Enteritidis Strains Research Articles

The two-component sensor factor envZ influences antibiotic resistance and virulence in the evolutionary dynamics of multidrug-resistant Salmonella enteritidis causing multisite invasive infections.

To assess the impact of mutations in the two-component sensor envZ on antibiotic resistance and virulence in the evolutionary dynamics of MDR Salmonella enteritidis (S. enteritidis). Five S. enteritidis isolates obtained from a patient with multisite invasive infections were analysed. Analysis of antibiotic resistance genes, virulence genes and SNP was performed through WGS. RNA sequencing, quantitative RT-PCR, virulence testing in a Galleria mellonella (G. mellonella) infection model and in vitro cell experiments were used to examine the effects of envZ mutations. WGS revealed identical resistance and virulence genes on an IncFIB(S)/IncFII(S)/IncX1 fusion plasmid in all strains. The faecal strains harboured envZ mutations, reducing outer membrane protein ompD and ompF transcriptional level. Virulence testing demonstrated elevated virulence in envZ mutant strains. In vitro experiments revealed increased adhesion, invasion and phagocytosis resistance in envZ mutants, along with reduced biofilm formation and growth rates. These findings highlight novel genetic locations on envZ influencing antibiotic resistance and virulence in clinical S. enteritidis strains. envZ mutations impact antibiotic resistance by down-regulating ompD and ompF expression and enhance virulence, contributing to multisite infections with increased fitness costs.

Emergence and Comparative Genome Analysis of Salmonella Ohio Strains from Brown Rats, Poultry, and Swine in Hungary.

Rats are particularly important from an epidemiological point of view, because they are regarded as reservoirs for diverse zoonotic pathogens including enteric bacteria. This study is the first to report the emergence of Salmonella serovar Ohio in brown rats (Rattus norvegicus) and food-producing animals in Hungary. We first reveal the genomic diversity of the strains and their phylogenomic relationships in the context of the international collection of S. Ohio genomes. This pathogen was detected in 4.3% (4/92) of rats, captured from multiple sites in Hungary. A whole-genome-based genotype comparison of S. Ohio, Infantis, Enteritidis, and Typhimurium strains showed that 76.4% (117/153) of the virulence and antimicrobial resistance genes were conserved among these serovars, and none of the genes were specific to S. Ohio. All S. Ohio strains lacked virulence and resistance plasmids. The cgMLST phylogenomic comparison highlighted a close genetic relationship between rat and poultry strains of S. Ohio from Hungary. These strains clustered together with the international S. Ohio genomes from aquatic environments. Overall, this study contributes to our understanding of the epidemiology of Salmonella spp. in brown rats and highlights the importance of monitoring to minimize the public health risk of rodent populations. However, further research is needed to understand the route of infection and evolution of this serovar.

First Data on WGS-Based Typing and Antimicrobial Resistance of Human Salmonella Enteritidis Isolates in Greece.

Salmonella enterica subsp. enterica serotype Enteritidis (S. Enteritidis) is one of the major causes of foodborne infections and is responsible for many national and multi-country foodborne outbreaks worldwide. In Greece, human salmonellosis is a mandatory notifiable disease, with laboratory surveillance being on a voluntary basis. This study aims to provide the first insights into the genetic characteristics and antimicrobial resistance profiles of 47 S. Enteritidis human isolates using whole-genome sequencing (WGS) technology. The S. Enteritidis population was mainly resistant to fluoroquinolones due to gyrA point mutations, whereas one isolate presented a multi-resistant plasmid-mediated phenotype. ST11 was the most frequent sequence type, and phylogenetic analysis through the cgMLST and SNP methods revealed considerable genetic diversity. Regarding virulence factors, 8 out of the 24 known SPIs and C63PI were detected. Due to the observed variability between countries, it is of utmost importance to record the circulating S. Enteritidis strains' structure and genomic epidemiology at the national level. WGS is a valuable tool that is revolutionizing our approach to Salmonella by providing a deeper understanding of these pathogens and their impact on human health.

Modulation of Salmonella virulence by a novel SPI-2 injectisome effector that interacts with the dystrophin-associated protein complex.

