Research Note: Analysis of microbial diversity on the shell surface of eggs collected from geographically distinct farms in China

Micro-organisms on the eggshell surface of affect the quality of the egg. Sometimes, these microbes even pose a serious threat to the health of the egg's consumer. Bacterial 16S rDNA and fungal internal transcribed spacer region were sequenced to analyze the microbial diversity on the shell surface of the eggs collected from 4 distinct regions of China: Guyuan (GY; 1.5 million hens), Langfang (LF; 0.1 million hens), Beihai (BH; 1.2 million hens), and Dongguan (DG; 0.2 million hens). The results showed a higher bacterial and fungal abundance on the eggs collected from the northern and southern China farms, respectively. The dominant bacterial phylum detected across all egg samples was Firmicutes. In addition, the shell surfaces of the DG and LF samples harbored abundant levels of Proteobacteria. The dominant fungal phyla detected across all egg samples were Ascomycota and Basidiomycota. The bacterial compositions on eggshell surfaces differed significantly across all geographic regions, and the fungal composition differed significantly between samples collected from the southern and northern farms (P < 0.05). The abundance and composition of microbial colonies on the eggshell surface varied based on their geographical location (climate and environment) and farming scale (management). Our findings provide an important reference for optimizing the cleaning and disinfection methods for fresh eggs collected from different sources.

Viable Campylobacter jejuni on Eggshells and Its Potential to Cross-contaminate Egg White and Yolk When Using a Manual Separation Technique, Determined by Culture and Propidium Monoazide (PMA) qPCR

Manual separation of egg yolk from egg white using the eggshell is common practice in private households. For this, the egg is cracked and both components are separated by passing the egg yolk back and forth between the two halves of the eggshell, allowing the egg white to drip down while the egg yolk remains in the shell. During this process, the egg content naturally gets in contact with the outside of the eggshell, which might lead to a cross-contamination with its microorganisms, thus was correspondingly assessed in this study. Campylobacter jejuni is one of the most important zoonotic pathogens that can be found on eggshells. Therefore, this bacterium was used to artificially contaminate the eggshells (n = 22) with concentrations of 3.1 ± 0.6 log10 cfu/g. After separating the egg yolk from the egg white, cross-contamination was determined using culture and qPCR. Altogether, cross-contaminations with C. jejuni were found in 15 egg white (68%) and in three egg yolk (14%) samples. Afterward, 90 eggs from 30 egg packs from different producers in and around Munich (Germany) were obtained for field study purposes. To address the problem of culturing due to a possible viable but nonculturable (VBNC) status of C. jejuni, a method to differentiate viable and dead C. jejuni on eggshell using 10 µM propidium monoazide (PMA) and qPCR was developed. As a result, seven egg packs (23%) were positive for C. jejuni. Of these, only one (3%) was contaminated with viable cells, but still in a concentration of 3.3 log10 cells/g shell. According to these results and considering that eggshells might also be naturally contaminated with other pathogens, the authors recommend avoiding the manual separation technique of egg white and yolk by the eggshell. Especially if raw egg white or yolk is used for preparation of not sufficiently heated foods, where contaminating pathogens are not inactivated during processing, this technique might be a safety hazard for the consumer.

Genome wide association analysis of cuticle deposition in laying hens

The cuticle is an invisible barrier that protects the internal egg contents from microorganisms entering through gas exchange pores. Eggs which have a good cuticle are least likely to be penetrated by microorganisms and improved cuticle cover should reduce vertical transmission of microorganisms and improve biosecurity. The aim was to carry out a genome wide association study for cuticle deposition in 3 independent populations of laying hens using tartrazine and lissamine green staining. Eggs from ∼8,000 hens represented 2 White Leghorn and 1 Rhode Island Red breed. Estimates of heritability using pedigree or genomic relationship matrices were in the 0.2 to 0.3 range. The results were breed specific. Across the populations, genomic regions on chromosomes 1, 2, 4, 5, and 8 were identified as significantly associated with cuticle deposition. No single loci had a large effect. A comparison was made with genes differentially expressed in the shell gland when cuticle deposition was manipulated, however none were obvious candidates for cuticle deposition. The results support the polygenic nature of the trait and the information will help in the future to understand the genetic variance and what might control cuticle deposition and the microbiological safety of the egg.

Dynamics of Bacterial Communities on Eggshells and on Nest Materials During Incubation in the Oriental Tit (Parus minor)

Eggshell bacterial communities may affect hatching success and nestling's condition. Nest materials are in direct contact with the eggshells, but the relationships with the eggshell microbiome during incubation have not been fully elucidated. Here, we characterize eggshell and nest material bacterial communities and their changes during incubation in the Oriental Tit (Parus minor). Bacterial communities on the nest material were relatively stable and remained distinct from the eggshell communities and had higher diversity and greater phylogenetic clustering than the eggshell communities from the same nest, resulting in lower phylogenetic turnover rate of nest material microbiome during incubation than expected by chance. While the species diversity of both communities did not change during incubation, we found significantly greater changes in the structure of bacterial communities on the eggshell than on the nest material. However, eggshell microbiome remained distinct from nest material microbiome, suggesting independent dynamics of the two microbiomes during incubation. We detected an increase in the relative abundance of several bacterial taxa on the eggshell that likely come from the bird's skin, feathers, cloaca/intestine, or uropygial secretion which suggests some exchange of bacteria between the incubating bird and the eggshell. Furthermore, incubation appeared to promote the abundance of antibiotic producing taxa on the eggshell, which may hypothetically inhibit growth of many bacteria including pathogenic ones. Our results suggest that the future studies should focus on simultaneous monitoring of absolute abundance as well as relative abundance in communities on eggshells, nest materials, and the incubating bird's body.

Development of an environmental contamination model to simulate the microbial bloom that occurs in commercial hatch cabinets

Microbial blooms that emerge in commercial hatch cabinets consist of apathogenic and pathogenic microorganisms, including Escherichia coli, Enterococcus faecalis, and Aspergillus fumigatus. Objectives of the present study included the development of a multipathogen contamination model to mimic commercial conditions and optimization of sampling methods to quantify bacterial or fungal presence within the hatch cabinet. The pathogen challenge mix (PM) was recreated from select bacterial or fungal isolates recovered from an egg homogenate (EH) derived from the contents of infertile eggs and late embryonic mortalities. Isolates selected for PM included Enterococcus faecalis (∼10⁸ CFU/egg), Staphylococcus aureus (∼10⁷ CFU/egg), Staphylococcus chromogenes (∼10⁷ CFU/egg), Aspergillus fumigatus (∼10⁶ spores/egg), and 2 Escherichia coli (∼10⁸ CFU/egg) isolates. Challenge (100 μL of PM or EH) was administered using a sterile loop to a 28 mm area on the blunt end of the eggshell at day 19 of embryogenesis (DOE). In 3 experiments, microbiological data were collected from environmental hatcher samples (open-agar plate method), fluff samples, postmortem whole-body chick rinse samples, and gastrointestinal tract (GIT) samples to evaluate select bacteria and fungi circulating within the hatch cabinet and colonization of GIT. Cumulative bacterial and fungal recovery from the PM hatching environment from DOE20 to hatch was higher than the nonchallenged group (NC) and EH group at ∼860 and ∼1,730 CFU, respectively. Bacterial recovery from GIT, fluff, and chick rinse samples were similar for the PM and EH group in Exp. 1. However, Aspergillus fumigatus recovery from fluff and chick rinse samples for the PM group was significantly (P < 0.001) higher than the NC and EH group. In Exp. 2 and 3, PM challenge significantly (P < 0.05) increased Gram-negative bacterial recovery from the GIT, fluff and chick rinse samples compared to both the NC and EH group. These data suggest this innovative multispecies environmental contamination model using PM could be utilized to evaluate strategies to mitigate microbial contamination in commercial hatch cabinets in a laboratory setting.

Properties, Genetics and Innate Immune Function of the Cuticle in Egg-Laying Species

Cleidoic eggs possess very efficient and orchestrated systems to protect the embryo from external microbes until hatch. The cuticle is a proteinaceous layer on the shell surface in many bird and some reptile species. An intact cuticle forms a pore plug to occlude respiratory pores and is an effective physical and chemical barrier against microbial penetration. The interior of the egg is assumed to be normally sterile, while the outer eggshell cuticle hosts microbes. The diversity of the eggshell microbiome is derived from both maternal microbiota and those of the nesting environment. The surface characteristics of the egg, outer moisture layer and the presence of antimicrobial molecules composing the cuticle dictate constituents of the microbial communities on the eggshell surface. The avian cuticle affects eggshell wettability, water vapor conductance and regulates ultraviolet reflectance in various ground-nesting species; moreover, its composition, thickness and degree of coverage are dependent on species, hen age, and physiological stressors. Studies in domestic avian species have demonstrated that changes in the cuticle affect the food safety of eggs with respect to the risk of contamination by bacterial pathogens such as Salmonella and Escherichia coli. Moreover, preventing contamination of internal egg components is crucial to optimize hatching success in bird species. In chickens there is moderate heritability (38%) of cuticle deposition with a potential for genetic improvement. However, much less is known about other bird or reptile cuticles. This review synthesizes current knowledge of eggshell cuticle and provides insight into its evolution in the clade reptilia. The origin, composition and regulation of the eggshell microbiome and the potential function of the cuticle as the first barrier of egg defense are discussed in detail. We evaluate how changes in the cuticle affect the food safety of table eggs and vertical transmission of pathogens in the production chain with respect to the risk of contamination. Thus, this review provides insight into the physiological and microbiological characteristics of eggshell cuticle in relation to its protective function (innate immunity) in egg-laying birds and reptiles.

