The eggshell quality of table eggs and how this affects food safety

The longitudinal effect of age and production system was evaluated for egg quality parameters and egg microbial load by following 2 flocks (Hy Line brown commercial layer), one conventional cage production system (CC) and one free range (FR). A horizontal study of the effect of flock age (22, 39, 55 and 79 wk) of the same strain of bird from the same CC was also evaluated for egg quality parameters and egg microbial load. From the CC and FR production systems, eggs were collected at the age of 25, 35, 45, 55, 65 and 75 wk with one extra collection at 85 wk from CC. For the eggshell and egg internal quality parameters, a significant main effect (

In vivo passage of Salmonella Typhimurium results in minor mutations in the bacterial genome and increases in vitro invasiveness

International audienceAbstractEggs and raw or undercooked egg-containing food items are frequently identified as the bacterial source during epidemiolocal investigation of Salmonella outbreaks. Multi-locus variable number of tandem repeats analysis (MLVA) is a widely used Salmonella typing method enabling the study of diversity within populations of the same serotype. In vivo passage, however, has been linked with changes in MLVA type and more broadly the Salmonella genome. We sought to investigate whether in vivo passage through layer hens had an effect on MLVA type as well as the bacterial genome and whether any mutations affected bacterial virulence. Layer hens were infected with either Salmonella Typhimurium DT9 (03-24-11-11-523) as part of a single infection or were co-infected with an equal amount of Salmonella Mbandaka. Salmonella shedding in both single and co-infected birds was variable over the course of the 16-week experiment. Salmonella Typhimurium and Salmonella Mbandaka were identified in feces of co-infected birds. Salmonella colonies isolated from fecal samples were subtyped using MLVA. A single change in SSTR-6 was observed in Salmonella Typhimurium strains isolated from co-infected birds. Isolates of Salmonella Typhimurium of both the parent (03-24-11-11-523) and modified (03-24-12-11-523) MLVA type were sequenced and compared with the genome of the parent strain. Sequence analysis revealed that in vivo passaging resulted in minor mutation events. Passaged isolates exhibited significantly higher invasiveness in cultured human intestinal epithelial cells than the parent strain. The microevolution observed in this study suggests that changes in MLVA may arise more commonly and may have clinical significance

The Relationship of Eggshell Structure to Eggshell Penetration by 'Salmonella' Typhimurium in Table Eggs

This project sought to correlate external shell features with underlying shell structures and examine if these structures are indicative of increased incidence of eggshell penetration by Salmonella Typhimurium. Eggs are an important nutrient and protein source in most cultures around the world, and the importance of food safety in intensive food production industries is likely to increase. Microbial infection of eggs is the source of approximately 49% of Salmonella food poisoning cases in Australia each year. The most significant source of these infections in Australia is Salmonella Typhimurium. Eggshell translucency is a phenomenon observed when an egg is candled over a light source; the underlying cause and incidence of eggshell translucency form the basis of our investigations of shell structures. In order to image eggshell structure, both Computed Tomography and Scanning Electron Microscopy were used to examine different structural components of the shell

PCR-based detection of genes encoding virulence determinants in Staphylococcus aureus from bovine subclinical mastitis cases

The present study was carried out to genotypically characterize Staphylococcus aureus (S. aureus) isolated from bovine mastitis cases. A total of 37 strains of S. aureus were isolated during processing of 552 milk samples from 140 cows. The S. aureus strains were characterized phenotypically, and were further characterized genotypically by polymerase chain reaction using oligonucleotide primers that amplified genes encoding coagulase (coa), clumping factor (clfA), thermonuclease (nuc), enterotoxin A (entA), and the gene segments encoding the immunoglobulin G binding region and the X region of protein A gene spa. All of the isolates yielded an amplicon with a size of approximately 1,042 bp of the clfA gene. The amplification of the polymorphic spa gene segment encoding the immunoglobulin G binding region was observed in 34 isolates and X-region binding was detected in 26 isolates. Amplification of the coa gene yielded three different products in 20, 10, and 7 isolates. The amplification of the thermonuclease gene, nuc, was observed in 36 out of 37 isolates. All of the samples were negative for the entA gene. The phenotypic and genotypic findings of the present strategies might provide an understanding of the distribution of the prevalent S. aureus clones among bovine mastitis isolates, and might aid in the development of steps to control S. aureus infections in dairy herds

