Eggshell Contamination Research Articles

Determination of Salmonella in egg shell and egg content in some selected areas of Bangladesh

Salmonellosis is one of the most common and widely distributed food-borne diseases. It constitutes a major public health burden and represents a significant cost in many countries. Salmonella are known for its wide range host and can cause clinical diseases in some hosts while in others, can be asymptomatic. Poultry and eggs are considered as major sources for different pathogenic Salmonella serotypes. Eggs produced locally under the small scale layer farm may present a hazard to consumers which may increase the spread of Salmonella in the environment. To investigate the occurrence of Salmonella, a total of 72 samples were taken from 6 poultry farm in some selected areas of Bangladesh. Sampling program was executed between October and December, 2013 and samples were tested using standard laboratory methods. Data was collected through direct interview and structured questionnaire. Our study shows that, true prevalence of Salmonella in egg shell and egg contents were 0.093% and 0.068% respectively. The highest apparent prevalence in Udayan poultry farm (50%) and lowest in Liza poultry farm (16.67%). The average frequency of egg shell contamination is positively correlated with re-use of egg tray without disinfection. To the best of our knowledge, this is the first investigation on Salmonella spp. in selected local egg production farms in Chittagong. Further detail study is highly recommended.International Journal of Natural Sciences (2015), 5(2) 66-72

A multi-pronged approach to the search for an alternative to formaldehyde as an egg disinfectant without affecting worker health, hatching, or broiler production parameters

Research was carried out to determine the effectiveness of 4 hatching eggs disinfection processes (i.e., disinfecting products and administration method) using a multi-pronged approach assessing the reduction of microbial eggshell contamination, the effects on worker exposure, hatching results and broiler performance, and, finally, suitability for use in commercial hatcheries. The 4 disinfection processes were: sodium dichlorocyanurate (DC) by thermonebulization, hydrogen peroxide 6% by nebulization (HP6), electrolyzed oxidizing water (EOW) by fogging, and hydrogen peroxide 30% vapor (HP30). In order to meet commercial hatchery conditions, the tested products were applied in an experimental hatchery by aerial disinfection in a dedicated room, not sprayed directly onto the eggs. Compared to the untreated control group, eggshell microbial load was significantly decreased by over 1 log10 cfu per egg in groups DC and HP30. These results were confirmed during a second experiment. In addition, these 2 products comply with legal requirements on worker exposure. Fertility and hatching results were significantly higher in group HP30 than in group DC, with no impact on chick quality and subsequent broiler performance. Under these study conditions, the disinfection process (i.e., administration of the product, contact with the eggs and aeration) lasted 65 min in group DC vs. 135 min in group HP30. When considering commercial hatchery conditions, this difference in application time confers a clear advantage on the DC process. Moreover, the investment required for HP30 is much higher than for DC. Overall, HP30 presented a clear advantage for hatching results whereas DC is a relatively more practical and less expensive disinfection process. To our knowledge, this is the first report on the use of hydrogen peroxide vapor as an egg disinfection process. Further research is needed to confirm the results of this study under commercial hatchery conditions.

