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J APPL POULT RES 2008. 17:376-382. doi:10.3382/japr.2007-00109
© 2008 Poultry Science Association
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Research Reports

Efficacy of Eugenol Against a Salmonella enterica serovar Enteritidis Experimental Infection in Commercial Layers in Production

G. Ordóñez*, N. Llopis{dagger} and P. Peñalver{dagger},1

* CESAC, Centre de Sanitat Avícola de Catalunya i Aragó, 43206 Reus, Spain, and {dagger} Lidervet S. L., 43006 Tarragona, Spain

Correspondence: 1 Corresponding author: ppenalver{at}lidervet.com


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
An experimental study (15-wk-old ISA Brown pullets) was conducted to establish the efficacy of the essential oil of Eugenia caryophyllata against Salmonella enterica serovar Enteritidis. The trial was composed of 4 groups. Pullets in groups 3 and 4 were fed with a commercial compound feed, and pullets in groups 1 and 2 were fed with the same feed plus the aromatic product at the dose of 250 g/Tm. At 19 wk old, the pullets in groups 1 and 3 were infected individually with an inoculum of 3.2 ± 0.8 x 107 cfu of Salmonella enterica serovar Enteritidis/ pullet. During the postinoculation period, samples of feces and eggs were cultured, and pullets were killed 30 d postinoculation. The aromatic product containing eugenol seems to aid in the cleaning of the intestinal and systemic infections, and it also plays an important role in the control of Salmonella cross contamination in eggs.

Key Words: eugenol • Eugenia caryophyllata • Salmonella enterica serovar Enteritidis • laying hen


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
For years, foodborne illnesses resulting from consumption of food contaminated with pathogenic bacteria, their toxins, or both have been of vital concern to public health [1]. Aromatic plants have been used since ancient times for their preservative and medicinal properties and to impart aroma and flavor to food. The pharmaceutical properties of these medicinal plants and spices are partially attributed to essential oils [2, 3].

Antimicrobial agents, including food preservatives, organic acids, and spices, have been used to inhibit foodborne bacteria and extend the shelf life of processed food [4]. Many naturally occurring compounds found in edible and medicinal plants, herbs, and spices have been shown to possess antimicrobial functions and could serve as a source of antimicrobial agents against food pathogens [5–7]. The phenolic compounds from the essential oils possess a high antimicrobial activity in vitro against food-borne pathogens.

Antibiotic growth-promoters (AGP) have been used for the control of pathogens such as Escherichia coli or Clostridium perfringens (that can have an influence on digestibility), or Salmonella (which, furthermore, is also responsible for zoonosis). Prebiotics, probiotics, or competitive exclusion mechanisms have been considered as a way of controlling the digestive tract microflora to make the proliferation of pathogens more difficult and favor the growth of beneficial microorganisms such as Lactobacillus [8].

Recently, the restrictions on the use of antibiotics as animal growth-promoters have encouraged the use of essential oils as alternatives to AGP. The metabolic properties of essential oils have been shown to increase digestibility and absorption of the nutrients by 5% and increase weight of the newborn litter by up to 18% [9]. In our field studies using an aromatic product composed of clove essential oil from a natural source as a natural alternative to AGP, this aromatic product has surprisingly shown a capacity to control Salmonella in eggs. This led to a study to observe the activity of clove essential oil in a controlled infection with Salmonella enterica serovar Enteritidis on an experimental farm [10] based on the studies of Humphrey et al. [11, 12], Aabo et al. [13], Berchieri et al. [14], Nakamura et al. [15], and Wigley et al. [16].


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Experimental Design
In the trial, 100 commercial 15-wk-old ISA Brown laying pullets were obtained from a flock [17] that had tested negatively for Salmonella in the feces 2 wk before moving them to the experimental farm in Reus (Tarragona), Spain (Centre de Sanitat Avícola de Catalunya i Aragó). The pullets were vaccinated following the standard program for commercial laying hens (excluding the vaccine against Salmonella spp.).

At the trial farm, the pullets were kept under observation and acclimatized for 9 d. After this period, they were distributed into 4 groups, with pullets in groups 1 and 2 fed on a daily basis during the whole length of the study, a commercial feed with the aromatic product containing eugenol [18] at the dose of 250 ppm. Pullets in group 3 and 4 were fed with the same feed without the aromatic product. None of the hens received any other medication than the one of its treatment.

