Resistance-Nodulation-Cell Division (RND) Transporter AcrD Confers Resistance to Egg White in Salmonella enterica Serovar Enteritidis

The excellent survival ability of Salmonella enterica serovar Enteritidis (S. Enteritidis) in egg white leads to outbreaks of salmonellosis frequently associated with eggs and egg products. Our previous proteomic study showed that the expression of multidrug efflux RND transporter AcrD in S. Enteritidis was significantly up-regulated (4.06-fold) in response to an egg white environment. In this study, the potential role of AcrD in the resistance of S. Enteritidis to egg white was explored by gene deletion, survival ability test, morphological observation, Caco-2 cell adhesion and invasion. It was found that deletion of acrD had no apparent effect on the growth of S. Enteritidis in Luria-Bertani (LB) broth but resulted in a significant (p < 0.05) decrease in resistance of S. Enteritidis to egg white and a small number of cell lysis. Compared to the wild type, a 2-log population reduction was noticed in the ΔacrD mutant with different initial concentrations after incubation with egg white for 3 days. Furthermore, no significant difference (p > 0.05) in the adhesion and invasion was found between the wild type and ΔacrD mutant in LB broth and egg white, but the invasion ability of the ΔacrD mutant in egg white was significantly (p < 0.05) lower than that in LB broth. This indicates that acrD is involved in virulence in Salmonella. Taken together, these results reveal the importance of AcrD on the resistance of S. Enteritidis to egg white.

Draft Genome Sequence of Salmonella enterica Serovar Enteritidis from Jos, Plateau State, Nigeria

Salmonella enterica serovar Enteritidis causes the highest incidence of human salmonellosis infections. Here, we describe the whole-genome sequence and annotation of Salmonella enterica serovar Enteritidis strain 1145s, isolated in Nigeria. The strain has a genome of 4.57 Mb with a GC content of 52% and contains one plasmid.

The Evolution of Fluoroquinolone Resistance in Salmonella under Exposure to Sub-Inhibitory Concentration of Enrofloxacin

The evolution of resistance in Salmonella to fluoroquinolones (FQs) under a broad range of sub-inhibitory concentrations (sub-MICs) has not been systematically studied. This study investigated the mechanism of resistance development in Salmonella enterica serovar Enteritidis (S. Enteritidis) under sub-MICs of 1/128×MIC to 1/2×MIC of enrofloxacin (ENR), a widely used veterinary FQ. It was shown that the resistance rate and resistance level of S. Enteritidis varied with the increase in ENR concentration and duration of selection. qRT-PCR results demonstrated that the expression of outer membrane porin (OMP) genes, ompC, ompD and ompF, were down-regulated first to rapidly adapt and develop the resistance of 4×MIC, and as the resistance level increased (≥8×MIC), the up-regulated expression of efflux pump genes, acrB, emrB amd mdfA, along with mutations in quinolone resistance-determining region (QRDR) gradually played a decisive role. Cytohubba analysis based on transcriptomic profiles demonstrated that purB, purC, purD, purF, purH, purK, purL, purM, purN and purT were the hub genes for the FQs resistance. The ‘de novo’ IMP biosynthetic process, purine ribonucleoside monophosphate biosynthetic process and purine ribonucleotide biosynthetic process were the top three biological processes screened by MCODE. This study first described the dynamics of FQ resistance evolution in Salmonella under a long-term selection of sub-MICs of ENR in vitro. In addition, this work offers greater insight into the transcriptome changes of S. Enteritidis under the selection of ENR and provides a framework for FQs resistance of Salmonella for further studies.

Tracking Salmonella Enteritidis in the Genomics Era: Clade Definition Using a SNP-PCR Assay and Implications for Population Structure

Salmonella enterica serovar Enteritidis (or Salmonella Enteritidis, SE) is one of the oldest members of the genus Salmonella, based on the date of first description and has only gained prominence as a significant bacterial contaminant of food over the last three or four decades. Currently, SE is the most common Salmonella serovar causing foodborne illnesses. Control measures to alleviate human infections require that food isolates be characterized and this was until recently carried out using Pulsed-Field Gel Electrophoresis (PFGE) and phage typing as the main laboratory subtyping tools for use in demonstrating relatedness of isolates recovered from infected humans and the food source. The results provided by these analytical tools were presented with easy-to-understand and comprehensible nomenclature, however, the techniques were inherently poorly discriminatory, which is attributable to the clonality of SE. The tools have now given way to whole genome sequencing which provides a full and comprehensive genetic attributes of an organism and a very attractive and superior tool for defining an isolate and for inferring genetic relatedness among isolates. A comparative phylogenomic analysis of isolates of choice provides both a visual appreciation of relatedness as well as quantifiable estimates of genetic distance. Despite the considerable information provided by whole genome analysis and development of a phylogenetic tree, the approach does not lend itself to generating a useful nomenclature-based description of SE subtypes. To this end, a highly discriminatory, cost-effective, high throughput, validated single nucleotide based genotypic polymerase chain reaction assay (SNP-PCR) was developed focussing on 60 polymorphic loci. The procedure was used to identify 25 circulating clades of SE, the largest number so far described for this organism. The new subtyping test, which exploited whole genome sequencing data, displays the attributes of an ideal subtyping test: high discrimination, low cost, rapid, highly reproducible and epidemiological concordance. The procedure is useful for identifying the subtype designation of an isolate, for defining the population structure of the organism as well as for surveillance and outbreak detection.