Study of Salmonella Typhimurium Infection in Laying Hens

Members of Salmonella enterica are frequently involved in egg and egg product related human food poisoning outbreaks worldwide. In Australia, Salmonella Typhimurium is frequently involved in egg and egg product related foodborne illness and Salmonella Mbandaka has also been found to be a contaminant of the layer farm environment. The ability possessed by Salmonella Enteritidis to colonize reproductive organs and contaminate developing eggs has been well-described. However, there are few studies investigating this ability for Salmonella Typhimurium. The hypothesis of this study was that the Salmonella Typhimurium can colonize the gut for a prolonged period of time and that horizontal infection through feces is the main route of egg contamination. At 14 weeks of age hens were orally infected with either S. Typhimurium PT 9 or S. Typhimurium PT 9 and Salmonella Mbandaka. Salmonella shedding in feces and eggs was monitored for 15 weeks post-infection. Egg shell surface and internal contents of eggs laid by infected hens were cultured independently for detection of Salmonella spp. The mean Salmonella load in feces ranged from 1.54 to 63.35 and 0.31 to 98.38 most probable number/g (MPN/g) in the S. Typhimurium and S. Typhimurium + S. Mbandaka group, respectively. No correlation was found between mean fecal Salmonella load and frequency of egg shell contamination. Egg shell contamination was higher in S. Typhimurium + S. Mbandaka infected group (7.2% S. Typhimurium, 14.1% S. Mbandaka) compared to birds infected with S. Typhimurium (5.66%) however, co-infection had no significant impact on egg contamination by S. Typhimurium. Throughout the study Salmonella was not recovered from internal contents of eggs laid by hens. Salmonella was isolated from different segments of oviduct of hens from both the groups, however pathology was not observed on microscopic examination. This study investigated Salmonella shedding for up to 15 weeks p.i which is a longer period of time compared to previously published studies. The findings of current study demonstrated intermittent but persistent fecal shedding of Salmonella after oral infection for up to 15 weeks p.i. Further, egg shell contamination, with lack of internal egg content contamination and the low frequency of reproductive organ infection suggested that horizontal infection through contaminated feces is the main route of egg contamination with S. Typhimurium in laying hens.

Vaccination of chickens decreased Newcastle disease virus contamination in eggs

Newcastle disease is an important health issue of poultry causing major economic losses and inhibits trade worldwide. Vaccination is used as a control measure, but it is unknown whether vaccination will prevent virus contamination of eggs. In this study, hens were sham-vaccinated or received one or two doses of inactivated LaSota vaccine, followed three weeks later by virulent Newcastle disease virus (NDV) challenge. Eggs were collected daily and shell, albumen and yolk were subjected to virus isolation, as were oral and cloacal swabs at 2 and 4 days post-challenge (dpc). A second experiment evaluated the distribution of the virus in the reproductive tract of non-vaccinates. All vaccinated chickens survived challenge, and the levels of virus shed from cloacal swabs were decreased significantly when compared to shams. In non-vaccinated hens, virus was detected in the ovary and all segments of the oviduct. Yolk, albumen and eggshell surface from eggs laid at day 4 and 5 post-infection by sham-vaccinated hens were positive for NDV, but eggs from LaSota vaccinated hens lacked virus in internal egg components (i.e. yolk and albumen) and had reduction in the number of positive eggshell surfaces. These results indicate virulent NDV can replicate in the reproductive tract of hens and contaminate internal components of eggs and eggshell surface, but vaccination was able to prevent internal egg contamination, reducing eggshell surface contamination, and reducing shedding from digestive and respiratory tracts in virulent NDV challenged hens.

Effect of light colour on egg production and egg contamination

The objective of this study was to compare the performance of laying hens, quality of air in poultry house, and microbial contamination of eggshell in laying hens kept under blue, green, red, and yellow light colour in enriched cages. The daily photoperiod consisted of 15 h light, light intensity of 10 lx at bird head level. The laying performance characteristics (hen-day egg production, mortality, and egg weight) were not affected by light colour. Similarly, microbial contamination of the air was not significantly different related to the light colour. There were significant interactions in eggshell contamination between the position of the cage floor and light colour in Escherichia coli (P ≤ 0.042) and Enterococcus (P ≤ 0.019). The highest number of Escherichia coli was detected in eggs from hens housed on the middle floor given yellow light (6.06 log colony forming units (cfu)/eggshell) and the lowest values (3.30 log cfu/eggshell) on the upper floor also under yellow light colour. Similar results were observed in Enterococcus, where the highest contamination was on the middle floor under yellow light colour (5.26 log cfu/eggshell), while the lowest contamination (2.45 log cfu/eggshell) was found on the upper floor under blue colour. The results of our study indicate that the light colour has a minor effect on microbial contamination but the significant influence was in the floor position. The highest microbial egg contamination was found on eggs from the middle floor.