The pullets were kept in separated wire cages, identified with specific numeric codes. According to the Directive 86/609/EEC and in application of the Decret 214/1997/DOGC regarding the regulation of animals destined for scientific experimentation, the hens were kept in the final pens with a minimal space of 550 cm2/ pullet.

After 3 wk on the experimental farm consuming feed added with a commercial product containing eugenol [18], the animals in group 1 (treated with essential oil) and group 3 (positive control) were inoculated with Salmonella Enteritidis. Inoculation into the crop was performed individually at a single dose of 1 mL using a syringe containing approximately 3.2 x 107 cfu Salmonella Enteritidis. Groups 2 (treated with essential oil) and 4 (negative control) were not inoculated (Table 1Go).


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  		Table 1. Detailed description of the experimental design of the study
 
During the postinoculation period, samples of feces and eggs were taken. Hens were slaughtered at 30 d postinoculation.

During the trial, water and food were supplied ad libitum. The drinking water given to the animals came directly from the mains. A 24-h lighting program was established. The sanitary condition of the feed was controlled and certified previously by the compound feed supplier to ensure the absence of Salmonella spp. In addition, the weight, feed consumption, and rate of lay of the hen were monitored during the trial.

Salmonella Culture
Salmonella Enteritidis was isolated using the ISO 6579:2002 test. This modified test is based on Rappaport-Vassiliadis semisolid media for selective Salmonella spp. from other bacteria in dust and feces samples. The detection of Salmonella necessitates 4 successive stages: preenrichment in nonselective liquid medium (buffered peptone water at 37 ± 1°C for 18 h ± 2 h), enrichment on selective semisolid medium (modified semisolid Rappaport-Vassiliadis agar plates incubated at 41.5 ± 1°C for 24 h ± 3 h; if a plate is negative after 24 h, it is incubated for further 24 ± 3 h), selective plating and identification (2 selective solid media are inoculated: xyloselysine-deoxycholate agar and Difco Brilliant Green agar [19], incubated at 37 ± 1°C and examined after 24 ± 3 h), and confirmation of identity stage (colonies of presumptive Salmonella are subcultured, then plated out, and their identity is confirmed by means of Triple Sugar Iron [20] and BBL Crystal Identification System Kit [21]). An antibody microarray assay was developed for Salmonella serotyping based on the Kauffmann-White scheme. Serum was analyzed for antibody against Salmonella using a commercial ELISA kit.

Aromatic Product
The aromatic product [18] was composed of essential oil from a natural source of Eugenia caryophyllata or Syzygium aromaticum [22], in an amorphous SiO2 inert carrier. The concentration of eugenol in the aromatic product was 20%. The components of the essential oil were chemically valuated through gas chromatography-quadrupole mass spectroscopy [23, 24]. It was observed that its profile is as described in the flavoring substances classifications [3, 25, 26] regarding E. caryophyllata.

Inoculum Preparation
The inoculum was developed in the Centre de Sanitat Avícola de Catalunya i Aragó from a field strain of Salmonella enterica serovar Enteritidis isolated from a naturally infected laying flock. The strain was kept in a pure culture and grown in a nutrient broth [27] at 37°C for 24 h. The microorganism count was carried out at a dilution of 10 bases in phosphate buffer [28] and plated onto solid medium Brilliant Green agar [19]. From the obtained count, the liquid medium was diluted to a concentration of 108 Salmonella Enteritidis/mL.

The inoculum solution was prepared 24 h before it was given to the hens, with a count of 8.5 ± 0.15 x 107 cfu Salmonella Enteritidis/mL. Another recount was carried out when the inoculum was given to the hens, with the result of 3.2 ± 0.08 x 107 cfu Salmonella Enteritidis/mL.

Collection of Samples
Fresh Feces
A 25-g sample of fresh feces per pen was collected from the bottom of the cage. Samples were analyzed collectively for each group 2 wk before the inoculation, 1 d before the inoculation, and after the challenge overnight feces were collected and analyzed weekly.

Eggs
The eggs laid were collected daily. They were analyzed collectively for each group 2 wk before the inoculation, 1 d before the inoculation, and weekly after the challenge.

Feed
Both feeds (with and without the commercial product) were cultured once before the trial started. Twenty-five grams per group was analyzed.

