Enterica Serotype Enteritidis Research Articles

Reduction of Nontyphoidal Salmonella enterica in Broth and on Raw Chicken Breast by a Broad-spectrum Bacteriophage Cocktail

Globally, nontyphoidal Salmonella (NTS) causes approximately 150 million foodborne illnesses annually; many of which are linked to poultry products. Thus, improving food safety interventions in the poultry sector can reduce foodborne illness associated with prevalent NTS serotypes. Bacteriophages (phages) have shown promise as food-safe alternatives to current antimicrobial practices. However, challenges such as limited host range, bactericidal effectiveness in practical production settings, and the risk of developing host resistance remain as barriers for the widespread use of phages in commercial poultry operations. A broad-spectrum three-phage cocktail was evaluated against S. enterica subsp. enterica serotypes Enteritidis, Typhimurium, and Kentucky. The impact of multiplicity of infection (MOI) on NTS growth was assessed in broth at 22°C for 18 hours (h). Then, phage cocktail efficacy was evaluated on raw chicken breast samples inoculated with the NTS cocktail and stored at 10°C or 22°C for 0, 1, and 5 days or 0, 4, 8, and 16 h, respectively. Most probable number (MPN) calculations were performed for NTS counts on chicken after phage treatment and storage at 10°C to account for samples with NTS counts below the detection limit. In general, a higher MOI corresponded to reduced NTS growth; however, residual nutrition in growth media and initial NTS contamination level affected samples treated with the phage cocktail at identical MOIs. On chicken, phage cocktail treatment significantly reduced NTS counts at 10°C and 22°C. After storage at 10°C for 5 days, NTS counts were reduced by >3.2 log compared to the control. After storage at 22°C for 16 h, NTS counts were reduced by >1.7 log compared to the control. Overall, the phage cocktail was effective at reducing a diverse set of prominent NTS strains in broth and on raw chicken breast, highlighting its potential for commercialization and use alongside other hurdles in poultry production.

Biofilm formation, antimicrobial resistance genes, and genetic diversity of Salmonella enterica subspecies enterica serotype Enteritidis isolated from food and animal sources in Iran

Salmonella enterica serovar Entritidis is an important pathogen in foodborne diseases and causes gastroenteritis. Several studies have investigated the genetic diversity of the strains of this bacterium. However, our knowledge of the discriminatory power of the molecular methods is limited. In total, 34 strains of S. enteritidis were isolated from food related to animals. Antibiotic resistance of the strains, antibiotic resistance genes, and biofilm formation capacity of the strains were evaluated. For the genetic analysis of the strains, PFGE was performed using AvrII restriction enzyme. Among the tested antibiotics, cefuroxime, nalidixic acid, and ciprofloxacin showed the highest resistance rates (79.4%, 47%, and 44.2%, respectively). Only three antibiotic-resistance genes were identified in these strains (blaTEM: 67.6%, tetA: 9%, and sul2: 3%). In total, 91% of the strains were biofilm producers. Clustering of strains using AvrII for 26 samples with the same XbaI PFGE profile showed that these strains were in one clone and had high homogeneity. In conclusion, it is better to use a combination of several typing methods for typing strains that are genetically very close so that the results are reliable.

Phenotypic and genotypic characterization of salmonella Enteritidis isolated from two consecutive Food‐Poisoning outbreaks in Sichuan, China

AbstractSalmonella enterica serotype Enteritidis (SE) is a primary pathogen that causes foodborne diseases in humans. Although whole‐genome sequencing (WGS) ‐based typing analyses have been increasingly used to investigate food‐poisoning outbreaks, they are rarely applied to the epidemiology of multiple Salmonella outbreaks in Sichuan, China. This study therefore isolated SE from patients and food of two consecutive food‐poisoning outbreaks during 2020 in Sichuan, China. We tracked outbreak origin using epidemiological investigation, serotyping, antimicrobial susceptibility testing (AST), pulsed‐field gel electrophoresis (PFGE), and WGS. We also determined phylogenetic relationships using PFGE, whole and core genome multilocus sequence typing (wg/cgMLST), and whole‐genome single nucleotide polymorphism (wgSNP) analyses. Epidemiological investigations identified a correlation between cake consumption and food poisoning. Thirteen strains isolated from patients and one strain isolated from the cake were confirmed as SE. Among the 14 strains, only six shared the same AST pattern (AMP‐AMS‐Sul‐STR). Isolates from patients and cakes were indistinguishable in PFGE results. All four methods, namely PFGE, wgMLST, cgMLST, and wgSNP were appropriate for bacterial typing in SE‐related outbreak investigation. However, wgSNP can assign 12 SE strains from the first outbreak to one cluster and assign two SE strains from the second outbreak to another cluster, while PFGE, wgMLST, cgMLST did not successfully distinguish the SE strains from different outbreaks. Thus, we conclude that SNP‐based phylogenetic analysis might be a viable method for differentiating SE strains at the outbreak level.