Effect of different feeding schedules on reproductive parameters and egg quality of broiler breeders

This experiment was carried out to evaluate the effects of three feeding schedules on egg production and egg quality of broiler breeders. The feeding schedules were: a single feeding at 8:00a.m.; twice daily feeding (50% at 8:00a.m. and 50% at 3:00p.m.) and single feeding at 3:00p.m. The total, 546 females and 63 males Cobb 500 broiler breeders were used from 28 to 40 weeks of age. The experimental design was completely randomized, with 3 treatments of 7 replicates with 26 females and 3 males. The nutritional requirements and management were according to the recommendations of the guideline. The following parameters were assessed weekly: total egg production, hatchable eggs, egg specific gravity, weight of egg shell, yolk, and albumen, as well as eggshell thickness. To measure the egg shell contamination was evaluated the aerobic mesophilic bacteria and total coliforms at 28, 32 and 36 week of age. Twenty three incubations were performed to evaluate fertility and incubation parameters. Laying rate was determined by 6 daily collections over the experimental period. Broiler breeders fed once in the afternoon had lower egg production than others feeding schedules. Hens fed once the afternoon had higher specific gravity (P=0.0063), shell weight (P=0.0009) and eggshell thickness (P=0.0001) than others. Similarly, hens fed once in the afternoon had more egg (P=0.0022) and yolk weight (P=0.0314) than hens fed in the morning. On the other hand, hens fed in the morning had the lowest embryonic mortality and increased hatchability of fertile egg. Broiler breeders fed at the late period of day had better parameters on eggs quality, no change on bacterial contamination than the others feeding schedules, however, it had the worst results in the embryonic mortality and hatchability of eggs.

DIAGNOSIS OF EGG MARKETING CONDITION IN SINOP - MT

The eggs, when manipulated in inadequate sanitary conditions, are considered as ways for development and multiplication of spoilage and pathogenic microorganisms. Thus, the objective was to evaluate the microbiological quality of eggs marketed out at Sinop – MT, through the identification of Salmonella spp., count of aerobic mesophile bacteria and enterobacteria. We collected 12 eggs from each establishment, three supermarkets and three fairs. Were not identified Salmonella spp. in egg shells and internal content. Escherichia coli was isolated from the internal contents of eggs come from an street fair. In aerobic mesophilic counts were obtained from eggs supermarkets counts CFU/g/egg shell of 5,8 x 10 5 , 1,21 x 10 5 e 4,7 x 10 3 . In relation to the fairs, the counts were 7,2 x 10 4 , 5,66 x 10 4 e 8,7 x 10 3 . The absence of Salmonella spp. the evaluated eggs classifies them as fit for consumption for compliance with current legislation. However, the presence of E. coli and the values of aerobic mesophilic counts and Enterobacteriaceae highlight the need to establish measures to reduce bacterial contamination of shell eggs sold out at Sinop, MT.

Characterization of Salmonella from Commercial Egg-Laying Hen Farms in a Central Region of Colombia.

Salmonellosis affects humans more frequently than any other foodborne disease, and it causes severe economic losses in the poultry industry. A cross-sectional study was carried out to estimate the prevalence of Salmonella spp. in laying hen farms in the Tolima region of Colombia. Fifteen egg-laying hen farms were sampled, and a total of 589 samples were cultured to isolate Salmonella spp. A total of 14 isolates of Salmonella spp. were recovered from five farms, resulting in a prevalence of 33.33% (95%, confidence interval = 14%-53%) at the farm level. Salmonella spp. were recovered from eggshells (57.15%, n = 8), feed (28.57%, n = 4), and environmental samples (14.29%, n = 2). Farm practices, such as the milling of feed (odds ratio [OR] = 24) and the storage of eggs in the henhouses (OR = 11.25), in addition to the feed type (OR = 7.64) and the use of bamboo for construction of the facility (OR = 5.24), were identified as risk factors for Salmonella spp. The 14 isolates were identified as Salmonella Enteritidis (n = 6) and Salmonella Shannon (n = 8), and both serovars were resistant to a number of antibiotics. Pulsed-field gel electrophoresis presented three different XbaI macrorestriction patterns. The Salmonella Enteritidis isolates all presented a single pattern, whereas the Salmonella Shannon isolates were grouped into two distinct patterns. The results indicate that Salmonella spp. could be recovered from various sources at laying hen farms, and eggshell contamination is a particular concern.