Tissues
Birds were killed at 15 and 29 d postinfection. Postmortem examination tissues were tested in accordance with the Standard Procedure of the Department of Bacteriology of the Centre de Sanitat Avícola de Catalunya i Aragó. At 15 d postinoculation, 5 hens/group were slaughtered to check for systemic infection. In each hen, samples were collected from ceca, ovary, liver, and spleen. All the samples from the animals of each group were analyzed individually. At 29 d postinoculation, again 5 hens/group were slaughtered. The tissues were analyzed in 2 pools by group: liver + spleen + ovary pool and a ceca pool. But in group 4, ceca were analyzed individually.

Blood
Five birds per flock were bled at 17 and 19 wk of age (before the experimental inoculation) and before killing at 15 and 29 d postinoculation. Sera were analyzed for antibody against Salmonella using a commercial ELISA kit.


   RESULTS AND DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Tables 2Go, 3Go, and 4Go show the bacteriologic results of isolation and identification of Salmonella Enteritidis in each of the groups. Analysis to detect Salmonella before the beginning of the trial in compound feed (Table 5Go) and hens (Table 2Go, blood) was shown to be negative. In 17-wk-old pullets, the analysis had to be carried out using just 23 individuals due to the bad state of 2 of the blood serum samples. Two positives in group 3 and 1 positive in group 4 were considered to be false positives, because the microbiology results were negative.


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  		Table 2. Salmonella Enteritidis isolations from feces, eggs, tested tissues, and serum antibodies detection in groups 1, 2, 3, and 41
 

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  		Table 3. Salmonella Enteritidis isolation in viscera in groups 1, 2, 3, and 41
 

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  		Table 4. Serologic results by ELISA1
 

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  		Table 5. Salmonella Enteritidis isolation and identification in environmental samples
 
Inoculum containing 3.2 x 107 cfu Salmonella Enteritidis per hen produced a systemic and intestinal infection with isolation in feces from 1 d postinfection (Table 2Go), internal tissues and reproductive tracts from 15 d postinfection (Table 2Go and 3Go), and eggs from 4 d postinfection (Table 2Go). Gast et al. [29, 30] found colonization of the reproductive and internal viscera after an experimental infection with Salmonella Enteritidis and Salmonella Heidelberg, in which nearly all cecal samples were positive for Salmonella at 7 d, as well as 83.3% of the liver samples, 83.3% of spleens, and 66.7% of ovaries. But at 21 d, the percentage of infections in the cecal samples declined by approximately 50%, and in the case of spleens, it ranged from 16.7 to 33.3%, ovaries <16.7%, and no positive results to Salmonella were found in liver. Bearing this in mind, viscera checks in the experimental study with the aromatic product were carried out individually 15 d postinoculation to get an overview of Salmonella distribution in the hens in each group, but once the systemic infection was proven to exist in every different group, viscera or ceca pools were carried out to determine the evolution of the infection.

Experimental oral infection in 19-wk-old pullets produced an intestinal infection with shedding and isolation in feces from d 1 postinoculation and continuously during the whole length of the trial in groups 3 (infected and no treatment) and 1 (infected and treatment; Table 2Go). The systemic infection was made evident at 15 d postinoculation, with Salmonella Enteritidis being detected in liver, spleen, ceca, and serologic tests in groups 3 (infected and no treatment) and 1 (infected and treatment; Table 3Go). From d 29 postinoculation onward, Salmonella was only found in ceca in group 3 (infected and not treated; Table 3Go).

Differences found among group 1 (infected and treated) and group 3 (infected and not treated) were that in group 1, the results in liver, spleen, and ovary were positive (systemic infection) at 15 d postinoculation but negative from 29 d postinoculation. In group 3, the results were positive for the liver-spleen-ovary pool until 29 d postinoculation (Tables 2Go and 3Go).

The treatment is apparently effective in group 1, because it probably prevents the colonization of ceca and viscera infection. Even though the animals were in a contaminated environment, 29 d postinoculation, the results in liver, spleen, and ovary were negative.