In Salmonella enterica, the injectisome machinery encoded by Salmonella pathogenicity island 2 (SPI-2) is conserved among the five subspecies and delivers proteins (effectors) into host cells, which are required for Salmonella virulence. The identification and functional characterization of SPI-2 injectisome effectors advance our understanding of the interplay between Salmonella and its host(s). Using an optimized method for preparing secreted proteins and a clinical isolate of the invasive non-typhoidal Salmonella enterica serovar Enteritidis strain D24359, we identified 22 known SPI-2 injectisome effectors and one new effector-SseM. SseM modulates bacterial growth during murine infection and has a sequence corresponding to a postsynaptic density-95/discs large/zonula occludens-1 (PDZ)-binding motif that is essential for interaction with the PDZ-containing host protein β-2-syntrophin and other components of the dystrophin-associated protein complex (DAPC). To our knowledge, SseM is unique among Salmonella effectors in containing a functional PDZ-binding motif and is the first bacterial protein to target the DAPC.

Genotypic and phenotypic analysis of Salmonella enterica serovar Derby, looking for clues explaining the impairment of egg isolates to cause human disease.

Salmonella enterica serovar Derby causes foodborne disease (FBD) outbreaks worldwide, mainly from contaminated pork but also from chickens. During a major epidemic of FBD in Uruguay due to S. enteritidis from poultry, we conducted a large survey of commercially available eggs, where we isolated many S. enteritidis strains but surprisingly also a much larger number (ratio 5:1) of S. Derby strains. No single case of S. Derby infection was detected in that period, suggesting that the S. Derby egg strains were impaired for human infection. We sequenced fourteen of these egg isolates, as well as fifteen isolates from pork or human infection that were isolated in Uruguay before and after that period, and all sequenced strains had the same sequence type (ST40). Phylogenomic analysis was conducted using more than 3,500 genomes from the same sequence type (ST), revealing that Uruguayan isolates clustered into four distantly related lineages. Population structure analysis (BAPS) suggested the division of the analyzed genomes into nine different BAPS1 groups, with Uruguayan strains clustering within four of them. All egg isolates clustered together as a monophyletic group and showed differences in gene content with the strains in the other clusters. Differences included variations in the composition of mobile genetic elements, such as plasmids, insertion sequences, transposons, and phages, between egg isolates and human/pork isolates. Egg isolates showed an acid susceptibility phenotype, reduced ability to reach the intestine after oral inoculation of mice, and reduced induction of SPI-2 ssaG gene, compared to human isolates from other monophyletic groups. Mice challenge experiments showed that mice infected intraperitoneally with human/pork isolates died between 1-7 days p.i., while all animals infected with the egg strain survived the challenge. Altogether, our results suggest that loss of genes functions, the insertion of phages and the absence of plasmids in egg isolates may explain why these S. Derby were not capable of producing human infection despite being at that time, the main serovar recovered from eggs countrywide.

Antimicrobial resistance and genome characteristics of Salmonella enteritidis from Huzhou, China.

Salmonella enteritidis is a main pathogen responsible for sporadic outbreaks of gastroenteritis, and therefore is an important public health problem. This study investigated the drug resistance and genomic characteristics of S. enteritidis isolated from clinical and food sources in Huzhou, Zhejiang Province, China, from February 1, 2021, to December 30, 2023. In total, 43 S. enteritidis strains isolated during the study period were subjected to virulence gene, drug resistance gene, genetic correlation, antibiotic resistance, and multilocus sequence typing analyses. All 43 isolates were identified as ST11, and contained 108 virulence-related genes. Drug sensitivity analysis of the 43 isolates showed resistance rates of 100% to nalidixic acid and 90.70% to ampicillin and ampicillin/sulbactam. Multidrug resistance is a serious issue, with 81.40% of strains resistant to three or more antibacterial drugs. Genome sequencing indicated that S. enteritidis possessed 23 drug resistance genes, of which 14 were common to all 43 isolates. Phylogenetic analysis based on core genome single-nucleotide polymorphisms divided the 43 S. enteritidis strains into three clusters, with the 10 samples from an outbreak forming an independent branch located in cluster 3.