Synergic Effect of Selected Ingredients and Calcium Chloride on the Technological, Molecular and Microbial Usefulness of Eggshells and Their Impact on Sensory Properties in a Food Model System

Lower levels of calcium in adults increase the risk for osteoporosis, and in children, low calcium levels can impact their potential adult height. The study objective was to analyze the bioavailability and physicochemical properties of a calcium preparation based on chicken eggs. The base calcium preparation was enriched with one of a variety of biologically active substances, inter alia, vitamin D3, vitamin K, lysine, lactose, magnesium chloride and inulin. The newly developed calcium preparations were subjected to structural analysis using X-ray diffraction and scanning electron microscopy, and the hydrodynamic diameter for the molecules was determined using the dynamic light scattering method and their zeta potential. To determine the optimum storage conditions of calcium preparations, their hygroscopicity and bulk density were determined. The calcium preparations were also added to selected food products, such as apple juice with mango, fruit dessert (jelly) and beef meatballs. The enriched food products were subjected to sensory analysis. The study demonstrated the significant influence of additives to calcium preparation in terms of its hygroscopicity and morphology. It was found that all products with the addition of analyzed preparations were characterized by high sensory desirability. The results presented in the study comprise the basis for the development of new food products, enriched with calcium.

Efficacy of six disinfection methods against extended-spectrum beta-lactamase (ESBL) producing E. coli on eggshells in vitro

The presence of extended-spectrum beta-lactamase (ESBL) producing Escherichia coli on poultry products is an important issue for veterinary and human health due to the zoonotic infection risk for producers and consumers. The present study focuses on testing the efficacy of six different disinfection methods on eggshell samples, aiming to reduce ESBL producing E. coli contamination on the hatching egg. Sterile eggshell cutouts were artificially contaminated with 10⁸ cfu/ml CTX-M-1 producing E. coli and used as a carrier model to analyze the efficacy of six disinfection methods. The contaminated samples were separated into two groups; 1) contaminated and disinfected, 2) contaminated and non-disinfected. Six independent disinfection protocols were performed following product specifications and protocols. Each eggshell sample was separately crushed, and the total viable bacterial count was calculated to determine the disinfection efficacy. Five out of six tested methods (formaldehyde gassing, hydrogen peroxide + alcohol spray, essential oils spray, peracetic acid foam, and low energetic electron radiation) demonstrated a reduction or completely eliminated the initial ESBL producing E. coli contamination. One method (essential oils as cold fog) only partly reached the expected efficacy threshold (reduction of >10² cfu/ml) and the result differed significantly when compared to the reference method i.e. formaldehyde gassing.

Dietary combined supplementation of iron and Bacillus subtilis enhances reproductive performance, eggshell quality, nutrient digestibility, antioxidant capacity, and hematopoietic function in breeder geese

A 3 × 2 factorial arrangement of treatments was conducted to investigate the effects of iron (Fe, 40, 60, and 80 mg/kg) and Bacillus subtilis (2.5 × 10⁹ and 5.0 × 10⁹ CFU/kg) supplementation on reproductive performance, egg quality, nutrient digestibility, hormone levels, antioxidant indices, and hematological parameters in breeder geese. A total of one hundredtwenty 46-week-old Wulong breeder geese were randomly assigned to 1 of 6 dietary treatments with 4 replicates per treatment and 5 geese per replicate for 10 wk following 1 wk of adaption. Dietary Fe supplementation increased egg weight (P = 0.036), fertility (P = 0.022), serum total antioxidant capacity (P = 0.022), red blood cell (P = 0.001), hematocrit (HCT, P < 0.001), hemoglobin (HGB, P = 0.005), and mean corpuscular volume (MCV, P < 0.001). Dietary B. subtilis supplementation increased egg production (P = 0.025), eggshell thickness (P = 0.020), apparent phosphorus digestibility (P < 0.001), serum follicle stimulating hormone (P = 0.043), total antioxidant capacity (P < 0.001), HCT (P < 0.001), HGB (P < 0.001), and MCV (P = 0.025), and reduced malondialdehyde level (P = 0.008). The birds fed diets supplemented with 60 mg/kg Fe and 5 × 10⁹ CFU/kg B. subtilis showed the highest percentage of hatched eggs (P = 0.004) and mean corpuscular hemoglobin (P < 0.001) among the 6 groups. Supplementation of 40 and 60 mg/kg Fe significantly increased the apparent digestibility of calcium compared with that of 80 mg/kg Fe in the birds fed 5.0 × 10⁹ CFU/kg B. subtilis (P = 0.004). Supplementation with 60 and 80 mg/kg Fe in the birds fed 5 × 10⁹ CFU/kg B. subtilis significantly decreased serum urea nitrogen level compared with other 4 groups (P = 0.022). In conclusion, the combination of Fe and B. subtilis effectively improves reproductive performance, eggshell quality, nutrient digestibility, antioxidant status, and hematopoietic function of breeder geese. Dietary addition of 60 mg/kg Fe and 5.0 × 10⁹ CFU/kg B. subtilis was an optimum supplementation dose.

Acetic acid, vinegar, and citric acid as washing materials for cuticle removal to improve hatching performance of quail eggs

The cuticle is the outmost layer of the eggshell and may affect the hatchability by modulating eggshell conductance. Three different solutions using acetic acid (AA), vinegar (V), and citric acid (CA) for cuticle removal by egg washing were developed, and the effects of cuticle removal on hatching performance of quail hatching eggs were evaluated. A total of 5,238 fresh quail hatching eggs were randomly divided into 9 treatments as follows: unwashed control, nondipped (CND); washed control, water dipped (CWD); standard control, 0.13% sodium hyperchlorite (CSH); 2% AA (AA2); 4% AA (AA4); 44.4% V (V2); 88.8% V (V4); 2% CA (CA2); and 4% CA (CA4). Overall, AA4, V4, and CA4 treatments significantly improved the hatchability of fertile eggs (95.42%, 94.16% and 95.66%, respectively) (P < 0.05) and the hatchability of CND, CWD, CSH, AA2, V2 and CA2 treatments were 90.98%, 93.00%, 92.27%, 79.44%, 90.37%, and 90.59%, respectively. The eggshell thickness and cuticle quality results showed that all AA, V, and CA solutions can effectively remove the quail eggshell cuticle, and AA4, V4 and CA4 significantly decreased eggshell thickness (P < 0.05). Microbial activity on the eggshell surface in all acid treatments was reduced significantly at day 0 of incubation (P < 0.05) and that significantly decreased than controlled treatments over the incubation period except AA2 treatment. Egg weight loss was lower for all acid treatments than that of the CND treatment (P < 0.05). There was no clear effect of treatments on chick quality. Hatch time in AA4, V4, and CA4 treatments slightly improved compared with controlled treatments (P > 0.05). There were no significant differences between treatments for chick livability and live weight at the first 21 D of life. Results of the present study indicate that cuticle removal with AA4, V4, or CA4 could effectively decrease the microbial activity on the eggshell surface during the incubation period and improve hatchability of quail hatching eggs without negative effects on hatch time and performance of quail chicks.

Preliminary evaluation of application of a 3-dimensional network structure of siloxanes Dergall preparation on chick embryo development and microbiological status of eggshells

The spatial network structure of Dergall is based on substances nontoxic to humans and the environment which, when applied on solid surfaces, creates a coating that reduces bacterial cell adhesion. The bacteriostatic properties of siloxanes are based on a purely physical action mechanism which excludes development of drug-resistant microorganisms. The aims of the present study were to 1) evaluate a Dergall layer formed on the eggshell surface regarding the potential harmful effects on the chick embryo; 2) evaluate antimicrobial activity and estimate the prolongation time of Dergall's potential antimicrobial activity. Dergall at a concentration of 0.6% formed a layer on the eggshell surface. In vitro testing of the potential harmful effects of Dergall by means of a hen embryo test of the chorioallantoic membrane showed no irritation reaction at a concentration of 3% and lower. The hatchability of the groups sprayed with a Dergall water solution with a concentration of 0 to 5% was 89.1 to 93.8% for fertilized eggs (P > 0.05) but decreased to 63.7% (P < 0.05) in the group sprayed with a 6% concentration of the solution. This phenomenon was caused by embryo mortality in the first week of incubation. At the concentration of 0.6%, Dergall exhibited strong antibacterial properties against bacteria such as Staphylococcus aureus, Escherichia coli, Shigella dysenteriae, Shigella flexneri, and Salmonella typhimurium. For Streptococcus pyogenes, the highest antibacterial activity of Dergall was reported in the concentrations of 100 and 50%. For Pseudomonas aeruginosa, no antibacterial activity of Dergall was generally observed, but in vivo testing showed a strong decrease of all gram-negative bacteria growth. Moreover, a prolonged antimicrobial effect lasting until 3 D after disinfection was observed, which makes Dergall a safe and efficient disinfectant.

