A multiplex real-time PCR for differential detection and quantification of Salmonella spp., Salmonella enterica serovar Typhimurium and Enteritidis in meats

Salmonella (S.) Typhimurium and S. Enteritidis are the major causative agents of food-borne illnesses worldwide. Currently, a rapid detection system using multiplex real-time polymerase chain reaction (PCR) has been applied for other food-borne pathogens such as Escherichia coli, Staphylococcus aureus and Streptococcus spp. A multiplex real-time PCR was developed for the simultaneous detection of Salmonella spp., especially S. Typhimurium and S. Enteritidis, in beef and pork. For the specific and sensitive multiplex real-time PCR, three representative primers and probes were designed based on sequence data from Genbank. Among the three DNA extraction methods (boiling, alkaline lysis, and QIAamp DNA Mini Kit), the QIAamp DNA Mini Kit was the most sensitive in this study. The optimized multiplex real-time PCR was applied to artificially inoculated beef or pork. The detection sensitivity of the multiplex real-time PCR was increased. The specificity of the multiplex real-time PCR assay, using 128 pure-cultured bacteria including 110 Salmonella isolates and 18 non-Salmonella isolates, was 100%, 100% and 99.1% for Salmonella spp., S. Typhimurium and S. Enteritidis, respectively. The sensitivity was 100%, 100% and 91.7% for Salmonella spp., S. Typhimurium and S. Enteritidis, respectively. The multiplex real-time PCR assay developed in this study could detect up to 0.54 ± 0.09 and 0.65 ± 0.07 log₁₀ CFU/ml for S. Typhimurium and S. Enteritidis for beef, 1.45 ± 0.21 and 1.65 ± 0.07 log₁₀ CFU/ml for S. Typhimurium and S. Enteritidis for pork, respectively, with all conditions optimized. Our results indicated that the multiplex real-time PCR assay developed in this study could sensitively detect Salmonella spp. and specifically differentiate S. Typhimurium from S. Enteritidis in meats.     

Integrated farm management to prevent Salmonella Enteritidis contamination of eggs

Salmonella Enteritidis in contaminated eggs is a public health hazard that may cause hospitalization or death in the elderly, infants, and individuals with impaired immune systems. Prevention of Salmonella Enteritidis infection of laying hens is an essential first step in reducing Salmonella Enteritidis outbreaks in humans. Multiple interventions at several stages during egg production can combine to reduce numbers of infected chickens and keep egg contamination to low levels. Every effort should be made to exclude Salmonella Enteritidis from egg production premises by implementing effective biosecurity measures, stocking the farm with Salmonella Enteritidis-free replacement pullets, controlling rodent and insect vectors, and denying wild birds and pets access to chicken houses. Diligent cleaning and disinfection of chicken houses before introduction of a new flock will minimize environmental exposure and indirect horizontal transmission of multiple pathogens, including Salmonella Enteritidis. Increased resistance of chickens to intestinal colonization by Salmonella Enteritidis can be attained by the use of probiotics, prebiotics, and synbiotics. Laying hens should be immunized with live and killed vaccines to stimulate mucosal and systemic immunity and reduce the prevalence of Salmonella Enteritidis-contaminated eggs. Shell eggs should be refrigerated as soon as possible after laying to keep Salmonella Enteritidis cells at low levels in any contaminated eggs. Comprehensive Salmonella Enteritidis-control programs have proven to be successful in reducing the incidence of Salmonella Enteritidis infections in both egg-laying flocks and humans.     

Assessment of 2 Salmonella enterica serovar Typhimurium-based vaccines against necrotic enteritis in reducing colonization of chickens by Salmonella serovars of different serogroups