These results are in line with literature data [6, 31, 32] that give rise to the conclusion that clove essential oil and eugenol have an in vitro antimicrobial activity against numerous bacteria, mainly enteric pathogens (Escherichia coli and Salmonella), with little effect on beneficial gut bacteria. Eugenol showed bactericidal activity against different strains of Salmonella [32]. Concerning the antimicrobial mechanisms of essential oils, it has been described that their constituents could get partitioned into the lipid bilayer of the cell membrane, rendering it more permeable, leading to leakage of vital cell contents [33]. The hydroxyl group of eugenol is also thought to bind to membrane proteins [34].

This antimicrobial activity may result in the control of the intestinal colonization by Salmonella, which is the point of entrance of the systemic and the reproductive tract infections [35–38]. Moreover, Salmonella Enteritidis has selective ability to colonize the reproductive organs, and the different egg parts (yolk, albumen, eggshell membranes, or eggshells) may become directly contaminated by Salmonella in the ovary and oviduct [36] before oviposition. The colonization of the ovary or the oviduct in laying hens can be produced by a systemic Salmonella Enteritidis infection and also by oral inoculation [35], as it was in the present work. Egg contamination by Salmonella Enteritidis can also be caused by penetration through the eggshell from contaminated feces after or during oviposition [35]. In this way, before eggshell deposition, forming eggs are subjected to descending infections from colonized ovarian tissue, ascending infections from colonized vaginal and cloacal tissues, and lateral infections from colonized upper oviduct tissue. The bactericidal action before the eggs are laid (by reduction in the amount of pathogen in the reproductive organs) and after deposition (avoiding the contamination with infected feces) can play an important role in the control of Salmonella infection.

Differences among groups not infected and treated (group 2) and not infected and not treated (group 4) were observed in the sampling of eggs; group 2 was always negative, whereas group 4 showed positive results at 12 and 19 d postinoculation. In the sampling of feces, group 4 showed positive results on d 1 postinoculation (Table 2Go). The data compiled demonstrate that the group not treated (group 4) was susceptible to environmental infection, whereas there were no positives in the treated group (group 2), which may be due to a greater resistance to the environmental infection due to the treatment with the aromatic product.

Essential oil of E. caryophyllata included in the aromatic product may have prevented cross contamination in eggs. The most important target in the control of a systemic infection is to prevent the presence of Salmonella in eggs. In group 1 (inoculated and treated), this was observed, because 19 d postinfection was the last positive result in eggs even though the environment was contaminated. By d 29 postinoculation, the same happened with ceca and viscera, which included ovary (Table 2Go).

The effect of the aromatic product on intestinal colonization, fecal elimination, systemic infection, and contamination of the eggs seems to be effective in elimination of the intestinal and systemic infection in the group given the essential oil. The effects were detectable 29 d postinoculation. Several internal studies not yet published indicate that the way E. caryophyllata works may be by stimulating the cellular immunity (neutrophils, macrophages, CD8 and CD4+ cells), which may encourage inflammatory processes that prevent the colonization of Salmonella in the intestine [39–41].

It is also important to point out that in the serologic results in the different groups, especially in group 1, the level of seropositivity observed was nearly 100%, a fact which indicates recent contact with Salmonella. Because the culture results were negative, this was considered to be due to postinfection residual immunity (Table 4Go).


   CONCLUSIONS AND APPLICATIONS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
REFERENCES AND NOTES
 

  1. The aromatic product containing 20% eugenol from clove essential oil (Eugenia caryophyllata) added to the feed of the hens prevented cross contamination in eggs.
  2. The aromatic product did not prevent the intestinal infection but seems to be effective in wiping out the intestinal and systemic infections.


   ACKNOWLEDGMENTS
 
This experimental study was supported by Lidervet S.L., but this company has not had any influence whatsoever on its design and results.