Comparative study of eggshell antibacterial effectivity in precocial and altricial birds using Escherichia coli

In this study, we compared the antibacterial effectivity of the eggs of six precocial and four altricial bird species using Escherichia coli, based on their eggshell traits. The ultrastructure of eggshell was observed using a scanning electron microscope (SEM). According to SEM results, eggs from precocial birds (chicken, turkey, quail, duck, ostrich, and goose) had cuticle on the eggshells, while eggs from altricial birds (pigeon, budgerigar, munia, and canary) did not. The environment/selection pressure may induce the divergent evolution process in eggs of precocial and altricial birds. The E. coli experiment results showed that chicken, turkey, quail, duck, and goose eggs, with a high cuticle opacity, exhibited a much lower E. coli penetration rate. In contrast, the eggs with poor (ostrich) or without (pigeon, budgerigar, munia, and canary) cuticle exhibited a higher penetration rate. It is suggested that cuticle is a main barrier against bacterial penetration in precocial birds’ eggs. Turkey and quail eggs showed the lowest E. coli contamination rate (3.33% and 2.22%, respectively), probably because of the tightly connected nanosphere structure on their cuticle. As for altricial birds’ eggs, the eggs of budgerigar, munia, and canary with small pore diameter (0.57 to 1.22 μm) had a lower E. coli penetration rate than pigeon eggs (45.56%, 66.67%, 50%, and 97.78%, respectively, P < 0.05), indicating that pore diameter played a significant role in defending against bacterial trans-shell invasion. We found that eggshell thickness and pore area decreased with egg size. The cuticle quality had no relationship with egg size, but was closely related to the bird species. The E. coli penetration rate of altricial birds’ eggs was significantly higher than that of precocial birds’ eggs, mainly because the pores are exposed on the eggshell surface and cuticle protection is absent. This study provides detailed information on the eggshell cuticle, which gives insight into the cuticle evolution process that occurred in precocial and altricial bird species. Moreover, the results of E. coli penetration may help understanding the antibacterial behavior in birds.

Biofilm Formation in Different Salmonella Serotypes Isolated from Poultry

Little is known about Salmonella biofilm assembly, making the prevention of the disease a challenge in the poultry production chain. The objective of the present study was then to evaluate biofilm formation from different serotypes of Salmonella spp. in both polystyrene plates and eggshells. Salmonella Gallinarum and S. Minnesota were both classified as producers of biofilms of moderate intensity. Interestingly, S. Gallinarum produces biofilm even though being a serotype without flagellum and not having the lux gene in its genome, suggesting that there might be other important structures and genes associated with biofilm formation. Regarding Enteritidis, Typhimurium, Typhimurium variant, and Heidelberg serotypes, despite having high counts, BFI (Biofilm Formation Index) showed low biofilm production, probably due to the scarcity of extracellular matrix produced by such strains. A turkey eggshell model was then used for S. Enteritidis and S. Heidelberg biofilm formation. The results from the microbial count and scanning electron microscopy showed that Salmonella serotypes were also able to generate biofilm in eggshells, suggesting the presence of biofilms in poultry producing farms, a main concern for the poultry production industry.

Ectoparasite Activity During Incubation Increases Microbial Growth on Avian Eggs

While direct detrimental effects of parasites on hosts are relatively well documented, other more subtle but potentially important effects of parasitism are yet unexplored. Biological activity of ectoparasites, apart from skin injuries and blood-feeding, often results in blood remains, or parasite faeces that accumulate and modify the host environment. In this way, ectoparasite activities and remains may increase nutrient availability that may favour colonization and growth of microorganisms including potential pathogens. Here, by the experimental addition of hematophagous flies (Carnus hemapterus, a common ectoparasite of birds) to nests of spotless starlings Sturnus unicolor during incubation, we explore this possible side effect of parasitism which has rarely, if ever, been investigated. Results show that faeces and blood remains from parasitic flies on spotless starling eggshells at the end of incubation were more abundant in experimental than in control nests. Moreover, eggshell bacterial loads of different groups of cultivable bacteria including potential pathogens, as well as species richness of bacteria in terms of Operational Taxonomic Units (OTUs), were also higher in experimental nests. Finally, we also found evidence of a link between eggshell bacterial loads and increased embryo mortality, which provides indirect support for a bacterial-mediated negative effect of ectoparasitism on host offspring. Trans-shell bacterial infection might be one of the main causes of embryo death and, consequently, this hitherto unnoticed indirect effect of ectoparasitism might be widespread in nature and could affect our understanding of ecology and evolution of host-parasite interactions.

Common cuckoos (Cuculus canorus) affect the bacterial diversity of the eggshells of their great reed warbler (Acrocephalus arundinaceus) hosts

The common cuckoo (Cuculus canorus) is an avian brood parasite, laying its eggs in the nests of other bird species, where these hosts incubate the parasitic eggs, feed and rear the nestlings. The appearance of a cuckoo egg in a host nest may change the bacterial community in the nest. This may have consequences on the hatchability of host eggs, even when hosts reject the parasitic egg, typically within six days after parasitism. The present study revealed the bacterial community of cuckoo eggshells and those of the great reed warbler (Acrocephalus arundinaceus), one of the main hosts of cuckoos. We compared host eggs from non-parasitized clutches, as well as host and cuckoo eggs from parasitized clutches. As incubation may change bacterial assemblages on eggshells, we compared these egg types in two stages: the egg-laying stage, when incubation has not been started, and the mid-incubation stage (ca. on days 5–7 in incubation), where heat from the incubating female dries eggshells. Our results obtained by the 16S rRNA gene sequencing technique showed that fresh host and cuckoo eggs had partially different bacterial communities, but they became more similar during incubation in parasitized nests. Cluster analysis revealed that fresh cuckoo eggs and incubated host eggs in unparasitized nests (where no cuckoo effect could have happened) were the most dissimilar from the other groups of eggs. Cuckoo eggs did not reduce the hatchability of great reed warbler eggs. Our results on the cuckoo-great reed warbler relationship supported the idea that brood parasites may change bacterial microbiota in the host nest. Further studies should reveal how bacterial communities of cuckoo eggshells may vary by host-specific races (gentes) of cuckoos.

Replacing conventional decontamination of hatching eggs with a natural defense strategy based on antimicrobial, volatile pyrazines

The treatment of hatching eggs relies on classic yet environmentally harmful decontamination methods such as formaldehyde fumigation. We evaluated bacteria-derived volatiles as a replacement within a fundamentally novel approach based on volatile organic compounds (VOCs), which are naturally involved in microbial communication and antagonism due to their high antimicrobial efficiency. Pyrazine (5-isobutyl-2,3-dimethylpyrazine) was applied passively and actively in prototypes of a pre-industry-scale utilization. Altogether, pyrazine decontamination rates of up to 99.6% were observed, which is comparable to formaldehyde fumigation. While active evaporation was highly efficient in all experiments, passive treatment showed reducing effects in two of four tested groups only. These results were confirmed by visualization using LIVE/DEAD staining microscopy. The natural egg shell microbiome was characterized by an unexpected bacterial diversity of Pseudomonadales, Enterobacteriales, Sphingomonadales, Streptophyta, Burkholderiales, Actinomycetales, Xanthomonadales, Rhizobiales, Bacillales, Clostridiales, Lactobacillales, and Flavobacteriales members. Interestingly, we found that especially low pyrazine concentrations lead to a microbiome shift, which can be explained by varying antimicrobial effects on different microorganisms. Micrococcus spp., which are linked to embryonic death and reduced hatchability, was found to be highly sensitive to pyrazines. Taken together, pyrazine application was shown to be a promising, environmentally friendly alternative for fumigation treatments of hatchery eggs.

Eggshells as a source for occupational exposure to airborne bacteria in hatcheries

Occupational exposure to high concentrations of airborne bacteria in poultry production is related to an increased risk of respiratory disorders. However, potential sources and formation of hatchery bioaerosols are rarely characterized. In this study, bacterial multiplication on fresh shell fragments from turkey hatching eggs under conditions present in a hatcher incubator was investigated. A 10⁵-fold amplification was observed both by colony count and total cell count gaining 4 × 10⁷ cfu/cells per gram eggshell within 30 hr of incubation. Furthermore, the bacterial community present on eggshells was analyzed by generation of 16S rRNA gene clone libraries and identification of eight isolates. RFLP analysis revealed no shift in community composition during incubation and Enterococcus faecalis and Enterococcus gallinarum were found as the predominant species on turkey eggshells, both have been classified as risk group 2 microorganisms (German TRBA 466). Since Enterococcus spp. were found as predominant species on turkey eggshells, contribution of this genus to bioaerosol formation was demonstrated. During different work activities with poult and eggshell handling concentrations of airborne enterococci up to 1.3 × 10⁴ cfu m^-3 were detected. In contrast, no enterococci were identified at a day without poult or eggshell processing. In conclusion, turkey hatching eggs carry a viable specific microflora from breeder flocks to hatcheries. After hatching of turkey poults, hatcher incubators and eggshell fragments provide appropriate conditions for excessive bacterial growth. Thus, high bacterial loads on eggshell fragments are a source of potential harmful bioaersols caused by air flows, poult activity, and handling of equipment.