Modelling the inactivation, survival and growth of Salmonella enterica under osmotic stress considering inoculum phase and serotype.

This study evaluated the behaviour of the Salmonella enterica serotypes in osmotically stressful BHI broth (0.940≤aw ≤ 0.960), assessing inoculum from two stages of the bacterial life cycle (exponential and stationary) and two temperatures (25°C and 35°C). Four S. enterica serotypes (Typhimurium, Enteritidis, Heidelberg and Minnesota) were grown in stressful BHI at 25°C. A mathematical model was proposed for describing the total microbial count as the sum of two subpopulations, inactivating and surviving-then-growing. When submitted to aw of 0.950 and 0.960, all strains showed a decreased count, followed by a period of unchanged count and then exponential growth (Phoenix Phenomenon). Strains inoculated at aw =0.940 and 0.945 showed inactivation kinetics only. Cells cultivated at 25°C and inoculated from the exponential phase were the most reactive to the osmotic stress, showing a higher initial population reduction and shorter adaptation period. The proposed model described the inactivation data and the Phoenix Phenomenon accurately. The results quantified the complex response of S. enterica to the osmotic environment in detail, depending on the inoculum characteristic and serotype evaluated. Quantifying these differences is truly relevant to food safety and improves risk analysis.

Contamination of street food with multidrug-resistant Salmonella, in Ouagadougou, Burkina Faso.

BackgroundGastrointestinal infections are a global public health problem. In Burkina Faso, West Africa, exposure to Salmonella through the consumption of unhygienic street food represents a major risk of infection requiring detailed evaluation.MethodsBetween June 2017 and July 2018, we sampled 201 street food stalls, in 11 geographic sectors of Ouagadougou, Burkina Faso. We checked for Salmonella contamination in 201 sandwiches (one per seller), according to the ISO 6579:2002 standard. All Salmonella isolates were characterized by serotyping and antimicrobial susceptibility testing, and whole-genome sequencing was performed on a subset of isolates, to investigate their phylogenetic relationships and antimicrobial resistance determinants.ResultsThe prevalence of Salmonella enterica was 17.9% (36/201) and the Salmonella isolates belonged to 16 different serotypes, the most frequent being Kentucky, Derby and Tennessee, with five isolates each. Six Salmonella isolates from serotypes Brancaster and Kentucky were multidrug-resistant (MDR). Whole-genome sequencing revealed that four of these MDR isolates belonged to the emergent S. enterica serotype Kentucky clone ST198-X1 and to an invasive lineage of S. enterica serotype Enteritidis (West African clade).ConclusionThis study reveals a high prevalence of Salmonella spp. in sandwiches sold in Ouagadougou. The presence of MDR Salmonella in food on sale detected in this study is also matter of concern.

Characterization of Salmonella Isolates Recovered from Stages of the Processing Lines at Four Broiler Processing Plants in Trinidad and Tobago.