Isolation of Some Bacterial Contamination of Egg Shell and yolk in Najaf governante

A total of 60 eggs collected from different sources including small farms (15 eggs), large farms (15 eggs), road side vendors (15 eggs) and supermarkets (15 eggs) were cultured for the bacteria in Najaf governante, Bacteria on egg shells have been implicated as a source of bacterial contamination and some of them Proteus spphas been implicated in food poisoning, E.coli and Salmonella spp have been found inegg shell and yolk .The family Enterobacteriaceaewere obtained with a higher proportion from shell membrane (54.4%) than from yolk samples (45.6%). There was no significant difference (P< 0.05) in the number of isolates between various sources indicating the contamination at farm level.

Effects of laying hens housing system on laying performance, egg quality characteristics, and egg microbial contamination

The objective of this study was to compare the performance, egg quality, and microbial contamination of egg shells from hens maintained in different housing systems, such as conventional and enriched cages, litter, and aviaries. The housing system significantly (P < 0.001) influenced the performance characteristics. The highest egg production, lowest daily feed consumption, and feed conversion ratio were measured in conventional cages compared to litter and aviaries. Higher egg shell and albumen qualities were observed in conventional cages, whereas hens housed in enriched cages and aviaries laid eggs with a higher yolk index (P < 0.001). The housing system significantly (P < 0.001) influenced the total count of bacteria on the egg surface and the microbial contamination of Enterococcus and Escherichia coli. The lowest values for the total count of bacterial contamination (P < 0.001) were found in eggs from conventional cages (4.05 log colony-forming units (CFU)/egg) and enriched cages (3.98 log CFU/egg). Eggs from aviaries had 5.49 log CFU per egg, and the highest level of contamination was observed in eggs that were laid on litter (6.24 log CFU/egg). The level of the microbial contamination of egg shells from litter and aviaries was by 2 log CFU higher than in eggs from cages. It could be concluded, from the viewpoint of egg safety, a more suitable substitute for conventional cages are enriched cages and aviaries than litter.  

Identifying risk factors for eggshell contamination by Bacillus cereus group bacteria in French laying farms

1. The growth of Bacillus cereus group bacteria often limits the shelf-life of pasteurised liquid egg products and is also a putative toxin producer. This study was performed to better understand the route of contamination by B. cereus in egg products by studying the factors affecting eggshell contamination on-farm. 2. Eggs were collected in warm and cold seasons in 50 conventional laying farms in Western France. Egg surfaces were analysed for the presence of B. cereus group bacteria, environmental measurements were recorded and production practices were identified through a questionnaire filled out by the farmers. 3. A total of 44% of the farms were contaminated by mesophilic and 10% by psychrotrophic B. cereus group bacteria. No significant effect of the season was observed, whatever the thermal type. Several procedures were associated with reduced eggshell contamination by mesophilic bacteria, including the limitation of dust formation from manure and feeding and efficient disinfection of the silo, houses and the sanitary wall between houses. 4. The research highlights the need to promote prevention strategies, from farm to fork, for the control of eggshell and putative subsequent egg product contamination by B. cereus group bacteria.