Identification of fungal metabolites from inside Gallus gallus domesticus eggshells by non-invasively detecting volatile organic compounds (VOCs)

The natural porosity of eggshells allows hen eggs to become contaminated with microbes from the nesting material and environment. Those microorganisms can later proliferate due to the humid ambient conditions while stored in refrigerators, causing a potential health hazard to the consumer. The microbes' volatile organic compounds (mVOCs) are released by both fungi and bacteria. We studied mVOCs produced by aging eggs likely contaminated by fungi and fresh eggs using the non-invasive detection method of gas-phase sampling of volatiles followed by gas chromatography/mass spectrometry (GC/MS) analysis. Two different fungal species (Cladosporium macrocarpum and Botrytis cinerea) and two different bacteria species (Stenotrophomas rhizophila and Pseudomonas argentinensis) were identified inside the studied eggs. Two compounds believed to originate from the fungi themselves were identified. One fungus-specific compound was found in both egg and the fungi: trichloromethane. Graphical abstract Trichloromethane is a potential biomarker of fungal contamination of eggs.

Salmonella enterica isolates from layer farm environments are able to form biofilm on eggshell surfaces

This study examined the eggshell biofilm forming ability of Salmonella enterica isolates recovered from egg farms. Multicellular behaviour and biofilm production were examined at 22 and 37°C by Congo red morphology and the crystal violet staining assay. The results indicated that the biofilm forming behaviour of Salmonella isolates was dependent on temperature and associated with serovars. Significantly greater biofilm production was observed at 22°C compared with 37°C. The number of viable biofilm cells attached to eggshells after incubation for 48 h at 22°C was significantly influenced by serovar. Scanning electron microscopic examination revealed firm attachment of bacterial cells to the eggshell surface. The relative expression of csgD and adrA gene was significantly higher in eggshell biofilm cells of S. Mbandaka and S. Oranienburg. These findings demonstrate that Salmonella isolates are capable of forming biofilm on the eggshell surface and that this behaviour is influenced by temperature and serovar.

Nest Bacterial Environment Affects Microbiome of Hoopoe Eggshells, but Not That of the Uropygial Secretion

The study of associations between symbiotic bacterial communities of hosts and those of surrounding environments would help to understand how bacterial assemblages are acquired, and how they are transmitted from one to another location (i.e. symbiotic bacteria acquisition by hosts). Hoopoes (Upupa epops) smear their eggshells with uropygial secretion (oily secretion produced in their uropygial gland) that harbors antibiotic producing bacteria. Trying to elucidate a possible role of nest material and cloaca microbiota in determining the bacterial community of the uropygial gland and the eggshells of hoopoes, we characterized bacterial communities of nest material, cloaca, uropygial gland and eggshells by the ARISA fingerprinting. Further, by adding material with scarce bacteria and antimicrobial properties, we manipulated the bacterial community of nest material and thus tested experimentally its effects on the microbiomes of the uropygial secretion and of the eggshells. The experiment did not influence the microbiome of the uropygial secretion of females, but affected the community established on eggshells. This is the first experimental evidence indicating that nest material influences the bacterial community of the eggshells and, therefore, probability of embryo infection. Some of the bacterial strains detected in the secretion were also in the bacterial communities of the nest material and of cloaca, but their occurrence within nests was not associated, which suggests that bacterial environments of nest material and cloaca are not sources of symbiotic bacteria for the gland. These results do not support a role of nest environments of hoopoes as reservoirs of symbiotic bacteria. We discuss possible scenarios explaining bacterial acquisition by hoopoes that should be further explored.

Preening as a Vehicle for Key Bacteria in Hoopoes

Oily secretions produced in the uropygial gland of incubating female hoopoes contain antimicrobial-producing bacteria that prevent feathers from degradation and eggs from pathogenic infection. Using the beak, females collect the uropygial gland secretion and smear it directly on the eggshells and brood patch. Thus, some bacterial strains detected in the secretion should also be present on the eggshell, beak, and brood patch. To characterize these bacterial communities, we used Automatic Ribosomal Intergenic Spacer Analysis (ARISA), which distinguishes between taxonomically different bacterial strains (i.e. different operational taxonomic units [OTUs]) by the size of the sequence amplified. We identified a total of 146 different OTUs with sizes between 139 and 999 bp. Of these OTUs, 124 were detected in the uropygial oil, 106 on the beak surface, 97 on the brood patch, and 98 on the eggshell. The highest richness of OTUs appeared in the uropygial oil samples. Moreover, the detection of some OTUs on the beak, brood patch, and eggshells of particular nests depended on these OTUs being present in the uropygial oil of the female. These results agree with the hypothesis that symbiotic bacteria are transmitted from the uropygial gland to beak, brood patch, and eggshell surfaces, opening the possibility that the bacterial community of the secretion plays a central role in determining the communities of special hoopoe eggshell structures (i.e., crypts) that, soon after hatching, are filled with uropygial oil, thereby protecting embryos from pathogens.

Detection of potential pathogenic aerobic bacteria from egg shell and egg contents of hen collected from poultry

This study was done to identify different pathogenic aerobic bacteria from egg shell and egg contents of hen. Egg shells and egg contents of 150 eggs collected from poultry were tested. Of 150 egg shells, 130 (86.67%) yielded growth of bacteria and 60 (40%) Esch. coli,.25 (16.67%) Providencia rettgeri, 5 (3.33%) Providencia alkalifaciens, 20 (13.33%) Citrobacter freundii, 10 (6.67%) Salmonella spp, 10 (6.67%) Enterobacter aerogenes were isolated. No bacteria were isolated from 150 egg contents. Total 14 (9.33%) Salmonella spp. from egg shells and 7 (4.67%) Salmonella spp. from egg contents were identified by PCR. Most of the identified serotypes were Salmonella Enteritidis (42.86% from egg shells and 71.43% from egg contents). All (100%) Salmonella Typhi and Salmonella Paratyphi A were sensitive to ciprofloxacin and ceftriaxone.

Eggshell bacterial load is related to antimicrobial properties of feathers lining barn swallow nests

The use of feathers to line bird's nests has traditionally been interpreted as having a thermoregulatory function. Feather-degrading bacteria growing on feathers lining nests may have antimicrobial properties, which may provide an additional benefit to lining nests with feathers. We test the hypothesis that the production of antimicrobial substances by feather bacteria affects the microbiological environment of the nest, and therefore the bacterial density on eggshells and, indirectly, hatching success. These effects would be expected to differ between nests lined with pigmented and white feathers, because bacteria grow differently on feathers of different colors. We experimentally manipulated the composition of pigmented and unpigmented feathers in nests of the barn swallow (Hirundo rustica) and studied the antimicrobial properties against the keratin-degrading bacterium Bacillus licheniformis of bacteria isolated from feathers of each color. Analyzed feathers were collected at the end of the incubation period, and antimicrobial activity was defined as the proportion of bacteria from the feathers that produce antibacterial substances effective against B. licheniformis. Our experimental manipulation affected antimicrobial activity, which was higher in nests with only white feathers at the beginning of incubation. Moreover, white feathers showed higher antimicrobial activity than black ones. Interestingly, antimicrobial activity in feathers of one of the colors correlated negatively with bacterial density on feather of the opposite color. Finally, antimicrobial activity of white feathers was negatively related to eggshell bacterial load. These results suggest that antimicrobial properties of feathers in general and of white feathers in particular affect the bacterial environment in nests. This environment in turn affects the bacterial load on eggshells, which may affect hatching success.

Detection of biological contaminants on foods and food surfaces using laser-induced breakdown spectroscopy (LIBS)

The rapid detection of biological contaminants, such as Escherichia coli O157:H7 and Salmonella enterica , on foods and food-processing surfaces is important to ensure food safety and streamline the food-monitoring process. Laser-induced breakdown spectroscopy (LIBS) is an ideal candidate technology for this application because sample preparation is minimal and results are available rapidly (seconds to minutes). Here, multivariate regression analysis of LIBS data is used to differentiate the live bacterial pathogens E. coli O157:H7 and S. enterica on various foods (eggshell, milk, bologna, ground beef, chicken, and lettuce) and surfaces (metal drain strainer and cutting board). The type (E. coli or S. enterica) of bacteria could be differentiated in all cases studied along with the metabolic state (viable or heat killed). This study provides data showing the potential of LIBS for the rapid identification of biological contaminants using spectra collected directly from foods and surfaces.

Effect of ultrasonic treatment on reduction of Esherichia coli ATCC 25922 and egg quality parameters in experimentally contaminated hens' shell eggs

BACKGROUND

In this study, hen eggs which were experimentally contaminated with Esherichia coli ATCC 25922 were used. Contaminated eggs were washed statically (S5 to S30; 0 kHz) and by ultrasonic waves (U5 to U30; 35 kHz) for given applications of time (5, 15 and 30 min), then the eggs were stored at 22°C for 14 days.