This cross-sectional study determined the prevalence, characteristics, and risk factors for contamination of chicken with Salmonella at four operating broiler processing plants in Trinidad. Standard methods were used to isolate and characterize the Salmonella isolates. The overall prevalence of Salmonella at the four processing plants was 27.0% (107/396). The whole carcass enrichment (WCE) method yielded a statistically significantly (p = 0.0014) higher frequency of isolation (53.9%; 97/180) than the whole carcass rinse (35.0%; 63/180) and neck skin methods (42.2%; 38/90). S. enterica serotypes Enteritidis, Javiana, and Infantis were the predominant serotypes isolated accounting for 20.8%, 16.7% and 12.5%, respectively, of the serotyped isolates. Risk factors included the use of over 100 contract farmers (OR 4.4), pre-chiller (OR 2.3), addition of chlorine to chiller (OR 3.2), slaughtering sick broilers (OR 4.4), and flocks with >50% mortality. Multi-drug resistance was detected in 12.3% (14/114) of the isolates of Salmonella. Resistance was high to kanamycin (85.7%) and doxycycline (74.6%) but low to amoxicillin-clavulanic acid (2.4%) and sulphamethoxazole-trimethoprim (0.8%). The occurrence of resistant Salmonella in chickens processed at commercial broiler processing plants has implications for salmonellosis and therapeutic failure in consumers of improperly cooked contaminated chickens from these plants in the country.

Antimicrobial and Antioxidant Activities of Two Medicinal Plants Cuphea aequipetala var. hispida (Cav.) Koehne and Eryngium comosum Delaroche F Against Bacteria Related to Equine Infections

Functional biocompounds beneficial for animals and humans are in Mexican folk herbs. Cuphea and Eryngium species presented antimicrobial potential. Natural antibiotic uses by ethnoveterinary research with medicinal plants in equine infection or digestive diseases need more scientific evidence. Staphylococcus aureus, Escherichia coli, Salmonella enterica serotype Enteritidis are etiological agents in horses responsible for stable infections, abortions, fetal or perinatal deaths, and resistant intrahospital infections. The main objective of the present research was to evaluate the potential of antimicrobial and antioxidant activities of two Mexican medicinal plants Cuphea aequipetala var. hispida (Cav.) Koehne and Eryngium comosum Delaroche F over Listeria monocytogenes ATCC 19115, Staphylococcus sp., E. coli ATCC 25922, and S. enterica serotype Enteritidis ATCC 13076 bacterium reference strains related to equine infections. Determination of total phenol, saponins, antioxidant activity (ABTS), and antimicrobial activity with diffusion-sensitive discs was performed in triplicate. All the strains were sensitive for both extracts except for E. coli strain that was inhibited only by C. aequipetala. Staphylococcus sp. and S. enterica strains were inhibited equally by both extracts. E. comosum extracts tested have shown the highest effect over L. monocytogenes. In summary, antimicrobial activity was similar to the reported activity of Eryngium species extracts with other different solvents. Present extracts are suggested as a potential alternative antibiotic; definitely, more specific equine pathogen inhibition tests are needed in feed additives for horse nutrition research. In conclusion, antimicrobial activities of Cuphea aequipetala var. hispida (Cav.) Koehne and Eryngium comosum Delaroche F over reference strains related to equine infections suggested these medicinal plants as potential antibiotic sources for horse diseases.

Prevalence of Salmonella serotypes S. Enteritidis and S. Typhimurium in poultry and poultry products

AbstractSalmonella continues to be a major food safety and public health threat. In the present study, Salmonella enterica subsp. enterica serotypes Enteritidis (SE) and Typhimurium (ST) were isolated from poultry and characterized for virulence, antimicrobial susceptibility, and biofilm formation. Prevalence of Salmonella serotypes in poultry was 3.35%; predominant serotypes isolated were S. Enteritidis (68.1%) and S. Typhimurium (31.8%). Source‐wise, Salmonella were isolated from retail market chicken meat (4.8%), live chicken at farm (2.5%), and table eggs (2.1%). Salmonella isolates produced invA gene of 284 bp (100%), spvR gene of 310 bp (77.27%), spvC gene of 571 bp (22.72%), and stn gene of 260 bp (100%) as virulence/ pathogenicity determinants. Salmonella isolates exhibited resistance to common antimicrobials; 72.7% isolates showed multiple resistance (≥3 antimicrobial class), highest resistance was observed for polymyxin‐B (81.8%) followed by nalidixic acid (72.7%), colistin (59.1%), ampicillin/tetracyline (45.5%), ampicillin + sulbactam (40.9%), cefodroxil (18.2%), streptomycin (9.1%), and cefazidine/ceftriaxone‐tazobactam (4.5%). Multiple antimicrobial resistance (MAR) index of poultry Salmonella isolates ranged from 0.11 to 0.35; wherein, 59.1% isolates showed MAR of >0.2. About 81.8% Salmonella isolates produced biofilm and were categorized as strong (13.6%), moderate (45.4%), and weak (22.7%) biofilm producers. Occurrence of antimicrobial resistant virulent Salmonella strains in poultry requires implementation of suitable strategies so as to protect the public health.