This study assessed the protective efficacy of oral vaccination with 2 experimental attenuated Salmonella Typhimurium-vectored vaccines for necrotic enteritis in protecting chickens against intestinal colonization by common serovars of Salmonella belonging to the 4 major serogroups affecting chickens. Birds were vaccinated orally with 1 × 10⁸ colony-forming units (CFU) of 1 of the vaccine strains χ9241 and χ9352, which express a plasmid-encoded partial recombinant hypothetical protein gene (tHP) of Clostridium perfringens, at days 1 and 7 of age, and then were challenged at 14 d of age with 10⁶ CFU of Salmonella serovars Anatum, Enteritidis, Heidelberg, Kentucky, or Typhimurium (representative serovars of serogroups B, C, D, and E). Birds were necropsied at 4 wk of age, and samples were collected to determine reduction in tissue and intestinal colonization. The chickens vaccinated with χ9241-tHP showed reduced colonization by Salmonella Enteritidis (serogroup D) and by Salmonella Heidelberg and Salmonella Typhimurium (serogroup B) compared with the control birds. No reduction in colonization was observed in the chickens vaccinated with χ9352-tHP. There was an association between the efficacy of these vaccine strains in protecting against necrotic enteritis, assessed on an earlier occasion, and their efficacy in protecting against Salmonella colonization. Thus, the choice of an attenuated Salmonella Typhimurium vaccine vector for delivery of heterologous antigens to chickens should be based partly on the vaccine’s value in protecting against colonization by serovars within serogroups B and D. Such vectors would have the additional benefit of reducing colonization of important Salmonella serovars.     

Risk factors of Salmonella infection in laying hens in Menoua Division,Western region of Cameroon (Central Africa)

Salmonella infections in poultry farms are overlooked in many African countries; yet these infections are mostly zoonotic with impact on both poultry industry and public health. Considering the impact of Salmonella in laying hens, and the role of laying hens as a source of Salmonella outbreak in human, knowledge of the status of Salmonella on laying hen farms as well as the factors influencing the presence of Salmonella is important. In a cross sectional study, cloacal swabs were collected from 270 commercial laying hens on 27 farms located in Menoua Division. These samples were cultured on standard media. A questionnaire was used to collect information on animals, farms and farmer’s characteristics. The prevalence of Salmonella was 93.34%; three zoonotic isolates namely S. Enteritidis (75.90%), S. Paratyphi (11.90%), and S. Typhimurium (5.60%) were identified. The location of farms was significantly associated with presence of Salmonella, and the risk of infection was 10-fold higher in Nkong-ni than Santchou (p < 0.05). Other potential risk factors such as flock size, age of the farm (infrastructure), or water source were not associated with Salmonella infection. The prophylactic measures against avian diseases in the country must include measures against Salmonella to protect poultry industry and public health.     

Efficacy of chlorine dioxide gas in reducing Escherichia coli and Salmonella from broiler house environments

Escherichia coli and Salmonella spp. are considered to be the major pathogens associated with human transmissible infectious diseases in the air of poultry houses. Chlorine dioxide (ClO₂) is an effective biocide against a wide range of microorganisms. Accordingly, this study investigated the efficiency of gaseous ClO₂ application for disinfecting broiler houses by collecting air samples before and after fumigation using a passive method. Fumigation was performed with 125 mL or 250 mL of ClO₂ liquid (containing 2,000 ppm of ClO₂) and 3 trials were conducted for each dose. A total of 27 petri dishes were used for each trial (for each type of bacteria: E. coli or Salmonella) and placed in 3 different locations (front, middle and back) and 3 different positions (top, middle and floor) of the broiler shed. Air samples were collected at 10 min, 1 h, 3 h, 6 h, and 12 h before and after fumigation to evaluate the air quality in terms of the concentration of E. coli and Salmonella. Both levels of ClO₂ were capable of reducing the concentration of E. coli from broiler house air during all measuring periods except 10 min, with highest disinfection rate being observed at 6 h. With the exception of 1 h, the concentration of Salmonella was also reduced after fumigation with ClO₂ in all measuring period; with the highest disinfection rate occurring at 6 h. Fumigation with ClO₂ had no negative effect on birds’ health condition. Taken together, these results suggest that the application of gaseous ClO₂ at the investigated levels can be an effective option for reducing bacterial load from broiler house environments.     