RESULTS

Depending on the time of ultrasonic application, a significant increase in egg shell strength (P < 0.01) was recorded. The highest value of the Haugh unit (67.93, 1 day) was observed on the eggs which were washed by ultrasonic waves. Yolk width values of ultrasonic washed eggs diminished. E. coli was completely removed by 30 min of ultrasonic application. During storage E. coli growth was not detected on the eggs which were washed by ultrasonic waves except the eggs in U5 group (2.04 log CFU eggshell⁻¹) on the first day of storage.

CONCLUSION

Depending on the time of ultrasonic application a significant increase in egg quality parameters (shell strength, albumen height, Haugh units, and yolk height) were observed. The application of ultrasound led to a significant reduction in E. coli numbers on egg shells.

Effects of vacuum packing on eggshell microbial activity and egg quality in table eggs under different storage temperatures

BACKGROUND

The aim of this study was to establish the effects of vacuum packing on eggshell microbial activity and egg quality traits in table eggs during 42 days of storage at 5 and 22 °C. Treatments were no vacuum packing (control) and vacuum packing (VP). Egg quality traits measured included egg weight loss, specific gravity, shell strength, albumen height, Haugh unit, yolk index, albumen pH, yolk pH, albumen colour and yolk colour.

RESULTS

VP eggs maintained higher specific gravity, albumen height, Haugh unit and yolk index and lower egg weight loss, albumen pH and yolk pH compared with control eggs after 42 days at 22 °C. VP eggs had lower levels of total aerobic mesophilic bacteria, Salmonella spp., Staphylococcus spp. and moulds/yeasts than control eggs over the storage period at both 5 and 22 °C. However, VP eggs had a higher level of coliforms than control eggs after 42 days at 5 °C.

CONCLUSION

The results indicated that vacuum packing extended the egg shelf life to at least 42 days compared with control eggs at 5 and 22 °C.

[Mycoplasma synoviae-associated egg-pole shell defects in laying hens]

Hens laying eggs with egg-pole shell defects (EPS) were examined in a clinical prospective study. 86 hens with EPS and 72 hens without EPS from three flocks were selected for this study. It could be proven serologically that hens with EPS had significant (p < 0.05) higher titers against Mycoplasma (M.) synoviae then hens without EPS. PCR tested cloacal swabs for M. synoviae were more frequently positive from hens with EPS (87%; n=72) then from hens without EPS (18%; n=13). Furthermore, M. synoviae could be cultivated from the oviduct of five hens with EPS. Additionally, M. synoviae-DNA was detectable in the albumen of nearly all eggs with EPS (n=48; 98%), contrary to the eggs without EPS (n=11; 26%). Ultrastructural investigation revealed that eggs with EPS showed considerable differences of the egg shell structure as well as the cross section dimension according to eggs without EPS. Due to the significantly more frequent detection of M. synoviae-DNA from the cloaca of chickens with EPS, is an involvement of M. synoviae in laying of EPS in the surveyed herds likely. Further infection experiments with the isolated M. synoviae were not perfomed, therefore about the causal pathogenic role of M. synoviae in the development of eggs with EPS in the surveyed herds can only be speculated.

Prevention of Salmonella enteritidis in shell eggs during production, storage, and transportation. Final rule

The Food and Drug Administration (FDA) is issuing a final rule that requires shell egg producers to implement measures to prevent Salmonella Enteritidis (SE) from contaminating eggs on the farm and from further growth during storage and transportation, and requires these producers to maintain records concerning their compliance with the rule and to register with FDA. FDA is taking this action because SE is among the leading bacterial causes of foodborne illness in the United States, and shell eggs are a primary source of human SE infections. The final rule will reduce SE-associated illnesses and deaths by reducing the risk that shell eggs are contaminated with SE.

Avian incubation inhibits growth and diversification of bacterial assemblages on eggs

Microbial infection is a critical source of mortality for early life stages of oviparous vertebrates, but parental defenses against infection are less well known. Avian incubation has been hypothesized to reduce the risk of trans-shell infection by limiting microbial growth of pathogenic bacteria on eggshells, while enhancing growth of commensal or beneficial bacteria that inhibit or competitively exclude pathogens. We tested this hypothesis by comparing bacterial assemblages on naturally incubated and experimentally unincubated eggs at laying and late incubation using a universal 16S rRNA microarray containing probes for over 8000 bacterial taxa. Before treatment, bacterial assemblages on individual eggs from both treatment groups were dissimilar to one another, as measured by clustering in non-metric dimensional scaling (NMDS) ordination space. After treatment, assemblages of unincubated eggs were similar to one another, but those of incubated eggs were not. Furthermore, assemblages of unincubated eggs were characterized by high abundance of six indicator species while incubated eggs had no indicator species. Bacterial taxon richness remained static on incubated eggs, but increased significantly on unincubated eggs, especially in several families of Gram-negative bacteria. The relative abundance of individual bacterial taxa did not change on incubated eggs, but that of 82 bacterial taxa, including some known to infect the interior of eggs, increased on unincubated eggs. Thus, incubation inhibits all of the relatively few bacteria that grow on eggshells, and does not appear to promote growth of any bacteria.

Assessing the prevalence of Salmonella enterica in poultry hatcheries by using hatched eggshell membranes

Salmonella enterica causes a number of significant poultry diseases and is also a major pathogen in humans. Most poultry infected by Salmonella become carriers; infection may also be fatal, depending on the particular serovar and the age of the bird at infection. Younger birds are more susceptible to infection by Salmonella, so it is critical that hatcheries monitor birds. We developed a method to use hatched eggshell membranes (HEM) to assess contamination by Salmonella in poultry hatching cabinets and to evaluate the prevalence of Salmonella in a goose hatchery and rearing farm. Comparison of the Salmonella isolation rate in hatching cabinets using 3 sampling methods showed that the highest Salmonella contamination was detected in HEM, and that these results differed significantly from those obtained from fluff samples and cabinet swab samples (P < 0.05). Analysis of HEM was also used to evaluate Salmonella contamination in goose, chicken, and duck hatcheries. The lowest Salmonella-positive rate was found for the chicken hatchery, followed by the goose and the duck hatcheries (P < 0.05). Six serogroups of Salmonella were detected in the 3 hatcheries: A, B, C1, C2, D, and E. The distribution of these serogroups differed among the hatcheries. Salmonella serogroup C1 was the major serogroup found in geese, compared with serogroup B in chickens and ducks. However, Salmonella Typhimurium was dominant in 1 goose hatchery and also in geese from this hatchery that had been transferred to a farm. Antibiotic susceptibility analysis showed that Salmonella Typhimurium strains isolated from the farm geese with diarrhea showed significantly higher resistance to doxycycline, colistin, sulfamethoxazole-trimethoprin, and cephalothin than those isolated from the hatchery (P < 0.05). Therefore, HEM as a detection target can be used to monitor Salmonella contamination in hatching cabinets and also be used to assess Salmonella prevalence in poultry hatcheries and rearing farms.

Pathogen prevalence and microbial levels associated with restricted shell eggs

Restricted shell eggs that do not meet quality standards for retail but maintain acceptable quality for inclusion in further processed eggs are often diverted to further processing. A study was conducted to characterize the microbiological populations present on and in these eggs. On a single day, restricted eggs were collected from three shell egg processing plants a total of three times (replicates). Six shells or egg contents were combined to create a pool. Ten pools of shells and contents were formed for each plant per replicate. Shells and membranes were macerated in 60 ml of diluent. Contents were stomacher blended to form a homogeneous mixture. Total aerobic microorganisms and Enterobacteriaceae were enumerated. The prevalence of Salmonella, Campylobacter, and Listeria was determined by cultural methods. Average aerobic counts were 4.3 log CFU/ml for the shells and 2.0 log CFU/ml for the contents. There were plant x replicate differences for both (P < 0.05 and P < 0.01, respectively). The average Enterobacteriaceae level associated with the shell was 2.4 log CFU/ml and less than 0.1 log CFU/ml for the egg contents, with 36.7% of the samples being positive. One shell sample (0.5% of total samples) was Campylobacter positive. Two shell samples (1.1% of total samples) were Salmonella positive. Twenty-one percent of samples were positive for Listeria (33 shells and 5 contents). Although current pasteurization guidelines are based on Salmonella lethality, the results of this study reiterate the need to revisit the guidelines to determine the effectiveness for other pathogenic species.

Public health investigations of Salmonella Enteritidis in catering raw shell eggs, 2002-2004

AIMS

In response to a dramatic change in the epidemiology of Salmonella Enteritidis in England and Wales thought to be associated with raw shell eggs, the Health Protection Agency initiated public health investigations to establish the incidence of Salmonella contamination and origin of eggs used by catering premises implicated in outbreaks of Salm. Enteritidis.