Isolation and Identification of Lactic Acid Bacteria Probiotic Culture Candidates for the Treatment of Salmonella enterica Serovar Enteritidis in Neonatal Turkey Poults.

Simple SummarySalmonella spp. continues to be one of the most important foodborne bacterial pathogens. S. enterica serotype Enteritidis (SE) that emerged as an important human illness during the 1980s is currently one of the most common non-typhoidal Salmonella serotypes worldwide. Poultry and their products (eggs and meat) are considered as one of the most important source of SE infection in humans. Due to restrictions in the addition of antibiotics in the feed of animals intended for human consumption, alternatives to these antibiotics have been sought. Probiotics have shown to reduce infection in turkey poults. However, studies are lacking to show how these probiotics influence the intestinal microbiome as well as how this microbiome is related to a lower infection by Salmonella. In the present study the effect of a Lactobacillus spp.-based probiotic on SE colonization was evaluated in two separate experiments. In both trials, a significant reduction in the incidence and log10 cfu/g of SE were observed in poults treated with the probiotic when compared with control poults (p ≤ 0.05). Results showed that the application of this probiotic culture could reduce SE cecal colonization in day-of-hatch turkey poults, although further research is needed to elucidate the mechanism of this response.The effect of Lactobacillus spp.-based probiotic candidates on Salmonella enterica serovar Enteritidis (SE) colonization was evaluated in two separate experiments. In each experiment, sixty-one day-of-hatch female turkey poults were obtained from a local hatchery. In both experiments, poults were challenged via oral gavage with 104 cfu/poult of SE and randomly allocated to one of two groups (n = 30 poults): (1) the positive control group and (2) the probiotic treated group. Heated brooder batteries were used for housing each group separately and poults were allowed ad libitum access to water and unmedicated turkey starter feed. 1 h following the SE challenge, poults were treated with 106 cfu/poult of probiotic culture via oral gavage or phosphate-buffered saline (PBS) to control groups. A total of 24 h post-treatment, poults were euthanized and the ceca and cecal tonsils from twenty poults were collected aseptically for SE recovery. In both trials, a significant reduction in the incidence and log10 cfu/g of SE were observed in poults treated with the probiotic when compared with control poults (p ≤ 0.05). The results of the present study suggest that the administration of this lactic acid-producing bacteria (LAB)-based probiotic 1 h after an SE challenge can be useful in reducing the cecal colonization of this pathogen in neonatal poults.

Characterization of Lactic Acid Bacteria as Probiotic Candidate to Overcome the Salmonellosis in Broiler

<p>can endanger human health if they contain antibiotic residues in livestock products that can cause resistance to germs in the human body when consuming them. Along with the enactment of a policy to limit the use of antibiotics in animal feed, the use of probiotics as a substitute is urgently needed. This research has been conducted in the Research Center for Veterinary Science in<br />order to produce probiotic candidates to control the growth of Salmonella sp in chickens that have the potential to pollute the environment and cause foodborne disease. Research on probiotics in chicken has conducted in Indonesian Research Center for Veterinary Science in order to produce probiotic candidates to control the growth of Salmonella sp. in chicken that potentially contaminated the environment causing foodborne disease. The present study aims to evaluate the probiotic potential of indigenous bacteria isolated from cattle in Bogor and select candidates to be used as probiotic. The study was initiated by screening local<br />isolates for probiotic, following by inhibition test against a target of pathogenic bacteria (Salmonella enterica serotype of Typhimurium B0046/ATCC 13311 and serotype of Enteritidis B2893/ATCC 13076), pathogenicity in vitro, survival in the<br />chicken gut, and the lifespan in the lyophilized container. The results showed that six isolates bacteria consisting of Aerococcus viridans B2776, Bifidobacterium dentium B2754 and B2755, Enterococcus faecium B2758, Lactobacillus casei B2752, and Streptococcus uberis B2757 had been selected as the candidate for probiotics. They had specifications namely: anti-microbial<br />substance (in vitro) against S. enterica serotype Typhimurium BCC B0046 and serotype Enteritidis BCC B2893, not pathogenic, able to form colonies in intestinal broilers for 40 days with concentrations of >1010 CFU/gram with lifespan up to one year (lyophilized), using protectant serum of inositol 5% or 7,5% skim milk at 5C with concentrations >log10 CFU/ml. The potential<br />characteristics qualified them as probiotics against pathogenic bacteria and could be used to control salmonellosis in the broiler.</p>