Leukocytic responses and intestinal mucin dynamics of broilers protected with Enterococcus faecium EF55 and challenged with Salmonella Enteritidis

The protective effect of Enterococcus faecium EF55 in chickens challenged with Salmonella enterica serovar Enteritidis phage type 4 (SE PT4) was assessed. The antibacterial effect on the bacterial microflora in the small intestine in relation to white blood cell count, phenotyping of peripheral blood and intestinal lymphocytes, functional activity of lymphocytes and phagocytes and mucin quantitation were investigated. Day-old chicks (85) were randomly divided into four groups. The probiotic group (EF) and Salmonella + probiotic group (EFSE) received E. faecium EF55 (10⁹ CFU – 3 g/group/day) for 21 days. The Salmonella group (SE) and EFSE group were infected with Salmonella Enteritidis (10⁸ CFU in 0.2 ml PBS) in a single dose per os on day four of the experiment. The control group chicks (C) were fed a commercial diet without added bacteria. Supplementation of EF55 in the diet of the chickens in the EFSE group, challenged with S. Enteritidis, caused the density of the intestinal mucin layer to increase significantly in non-specific regions (duodenum and jejunum), but decrease significantly in target regions (caeca) for S. Enteritidis. Probiotic treatment also appeared to result in a significantly higher number of lymphocytes in peripheral blood and a tendency to increase CD3, CD4, CD8, and IgM positive cells 3 days post-infection with S. Enteritidis. The results demonstrated an antibacterial effect and suggested that EF55 had a moderating effect on intestinal mucin production and leukocytic response in the early phase of S. Enteritidis infection.     

On-farm risk factors for Salmonella Enteritidis contamination

Forty layer farms from 2 states participated in a study to examine the risk factors and incidence of Salmonella Enteritidis from multiple samples, including environmental drag swabs from the bird areas, feed, water, flies, rodents, live rodent traps, and environmental swabs from areas occupied by other livestock. Twenty-four of these farms had between 3,000 and 31,000 bird flocks (medium-sized flocks) and 16 had less than 3,000 birds (small-sized flocks). All were housed in cage-free production systems. Twenty-two farms included outside pasture areas for the birds. Most of the participants had just come under the FDA Egg Rule and had not yet tested their flocks (flocks under 3,000 birds are exempt) for Salmonella Enteritidis. Many, however, obtained their pullets from commercial Salmonella Enteritidis-clean breeder sources hatched in National Poultry Improvement Plan hatcheries. Vaccination against Salmonella Enteritidis was performed on 21 of the 40 farms (combination of live and killed vaccines). Salmonella Enteritidis was detected on 7 out of the 40 farms, primarily in rodents, their feces, or from swabs taken inside live traps. Of these 7 Salmonella Enteritidis-positive farms, 3 farms that had vaccinated their pullets with live Salmonella Typhimurium vaccine and killed-Salmonella Enteritidis vaccine; no Salmonella Enteritidis was isolated from the environmental drag swabs taken from the bird area or from the eggs on these farms. However, on the farms that had not vaccinated for Salmonella Enteritidis, the organism was isolated from 4 environmental drag swabs and 3 egg pools. The last 4 farms had flocks under 3,000 birds. No Salmonella Enteritidis was isolated from any of the samples of feed, flies, water, or swabs taken from other livestock areas. Based on the initial findings in this study, we suggest the 2 most important risk factors for Salmonella Enteritidis contamination inside the bird area and in the eggs in these small- and medium-sized flocks are the presence of infected rodents and the absence of an Salmonella Enteritidis vaccination program.     

Salmonella Incidence in Broilers from Breeders Vaccinated with Live and Killed Salmonella

Salmonella reduction in broilers from commercial broiler breeders vaccinated with live and killed Salmonella vaccines was evaluated. Broiler breeders were vaccinated with Poulvac ST live Salmonella Typhimurium vaccine at 1 d of age, and this was repeated at 2 and 6 wk of age. The breeders were then administered a killed autogenous oil emulsion adjuvanted vaccine containing Salmonella Kentucky, Salmonella Heidelberg, and Salmonella Hadar, at 10 and 18 wk of age. From the ages of 36 to 52 wk, eggs from the breeder flock were hatched, and progeny were challenged in 4 separate experiments at 1 d of age by oral gavage with 1 × 10⁶ cfu/chick by either Salmonella Kentucky, Salmonella Heidelberg, Salmonella Hadar, or Salmonella Enteritidis, each containing resistance to naladixic acid at 32 μg/mL. At 17 to 21 d of age, the broilers were euthanized, and 1 side of the cecum was cultured for Salmonella, and the other side of the cecum was used for enumeration on positive samples. Recovered Salmonella was confirmed to be the challenge strain by O-antisera grouping. This study indicated a difference in Salmonella incidence and enumeration between the vaccinated and nonvaccinated breeder groups for certain species. When challenged with serotypes Salmonella Kentucky, Salmonella Hadar, and Salmonella Heidelberg, protection was noted with a reduction of 28, 17, and 11%, respectively, when compared with the control groups. However, protection was not seen when challenged with S. enteritidis. Under the conditions of this study, live and killed vaccination of commercial broiler breeders with Salmonella contributes protection to progeny when challenged at 1 d of age.     