METHODS AND RESULTS

Between October 2002 and November 2004, 16 971 eggs were sampled and Salmonella were recovered from 3.4%. Salmonella was isolated from 5.5% and 6.3% of Spanish and eggs of unknown origin, respectively, used in catering premises linked to outbreaks, a level significantly higher than that (1.1%) found in nonLion Quality UK eggs sampled. The small sample of UK Lion Quality eggs tested (reflecting their lack of use in premises visited) did not contain Salmonella. Several phage types of Salm. Enteritidis other than phage type 4 (PT 4) were identified with nonUK eggs.

CONCLUSIONS

Eggs from Spain were implicated as a major source of infection. Eggs were contaminated more frequently with Salmonella when shells were dirty and/or cracked, and stored at above 8 degrees C.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of Spanish eggs by the catering sector has been identified as a consistent significant factor in many of the outbreaks caused by Salm. Enteritidis nonPT4 in England and Wales during 2002-2004. Advice to caterers and hospitals that raw shell eggs should not be used in food that will either not be cooked or only lightly cooked should be reinforced.

Screening of various foodstuffs for occurrence of Coxiella burnetii in Switzerland

The epidemiology of Q-fever in Switzerland is largely unknown. For this reason, a screening programme for the presence of Coxiella burnetii in bulk milk samples from cows, sheep and goats and in shell eggs produced in and imported into Switzerland was conducted. In total, 17 of 359 (4.7%) of analysed bovine milk samples from two randomly selected cheese dairies were tested positive for C. burnetii by nested PCR. Furthermore, the findings with samples from one dairy showed that the agent seemed to persist over time in the herds of cattle of certain farms. Although no extensive prevalence study was undertaken, our results indicate that C. burnetii appears to be quite frequent in cattle. As for 81 ovine and 39 caprine bulk milk samples, they were all tested negative for C. burnetii. Finally, 504 shell eggs were also found to be negative for C. burnetii with PCR testing. The results of the study are discussed under inclusion of epidemiological data for human and animal coxiellosis and the current Swiss legal regulations for the control of C. burnetii in cattle.

Evaluation of a combination of sodium hypochlorite and polyhexamethylene biguanide as an egg wash for red-eared slider turtles (Trachemys scripta elegans) to suppress or eliminate Salmonella organisms on egg surfaces and in hatchlings

OBJECTIVE

To evaluate a combination of 2 nonantibiotic microbicide compounds, sodium hypochlorite (NaOCl) and polyhexamethylene biguanide (PHMB), as a treatment to suppress or eliminate Salmonella spp from red-eared slider (RES) turtle (Trachemys scripta elegans) eggs and hatchlings.

SAMPLE POPULATION

2,738 eggs from 8 turtle farms in Louisiana.

PROCEDURES

Eggs were randomly sorted into 3 or, when sufficient eggs were available, 4 treatment groups as follows: control, pressure-differential egg treatment with NaOCl and gentamicin, NaOCl and PHMB bath treatment, and pressure-differential egg treatment with NaOCl and PHMB. Bacterial cultures were performed from specimens of eggs and hatchlings and evaluated for Salmonella spp.

RESULTS

RES turtle eggs treated with NaOCl and PHMB as a bath (odds ratio [OR], 0.2 [95% confidence interval (CI), 0.1 to 0.3]) or as a pressure-differential dip (OR, 0.01 [95% CI, 0.001 to 0.07]) or with gentamicin as a pressure-differential dip (OR, 0.1 [95% CI, 0.06 to 0.2]) were significantly less likely to have Salmonella-positive culture results than control-group eggs.

CONCLUSIONS AND CLINICAL RELEVANCE

Concern over reptile-associated salmonellosis in children in the United States is so great that federal regulations prohibit the sale of turtles that are < 10.2 cm in length. Currently, turtle farms treat eggs with gentamicin solution. Although this has reduced Salmonella shedding, it has also resulted in antimicrobial resistance. Results of our study indicate that a combination of NaOCl and PHMB may be used to suppress or eliminate Salmonella spp on RES turtle eggs and in hatchlings.

Eggshell penetration of various types of hens' eggs by Salmonella enterica serovar Enteritidis

Egg weight, shell thickness, number of pores, cuticle deposition, eggshell strength (dynamic stiffness and damping ratio), and the ability of Salmonella enterica serovar Enteritidis (SE) to penetrate the eggshell were determined. Penetration was assessed by filling the eggs with a selective medium that allowed viewing of Salmonella growth on the inside of the shell and membrane complex. After inoculation of each shell with on average 2.71 log CFU, the eggs were stored for up to 14 days at 20 degrees C and 60% relative humidity. Commercially available eggs were used. At 14 days of storage, only 6.0% of the eggs from free-range hens and 16.0% of the generic (i.e., eggs from hens in conventional battery cages that were given standard feed) white eggs were penetrated. The generic brown, organic, and omega-3-enriched eggs were penetrated at a frequency of 30 to 34%. In a second experiment it was shown that the layer strains of the hen (ISA-Brown Warren versus Bovans Goldline), which were kept in furnished cages, did not affect eggshell penetration by SE. For Bovans Goldline hens, the housing system (furnished cage versus aviary) did not affect penetration, while a trend was visible toward a higher fraction of penetrated eggshells when hens were fed corncob mix rather than standard feed. Eggshell penetration was observed more frequently in the absence of cuticle spots and for eggs having lower dynamic stiffness values. Shell contamination at the end of storage was highly correlated with SE penetration.

Comparison of eggshell hygiene in two housing systems: Standard and furnished cages

1. The hygienic properties of eggs produced in two designs of furnished cage were investigated and compared to two standard cage designs. 2. At 28, 37, 47 and 58 weeks of age, the proportion of dirty eggs was higher in one of the furnished cage designs while, in the other, it was similar to standard cages. 3. At 27, 33 and 60 weeks, the bacterial load on the eggshell (total aerobic bacteria and enterococci) was higher in furnished cage designs. A seasonal effect was observed with lower counts at 60 weeks (winter) than at 27 weeks (summer). 4. More dirty eggs and a higher bacterial load were observed in eggs laid outside the nests, which suggests egg hygiene in furnished cages could be similar to standard cages if the equipment in furnished cages was improved to enhance nest laying.

Bacterial shell contamination in the egg collection chains of different housing systems for laying hens

The bacterial eggshell contamination of eating eggs in different commercial housing systems; two conventional cages, one organic aviary system and one barn production, were compared. The total counts of aerobic bacteria and the total counts of Gram-negative bacteria on the shell were used to detect key points where contamination occurred and to study the progress of contamination in the egg collection and transportation chains. The key points in the chain were those where eggs accumulated on a short conveyor belt, initial shell contamination in the alternative housing systems and extra nest-boxes placed on the ground. The high bacterial load of floor eggs (>6.3 log CFU total aerobic flora/eggshell) explains why they cannot be used for eating. On average higher initial shell contamination with total counts of aerobic bacteria was found for eggs from the alternative housing systems compared to the conventional systems; respectively 5.46 compared to 5.08 log CFU/eggshell. However, initial contamination with total counts of Gram-negative bacteria on the shells was less in the alternative systems: 3.31 compared to 3.85 log CFU/shell. Initial bacterial shell contamination tended to correlate positively with the concentration of bacteria in the air of the poultry houses. Storing shell eggs, whether temporarily refrigerated or not, for 9 d or more, resulted in a decrease in bacterial eggshell contamination for both bacterial variables.

Observations on Salmonella contamination of eggs from infected commercial laying flocks where vaccination for Salmonella enterica serovar Enteritidis had been used

Eggs were collected monthly from 12 cage-layer flocks on four farms where Salmonella Enteritidis was present in vaccinated flocks despite vaccination with an S. Enteritidis bacterin. Where possible, hens were also taken for culture at the end of the laying period, and faecal and environmental samples were taken from the laying houses before and after cleaning and disinfection. Twenty-four batches of six egg shells from the 13 652 tested (0.18% [0.11 to 0.26 CI(95)] single egg equivalent) were positive for S. Enteritidis and 54 (0.40% [0.30 to 0.52 CI(95)] single egg equivalent) for other serovars. Six batches of 13 640 (0.04% [0.02 to 0.10 CI95] single egg equivalent) egg contents, bulked in six egg pools, contained S. Enteritidis and three batches contained other serovars. In addition three further batches contained S. Enteritidis in both contents and shells, and two other batches contained other serovars in both. The total level of contamination by S. Enteritidis of both contents and shells found in vaccinated flocks was therefore 33 batches/13 682 eggs(0.24% [0.17 to 0.34 CI(95)] single egg equivalent). The total of contamination for any Salmonella serovar was 92 batches/13 682 eggs (0.68% [0.55 to 0.84 CI(95)] single egg equivalent). These results contrast with the findings of testing of eggs from three unvaccinated flocks prior to this study where 21 batches of egg shells from a total of 2101 eggs (1.0% [0.63 to 1.56 CI(95)] single egg equivalent) and six batches of contents from 2051 eggs (0.29% [0.11 to 0.64 CI95] single egg equivalent) were contaminated with S. Enteritidis. S. Enteritidis was found in 67/699 (9.6%) of vaccinated spent hens and 64/562 (11.4%) of bulked fresh faecal samples taken from laying houses. Failure to adequately clean and disinfect laying houses and to control mice appeared to be a common feature on the farms.