Detection of Salmonella from animal sources in South Africa between 2007 and 2014.

Retrospective laboratory-based surveillance was conducted on Salmonella serotypes isolated from various animal species from 2007 to 2014 at the Agricultural Research Council, Onderstepoort Veterinary Research Institute, South Africa. During the surveillance period, 1229 salmonellae isolations were recorded. Around 108 different serotypes were recovered from nine different food and non-food animal host species. The three most common serotypes were Salmonella enterica subspecies enterica serotype Heidelberg (n = 200), Salmonella enterica subspecies enterica serotype Enteritidis (n = 170) and Salmonella enterica subspecies enterica serotype Typhimurium (n = 146). These were followed by Salmonella enterica subspecies enterica serotype Anatum (n = 62) and Salmonella enterica subspecies enterica serotype Infantis (n = 57). Salmonella enterica subspecies enterica serotype Schwarzengrund and Salmonella enterica subspecies enterica serotype Muenchen were recovered in 50 and 48 cases, respectively. Of the total number of isolations recorded during the period under review, 871 (70.8%) occurred in poultry and other birds, 162 (13.2%) in horses, 116 (9.4%) in cattle, 26 (2.1%) in sheep and goats, 22 (1.8%) in rhinoceroses, 16 (1.3%) in pigs, 8 (0.6%) in crocodiles, 6 (0.5%) in cats and 6 (0.5%) in leopards. Food animals accounted for 83.5% of the total isolations, with cattle and poultry representing approximately 72.7%. Forty-two (3.4 %) isolates were found from non-food animals that include rhinoceroses (n = 22), crocodiles (n = 8), leopards (n = 6) and cats (n = 6). Salmonella Heidelberg was the most frequently isolated serotype, whereas S. Typhimurium had the widest zoological distribution. Clinical laboratory isolation of different Salmonella serotypes from various hosts may aid in recognising the threat to livestock, public and environmental health. Moreover, it may also highlight the potential zoonotic and food safety risk implications of the detected Salmonella serotypes.

Characterization and Protective Efficacy of Type III Secretion Proteins as a Broadly Protective Subunit Vaccine against Salmonella enterica Serotypes.

Nontyphoidal Salmonella enterica serotypes (NTS) are the leading cause of hospitalization and death due to foodborne illnesses. NTS are the costliest of the foodborne pathogens and cause ∼$4 billion annually in health care costs. In Africa, new invasive NTS are the leading cause of bacteremia, especially in HIV-positive children and adults. Current vaccines against S. enterica are not broadly protective and most are directed at the typhoid-causing serotypes, not the NTS. All S. enterica strains require two type III secretion systems (T3SS) for virulence. The T3SS needle tip protein and the first translocator are localized to the T3SS needle tip and are required for pathogenesis of S. enterica Collectively they are 95 to 98% conserved at the amino acid sequence level among all S. enterica strains. The Salmonella pathogenicity island 1 or 2 tip and first translocator proteins were genetically fused to produce the S1 and S2 fusion proteins, respectively, as potential vaccine candidates. S1 and S2 were then characterized using spectroscopic techniques to understand their structural and biophysical properties. Formulated at the proper pH, S1, S2, or S1 plus S2 (S1S2), admixed with adjuvant, was used to immunize mice followed by a lethal challenge with S. enterica serotype Typhimurium or S. enterica serotype Enteritidis. The S1S2 formulation provided the highest protective efficacy, thus demonstrating that an S1S2 subunit vaccine can provide broad, serotype-independent protection, possibly against all S. enterica serotypes. Such a finding would be transformative in improving human health.