Estimation of the Rate of Egg Contamination from Salmonella‐Infected Chickens

Salmonella enterica serovar Enteritidis (S. Enteritidis) is one of the most prevalent causes for human gastroenteritis and is by far the predominant Salmonella serovar among human cases, followed by Salmonella Typhimurium. Contaminated eggs produced by infected laying hens are thought to be the main source of human infection with S. Enteritidis throughout the world. Although previous studies have looked at the proportion of infected eggs from infected flocks, there is still uncertainty over the rate at which infected birds produce contaminated eggs. The aim of this study was to estimate the rate at which infected birds produce contaminated egg shells and egg contents. Data were collected from two studies, consisting of 15 and 20 flocks, respectively. Faecal and environmental sampling and testing of ovaries/caeca from laying hens were carried out in parallel with (i) for the first study, testing 300 individual eggs, contents and shells together and (ii) for the second study, testing 4000 eggs in pools of six, with shells and contents tested separately. Bayesian methods were used to estimate the within-flock prevalence of infection from the faecal and hen post-mortem data, and this was related to the proportion of positive eggs. Results indicated a linear relationship between the rate of contamination of egg contents and the prevalence of infected chickens, but a nonlinear (quadratic) relationship between infection prevalence and the rate of egg shell contamination, with egg shell contamination occurring at a much higher rate than that of egg contents. There was also a significant difference in the rate of egg contamination between serovars, with S. Enteritidis causing a higher rate of contamination of egg contents and a lower rate of contamination of egg shells compared to non-S. Enteritidis serovars. These results will be useful for risk assessments of human exposure to Salmonella-contaminated eggs.

HOTAIR TREATMENT, IN NATURAL CONVECTION CONDITIONS, FOR EGG SURFACE DECONTAMINATION

In order to improve the animal welfare, the Council Directive 1999/74/EC (defining minimum standards for the welfare of laying hens) will ban conventional cage systems from 2012, in favor of enriched cages or floor systems. As a consequence an increased risk of bacterial contamination of eggshells is expected. This has lead toward the development of efficient techniques to reduce eggshell contamination by bacterial pathogens, and thus to prevent any potential or additional food safety risk for Human health. The objectives of this research were to develop and validate a numerical model useful to study the physics of treatment with hot air, in natural convection conditions, and then to assess the impact of the treatment on egg quality and Salmonella Enteritidis inactivation on the shell. As regards the decontamination effectiveness, a reduction in microbial load up to 2.6 log10 after 200 minutes was observed. A linear correlation between the time of treatment and the microbial decimal reduction (R2 0.92) was also observed. This suggests the opportunity of further study with longer treatment. Moreover the results about weak action on quality parameters suggest the practical feasibility of a transportation system for eggs, from production to sorting plant, in heated container.

HOT AIR TREATMENT, IN NATURAL CONVECTION CONDITIONS, FOR EGG SURFACE DECONTAMINATION

In order to improve the animal welfare, the Council Directive 1999/74/EC (defining minimum standards for the welfare of laying hens) will ban conventional cage systems from 2012, in favor of enriched cages or floor systems. As a consequence an increased risk of bacterial contamination of eggshells is expected. This has lead toward the development of efficient techniques to reduce eggshell contamination by bacterial pathogens, and thus to prevent any potential or additional food safety risk for Human health. The objectives of this research were to develop and validate a numerical model useful to study the physics of treatment with hot air, in natural convection conditions, and then to assess the impact of the treatment on egg quality and Salmonella Enteritidis inactivation on the shell. As regards the decontamination effectiveness, a reduction in microbial load up to 2.6 log10 after 200 minutes was observed. A linear correlation between the time of treatment and the microbial decimal reduction (R2 0.92) was also observed. This suggests the opportunity of further study with longer treatment. Moreover the results about weak action on quality parameters suggest the practical feasibility of a transportation system for eggs, from production to sorting plant, in heated container.

Cage hygiene, laying location, and egg quality: The effects of linings and litter provision in furnished cages for laying hens