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

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 × 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.     

Antibacterial Effect of Trans-Cinnamaldehyde on Salmonella Enteritidis and Campylobacter jejuni in Chicken Drinking Water,

Salmonella Enteritidis and Campylobacter jejuni are 2 major foodborne pathogens in the United States, estimated to cause more than 3 million cases of human illness annually. Chickens are the natural hosts of these bacteria, and their drinking water can be a source of S. Enteritidis and C. jejuni, contributing to the colonization of birds. In this study, trans-cinnamaldehyde (TC), a natural, generally recognized as safe ingredient in cinnamon oil was evaluated for its efficacy to inactivate S. Enteritidis and C. jejuni in the drinking water of chickens. Well water containing 0, 0.016, 0.03, and 0.06% TC was inoculated with a 5-strain mixture of S. Enteritidis or C. jejuni (˜6 log₁₀ cells/mL). Water samples containing 1% chicken feces or feed were also included. The samples were incubated at 12.5 or 25°C for 7 d and analyzed for bacterial populations on d 0, 1, 3, 5, and 7. Duplicate samples of treatments and control were included, and the study was replicated 3 times. Trans-cinnamaldehyde at 0.06% inactivated Salmonella completely after 24 h in water with 1% feces at both temperatures. In water containing 1% feed, TC (0.06%) reduced S. Enteritidis to undetectable levels after 3 d at 12.5°C or 7 d at 25°C. Presence of feed or feces in water reduced the antibacterial effect (P < 0.001) of TC. The effect of TC on C. jejuni was more pronounced than that on S. Enteritidis. The TC at 0.06% completely inactivated the pathogen after 1 d of incubation at both temperatures. The presence of feces or feed did not have any effect (P > 0.001) on the antibacterial property of TC on C. jejuni. Results indicate that TC is effective in killing S. Enteritidis and C. jejuni in chicken drinking water and may decrease the likelihood that water will contribute to colonization of chickens by these pathogens.     

Poultry as a possible source of non-typhoidal Salmonella enterica serovars in humans in Bangladesh

We investigated Salmonella enterica isolates from human clinical cases of gastroenteritis to determine the distribution of non-typhoidal Salmonella serovars in the human population, and compared them to isolates originating from poultry by serotyping, phage typing, plasmid profiling, pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) to evaluate the potential role of poultry in human non-typhoidal salmonellosis in Bangladesh. Nine different serovars were identified among the human isolates of which Salmonella Paratyphi B var Java (S. Java), S. Kentucky, S. Enteritidis, S. Virchow and S. Weltevreden also were commonly isolated from poultry. The poultry isolates belonging to S. Java, S. Kentucky and S. Enteritidis were indistinguishable from human isolates or genetically closely related, based on PFGE profiles and MLST. S. Kentucky clone ST198 and S. Java clone ST43 both well-known cause of human infections were also isolated from poultry.     

Salmonella Typhimurium in chicken manure reduced or eliminated by addition of LT1000

Poultry are normally reared on bedding materials such as wood shavings or rice hulls. Poultry litter reuse for multiple flocks has become economically important in modern broiler production. However, this practice results in the litter serving as a reservoir of numerous microbial organisms, including, yeasts, molds, multiple types of viruses, and bacterial pathogens such as Salmonella, Escherichia, Campylobacter, Clostridium, Staphylococcus, and Pseudomonas. The foodborne pathogens are of particular importance for poultry producers. During the preharvest feed withdrawal period, consumption of contaminated litter and feces by the birds can lead to infection of the upper gastrointestinal tract with Salmonella, which presents substantial problems at processing. The current study was conducted to determine whether the use of a liquid bacterial product (LBP), such as LT1000, could reduce the load of Salmonella Typhimurium in poultry manure. The LBP was added to sterile poultry manure then challenged with 10⁸ cfu/mL of Salmonella Typhimurium. The concentration of Salmonella Typhimurium was measured over 9 d or until the Salmonella Typhimurium was no longer detected. In 91% of the trials, Salmonella Typhimurium was completely eliminated within 9 d. This demonstrates that the LBP used in the current study has the potential to substantially improve the overall microbiological safety of used poultry litter.     