Integrated Analysis of Cecal Microbiome and Metabolome Revealed Different Inflammatory Reponses to Salmonella Enterica Serovar Enteritidis Between Reciprocal Crosses of Chicken

Background: Salmonella enterica serovar Enteritidis (S. Enteritidis) bacteria can colonize intestinal tract of chicken and transmit to humans, while the intestinal microbiota are resistant to their colonization. Our knowledge of the interplay between host, pathogen and microbiota is scarce, particularly in context of different genetic background of the host, such as the reciprocal cross.Results: Comprehensive analysis of microbiome and metabolome showed that 23.4% of genera and 11.6% of metabolites in the Cross, and 17.2% of genera and 25.1% of metabolites in the Reverse-cross were altered (P<0.05) in response to Salmonella infection. In comparison of the reciprocal crosses, all the co-differential genera and 73.1% of the co-differential metabolites were opposite in alteration trend. Phenylpropanoids and lipids were increased significantly in the Cross and in the Reverse-cross, respectively.Conclusions: A more extensive inflammatory response to S. Enteritidis might be triggered in the Reverse-cross than in the Cross, and the regulatory modes were different. The Reverse-cross upregulated pro- and anti-inflammatory factors simultaneously, while the Cross was aided with the phenylpropanoids produced by intestinal bacteria.

Inactivation of Salmonella enterica Serovar Enteritidis on Chicken Eggshells Using Blue Light

Salmonella enterica serovar Enteritidis (S. Enteritidis) is a pathogen that poses a health risk. Blue light (BL), an emerging sanitization technology, was employed for the first time in the present study to inactivate S. Enteritidis on eggshell surfaces and its influence on maintaining eggshell freshness was investigated systematically. The results showed that 415 nm-BL irradiation at a dose of 360 J/cm2 reduced 5.19 log CFU/mL of S. Enteritidis in vitro. The test on eggshells inoculated with S. Enteritidis showed that a BL dose at 54.6 J/cm2 caused a 3.73 log CFU reduction per eggshell surface and the impact of BL inactivation could be sustained in post-5-week storage. The quality of the tested eggs (weight loss, yolk index, Haugh unit (HU) and albumen pH) demonstrated that BL treatments had negligible effects on the albumen pH of eggs. However, compared to the control, BL-treated eggs showed lower weight loss and higher HU after 5 weeks of storage at 25 °C and 65% humidity and yolk index in the control group could not be determined after 5 weeks of storage. Besides, the total amino acid content of the BL-treated egg was higher than the control, exhibiting an advantage of BL irradiation in maintaining the nutrient quality of whole eggs. The current study determined the efficacy of BL against S. Enteritidis on eggshell and suggested that BL could be an effective application in maintaining the freshness and quality of eggs.

Phenotypic Antimicrobial Resistance Patterns in Salmonella typhimurium and Enteritidis Strains Isolated from Human, Food, and Environmental Samples of Broiler Meat Production Chain in Punjab

The emergence of antimicrobial resistance is a growing public health issue worldwide due to extensive use in agriculture, food, and veterinary medicine. The rate of antimicrobial resistance varies with different antibiotics and serotypes but Salmonella enterica serovar Enteritidis is one of the most widespread serotypes which is comparatively more susceptible to antimicrobial resistance followed by S. Typhimurium. A total of 71 Salmonella strains (S. Typhimurium, n=45; S. Enteritidis, n=26) isolated from humans, food and the environment were used in the study. Both isolates were confirmed through PCR by targeting their specific spy and sdf genes respectively. Kirby-Bauer disc diffusion method was used to determine antimicrobial susceptibility against 10 antibiotics used. An exponentially high level of resistance was found in S. Typhimurium strains. The highest level of resistance was found against amoxicillin (97.78%) followed by tetracycline (95.56%), gentamicin (93.33%), trimethoprim (86.67%), streptomycin (84.44%), nalidixic acid (77.78%), sulphafurazole (64.44%), ampicillin (62.22%), chloramphenicol (46.67%) and least resistance was found against ciprofloxacin (31.11%). Four penta MDR (ACSSuT) and two tetra MDR (ASSuT) resistance patterns were found S. Typhimurium strains. In S. Enteritidis strains, a high level of resistance was found against sulphonamides and streptomycin (92.31%) with the least resistance against ciprofloxacin (11.54%). Two penta MDR (ACSSuT) and six tetra MDR (ASSuT) resistance patterns were found. The presence of high antimicrobial resistance in zoonotic S. Typhimurium and Enteritidis in the broiler meat production chain is alarming. Immediate action and appropriate measures are required to control over the counter and irrational use of antibiotics both in poultry and humans. © 2021 Friends Science Publishers