Draft Genome Sequences of 64 Salmonella enterica Serotype Enteritidis Isolates Obtained from Wild Mice.

ABSTRACTSalmonella enterica serotype Enteritidis is a foodborne pathogen of global concern, because it is frequently isolated from foods and patients. Draft genome sequences are reported here for 64 S. Enteritidis strains isolated from the intestines and spleens of mice caught live on chicken farms in the U.S. Northeast. The availability of these genomes provides baseline information on the genomic diversity of S. Enteritidis during the 1990s, when foodborne outbreaks traced to internal contamination of eggs were prevalent.

Salmonella Enteritidis in Layer Farms of Different Sizes Located in Northern China: On-Farm Sampling and Detection by the PCR Method

ABSTRACT Salmonella enterica subspecies enterica serotype Enteritidis (SE) has caused foodborne infections over decades. It is transmitted mainly from contaminated eggs to humans. SE is commonly present in layer houses, and closely interacts with environmental factors. The objective of the present study was to develop a viable PCR method to identify SE in environmental samples collected in layer farms of different sizes, and to evaluate SE contamination status in four main egg-production provinces of northern China. After specificity retrieval using Primer-BLAST against the NCBI database, three SE specific oligonucleotide primers were selected as candidate primers. The primers targeting Prot6e gene were adopted and primers targeting Sdf I were also selected to validate the results, after testing eight different types of pooled poultry environmental samples (overshoe, air, drinking nipple, feed, egg collection belt, eggshell, air inlet, and air outlet) by PCR. A PCR detection limit of 1 CFU/mL was determined using cell lysates from pure cultures. Testing time was less than 48 h. On-farm samples were collected from two layer farm sizes (one housing more than 50,000 layers, and the other, less than 50,000 layers) in each province. The applied PCR method was shown to be simple, inexpensive and effective for screening SE in a large amount of farm samples. The study identified only one SE-positive farm, which a large farm and where nine samples were found to be contaminated with SE: drinking nipples (3), egg collection belt (1), air inlet (1), air (1), overshoe (1) and eggshell (2).

Genetic diversity and virulence genes of Salmonella enterica subspecies enterica serotype Enteritidis isolated from meats and eggs.

Salmonella enterica subspecies enterica serotype Enteritidis (S. Enteritidis) is one of the leading causes of food-borne gastroenteritis associated with the consumption of contaminated food products of animal origin. Little is known about the genetic diversity and virulence content of S. Enteritidis isolated from poultry meats and eggs in Iran. A total of 34S. Enteritidis strains were collected from different food sources of animal origin in Tehran from May 2015 to July 2016. All of the S. Enteritidis strains were serotyped, antimicrobial susceptibility tested, and characterized for virulence genes. Pulsed-field gel electrophoresis (PFGE) was also applied for comparison of genetic relatedness. All of the strains harbored invA, hilA, ssrA, sefA, spvC, and sipA genes. A high prevalence of resistance against certain antibiotics such as cefuroxime (79.4%), nalidixic acid (47%), and ciprofloxacin (44.2%) was also observed. Regarding PFGE, S. Enteritidis strains from different sources showed considerable overlap, suggesting the lack of diversity among these isolates. Moreover, no correlation between virulence profiles or antibiotypes and PFGE clusters was observed. In conclusion, our study provided valuable information on virulence gene content, antibiotic resistance, and genetic diversity of S. Enteritidis isolated from food sources.

Whole-Genome Sequencing Analysis of Salmonella enterica Serovar Enteritidis Isolates in Chile Provides Insights into Possible Transmission between Gulls, Poultry, and Humans.