A temporal study of Salmonella serovars from environmental samples from poultry breeder flocks in Ontario between 1998 and 2008

A temporal study was carried out to determine Salmonella prevalence, trends, major serovars, and their clusters from environmental samples, in poultry breeder flocks in Ontario between January 1998 and December 2008. Surveillance data were obtained from the Ontario Hatchery and Supply Flock Policy. Logistic regression with a random effect for flock was used to identify factors [poultry type, year (trend) and season] associated with the prevalence of Salmonella. A cluster detection test was used to identify clusters of common serovars. The period prevalence of Salmonella was 47.4% in broiler-breeder, 25.7% in layer-breeder, and 19.6% in turkey-breeder flocks. The overall trend in the prevalence of Salmonella was decreasing for all breeder types, due primarily to decreasing trends of Salmonella Heidelberg. The seasonal effects varied by year with the highest probability of Salmonella occurring in different seasons. The 4 most common serovars identified were Salmonella Heidelberg, Kentucky, Hadar, and Typhimurium in broiler-breeders; Salmonella Heidelberg, Brandenburg, Thompson, and Typhimurium in layer-breeders; and Salmonella Heidelberg, Saintpaul, Brandenburg, and Muenster in turkey-breeders. Salmonella Enteritidis was infrequently isolated in all poultry breeder types. Temporal clusters of different serovars were identified in all poultry breeder types. Clusters of Salmonella Heidelberg, Typhimurium, and Hadar from environmental samples from breeder flocks were detected during a similar period to clusters from hatchery fluff samples from the same population. Therefore, interventions at the breeder flock-level might help to reduce transmission of Salmonella from breeder flocks to hatcheries and possibly, to lower levels of the poultry production chain.     

Bactericidal Effect of Several Chemicals on Hatching Eggs Inoculated with Salmonella serovar Typhimurium

Breeder flocks and commercial hatcheries represent an early contamination point for Salmonella entry into commercial integrated poultry operations. Utilizing effective antimicrobial treatments for hatching eggs is a critical part of reducing the incidence of Salmonella-colonized chicks on the farm. The objective of this study was to evaluate the bactericidal effect of several chemicals on Salmonella-contaminated hatching eggs. Four replications (n = 10/treatment per replicate) were conducted to determine the efficacy of 7 commercially available compounds. The compounds tested were as follows: 1) hydrogen peroxide, 2) water-oil emulsion droplets stabilized by detergent, 3) peroxyacetic acid, 4) 4 quaternary ammonium compounds attached to a polymer, 5) 2 quaternary ammonium compounds, 1 biguanide compound and bronopol attached to a polymer, 6) N-alkyl dimethyl benzyl ammonium chloride and stabilized urea, and 7) polyhexamethylenebiguanide hydrochloride. A naladixic acid-resistant Salmonella serovar Typhimurium was inoculated (10³ cfu/mL) onto fertile hatching eggs by drip-inoculation. Controls included a positive control (no spray application) and a water control (spray containing water to take into account rinsing effects). Compounds 5 and 7 had a 100% reduction, and both of these chemicals included a biguanide. Compounds 4 and 3 were also effective with a 95 and 93.5% reduction, respectively. Compounds 6 and 2 were the least effective of all chemicals, with a reduction of 47.5 and 40%, respectively. Hydrogen peroxide (compound 1), which has been used by the poultry industry, had a 70% reduction, and the water control produced a 10% reduction due to the rinsing effect. Several antimicrobials tested were more effective than hydrogen peroxide. More detailed studies will be required to adequately evaluate these antimicrobials.     