Eggshell factors influencing eggshell penetration and whole egg contamination by different bacteria, including Salmonella enteritidis

Trans-shell infection routes and whole egg contamination of 7 selected bacterial strains; Staphylococcus warneri, Acinetobacter baumannii, Alcaligenes sp., Serratia marcescens, Carnobacterium sp., Pseudomonas sp. and Salmonella enteritidis, recovered from egg contents, were studied. The first objective was to correlate bacterial eggshell penetration with various eggshell characteristics and bacterial strains. An agar approach was used to assess the eggshell penetration. The second objective was to assess the contamination of whole eggs with the bacterial strains; whole intact eggs were used in this case. The intact shells of agar-filled and whole eggs were inoculated with 10(3) -10(4) cfu of the selected strains. During 3 weeks storage at 20 degrees C and 60% relative humidity, the bacterial eggshell penetration was regularly monitored. The whole egg contamination was only analyzed after 3 weeks. The eggshell characteristics such as area eggshell, shell thickness and number of pores did not influence the bacterial eggshell penetration. For each individual bacterial strain the mean cuticle deposition was lower for penetrated compared to non-penetrated eggshells. For the individual strain Carnobacterium sp. and for the global results of all strains this difference was statistical significantly. The whole egg contamination was not influenced by neither the area of the eggshell nor the porosity of the eggshell. The results of the agar approach indicate that the Gram-negative, motile and non-clustering bacteria penetrated the eggshell most frequently; Pseudomonas sp. (60%) and Alcaligenes sp. (58%) were primary invaders followed by S. enteritidis (43%). All selected strains were able to penetrate; penetration was observed most frequently after ca. 4-5 days. Particularly S. enteritidis was a primary invader of whole eggs: the membranes and/or the content of 32% of the whole eggs was contaminated. The remaining bacterial eggshell contamination with the selected strain was determined after 3 weeks storage. Penetrated eggshells and contaminated whole eggs showed a significantly higher bacterial contamination on the eggshell compared to non-penetrated eggshells and non-contaminated whole eggs respectively (global results of all strains). The influence of hen age on bacterial eggshell penetration and egg content contamination was not significant. While the agar approach is suitable to study the influence of the eggshell characteristics on the bacterial eggshell penetration, the intact egg approach gives an estimation of the penetration of the shell followed by the probability of survival and migration in whole eggs.

Influence of eggshell condensation on eggshell penetration and whole egg contamination with Salmonella enterica serovar enteritidis

Shells of agar-filled and whole eggs were inoculated with 10(3) to 10(4) CFU of Salmonella enterica serovar Enteritidis per eggshell. The agar-filled eggs were used to study bacterial eggshell penetration, and the whole egg results were used to characterize contamination of the egg contents. In each group, half of the eggs were stored for 21 days at 20 degrees C and 60% relative humidity (RH), and the other half was stored for 24 h at 6 degrees C and then for 20 days at 20 degrees C. The latter conditions resulted in condensation on the eggshell for 30 min from the moment the eggs were placed in the 20 degrees C chamber. Taking into account the ages at which hens were studied (39, 53, and 67 weeks), an average of 62% of the eggshells with condensate were penetrated compared with 43% for the control group; this difference was significant (P < 0.01). No significant difference in whole egg contamination was found; 18% of the control eggs were contaminated compared with 22% of the condensate eggs. Whole egg contamination was significantly higher for eggs from the hens at an older age (67 weeks). This difference probably was not due to a higher penetration potential because differences were not observed for the corresponding agar-filled eggs. Condensation on the eggshell seemed to encourage bacterial penetration of the eggshell but had a smaller impact on whole egg contamination.

Eggshell characteristics and penetration by Salmonella enterica serovar Enteritidis through the production period of a layer flock

1. Egg weight, shell thickness, number of pores, cuticle deposition and ability of Salmonella enterica serovar Enteritidis (SE) to penetrate the shell were determined for eggs from one layer flock through the entire production period. 2. Penetration was assessed by filling the eggs with a selective medium that allowed visualising Salmonella growth on the inside of the shell and membrane complex. After inoculation of each shell with on average 2.59 log cfu, the eggs were stored for up to 20 d at 20 degrees C and 60% relative humidity (RH). 3. On average 38.7% of the eggshells became penetrated. Mostly penetration occurred on d 3. Although it affected all shell characteristics studied, hen age did not significantly influence eggshell penetration. 4. No correlations were observed between any of the shell characteristics studied and the ability of SE to penetrate the shell. The growth of SE on the shell is of major importance because shell contamination at 20 d of storage and SE penetration were highly correlated.

Identifying the components in eggshell membrane responsible for reducing the heat resistance of bacterial pathogens

The biological activity (D-value determination) of eggshell membrane (ESM) was examined to determine the membrane components and mechanisms responsible for antibacterial activity. Biological and enzymatic activities (i.e., beta-N-acetylglucosaminidase [beta-NAGase], lysozyme, and ovotransferrin) of ESM denatured with trypsin, lipases, or heat were compared with those of untreated ESM. Trypsin-treated ESM lost all biological activity (D-values at 54 degrees C were 5.12 and 5.38 min for immobilized and solubilized trypsin, respectively) but showed no significant loss of enzymatic activities. Treatments with porcine lipase and a lipase cocktail did not impact biological or enzymatic activities. Heat denaturation of ESM (at 80 and 100 degrees C for 15 min) resulted in significant decreases in biological activity (D-values of 3.99 and 4.43 min, respectively) and loss of beta-NAGase activity. Lysozyme and ovotransferrin activities remained but were significantly reduced. Purified ESM and hen egg white components (i.e., beta-NAGase, lysozyme, and ovotransferrin) were added to Salmonella Typhimurium suspensions (in 0.1% peptone water) at varying concentrations to evaluate their biological activity. D-values at 54 degrees C were 4.50 and 3.68 min for treatment with lysozyme or beta-NAGase alone, respectively, and 2.44 min for ovotransferrin but 1.47 min for a combination of all three components (similar to values for ESM). Exposure of Salmonella Typhimurium cells to a mixture of ovotransferrin, lysozyme, and beta-NAGase or ESM resulted in significant increases in extracellular concentrations of Ca2+, Mg2+, and K+. Transmission electron microscopic examination of Salmonella Typhimurium cells treated with a combination of ovotransferrin, lysozyme, and beta-NAGase revealed membrane disruption and cell lysis. The findings of this study demonstrate that ovotransferrin, lysozyme, and beta-NAGase are the primary components responsible for ESM antibacterial activity. The combination of these proteins and perhaps other ESM components interferes with interactions between bacterial lipopolysaccharides, sensitizing the outer bacterial membrane to the lethal affects of heat and possibly pressure and osmotic stressors.

Microbial health risk posed by table eggs in Trinidad

A survey of the microbial quality of table eggs sold in Trinidad was conducted. For 23 poultry layer farms each visited twice approximately 1 month apart, 25 pooled eggs constituted a composite sample, for 14 shopping malls each visited twice approximately 1 month apart, six pooled eggs made a composite sample and for a total of 102 other retailers across the country each visited once over a 4-month period, six pooled eggs constituted a composite sample. Swabs of egg shells and egg content were tested for selected bacteria. Twenty-four (13.0%), 68 (37.0%), and two (1.1%) of a total of 184 composite eggs (shells, egg content or both) sampled were positive for Salmonella, Escherichia coli, and Campylobacter respectively. All 184 samples tested were negative for Listeria spp. Salmonella was recovered from seven (3.8%) egg shell samples only compared with 14 (7.6%) egg content samples only positive for the pathogen. Fifty-two (28.3%) egg shell samples and seven (3.8%) egg content samples were positive for E. coli. Both isolates of Campylobacter coli originated from egg contents. Of a total of 24 composite egg samples positive for Salmonella, eight different serotypes of Salmonella were isolated from a total of 24 Salmonella-positive composite eggs of which S. Enteritidis was the most prevalent, 58.3% (14/24). Salmonella Georgia was isolated for the first time in Trinidad. Failure to properly handle or heat table eggs sold in Trinidad poses a potential health hazard to consumers because of their poor microbial quality.

The effect of a commercial UV disinfection system on the bacterial load of shell eggs

AIMS

To study the effect of UV irradiation on the bacterial load of shell eggs and of a roller conveyor belt.

METHODS AND RESULTS

The natural bacterial load on the eggshell of clean eggs was significantly reduced by a standard UV treatment of 4.7 s; from 4.47 to 3.57 log CFU per eggshell. For very dirty eggs no significant reduction was observed. Eggs inoculated with Escherichia coli and Staphylococcus aureus (4.74 and 4.64 log CFU per eggshell respectively) passed the conveyor belt and were exposed to UV for 4.7 and 18.8 s. The reduction of both inoculated bacteria on the eggshell was comparable and significant for both exposure times (3 and 4 log CFU per eggshell). Escherichia coli was reduced but still detectable on the conveyor rollers. The internal bacterial contamination of eggs filled up with diluent containing E. coli or S. aureus was not influenced by UV irradiation.