Characterization of the prevalence of Salmonella in different retail chicken supply modes using genome-wide and machine-learning analyses

Salmonella is a foodborne pathogen that causes salmonellosis, of which retail chicken meat is a major source. However, the prevalence of Salmonella in different retail chicken supply modes and the threat posed to consumers remains unclear. The prevalence, serotype distribution, antibiotic resistance, and genomic characteristics of Salmonella in three supply modes of retail chicken (live poultry, frozen, and chilled) were investigated using whole-genome sequencing (WGS) and machine learning (ML). In this study, 480 retail chicken samples from live poultry, frozen, and chilled supply modes in Guangzhou from 2020 to 2021, as well as 253 Salmonella isolates (total isolation rate = 53.1 %), were collected. The prevalence of isolates in the live poultry mode (67.5 %, 81/120) was statistically higher than in the frozen (50.0 %, 120/240) and chilled (43.3 %, 52/120) (P < 0.05) modes. Serotype identification showed significant differences in the serotype distribution of Salmonella in different supply modes. S. Enteritis (46.7 %) and S. Indiana (14.2 %) were predominant in the frozen mode. S. Agona (23.5 %) and S. Saintpaul (13.6 %) were predominant in live poultry, while S. Enteritis (40.4 %) and S. Kentucky (17.3 %) were predominant in chilled mode. Antibiotic testing showed that frozen mode isolates were more resistant; the multidrug-resistant (MDR) rate of isolates in the frozen mode reached 91.8 %, significantly higher than in the chilled (86.5 %) and live (74.1 %) (P < 0.05) modes. WGS was performed on 155 top serotypes (S. Enteritidis, S. Kentucky, S. Indiana, and S. Agona). The antibiotic resistance gene analysis showed that the abundance and carrying rate of antibiotic resistance genes of Salmonella in the frozen mode (54 types, 16.1 %) were significantly higher than in other modes (live poultry: 36 types, 9.4 %, P < 0.05; chilled: 31 types, 11.6 %). The blaNDM-1 and blaNDM-9 genes encoding carbapenem resistance were found in frozen mode isolates on a complex transposon consisting of TnAS3-IS26. Virulence factors and plasmid replicons were abundant in the studied frozen mode isolates. In addition, single nucleotide polymorphism (SNP) phylogenetic tree results showed that in the frozen supply mode, the S. Enteritidis clonal clade continued to contaminate retail chicken meat and was homologous to S. Enteritidis strains found in farm chicken embryos, slaughterhouse chicken carcasses, and patients from hospitals in China (SNP 0 = 10). Notably, the pan-genome-based ML model showed that characteristic genes in frozen and live poultry isolates differed. The narZ gene was a key characteristic gene in frozen isolates, encoding nitrate reductase, relating to anaerobic bacterial growth. The ydgJ gene is a key characteristic gene in the live mode and encodes an oxidoreductase related to oxidative function in bacteria. The high prevalence of live poultry mode Salmonella and the transmission of frozen mode MDR Salmonella in this study pose serious risks to food safety and public health, emphasizing the importance of improving disinfection and cold storage measures to reduce Salmonella contamination and transmission. In conclusion, the continued surveillance of Salmonella across different supply models and the development of an epidemiological surveillance system based on WGS is necessary.

Prevalence and antimicrobial susceptibility of Salmonella enteritidis and Salmonella typhimurium isolated from hen eggs and quail eggs in Karaj, Iran.

Different Salmonella serotypes are considered one of the most important food pathogens in the world. Poultry meat and eggs are the primary carriers of Salmonella in human populations. This study aimed to estimate the Salmonella enteritidis and Salmonella typhimurium contamination rates of retail hen and quail eggs in Karaj, Iran. Moreover, the antimicrobial resistance patterns of the strains were evaluated, and the efficiency of the standard culture method and multiplex polymerase chain reaction (m-PCR) were compared. In this descriptive cross-sectional study over 1 year (Jan-Dec 2022), 150 commercial and 150 backyard hen eggs and 300 commercial quail eggs, without cracks and fractures, were collected randomly from best selling groceries in Karaj city. All samples were examined for Salmonella contamination independently by standard culture and m-PCR approaches. A standard disc diffusion method was employed to assess the antimicrobial susceptibility of the strains against 18 antimicrobial agents. Out of 300 examined eggs, 2 S. enteritidis strains were isolated from the shell of backyard hen eggs. The same serotype was also detected in the contents of one of these two eggs. One S. typhimurium was isolated from the shell of a commercial hen egg. Overall, the Salmonella contamination of the shell and contents was 1% and 0.3%, respectively. Salmonella was not isolated from the eggshells or the contents of the quail eggs. There was complete agreement between the results of m-PCR and the standard culture methods. Among the 18 tested antibiotics, the highest resistance was recorded for colistin (100%), followed by nalidixic acid (75%). As most Salmonella spp. are associated with human food poisoning, continuous surveillance is required to effectively reduce the risk posed by contaminated poultry eggs. Furthermore, mandatory monitoring of antimicrobial use on Iranian poultry farms is recommended.