Impact of added sand on the recovery of Salmonella,Campylobacter, Escherichia coli,and coliforms from prechill and postchill commercial broiler carcass halves

Salmonella and Campylobacter are often associated with raw poultry products and continue to be leading causes of food-borne gastroenteritis in the United States. As a result, the presence of these organisms on broiler carcasses is monitored on a routine basis. Abrasive rinsing methods (e.g., adding glass beads) have been shown to increase the level of bacteria recovered from carcasses or carcass parts. The objective of this study was to evaluate the addition of sand to the rinse on bacterial enumeration and the prevalence of Salmonella and Campylobacter recovered from broiler carcasses. During each of 4 replications, 6 prechill and 6 postchill broiler carcasses were collected from a commercial processing plant. All carcasses were split along the dorso-ventral midline. Carcass halves were rinsed in buffered peptone water, whereas the companion half was rinsed in buffered peptone water with sterile sand added. All carcass halves were rinsed for 1 min and the rinsate was collected. Salmonella, coliforms, and Escherichia coli were enumerated and the prevalence of Salmonella and Campylobacter was determined. Salmonella and Campylobacter were isolated from 17 and 50% of the carcass halves, respectively. There was no significant (P > 0.05) difference in Salmonella or Campylobacter prevalence from carcass halves rinsed with or without sand. The addition of sand to the rinse had no effect on the number of Salmonella, coliforms, or E. coli recovered from prechill or postchill carcass halves. These results show that adding sand to the rinse liquid did not improve the recovery of bacteria present on the carcass in either moderate (2.6 log₁₀ cfu/mL rinsate) or low numbers (<3 cfu/mL of rinsate).     

Introduction: Reducing Salmonella Enteritidis contamination of shell eggs

Salmonella Enteritidis is a leading food-borne pathogen in the United States, with many outbreaks in humans traced back to shell eggs. As a result, the implementation of effective strategies for reducing Salmonella Enteritidis in commercial layer flocks has become a critical public health and economic objective. In this paper, we share the findings of 2 multistate USDA-National Integrated Food Safety Initiative grant teams and their work aimed at Salmonella Enteritidis reduction in shell eggs. One project, led by K. Venkitanarayanan, is using plant-derived antimicrobial molecules as dietary supplements to reduce Salmonella Enteritidis colonization of the digestive and reproductive tract of chickens. The same molecules are being evaluated for their effect on Salmonella Enteritidis in egg wash solutions. The project led by S. Kariyawasam used on-farm investigation and novel bacterial typing methods to study Salmonella Enteritidis transmission in diverse layer environments to update and optimize Egg Quality Assurance Programs that will significantly reduce Salmonella Enteritidis contamination of shell eggs. The current US Food and Drug Administration Egg Safety Rule and Egg Quality Assurance Programs are based on critical control points and best management practices developed from studies of large flocks (>50,000 hens) conducted in the 1990s, indicating that opportunities exist to improve preharvest programs to reduce Salmonella Enteritidis contamination. This paper will share the findings of these 2 projects.     

The effects of a competitive exclusion product and two probiotics on Salmonella colonization and nutrient digestibility in broiler chickens

Competitive exclusion (CE) cultures, given as a single dose on the day of hatch, together with good hygienic practices has been shown to be a novel approach to control Salmonella in poultry. The ability of the CE product Broilact and 2 probiotics, FloraMax-B11 and Colostrum, to prevent Salmonella colonization in newly hatched chickens was evaluated employing a slightly modified Mead-model chicken assay. In a parallel study the effect of the 3 treatments on the production of volatile fatty acids in the ceca were determined. In the Salmonella study 2 separate experiments were done. In the first experiment all 3 treatment materials were given as a single dose on d 1. In the second experiment, which consisted only of Broilact and FloraMax-B11, the latter was given in the drinking water during the 3 first d after hatch. In both experiments the chicks were challenged with Salmonella enterica serovar Infantis on d 2. The results of the present study show that Broilact was superior to the 2 other treatment materials in protecting the newly hatched chickens against Salmonella colonization. The parallel study showed only minor differences among the different treatments. Based on the results of the Salmonella challenge study, it was concluded that Broilact was the only treatment material that was established in the gut of the newly hatched chickens in such a way that the colonization of Salmonella was prohibited.     

