral materials is deposited on the outside. This layer is made up of different minerals that increase the shell’s protective value and resist bacterial penetration in the short term. The most effective barrier is the inner membrane, which has a tighter meshwork than the outer one. Bacterial organisms can only penetrate the outer shell of an egg after four or eight days.

The eggshell’s thickness and pore area decreased with egg size. The thickness of the cuticle layer did not correlate with egg size, but the number of eggs had an inverse relationship with eggshell pore density. Pore density did not have any effect on bacterial penetration, although a high cuticle layer helps to prevent bacteria from entering the egg’s interior.


Eggshells are one of the most important barrier elements to prevent bacterial penetration into the interior of the egg. Bacteria most commonly infect eggs through soil, litter, and equipment. Despite this, eggs have remarkable antimicrobial properties. Numerous factors influence the size of the bacterial contamination.

Some species penetrate eggshells more easily than others. Another important factor is the level of contamination and the number of microorganisms presents inside the egg. High temperatures are also negative for eggshell quality. Aside from these factors, eggshell quality also affects bacterial penetration.

The eggshell protects the fecal fluid inside the uterus from bacteria. In the case of chicken eggs, bacterial penetration can occur via the retrograde movement of fecal fluid from the cloaca. Researchers have attributed antimicrobial protection to egg white proteins and the eggshell matrix. Eggshell matrix, when partially purified, exhibits antimicrobial activity against Bacillus cereus, Pseudomonas aeruginosa, and lysozyme.

Microorganisms found close to the egg shells may be a selective force in avian hatching. Although it is not yet known whether or not these microorganisms are harmful to the embryos, the presence of these organisms in the egg chamber may reflect the exposure of the hen to pathogenic bacteria during her lifetime.

Moreover, a greater proportion of nonpathogenic bacteria may indicate that parental immunity is aiming to limit bacterial colonization of the egg. However, more studies are needed to determine whether the bacterial colonization process is horizontal or vertical, as well as whether or not bacteria are present in the egg at physiological salt concentrations.

Genetic Selection

The cuticle of a chicken egg provides an effective barrier against bacterial penetration. Through genetic selection, egg cuticle deposition is enhanced, reducing the risk of contamination. During bacterial penetration experiments, eggs from two pedigree lines with good cuticle thickness were less susceptible to penetration. Compared with those from hens with a poor cuticle, eggs from a good cuticle breed had a lower bacterial growth rate.

In addition, the porosity of the eggshell affects bacterial penetration. A higher porosity at the blunt pole decreases the risk of bacterial penetration. Porosity at the apex does not influence the rate of bacterial penetration of a chicken eggshell. However, porosity has been associated with a greater risk of bacterial penetration. Genetic selection of chicken eggs in resisting bacterial penetration may have evolved for this trait.

A genetic selection of chicken eggs that have adapted to resist bacterial penetration may be beneficial in reducing the risk of microbial infections. This trait is especially important for commercial hatcheries where heavy contamination is common. Among the pathogenic organisms in chicken eggs include Enterococcus faecalis and E. coli. These microorganisms can enter eggs by any route and site, affecting both animal and human health.

Storage time

The quality of the cuticle and its ability to resist bacterial penetration decreased with storage time in both room temperature and cold storage. Bacteria numbers in egg whites increased in both cases and the cuticle content decreased. Bacteria in egg whites were not detected in the first 21 days of storage, but bacterial numbers increased on the fourth and fifth days. This study provides important insights into egg storage.

In recent years, scientists have studied the antibacterial properties of hen egg albumen and the antimicrobial properties of different lysozymes. In addition, Clavijio, R.I. and Duboccage, L., identified genes involved in the survival of Salmonella in chicken egg albumen. The antimicrobial activity of lysozyme decreases with storage time and its content increases as bacterial invasion risk increases.

Although these findings suggest the presence of bacteria in eggs, there is no solid evidence that a single bacterium could survive in eggs beyond three weeks. The best results are expected for eggs stored at a higher temperature and relative humidity.

The longer the eggs are stored at low temperatures, the less resistance they have to resist bacterial penetration. In addition, storage time is a factor in determining the quality of chicken eggs, so long as proper hygiene practices are followed.

Genetic resistance to Salmonella Enteritidis

In addition to the cuticle, chicken eggs also have other internal factors that determine their resistance to bacterial penetration. These factors include the eggshell’s quality, porosity, and cuticle deposition. The elasticity of the shell also affects bacterial penetration. In this study, researchers examined cuticle deposition in 10 different bird species. Their findings show that chicken eggs exhibit higher resistance to bacterial penetration than duck eggs.

Salmonella enteritidis was inoculated into chicken eggs at 5 degC, but could not penetrate the egg shell or its contents. This low temperature was attributed to an increased expression of genes such as yaiC, fimA, and fliA. Salmonella remained within the egg shell for more than a day. Consequently, these genes may be important in bacterial survival in the egg.

A chicken eggshell contains a thin, layered, and semipermeable membrane. These membranes regulate air circulation and evaporation. They also prevent bacterial penetration. A thick, colorless wax membrane surrounding the shell is known as the cuticle and acts as a bacteriostatic. Washing the eggshell may dissolve the cuticle, which is the protective coating of the eggshell.

The external structure of chicken eggs is essential for embryonic development. Incubation is the time when a hen’s eggs form. They consist of a yolk, vitelline membrane, and eggshell. The yolk contains nutrients, energy, and a combination of chemical and molecular defenses. Because the embryo must survive against the threat of bacterial contamination, the eggshell must remain free of bacteria to maintain its vitality.

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