Antimicrobial Resistance and the Genomic Epidemiology of Multidrug-Resistant Salmonella enterica serovar Enteritidis ST11 in China.

With the recent evolution of multidrug-resistant strains, the genetic characteristics of foodborne Salmonella enterica serovar Enteritidis and clinical isolates have changed. ST11 is now the most common genotype associated with S. Enteritidis isolates. A total of 83 strains of S. Enteritidis were collected at the General Hospital of the People's Liberation Army. Of these, 37 were from aseptic sites in patients, 11 were from the feces of patients with diarrhea, and the remaining 35 were of chicken-origin. The minimum inhibitory concentration of S. Enteritidis was determined by the broth microdilution method. Genomic DNA was extracted using the QiAamp DNA Mini Kit, and whole-genome sequencing (WGS) was performed using an Illumina X-ten platform. Prokka was used for gene prediction and annotation, and bioinformatic analysis tools included Resfinder, ISFinder, Virulence Factor Database, and PlasmidFinder. IQ-TREE was used to build a maximum likelihood phylogenetic tree. The phylogenetic relationship and distribution of resistance genes was displayed using iTOL. Comparative population genomics was used to analyze the phenotypes and genetic characteristics of antibiotic resistance in clinical and chicken-origin isolates of S. Enteritidis. The chicken-origin S. Enteritidis isolates were more resistant to antibiotics than clinical isolates, and had a broader antibiotic resistance spectrum and higher antibiotic resistance rate. A higher prevalence of antibiotic-resistance genes was observed in chicken-origin S. Enteritidis compared to clinical isolates, along with distinct patterns in the contextual characteristics of these genes. Notably, genes such as blaCTX-M and dfrA17 were exclusive to plasmids in clinical S. Enteritidis, whereas in chicken-origin S. Enteritidis they were found in both plasmids and chromosomes. Additionally, floR was significantly more prevalent in chicken-origin isolates than in clinical isolates. Careful analysis revealed that the delayed isolation of chicken-origin S. Enteritidis contributes to accelerated gene evolution. Of note, certain resistance genes tend to integrate seamlessly and persist steadfastly within the chromosome, thereby expediting the evolution of resistance mechanisms against antibiotics. Our comparative analysis of virulence genes in S. Enteritidis strains from various sources found no substantial disparities in the distribution of other virulence factors. In summary, we propose that chicken-origin S. Enteritidis has the potential to cause clinical infections. Moreover, the ongoing evolution and dissemination of these drug-resistant genes poses a formidable challenge to clinical treatment. Constant vigilance is needed to monitor the dynamic patterns of drug resistance in S. Enteritidis strains sourced from diverse origins.

Isolation, Identification, Antimicrobial Resistance, Genotyping, and Whole-Genome Sequencing Analysis of Salmonella Enteritidis Isolated from a Food-Poisoning Incident.

Salmonella enterica is a common pathogen in humans and animals that causes food poisoning and infection, threatening public health safety. We aimed to investigate the genome structure, drug resistance, virulence characteristics, and genetic relationship of a Salmonella strain isolated from patients with food poisoning. The pathogen strain 21A was collected from the feces of patients with food poisoning, and its minimum inhibitory concentration against commonly used antibiotics was determined using the strip test and Kirby-Bauer disk methods. Subsequently, WGS analysis was used to reveal the genome structural characteristics and the carrying status of resistance genes and virulence genes of strain 21A. In addition, an MLST-based minimum spanning tree and an SNP-based systematic spanning tree were constructed to investigate its genetic evolutionary characteristics. The strain 21A was identified by mass spectrometry as S. enterica, which was found to show resistance to ampicillin, piperacillin, sulbactam, levofloxacin, and ciprofloxacin. The WGS and bioinformatics analyses revealed this strain as Salmonella Enteritidis belonging to ST11, which is common in China, containing various resistance genes and significant virulence characteristics. Strain 21A was closely related to the SJTUF strains, a series strains from animal, food and clinical sources, as well as from Shanghai, China, which were located in the same evolutionary clade. According to the genetic makeup of strain 21A, the change G > A was found to be the most common variation. We have comprehensively analyzed the genomic characteristics, drug resistance phenotype, virulence phenotype, and genetic evolution relationship of S. Enteritidis strain 21A, which will contribute towards an in-depth understanding of the pathogenic mechanism of S. Enteritidis and the effective prevention and control of foodborne diseases.

Anti-Salmonella Activity of a Novel Peptide, KGGDLGLFEPTL, Derived from Egg Yolk Hydrolysate.