This study investigates the influence of litter provision and linings used for nests and pecking and scratching areas on cage hygiene, laying location, and egg quality. Research was carried out in furnished cages, each housing 60 beak-trimmed ISA Brown hens. Four different treatments were compared in a factorial arrangement, including 2 different nest linings (artificial turf vs. plastic mesh), either used alone or combined with the use of litter (wheat bran) spread over the rubber mat in the pecking and scratching area (PSA). An additional treatment, using artificial turf mat in the PSA and nests (as commonly used in commercial flocks), was used to compare the effect of PSA lining in the other treatments. We observed laying location, the number of dirty and broken eggs, the microbiological contamination of eggshells according to laying location, and general cage hygiene. The use of nests for laying decreased when they were lined with plastic mesh. Eggs laid outside the nest were of lower quality than those laid inside it, and this was particularly true for eggs laid in the PSA. Although hygiene was low on artificial turf mats, eggs laid on PSA covered with a rubber mat were dirtier and had a higher count of mesophilic bacteria on the eggshell than those laid on PSA covered with an artificial turf mat. Rubber mats in PSA were rapidly destroyed and proved to be unsuitable. The provision of litter had no effect on cage hygiene but substantially increased wear on mats. This study shows nest lining and litter provision methods to be key factors that need to be taken into account to encourage the use of nest boxes for laying, and hence, to ensure good egg quality. Further research into new linings for PSA is needed for the future improvement of egg-laying conditions.

Possible horizontal transmission of Salmonella via reusable egg trays in Thailand

Salmonella contamination of eggshells, egg contents, reusable egg trays, and various environmental samples was assessed. Although the overall Salmonella contamination rate from egg farms was low (3.2%), over a quarter (26.7%) of egg trays from farms and more than one third (36.7%) of trays from the market were contaminated. Salmonella strains isolated from reusable egg trays were analyzed by serotyping, antimicrobial susceptibility test and XbaI pulsed-field gel electrophoresis (PFGE) typing. Five serovars (S. Braenderup, S. Emek, S. Weltevreden, S. Stanley, and S. Derby) were isolated, and half of the strains assessed were found to be resistant to one or more of the six antimicrobial agents examined. The overall resistance rates to nalidixic acid, trimethoprim-sulfamethoxazole, tetracycline, and ampicillin were 40.7%, 36.0%, 26.7% and 3.5%, respectively. The PFGE types were matched against sample location and drug resistance. S. Braenderup PFGE type A2 (susceptible to all tested drugs) was isolated from all sample sites; PFGE type A2 (resistant to nalidixic acid) was isolated from Farm C and the market. S. Braenderup PFGE type A1 (resistant to four drugs) was isolated from Farms A and C. S. Weltevreden PFGE type C3 (susceptible to all tested drugs) was isolated from Farms A and B and type C4 (susceptible to all tested drugs) was isolated from Farm A and the market. The distribution of the related genotypes and resistance patterns of Salmonella in egg farms and the market indicate drug-resistant strains of Salmonella may be spread on reusable egg trays.

Deletion of theaceEgene (encoding a component of pyruvate dehydrogenase) attenuatesSalmonella entericaserovar Enteritidis

Salmonella enterica serovar Enteritidis (S. Enteritidis) is a major food-borne pathogen. From a transposon insertion mutant library created previously using S. Enteritidis 10/02, one of the mutants was identified to have a 50% lethal dose (LD(50) ) at least 100 times that of the parental strain in young chicks, with an attenuation in a poorly studied gene encoding a component of pyruvate dehydrogenase, namely the aceE gene. Evaluation of the in vitro virulence characteristics of the ΔaceE∷kan mutant revealed that it was less able to invade epithelial cells, less resistant to reactive oxygen intermediate, less able to survive within a chicken macrophage cell line and had a retarded growth rate compared with the parental strain. Young chicks vaccinated with 2 × 10(9) CFU of the ΔaceE∷kan mutant were protected from the subsequent challenge of the parental strain, with the mutant colonized in the liver and spleen in a shorter time than the group infected with the parental strain. In addition, compared with the parental strain, the ΔaceE∷kan mutant did not cause persistent eggshell contamination of vaccinated hens.