   REFERENCES AND NOTES
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 

  1. Thorns, C. J. 2000. Bacterial food-borne zoonoses. Rev. Sci. Tech. Off. Int. Epiz. 19:226–239.
  2. Larhsini, M., L. Oumoulid, and H. B. Lazrek. 2001. Antibacterial activity of some Moroccan medicinal plants. Phytother. Res. 15:250–252.[CrossRef][Web of Science][Medline]
  3. Peñalver, P. 2005. Aromaterapia. Lidervet, Tarragona, Spain.
  4. Burt, S. A., and R. D. Reinders. 2003. Antibacterial activity of selected plant essential oils against Escherichia coli O157:H7. Lett. Appl. Microbiol. 36:162–167.[CrossRef][Web of Science][Medline]
  5. Beuchat, L. R. 2001. Control of foodborne pathogens and spoilage microorganisms by naturally occurring antimicrobials. Pages 162–167 in Microbial Food Contamination. C. L. Wilson and S. Droby, ed. CRC Press, Boca Raton, FL.
  6. Deans, S. G., and G. A. Ritchie. 1987. Antimicrobial properties of plant essential oils. Int. J. Food Microbiol. 5:165–180.[CrossRef][Web of Science]
  7. Janssen, A. M., J. J. Scheffer, A. Baerheim Svendsen, and Y. Aynehchi. 1985. Composition and antimicrobial activity of the essential of Ducrosia anhetifolia. Pages 213–216 in Essential Oils and Aromatics Plants. A. B. Svendsen and J. J. Scheffer, ed. Martinus Nijhoff Publishers, Dordrecht, the Netherlands.
  8. Van Immerseel, F., J. B. Russell, M. D. Flythe, I. Gantois, L. Timbermont, F. Pasmans, F. Haesebrouck, and R. Ducatelle. 2006. The use of organic acids to combat Salmonella in poultry: A mechanistic explanation of the efficacy. Avian Pathol. 35:182–188.[CrossRef][Web of Science][Medline]
  9. Costa, P., S. Salado, P. Medel, and J. J. Asensio. 1999. Productos naturales de origen vegetal: Una alternativa a los aditivos antimicrobianos en alimentación animal. Anaporc 190:51–57.
  10. Huerta, B., F. Ponsa, G. Ordóñez, N. Fernández, and P. Peñalver. 2005. Estudio de eficacia de aceites esenciales ante una infección experimental de Salmonella Enteritidis en gallinas ponedoras en producción. Pages 119–124 in Comunicaciones del XLII Symposium WPSA-AECA. WPSA, Cáceres, Spain.
  11. Humphrey, T. J., H. Baskerville, H. Chart, and B. Rowe. 1989. Infection of egg-laying hens with Salmonella Enteritidis PT4 by oral inoculation. Vet. Rec. 125:531–532.[Web of Science][Medline]
  12. Humphrey, T. J., A. Baskerville, A. Whitehead, B. Rowe, and A. Henley. 1993. Influence of feeding patterns on the artificial infection of laying hens with Salmonella Enteritidis PT4. Vet. Rec. 132:407–409.[Abstract]
  13. Aabo, S., J. P. Christensen, M. S. Chadfield, B. Carstersen, J. L. Olsen, and M. Bisgaard. 2002. Quantitative comparision of intestinal invasion of zoonotic serotypes of Salmonella enterica in poultry. Avian Pathol. 31:41–47.[CrossRef][Web of Science][Medline]
  14. Berchieri, A., Jr., P. Wigley, K. Page, C. K. Murphy, and P. A. Barrow. 2001. Further studies on vertical transmission and persistence of Salmonella enterica serovar Enteritidis phage type 4 in chickens. Avian Pathol. 30:297–310.[CrossRef][Web of Science][Medline]
  15. Nakamura, M., N. Nagamine, and S. Suzuki. 1993. Long-term shedding of Salmonella Enteriditis in chickens which received a contact exposure within 24 hrs of hatching. J. Vet. Med. Sci. 55:649–653.[Web of Science][Medline]
  16. Wigley, P., A. Berchieri, K. L. Page, A. L. Smith, and P. A. Barrow. 2001. Salmonella enterica serovar Pullorum persists in splenic macrophages and in the reproductive tract during persistent, disease-free carriage in chickens. Infect. Immun. 69:7873–7879.[Abstract/Free Full Text]
  17. ISA Brown laying hens, José Ruano Juncosa S.L., Reus, Spain.
  18. Liderfeed, Lidervet, S. L., Tarragona, Spain
  19. 22850, Difco, Lawrence, KS.
  20. Triple Sugar Iron, Difco, Sparks, MD.
  21. OBL Crystal Identification System Kit, Becton Dickinson Diagnostic Instrument System, Sparks, MD.