The present study aimed to characterize the mode of action of a novel antimicrobial peptide isolated from egg yolk hydrolysate. The EYHp6, KGGDLGLFEPTL, exhibited inhibition against Salmonella enterica serovar Typhimurium TISTR 292 and S. enterica serovar Enteritidis DMST 15679 with a MIC value of 2 mM. In contrast, S. enterica serovar Newport ATCC 6962 and other strains of Typhimurium and Enteritidis were inhibited at 4 mM. EYHp6 increased the cell membrane permeability of S. Typhimurium TISTR 292, leading to DNA leakage. Membrane integrity determined by propidium iodide and SYTO9 staining visualized by confocal microscopy demonstrated that EYHp6 at 1 × MIC induced disruption of cell membranes. Electron microscopy revealed that treatment of S. Typhimurium with EYHp6 led to damage to the cell membrane, causing the leakage of intracellular contents. Synchrotron-based Fourier-transform infrared spectroscopy indicated that EYHp6 killed S. Typhimurium by targeting fatty acids and nucleic acids in the cell membrane. The peptide did not show hemolytic activity up to 4 mM. These findings suggest that EYHp6 could be a promising antibacterial agent for controlling the growth of S. enterica.

Clinical Characteristics, Antimicrobial Resistance, Virulence Genes and Multi-Locus Sequence Typing of Non-Typhoidal Salmonella Serovar Typhimurium and Enteritidis Strains Isolated from Patients in Chiang Mai, Thailand.

Non-typhoidal salmonellosis (NTS) caused by ingesting Salmonella enterica contaminated food or drink remains a major bacterial foodborne disease. Clinical outcomes of NTS range from self-limited gastroenteritis to life-threatening invasive NTS (iNTS). In this study, we isolated Salmonella spp. from the stool and blood of patients hospitalized at Maharaj Nakorn Chiang Mai Hospital, Chiang Mai, Thailand, between 2016-2021 (a total of 395 cases). Then, serovar Typhimurium and Enteritidis were identified and further characterized by multiplex PCR, and multi-locus sequence typing. Our data show that multidrug resistance (MDR) sequence type 34 (ST34) and ST11 are the predominant sequence types for serovars Typhimurium and Enteritidis, respectively. Most S. Typhimurium ST34 lacks spvB, and most S. Enteritidis ST11 harbor sseI, sodCI, rpoS and spvB genes. NTS can be found in a wide range of ages, and anemia could be a significant factor for S. Typhimurium infection (86.3%). Both S. Typhimurium (6.7%) and S. Enteritidis (25.0%) can cause iNTS in immunocompromised patients. S. Typhimurium conferred MDR phenotype higher than S. Enteritidis with multiple antibiotic resistance indexes of 0.22 and 0.04, respectively. Here, we characterized the important S. Typhimurium, S. Enteritidis, and human clinical factors of NTS within the region.

Effect of hawthorn vinegar-based marinade on the quality parameters of beef tenderloins

In the current study, it was hypothesized to evaluate the potential effects of hawthorn vinegar-based marinade at 3 different concentrations (25%, 50%, and 100%) and marination duration (2, 6, and 24 h) on the physicochemical, microbiological, textural properties, microstructure, and sensory attributes of tenderloins. It was also aimed to identify and quantify the bioactive compounds present in the hawthorn vinegar that contribute to the aforementioned properties of tenderloins. The levels of organic acids, individual phenolic and flavonoid compounds, volatiles, in-vitro antioxidant capacity (DPPH, ABTS, and FRAP) of the hawthorn vinegar were analyzed. In addition, minimum inhibitory concentration (MIC), and inhibition zones were determined against Escherichia coli O157:H7, Salmonella Typhimurium, S. Enteritidis, and Listeria monocytogenes strains. A total of five organic acids, 21 phenolic and flavonoid compounds and 51 volatiles were determined in the hawthorn vinegar, and displayed strong antioxidant capacity determined by DPPH (470.93 ± 28.55 mg TEAC/L), ABTS (706.03 ± 4.88 mg TEAC/L) and FRAP (59.15 ± 0.50 mM FE/L) tests. The MIC and inhibition zones of the hawthorn vinegar ranged between 5.21 and 6.25%, and 9.41–11.43 mm against tested pathogens, respectively. In the tenderloin experiment, all marination treatments significantly changed the physicochemical and textural properties, microbiological status, and microstructure of the tenderloins (P < 0.05). Among them, the most effective treatment was the marination with 100% hawthorn vinegar for 24 h. In this treatment, the hardness, chewiness, springiness, and gummines values of the tenderloins were found lower than untreated tenderloins (P < 0.05). Furthermore, this treatment provided a high reduction in the number of pathogens ranging between 3.08 and 3.82 log10 CFU/g (P < 0.05) compared to the control. Although no differences were found among the groups (P > 0.05), flavor, odor, appearance, texture, and color scores of the tenderloins marinated with 100% hawthorn vinegar for 24 h were found higher than the non-marinated samples. The results of this study revealed that hawthorn vinegar contains certain levels of bioactive compounds which can help to improve the microbiological quality and textural properties of the meat parts.