Salmonella contamination in shell eggs exposed to modified-pressure imaging for microcrack detection

Microcracks in egg shells are a food safety risk and are difficult for professional human graders to detect. Modified-pressure imaging technology with 99.6% accuracy has been developed to detect microcracks. This study was conducted to determine whether the microcrack detection system would increase penetration of Salmonella into egg contents or lead to cross-contamination within the system. Thirty dozen grade A large white retail eggs were used for each of 3 replicates. Cracked eggs were removed and 72 eggs/replicate were dip inoculated in buffered peptone water containing 10(5) cfu/mL of nalidixic acid-resistant Salmonella Typhimurium (ST), whereas 144 eggs were dipped in sterile buffered peptone water. All eggs were incubated overnight at 25°C before imaging. Forty-five eggs of each treatment were imaged in the following order: control, inoculated, control. Imaged and nonimaged eggs from each treatment were used for cultural analysis of a shell rinse, shell emulsion, and contents sample for each egg. The ST levels were monitored on brilliant green sulfa agar with 200 mg/L of nalidixic acid. Egg contents were also enriched to determine the prevalence of ST in low levels. Salmonella Typhimurium was not detected on or in any of the control eggs, including the eggs imaged after the inoculated eggs. The highest level of ST was detected in inoculated shell emulsions (4.79 log cfu/mL). No differences in ST levels were found for any sample location between imaged and nonimaged inoculated eggs. Therefore, the modified-pressure imaging system for microcrack detection did not result in microbial cross-contamination or increase the level of microbial penetration in inoculated eggs. The imaging system can be used to assess eggs for cracks without negative food safety implications.

Detection of Salmonella and Escherichia coli in Egg Shell and Egg Content from Different Housing Systems for Laying Hens

Polymerase Chain Reaction (PCR) assay and conventional microbiological methods were used to detect bacterial contamination of egg shells and egg content in different commercial housing systems, the open house and evaporative cooling systems. A PCR assay was developed for direct detection using a set of primers specific for the invasion by invA gene for Salmonella and uidA gene, encoding $-glucuronidase for Escherichia coli. PCR detected the presence of Salmonella in 2 (5%) samples of egg shells from the evaporative cooling system, while conventional cultural methods detected no Salmonella from the same samples. No Salmonella was detected from the open house system. The frequency of PCR positive samples for E. coli was 35% (16/40) isolated from the open house system and 42% (16/38) from the evaporative cooling system. Two samples screened for E. coli in egg content was also detected by PCR. In comparison, detection of E. coli by culture, done simultaneously with PCR, was 17.5% (7/40) sensitive in the open house system and 31.5% (12/38) sensitive in the evaporative cooling system. Results indicated that this PCR procedure is a sensitive method for Salmonella and E. coli detection. The contamination of Salmonella and E. coli was found at a high frequency in the evaporative cooling system compared with the open house system.

Effects on Salmonella shell contamination and trans-shell penetration of coating hens' eggs with chitosan

Chitosan is a biopolymer with antimicrobial activity and film-forming properties. In this study, the effects on Salmonella shell contamination and trans-shell penetration of coating hens' eggs with chitosan was evaluated. A chitosan was selected from eight types (four non-commercial and four commercial) based on its antimicrobial activity against Salmonella enterica serovar Enteritidis ( S. Enteritidis). For this purpose, a contact plate method was developed and chitosans were applied at a concentration of 0.25% (w/v). A commercial type with a molecular weight of 310–375 kDa and a deacetylation degree of 75% that reduced S. Enteritidis by 0.71 log 10 colony forming units compared to the control (without chitosan) was selected for further studies. The chitosan was shown to have antimicrobial activity against other egg borne bacteria, i.e., Acinetobacter baumannii, Alcaligenes sp., Carnobacterium sp., Pseudomonas sp., Serratia marcescens and Staphylococcus warneri, and against S. enterica serovar Typhimurium, Escherichia coli and Listeria monocytogenes. The effects of various concentrations of the selected chitosan (0.25%, 1% and 2%) on Salmonella shell contamination and trans-shell penetration were assessed using the agar molding technique. Effective reduction of eggshell contamination could not be demonstrated, but trans-shell penetration was significantly reduced in the presence of a 2% chitosan eggshell coating, with only 6.1% of the eggs being penetrated compared to 24.5% of the uncoated eggs. It was concluded that the 2% chitosan coating has the potential to reduce contamination of egg contents resulting from trans-shell penetration by S. Enteritidis.