Egg quality and food safety of table eggs: Egg quality and age of flock - A horizontal study

Eggs were collected from commercial caged layer flocks in early, mid, late and very late lay. Eggs were candled and scored for translucency. Cuticle cover was estimated using MST cuticle stain and a Konica Minolta hand-held spectrophotometer. Traditional measures of egg quality were determined using specialised equipment (TSS, U.K.) Shell ultrastructural features were scored following plasma ashing of shell samples and viewing under a benchtop scanning electron microscope. Translucency tended to be higher in late lay flocks and shell quality was lower. Cuticle cover was relatively uniform for young flocks but much more variable in older flocks. The incidence of unfavourable shell ultrastructural features was higher for older flocks. This study is on-going so, as the sample size increases, new insights will be obtained

Ultrastructural changes in the oviduct of the laying hen during the laying cycle

The ultrastructural changes occurring in the fully functional oviduct of Isa Brown laying hens were studied during various stages of the laying cycle. Hens were killed at different positions of the egg in the oviduct. The oviduct was lined by ciliated and non-ciliated cells (also referred to as granular cells). The granular cells in the infundibulum contributed to secretion during egg formation, whereas ciliated cells showed little evidence of secretion. Ultrastructural changes were recorded in the granular and glandular cells of the distal infundibulum. In the magnum, the surface ultrastructure revealed glandular openings associated with the ciliated and granular cells. Cyclic changes were recorded in the glandular cells of the magnum. With respect to the three observed types of glands, the structure of gland type A and C cells varied at different egg positions in the oviduct, whereas type B cells represented a different type of gland cell containing amorphous secretory granules. The surface epithelium of the isthmus was also lined by mitochondrial cells. Two types of glandular cell (types 1 and 2) were recorded in the isthmus during the laying cycle. Intracisternal granules were found in type 2 cells of the isthmus. A predominance of glycogen particles occurred in the tubular shell gland. The granular cells in the shell gland contain many vacuoles. During egg formation, these vacuoles regressed following the formation of extensive rough endoplasmic reticulum; the reverse also occurred. The disintegrated material found in the vacuoles may have been derived from the disintegrating granules

Pathogenesis of two strains of infectious bronchitis virus for the oviduct of unvaccinated laying hens

The pathogenesis of Infectious Bronchitis Virus (IBV) for different parts of the oviduct was studied in unvaccinated Isa Brown laying hens exposed to T and N1/88 strains of IBV. Two hens from T and one hen from N1/88 infected groups went out of lay. Ultrastructural findings revealed that the infundibulum and magnum were more negatively affected than the isthmus, tubular shell gland and shell gland pouch. However, all parts of the oviduct of hens out of lay showed severe cytopathology. Overall, T strain was more pathogenic for the fully functional oviduct than N1/88. Virus particles were recorded on the 10th day p.i. and severe cytopathology was observed between 10 and 12 days p.i

Egg Quality and Food Safety of Table Eggs: Egg Quality and Age of Flock - A Horizontal Study

Eggs were collected from commercial caged layer flocks in early, mid, late and very late lay. Eggs were candled and scored for translucency. Cuticle cover was estimated using MST cuticle stain and a Konica Minolta hand-held spectrophotometer. Traditional measures of egg quality were determined using specialised equipment (TSS, U.K.) Shell ultrastructural features were scored following plasma ashing of shell samples and viewing under a benchtop scanning electron microscope. Translucency tended to be higher in late lay flocks and shell quality was lower. Cuticle cover was relatively uniform for young flocks but much more variable in older flocks. The incidence of unfavourable shell ultrastructural features was higher for older flocks. This study is on-going so, as the sample size increases, new insights will be obtained

Effects of Australian strains of infectious bronchitis virus on internal and external quality of hen eggs

The effects of two Australian strains of infectious bronchitis virus (IBV-T and N1/88) on the internal and external quality of eggs were studied in unvaccinated Isa Brown hens in full lay. Overall, there was no decline in egg production in either of the infected groups. However, there were some long-lasting negative effects on the egg internal quality of T-infected hens. Negative effects on internal quality in the N1/88-infected group were relatively short term. Yolk colour score was lower only in T-infected hens. Egg shell quality was affected only in terms of loss of egg shell colour. IBV infection resulted in paler egg shells in both the infected groups. Paler egg shells may not be regarded well by consumers. The egg shape index was lower in both infected groups