Development of toxin-antitoxin self-destructive bacteria, aimed for salmonella vaccination

The most common source of foodborne Salmonella infection in humans is poultry eggs and meat, such that prevention of human infection is mostly achieved by vaccination of farm animals. While inactivated and attenuated vaccines are available, both present drawbacks. This study aimed to develop a novel vaccination strategy, which combines the effectiveness of live-attenuated and safety of inactivated vaccines by construction of inducible self-destructing bacteria utilizing toxin-antitoxin (TA) systems. Hok-Sok and CeaB-CeiB toxin-antitoxin systems were coupled with three induction systems aimed for activating cell killing upon lack of arabinose, anaerobic conditions or low concentration of metallic di-cations. The constructs were transformed into a pathogenic Salmonella enterica serovar Enteritidis strain and bacteria elimination was evaluated in vitro under specific activating conditions and in vivo following administration to chickens. Four constructs induced bacterial killing under the specified conditions, both in growth media and within macrophages. Cloacal swabs of all chicks orally administered transformed bacteria had no detectable levels of bacteria within 9 days of inoculation. By day ten, no bacteria were identified in the spleen and liver of most birds. Antibody immune response was raised toward TA carrying Salmonella which resembled response toward the wildtype bacteria. The constructs described in this study led to self-destruction of virulent Salmonella enteritidis both in vitro and in inoculated animals within a period which is sufficient for the induction of a protective immune response. This system may serve as a safe and effective live vaccine platform against Salmonella as well as other pathogenic bacteria.

Molecular characterization of virulence genes in poultry-originated Salmonella Enteritidis and Salmonella Typhimurium

Salmonella Enteritidis and Salmonella Typhimurium are the most common serovars observed in human salmonellosis while contaminated poultry products are the major source of Salmonella transmission to humans. Therefore, high pathogenicity of poultry-originated S. Enteritidis and S. Typhimurium strains poses a serious risk to human health. This study analyzed the virulence genes of broiler chicken-originated S. Enteritidis and S. Typhimurium strains. SipA, sipD, sopB, sopD, sopE, sopE2, sitC, sifA, ssaR, spvC and pefA genes were investigated in a total of 137 strains consisting of 105 S. Enteritidis and 32 S. Typhimurium. Nine strains (6.6%) had all genes. No negative strain was detected for all genes. SopE was found in all strains (100%). SitC (89.1%), ssaR (83.9%), sipA (70.1%), sipD (73.0%), sopE2 (68.6%), spvC (68.6%) and pefA (73.0%) were also highly prevalent. Noticeable differences were observed between serovars in terms of sopE2, spvC and pefA prevalence: 77.1%, 80% and 82.9%, respectively, of S. Enteritidis strains were sopE2, spvC and pefA positive while 40.6%, 31.3% and 40.6% of S. Typhimurium strains were positive. This finding indicates that S. Enteritidis is more frequent than S. Typhimurium in poultry populations thanks to higher virulence. Based on virulence gene distribution, the strains were divided into 44 different virulence genotypes, with the major genotype 4 (15.3%) carrying 8 of the 11 genes. The majority of strains (75.9%) were positive for at least 6 genes. S. Enteritidis and S. Typhimurium strains were highly virulent and pose a threat as a zoonotic infection.

Genomic and phylogenetic analysis of Salmonella enterica serovar Enteritidis strains linked to multiple outbreaks in Brazil.