ABSTRACTSalmonella enterica subsp. enterica serotype Enteritidis is a major cause of human salmonellosis worldwide; however, little is known about the genetic relationships between S. Enteritidis clinical strains and S. Enteritidis strains from other sources in Chile. We compared the whole genomes of 30 S. Enteritidis strains isolated from gulls, domestic chicken eggs, and humans in Chile, to investigate their phylogenetic relationships and to establish their relatedness to international strains. Core genome multilocus sequence typing (cgMLST) analysis showed that only 246/4,065 shared loci differed among these Chilean strains, separating them into two clusters (I and II), with cluster II being further divided into five subclusters. One subcluster (subcluster 2) contained strains from all surveyed sources that differed at 1 to 18 loci (of 4,065 loci) with 1 to 18 single-nucleotide polymorphisms (SNPs), suggesting interspecies transmission of S. Enteritidis in Chile. Moreover, clusters were formed by strains that were distant geographically, which could imply that gulls might be spreading the pathogen throughout the country. Our cgMLST analysis, using other S. Enteritidis genomes available in the National Center for Biotechnology Information (NCBI) database, showed that S. Enteritidis strains from Chile and the United States belonged to different lineages, which suggests that S. Enteritidis regional markers might exist and could be used for trace-back investigations. IMPORTANCE This study highlights the importance of gulls in the spread of Salmonella Enteritidis in Chile. We revealed a close genetic relationship between some human and gull S. Enteritidis strains (with as few as 2 of 4,065 genes being different), and we also found that gull strains were present in clusters formed by strains isolated from other sources or distant locations. Together with previously published evidence, this suggests that gulls might be spreading this pathogen between different regions in Chile and that some of those strains have been transmitted to humans. Moreover, we discovered that Chilean S. Enteritidis strains clustered separately from most of S. Enteritidis strains isolated throughout the world (in the GenBank database) and thus it might be possible to distinguish the geographical origins of strains based on specific genomic features. This could be useful for trace-back investigations of foodborne illnesses throughout the world.

Evaluation and Comparison of the Antimicrobial Activity Of Bifidobacteria bifidum and Bifidobacteria infantis as Probiotic Bacteria against Salmonella enterica Serotype Enteritidis

1.1. Background: Using the antimicrobial assays for determining the inhibitory effects of many compounds and also microorganisms has been ordinary in researching food and drug laboratories. During the last decades, the prevalence of foodborne diseases due to contaminated food as well as demand for natural and healthy foods has increased. Using probiotics for this purpose and for inhibiting growth of food pathogens is an interesting topic. 1.2. Objective: The aim of this study was to investigate three different methods namely spot on lawn assay, agar well diffusion assay(Cup plate assay) and agar disk diffusion assay and to compare the methods by the means of SPSS program for the antibacterial effects of Bifidobacterium bifidum and Bifidobacterium infantis against salmonella enterica serotype Enteritidis. 1.3. Material and methods: Supernatant and sediment of the two probiotic bacteria culture was tested in three different assays (spot-on-lawn, well diffusion and disk diffusion) against salmonella. 1.4. Results: In this study Well diffusion assay (Cup plate assay) was the best method to identify the antagonism of microorganisms and spot- on lawn method was the worse. Also in all three methods, the supernatant was significantly more effective than sediment in inhibiting the pathogen.Results showed that in all three assays, sediment and supernatant of Bifidobacterium infantis culture had a greater inhibition effect on salmonella than Bifidobacterium bifidum but the difference was not significant from statistical analyses point of view. 1.5. Discussion: Better functioning of Well diffusion assay (Cup plate method) could be explained by high accuracy and volume of supernatant used in this method. The inhibition zone in all three methods could be related to metabolites such as Acids, Diacetyle, Hydrogen proxide, Bacteriocins,…produced by probiotics.

Application of a virulent bacteriophage cocktail leads to reduction of Salmonella enterica serovar Enteritidis counts in processed meat products

ABSTRACTSalmonella enterica serotype Enteritidis (SE) is a major cause of food-borne disease outbreaks worldwide. We evaluated the effectiveness of five lytic bacteriophages applied as a cocktail to reduce the counts of SE in two types of processed meat products: cooked (turkey ham (TB) and chicken sausage (CS)) and cured sausage (Italian salami (IS) and barbecue sausage (BS)). Groups of 25 samples each were contaminated with SE, treated with a phage cocktail using a multiplicity of infection of 105 and then incubated for ten days at 18°C and 4°C. A significant reduction in bacteria was obtained on days 3, 6 and 10 in all matrices incubated at 18°C (from 0.48 to 2.12 log Colony Forming Units (CFU) g−1) and at 4°C (from 0.23 to 2.06 log CFU g−1), with the exception of BS at day 3 at 4°C, and IS at both incubation temperatures throughout the trial. The viral titre remained stable in all matrices analysed except in BS. These results show the effectiveness of this bacteriophage cocktail against S. enterica serovar Enteritidis in some processed meat products such as CS, BS and TB.