CONCLUSIONS

There is a significant lethal effect of UV irradiation on the bacterial contamination of clean eggshells and recent shell contamination, contamination of rollers can be controlled and the internal contamination of eggs is not reduced.

SIGNIFICANCE AND IMPACT OF THE STUDY

The penetration of UV into organic material appears to be poor and UV disinfection can be used as an alternative for egg washing.

Recovery of Salmonella from commercial shell eggs by shell rinse and shell crush methodologies

Salmonella is the most important human pathogen associated with shell eggs. Salmonella Enteritidis is the serotype most often implicated in outbreaks, although other serotypes have been recovered from eggs and from the commercial shell egg washing environment. Many sample methods are used to recover microorganisms from eggshells and membranes. A shell rinse and modified shell-and-membrane crush method for recovery of Salmonella were compared. Eggs were collected from 3 commercial shell-washing facilities (X, Y, and Z) during 3 visits. Twelve eggs were collected from each of 10 to 12 locations along the egg processing chain. After being transported back to the laboratory, each egg was sampled first by a shell rinse method and then by a shell crush method. For each technique (rinse or crush), 2 pools of 5 eggs per location sampled were selectively enriched for the recovery of Salmonella. Presumptive samples positive for Salmonella were confirmed serologically. Overall, there were 10.1% (40/396) Salmonella-positive pooled samples. Salmonella were recovered by the shell rinse and shell crush techniques (4.8 vs. 5.3%, respectively). Plant X yielded 21.5% Salmonella positives, whereas less than 5% of samples from plants Y and Z were found to be contaminated with the organism (4.2 and 4.5%, respectively). Salmonella was recovered more often from unwashed eggs (15.8%) than from washed eggs (8.3%). For some eggs, Salmonella was only recovered by one of the methods. Use of both approaches in the same experiment increased sampling sensitivity, although in most cases, crushing provided more sensitive Salmonella recovery.

Impact of commercial processing on the microbiology of shell eggs

Shell egg microbiology has been studied extensively, but little information is available on how modern U.S. processing conditions impact microbial populations. As regulations are being drafted for the industry, such information can be important for determining processing steps critical to product safety. Five different shell egg surface microbial populations (aerobic bacteria, yeasts and molds, Enterobacteriaceae, Escherichia coli, and Salmonella) were monitored at 12 points along the processing line (accumulator, prewash rinse, washer 1, washer 2, sanitizer, dryer, oiler, scales, two packer head lanes, rewash entrance, and rewash exit). Three commercial facilities were each visited three times, a total of 990 eggs were sampled, and 5,220 microbiological samples were subsequently analyzed. Although variations existed in concentrations of microorganisms recovered from each plant, the patterns of fluctuation for each population were similar at each plant. On average, aerobes, yeasts and molds, Enterobacteriaceae, and E. coli prevalence were reduced by 30, 20, 50, and 30%, respectively, by the end of processing. The microbial concentrations (log CFU per milliliter) in the egg rinse collected from packer head lanes were decreased by 3.3, 1.3, 1.3, and 0.5, respectively, when compared with those of rinses collected from eggs at the accumulator. Salmonella was recovered from 0 to 48% of pooled samples in the three repetitions. Higher concentrations of Salmonella were recovered from preprocessed than from in-process or ready-to-pack eggs. These data indicate that current commercial practices decrease microbial contamination of egg shell surfaces.

Correlation of eggshell strength and Salmonella enteritidis contamination of commercial shell eggs

Shell quality has been identified as a heritable trait that can be manipulated by genetic selection. Previous research has concluded that many methods of determining shell quality produce variable results. With the development of newer, more precise measuring technologies, shell strength can now be assessed in a consistent, objective fashion. A research project was conducted to determine what role shell strength might play in affecting external Salmonella Enteritidis contamination of egg contents. Visibly clean eggs were collected from an in-line shell egg-processing facility at the accumulator. Eggs were inoculated by dipping in a concentrated suspension of nalidixic acid-resistant Salmonella Enteritidis. After storage, eggs were assessed for shell strength and both external and internal Salmonella Enteritidis contamination. In the first study, there was a significant difference (P < 0.05) in shell strength among the three replicates. No differences between treatments were found for shell strength or Salmonella Enteritidis contamination of contents. In the second study, there were no replicate differences for any of the monitored factors. When rinsate and content samples were enriched, 100% of the rinsates were positive for Salmonella Enteritidis. No content samples were shown to be contaminated with Salmonella Enteritidis during direct plating, but 3 to 5% of the samples from each replicate were positive after enrichment. Correlation analysis of the results from each study found only weak correlations between shell strength and Salmonella Enteritidis contamination on eggshell surface or contents. Within the range of shell strengths recorded in this study, the correlation analysis suggests that shell strength does not play a major role in Salmonella Enteritidis contamination. Further work with eggs that represent a greater range of shell strengths could provide a clearer indication of the interaction of shell strength and Salmonella Enteritidis contamination.

Shell rinse and shell crush methods for the recovery of aerobic microorganisms and enterobacteriaceae from shell eggs

Recovery of bacteria from shell eggs is important for evaluating the efficacy of processing and the quality and safety of the final product. Shell rinse (SR) techniques are easy to perform and widely used. An alternative sampling method involves crushing and rubbing the shell (CR). To determine the most appropriate method for recovering microorganisms from shell eggs, 358 shell eggs were collected from a commercial egg processor and sampled by SR and CR techniques. Total aerobic mesophiles and Enterobacteriaceae were enumerated on plate count and violet red bile glucose agar plates, respectively. Unwashed, in process, and postprocess eggs were evaluated in the study. Aerobic microorganism prevalence for eggshells sampled was similar for both methods (approximately 100%), but the log CFU per milliliter values were higher in the SR than the CR samples (3.2 and 2.2, respectively). Average Enterobacteriaceae recovery was similar for both methods (45 versus 40% for the SR and CR methods, respectively) when all eggs were considered together. This population was detected more often by SR when unwashed eggs were sampled (90 versus 56% for the SR and CR methods, respectively), equally by SR and CR for in-process eggs (30 versus 29.3% for the SR and CR methods, respectively), but more often by CR for postprocess eggs (10 versus 36% for the SR and CR methods, respectively). The SR technique was easier to perform and recovered larger numbers of aerobic organisms, particularly for unwashed eggs. However, the CR technique was more efficient for recovery of Enterobacteriaceae from postprocess eggs. Stage of shell egg processing may be an important consideration when choosing egg sampling methods.

Genotypic and phenotypic characteristics of Yersinia enterocolitica isolated from the surface of chicken eggshells obtained in Argentina

The prevalence of Yersinia enterocolitica on chicken eggshell surfaces in San Luis, Argentina, was investigated. The pathogenic potential of recovered isolates was assessed by means of phenotypic virulence tests and the presence of the 72-kb pYV plasmid. Antimicrobial susceptibility was determined by the agar diffusion method. DNA digested with XbaI was analyzed by pulsed-field gel electrophoresis (PFGE), and relationships between genomic DNA profiles were established. Eight Y. enterocolitica B2 O:9 strains were recovered after enrichment, for a prevalence of 2.27%. All strains harbored the virulence pYV plasmid, bound Congo red, grew in a low-calcium medium, and autoagglutinated at 37 degrees C. They lacked pyrazinamidase activity and did not hydrolyze esculin. These Y. enterocolitica strains were susceptible to amikacin, ciprofloxacin, chloramphenicol, and trimethoprim-sulfamethoxazole and were resistant to rifampin. According to the genomic DNA patterns obtained by PFGE, the isolates clustered into two groups, I and II. The highest similarity coefficient observed between Y. enterocolitica strains was 0.947. Microbiological controls on production stages of eggs and good culinary practices are necessary to reduce the risk of Y. enterocolitica infection for consumers.

Bacterial eggshell contamination in conventional cages, furnished cages and aviary housing systems for laying hens

The influence of housing system on the initial bacterial contamination of the eggshell was studied. Two long-term experiments were performed. Bacterial eggshell contamination, as expressed by total count of aerobic and Gram-negative bacteria, was periodically analysed for eggs from a conventional cage, a furnished cage with nest boxes containing artificial turf or grids as nest-floor material and an aviary housing system. Results were log-transformed prior to statistical analyses. For both experiments no systematic differences were found between the conventional cage and furnished cage. The type of nest-floor material in the nest boxes of the furnished cages also did not systematically influence the bacterial contamination. A possible seasonal influence on contamination with a decrease in the winter period (up to > 0.5 log cfu/eggshell) of total count of aerobic and Gram-negative bacteria was observed in the first experiment. The contamination with total aerobic flora was higher (more than 1.0 log) on eggs from the aviary housing system compared to the conventional and the furnished cage systems. For Gram-negative bacteria this was not the case. During the entire period of both experiments, independent of housing system, shell contamination was not influenced by age of hens or period since placing the birds in the houses. For the total count of aerobic bacteria a restricted positive correlation (r2 = 0.66) was found between the concentration of total bacteria in the air of the poultry houses and initial shell contamination.