Salmonella enterica subsp. enterica serovar Enteritidis (SE) has become the prevalent serovar isolated from gastroenteritis cases in Brazil since the 1990s. To better understand the genomic diversity and phylogenetic relationship amongst SE epidemic isolates from Brazil, 30 SE isolates from a variety of implicated foods and case patients of outbreaks between 1999 and 2006 were selected for genome comparison analyses. SE genomes were also compared against publicly available Brazilian SE isolates from pre- and postepidemic period. MLST analysis revealed that all isolates belong to sequence type (ST) 11. A total of seven Salmonella pathogenicity islands (SPIs) (SPI-1, SPI-3-5, SPI-13, SPI14, and C63PI) were identified in the evaluated genomes and all studied SE genomes carried similar prophage profiling. Resistome analysis revealed the presence of resistance genes to aminoglycosides [aac(6')laa, aph(3")-lb, aph(6)-ld], as well as point mutations in gyrA. Phylogenetic analysis demonstrated that certain isolates have circulated in Brazil for years and been involved in distinct outbreaks.

RyhB Paralogs Downregulate the Expressions of Multiple Survival-Associated Genes and Attenuate the Survival of Salmonella Enteritidis in the Chicken Macrophage HD11

RyhB-1 and RyhB-2 are small non-coding RNAs in Salmonella that act as regulators of iron homeostasis by sensing the environmental iron concentration. Expressions of RyhB paralogs from Salmonella Typhimurium are increased within microphages. RyhB paralogs restrain the growth of S. Typhimurium in RAW264.7 macrophages by modulating the expression of Salmonella pathogenicity island 1 (SPI-1) genes sicA and rtsB. However, little is known about the regulatory role of RyhBs and their virulence-associated targets in Salmonella Enteritidis. We studied candidate targets of RyhB paralogs via RNA-Seq in conditions of iron limitation and hypoxia. RyhB paralogs were expressed when the S. Enteritidis strain CMCC(B)50336 (SE50336) interacted with the chicken macrophage line HD11. We analyzed gene expression associated with Salmonella survival and replication in macrophages in wild-type strain SE50336 and the RyhB deletion mutants after co-incubation with HD11 and screened out targets regulated by RyhBs. The expressions of both RyhB-1 and RyhB-2 were increased after co-incubation with HD11 for 8 h and several survival-associated genes within macrophages, such as ssaI, sseA, pagC, sodC, mgtC, yaeB, pocR, and hns, were upregulated in the ryhB-1 deletion mutant. Specifically, ssaI, the type-three secretion system 2 (T3SS-2) effector encoded by SPI-2, which promoted the survival of Salmonella in macrophages, was upregulated more than 3-fold in the ryhB-1 deletion mutant. We confirmed that both RyhB-1 and RyhB-2 downregulated the expression of ssaI to repress its mRNA translation by directly interacting with its coding sequence (CDS) region via an incomplete complementary base-pairing mechanism. The SPI-2 gene sseA was indirectly modulated by RyhB-1. The survival assays in macrophages showed that the ability of intracellular survival of ryhB-1 and/or ryhB-2 deletion mutants in HD11 was higher than that of the wild-type strain. These results indicate that RyhB paralogs downregulate survival-related virulence factors and attenuate the survival of S. Enteritidis inside chicken macrophage HD11.

Evaluation of phage—antibiotic combinations in the treatment of extended-spectrum β-lactamase-producing Salmonella enteritidis strain PT1

Foodborne infections caused by Salmonella spp. are among the most common foodborne diseases in the world. We isolated a lytic phage against extended-spectrum beta-lactam producing S. Enteritidis strain PT1 derived from chicken carcass. Results from electronmicrography indicated that phiPT1 belonged to the family, Siphoviridae, in the order, Caudovirales. Phage phiPT1 was stable at temperatures from 4 °C to 60 °C and inactivated at 90 °C. phiPT1 retained a high titer from pH 4 to pH 10 for at least 1 h. Nevertheless, it displayed a significant decrease (p < 0.05) in titer at pH 11 and 12, with phage titers of 5.5 and 2.4 log10 PFU/mL, respectively. The latent time and burst size of phiPT1 were estimated to be 30 min and 252 PFU/infected cell, respectively. The virulence of phage phiPT1 was evaluated against S. Enteritidis strain PT1 at different MOIs. phiPT1 reduced Salmonella proliferation relative to the negative control (MOI 0) at all MOIs (P < 0.05). However, there is no significant difference among the MOIs (P > 0.05). The phage-antibiotic combination analysis (PAS) indicated that synergism was not detected at higher phiPT1 titer (1012 PFU/mL) with all tested antibiotics at all subinhibitory concentrations. However, synergistic activities were recorded at 0.25 × MIC of four tested antibiotics: cefixime, gentamicin, ciprofloxacin, and aztreonam in combination with phage at 104, 106 and 108 PFU/mL (ΣFIC ≤0.5). Synergism was detected for all antibiotics (0.1 × MIC) except meropenem and colistin in combination with phiPT1 at 104, 106 and 108 PFU/mL (ΣFIC ≤0.5). Synergism also displayed at the lowest concentrations of all antibiotics (0.01 MIC) in combination with phiPT1 at all titers except 1012 PFU/mL. Such characteristic features make phiPT1 to be a potential candidate for therapeutic uses.

