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

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

Effects of two strains of infectious bronchitis virus on unvaccinated laying hens

Preliminary studies were conducted on unvaccinated laying hens to investigate the effects of two strains of infectious bronchitis virus (T strain and N1/88 strain) on unprotected birds during lay. Clinical symptoms associated with the respiratory system were observed in the T-strain and N-strain groups but not the control and some birds in the T-strain group had enlarged kidneys. Feed intake tended to be depressed in the challenged birds at one week post-challenge and production was reduced in the T-strain group at 3 weeks post-challenge. However, there were relatively few effects of challenge on egg quality except that yolk colour was depressed in the T-strain group. There were no significant effects on excreta moisture for any group. IBV antibody titres increased in response to challenge in the T-strain group but only some challenged birds produced antibodies in the N-strain group within 3 weeks post-challenge. Virus was re-isolated from the kidneys of T-strain birds at all sampling times post-challenge but only at 6-16 days for the N-strain group. Sequential histopathological changes revealed that IBV multiplies initially in the Harderian gland, then in the tracheal mucosa and simultaneously in the kidney and oviduct. The severity and persistence of lesions were greater in the shell gland and kidney of T infected birds whereas, in the trachea and Harderian gland, the effects of the two IBV strains were similar. N1/88 seemed to be more pathogenic for the magnum region of the oviduct

Egg and eggshell quality during experimental IBV infection in unvaccinated laying hens

The effect of two strains of infectious bronchitis virus (IBV-T and N1/88 strains) on internal and external quality of eggs was studied in unvaccinated Isa Brown hens in full lay. Overall, there was no decline in egg production in either of the infected groups. Long-lasting effects were observed on egg internal quality of T strain-infected hens. Effects on internal quality in the N1/88 strain-infected group were more short term. The only significant effect of IBV infection on shell quality measurements was paler egg shells from the T-infected birds for the first 5 weeks post-infection

Ultrastructural study of infectious bronchitis virus infection in infundibulum and magnum of commercial laying hens

The infundibulum and magnum of the oviduct were examined in hens in full lay which were infected with two Australian strains of infectious bronchitis virus (IBV). The ultramicroscopic changes in the infundibulum and magnum were compared with control hens which had eggs at different positions in the oviduct. The ciliated and granular cells of the surface epithelia and secretory epithelial cells of the tubular glands were the target cells of IBV. No pathological changes were recorded during 2–8 days post-infection (p.i.). Patchy loss of cilia occurred at 10–14 days p.i. Between 16 and 24 days p.i., there was no cilia loss and lymphoid nodules were observed in the muscularis layer of the infundibulum and magnum of some hens from both infected groups. Virus particles were detected mostly in the rough endoplasmic reticulum (RER) and Golgi complex between 10 and 12 days p.i. Cytopathology was noticed in various cell organelles between the 10th and 14th days p.i. There was an increase in RER deposits in infected cells, irrespective of egg position in the oviduct. The magnum was more affected than the infundibulum. Cellular changes were more severe in the infundibulum and magnum of T-infected hens as compared to N1/88-infected hens. Eggs with watery whites which were laid by infected hens could be attributed to cytopathological changes in the granular epithelial cells and tubular gland epithelial cells of the magnum resulting in reduced synthesis of albumen proteins. IBV can cause pathology in parts of the fully functional oviduct which may persist up to the 30th day p.i. However, both the challenge strains of IBV can cause a small number of hens to cease production. Loss of cilia in both the infundibulum and magnum pose a potential threat of secondary bacterial infection and also may affect fertility in breeder hens