Salmonella enterica subsp. enterica isolated from chicken carcasses and environment at slaughter in Reunion Island: prevalence, genetic characterization and antibiotic susceptibility

Salmonella contamination of 71 chicken broiler flocks was investigated at the slaughterhouse in Reunion Island between October 2007 and January 2009. Samples were collected from live broiler chickens and chicken carcasses as well as the slaughterhouse environment. Salmonella spp. was isolated from 40 of 71 (56 % with a confidence interval 5 % [45–67]) broiler chicken flocks at slaughter. The most prominent serovars were Blockley (31 %), Typhimurium and Brancaster (14 %), Hadar (10 %), Salmonella multidrug resistant clinical organisms serotypes 1,4,[5],12:i:-, and Virchow (8 %) and Livingstone, St. Paul, Seftenberg, Llandoff, Infantis and Indiana. At the farm, 27 % of the broiler chicken flocks tested positive for Salmonella spp. Salmonella spp. was isolated from 124 of 497 environmental samples (25 %). In most cases, there was no relationship between pulsed field gel electrophoresis (PFGE) pattern and antibiotic resistance pattern. The predominant Salmonella serovars were susceptible to most of the tested antibiotic drugs, but S. Hadar exhibited multidrug resistance. This study highlighted the primary source of Salmonella was the farm of origin and downstream stages in processing could not remedy to but amplify this Salmonella contamination.     

Prevalence and antimicrobial resistance of Salmonella isolates in Moroccan laying hens farms

Increasing emergence of salmonellosis presents a threat to the effective control of foodborne disease in humans. The purpose of this study was to evaluate the prevalence of drug susceptibility and molecular characteristics of non-typhoidal Salmonella (NTS) isolated from laying hens (LH) in 3 Moroccan regions, Rabat-Salé-Zemmour-Zaër (RSZZ), Souss-Massa-Drâa (SMD), and the grand Casablanca (GC). A total of 351 samples were collected from 30 consumer egg laying houses at the end of the egg laying period from April to July 2011. Sixty-four out of these 351 examined samples were contaminated by Salmonella. The Salmonella isolated strains were then serotyped and tested for drug susceptibility and analyzed by polymerase chain reaction (PCR) for the presence of the invasion-associated genes invA and spvC and nalidixic acid resistance-associated qnr gene. The prevalence of NTS infection in LH was estimated to be 73.3%. Seven Salmonella enterica serovars were identified: Enteritidis (37.5%), Kentucky (31.2%), Infantis (10.9%), Typhimurium (6.2%), Thompson (6.2%), Agona (4.6%), and Amsterdam (3.1%). Drug susceptibility testing showed that 65.6% of Salmonella were resistant to at least one antibiotic and 25% were resistant to ciprofloxacin. All isolates were positive for the invasion gene invA and 28% of them were positive for the virulence gene spvC. All nalidixic acid-resistant S. Enteritidis isolates were negative for qnr plasmid genes. Our findings clearly suggest the necessity to establish an NTS monitoring and control program for LH in Morocco.     

Concentration and prevalence of Escherichia coli O157 and Salmonella serotypes in sheep during slaughter at two Australian abattoirs

Objective This study aimed to determine the presence and concentration of Escherichia coli O157 and Salmonella spp. on fleece, faeces and carcases of sheep during slaughter. Procedure Faeces, fleece and pre-chill carcase samples were collected from 164 sheep slaughtered at two Australian abattoirs. The presence of E. coli O157 and Salmonella spp. were determined by use of automated immunomagnetic separation (AIMS) with enumeration by use of the ‘most probable number’ (MPN) method. Results Escherichia coli O157 was isolated from 5% of faeces, 3% of fleeces and 0.6% of pre-chill carcases. The mean log₁₀ count of E. coli O157 positive faecal samples was 2.32 MPN/g, but counts on fleeces and carcases were below the countable limit (−1 log₁₀ MPN/cm²). Salmonella spp. were isolated from 20% of faeces, 13% of fleeces and 1.3% of pre-chill carcases. The mean log₁₀ count of Salmonella spp. in faeces was 1.43 MPN/g and on fleece was −0.24 MPN/cm², but counts on carcases were below the countable limit (−1 log₁₀ MPN/cm²). Conclusion The prevalence and concentration of pathogens were low in the sheep tested in this study, indicating a low risk of human infection from products derived from these animals.