Antimicrobial resistance patterns and virulence gene profiles of Salmonella enteritidis and Salmonella typhimurium recovered from patients with gastroenteritis in three cities of Iran.

This study evaluated distribution of virulence factors and antibiotic resistance in clinical isolates of Salmonella enteritidis and Salmonella typhimurium in three cities of Iran. Altogether 48 S. enteritidis and S. typhimurium isolates were collected from patients at certain Iranian hospitals between May 2018 and September 2021. Antimicrobial susceptibility testing was performed by disk diffusion and broth microdilution methods. The presence of antibiotic-resistance genes (blaTEM,blaSHV,blaCTX-M,blaNDM,strA, strB, aadA1, tetA, tetB, floR, sul1, sul2, dfrA), integrons (classe 1 and 2), and virulence-associated genes (invA, stn, sopB, spvC, rck, phoPQ) was investigated by PCR and sequencing. Antimicrobial agents like trimethoprim-sulfamethoxazole and imipenem represent highly efficient agents with 97% susceptibility. S. enteritidis and S. typhimurium exhibited high resistance to ciprofloxacin (n = 20, 71.43%) and ceftazidime (n = 9, 45%), respectively. Overall, 3 (6.25%), 13 (27.08%), and 6 (12.5%) isolates were divided into strong, moderate, and weak biofilm producers, respectively. Moreover, blaCTX-M,blaTEM, blaSHV, sul1, sul2, tetA, tetB, floR, strA, and strB resistant genes were detected in 10 (20.8%), 5 (10.4%), 1(2.08%), 7 (14.58%), 1 (2.08%), 3 (6.25%), 2 (4.1%), 1 (2.08%), 2 (4.1%), 2 (4.1%), respectively. Furthermore, 7 (14.58%) strains had classe 1 integron. All tested S. enteritidis strains had invA and sopB, and all S. typhimurium strains had invA and phoPQ. However, spvC remained undetected in all isolates. Extensive surveillance and efficient control measures against infection help to stop the upsurge of various antibiotic-resistant isolates.

SENSITIVITY OF MICROORGANISMS ISOLATED FROM PATHOLOGICAL MATERIAL TO ANTIMICROBIAL PREPARATION

Excessive and uncontrolled use of antibiotics commonly results in the emergence of antimicrobial resistance (AMR). Therefore, the main aim of these studies was to determine the antibiotic susceptibility of microorganisms isolated from the pathological material.&#x0D; The article describes the susceptibility of isolated strains to the following antibiotics: ampicillin, amoxicillin, oxacillin, ofloxacin, streptomycin, cefazolin, gentamicin, amikacin, amoxiclav, erythromycin, enrofloxacin, lincomycin, tetracycline, doxycycline, vancomycin, rifampicin, ciprofloxacin, norfloxacin, tylosin, nitrofurantoin, polymyxin B.&#x0D; During the study of six Escherichia coli and three Salmonella enteritidis strains, it was ascertained that they demonstrated different susceptibility to the studied antibiotics, in particular, only two E. coli isolates, which is 33,3 %, were resistant to streptomycin, 50 % of the isolated strains were susceptible.&#x0D; When determining the susceptibility, it was established that all isolated E. coli isolates were resistant to cefazolin, vancomycin, oxacillin, and 83,3 % were resistant to amoxicillin, ampicillin, vancomycin, amoxiclav, rifampicin.&#x0D; 33,3 % of Salmonella enteritidis isolates were moderately susceptible to streptomycin, amoxicillin, and ampicillin, and 66,7 % were sensitive to ciprofloxacin, norfloxacin, and enrofloxacin.&#x0D; All isolated S. enteritidis strains were found to be resistant to cefazolin, tylosin, vancomycin, oxacillin, lincomycin, and erythromycin, 100 % susceptible to ciprofloxacin, amikacin, and ofloxacin and 68,7 % moderately susceptible to amoxicillin and gentamicin.