  22. Medical Economics. 2007. Page 201 in Physician’s Desk Reference for Herbal Medicines. 4th ed. J. Gruenwald, T. Brendler, and C. Jaenicke, ed. Thomson Healthcare Inc., Montvale, NJ.
  23. Council of Europe. 2004–2005. European Pharmacopoeia. 5th ed. Council of Europe, Strasbourg, France.
  24. 5973, Hewlett-Packard, Palo Alto, CA
  25. Bauer, K., D. Garde, and H. Surburg. 2001. Common Fragance and Flavor Materials: Preparation, Properties, and Uses. 4th ed. Wiley-Vch, Weinheim, Germany.
  26. Bruneton, J. 2001. Pages547–549 in Fitoquímica y Plantas Medicinales. 2nd ed. Acribia, Zaragoza, Spain.
  27. CM67, Oxoid, Basingstoke, UK.
  28. 15525, Merck, Whitehouse Station, NJ.
  29. Gast, R. K., J. Guard-Petter, and P. S. Holt. 2003. Effect of prior serial in vivo passage on the frequency of Salmonella Enteritidis contamination in eggs from experimentally infected laying hens. Avian Dis. 47:633–639.[CrossRef][Web of Science][Medline]
  30. Gast, R. K., J. Guard-Bouldin, and P. S. Holt. 2005. The relationship between the duration of fecal shedding and the production of contaminated eggs by laying hens infected with strains of Salmonella Enteritidis and Salmonella Heidelberg. Avian Dis. 49:382–386.[CrossRef][Web of Science][Medline]
  31. Feres, M., L. C. Figueiredo, I. M. Barreto, M. N. Coelho, M. W. Araújo, and S. C. Cortelli. 2005. In vitro antimicrobial activity of plant extracts and propolis in saliva samples of healthy and periodontally-involved subjects. J. Int. Acad. Periodontol. 7:90–96.[Medline]
  32. Friedman, M., P. R. Henika, and R. E. Mandrell. 2002. Bactericidal activities of plant essential oils and some of their isolated constituents against Campylobacter jejuni, Escherichia coli, Listeria monocytiogenes, and Salmonella enterica. J. Food Prot. 65:1545–1560.[Web of Science][Medline]
  33. Edris, A. E. 2007. Pharmaceutical and therapeutic potentials of essential oils and their individual volatile constituents: A review. Phytother. Res. 21:308–323.[CrossRef][Web of Science][Medline]
  34. Di Pasqua, R., G. Betts, N. Hoskins, M. Edwards, D. Ercolini, and G. Mauriello. 2007. Membrane toxicity of antimicrobial compounds from essential oils. J. Agric. Food Chem. 55:4863–4870.[CrossRef][Web of Science][Medline]
  35. De Buck, J., F. Van Immerseel, F. Haesebrouck, and R. Ducatelle. 2004. Colonization of the chicken reproductive tract and egg contamination by Salmonella. J. Appl. Microbiol. 97:233–245.[CrossRef][Medline]
  36. Gama, N. M. S. Q., J. R. Berchieri, and S. A. Fernandes. 2003. Occurrence of Salmonella sp. in laying hens. Rev. Bras. Cien. Avic. 5:15–21.
  37. Gast, R. K., J. Guard-Bouldin, and P. S. Holt. 2004. Colonization of reproductive organs and internal contamination of eggs after experimental infection of laying hens with Salmonella Heidelberg and Salmonella Enteritidis. Avian Dis. 48:863–869.[CrossRef][Web of Science][Medline]
  38. Humphrey, T. J., H. Baskerville, H. Chart, B. Rowe, and A. Whitehead. 1991. Salmonella Enteritidis PT4 infection in specific pathogen free hens: Influence of infecting dose. Vet. Rec. 129:482–485.[Abstract]
  39. Barrow, P. A. 2007. Salmonella infections: Immune and non-immune protection with vaccines. Avian Pathol. 36:1–13.[CrossRef][Web of Science][Medline]
  40. Barrow, P. A., N. Bumstead, K. Marston, M. A. Lovell, and P. Wigley. 2004. Faecal shedding and intestinal colonization of Salmonella enterica in in-bred chickens: The effect of host-genetic background. Epidemiol. Infect. 132:117–126.[CrossRef][Medline]
  41. Barrow, P. A., M. A. Lovell, C. K. Murphy, and K. Page. 1999. Salmonella infection in a commercial line of ducks; Experimental studies on virulence, intestinal colonization and immune protection. Epidemiol. Infect. 123:121–132.[CrossRef][Medline]




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