Prevalence and Characteristics of Salmonella Serotypes Isolated from Fresh Produce Marketed in the United States

Salmonella continues to rank as one of the most costly foodborne pathogens, and more illnesses are now associated with the consumption of fresh produce. The U.S. Department of Agriculture Microbiological Data Program (MDP) sampled select commodities of fresh fruit and vegetables and tested them for Salmonella, pathogenic Escherichia coli, and Listeria. The Salmonella strains isolated were further characterized by serotype, antimicrobial resistance, and pulsed-field gel electrophoresis profile. This article summarizes the Salmonella data collected by the MDP between 2002 and 2012. The results show that the rates of Salmonella prevalence ranged from absent to 0.34% in cilantro. A total of 152 isolates consisting of over 50 different serotypes were isolated from the various produce types, and the top five were Salmonella enterica serotype Cubana, S. enterica subspecies arizonae (subsp. IIIa) and diarizonae (subsp. IIIb), and S. enterica serotypes Newport, Javiana, and Infantis. Among these, Salmonella serotypes Newport and Javiana are also listed among the top five Salmonella serotypes that caused most foodborne outbreaks. Other serotypes that are frequent causes of infection, such as S. enterica serotypes Typhimurium and Enteritidis, were also found in fresh produce but were not prevalent. About 25% of the MDP samples were imported produce, including 65% of green onions, 44% of tomatoes, 42% of hot peppers, and 41% of cantaloupes. However, imported produce did not show higher numbers of Salmonella-positive samples, and in some products, like cilantro, all of the Salmonella isolates were from domestic samples. About 6.5% of the Salmonella isolates were resistant to the antimicrobial compounds tested, but no single commodity or serotype was found to be the most common carrier of resistant strains or of resistance. The pulsed-field gel electrophoresis profiles of the produce isolates showed similarities with Salmonella isolates from meat samples and from outbreaks, but there were also profile diversities among the strains within some serotypes, like Salmonella Newport.

Assessment of the effect of a Salmonella enterica ser. Typhimurium culture supernatant on the single-cell lag time of foodborne pathogens

The objective of this study was the in vitro evaluation of the effect of a cell-free microbial supernatant, produced by a luxS-positive Salmonella enterica ser. Typhimurium strain, on the single-cell growth kinetic behavior of two strains of S. enterica (serotypes Enteritidis and Typhimurium) and a methicillin-resistant Staphylococcus aureus strain. The single-cell lag time (λ) of the pathogens was estimated in the absence and presence (20% v/v) of microbial supernatant based on optical density measurements. As demonstrated by the obtained results, the tested microbial supernatant had a strain-specific effect on the single-cell λ and its variability. Although the mean λ values were similar in the absence and presence of microbial supernatant in the case of Salmonella Enteritidis, a significant (P≤0.05) reduction and increase in the mean value of this parameter in the presence of microbial supernatant were observed for Salmonella Typhimurium and St. aureus, respectively. With regard to the effect of the tested microbial supernatant on the single-cell variability of λ, similar λ distributions were obtained in its absence and presence for S. Enteritidis, while considerable differences were noted for the other two tested organisms; the coefficient of variation of λ in the absence and presence of microbial supernatant was 41.6 and 69.8% for S. Typhimurium, respectively, with the corresponding values for St. aureus being 74.0 and 56.9%. As demonstrated by the results of bioassays, the tested microbial supernatant exhibited autoinducer-2 activity, indicating a potential association of such quorum sensing compounds with the observed effects. Although preliminary in nature, the collected data provide a good basis for future research on the role of quorum sensing in the single-cell growth behavior of foodborne pathogens.