The Prevalence and Epidemiology of Salmonella in Retail Raw Poultry Meat in China: A Systematic Review and Meta-Analysis

Genomic and resistome analysis of Salmonella enterica isolates from retail markets in Yichun city, China

Nontyphoidal Salmonella (NTS) causes global outbreaks of foodborne disease. The main source of Salmonella for humans is animal-borne foods; however, the monitoring of Salmonella in the food chain via genomic platforms was limited in China. This study evaluated the prevalence, resistome, and virulome diversity of Salmonella strains identified from pork, retail environment, aquatic products, and poultry eggs of retail markets in Yichun city, Jiangxi province. The overall incidence of Salmonella was 9.4 %, with a higher contamination rate observed in pork at 13.5 %, followed by the retail environment at 7.69 %. The genomic analysis of the isolates revealed a total of fifteen distinct serovars, with serovar Enteritidis being the most prevalent (64.3 %). The phenotypic resistance analysis conducted by the broth microdilution method, revealed that 81.12 % of the isolates exhibited multidrug resistance (MDR), with high resistance to trimethoprim/sulphonamides (100 %), followed by tetracycline (99.3 %) and streptomycin (99.3 %). Genotypic analysis of antimicrobial resistance identified 80 antimicrobial-resistant genes (ARGs), with mdf(A), aph(3')-Ib, tet(A), dfrA12, floR, bla TEM-1B , qnrS3, and sul2, conferring resistance to different antimicrobial classes, being the predominant ARGs. Additionally, forty ESBL genes, particularly critical genes such as bla CTX-M and bla NDM-1, were also identified in Salmonella isolates. The IncR, IncFIB (K), and IncX1 plasmid replicons were widely prevalent and served as significant reservoirs of horizontally acquired foreign genes. Moreover, key virulence genes such as cdtB, lpf and sef were also detected, in addition to Salmonella pathogenicity islands SPI-1 and SPI-2. This study reveals the prevalence of multidrug-resistant and virulent strains of Salmonella serovars in the markets of Yichuan city, posing a risk of human infections. The gained knowledge provided essential baseline information that may be utilized for regular tracking of MDR Salmonella transmission in the food chain to minimize potential future outbreaks.

The prevalence, distribution, and diversity of Salmonella isolated from pork slaughtering processors and retail outlets in the Shandong Province of China

Salmonella is a foodborne pathogen of global significance and is highly prevalent in pork. This study investigated the prevalence, contamination distribution, virulence genes and antibiotic resistance of Salmonella in 3 pork processors in the Shandong Province of China. Samples were collected from 13 different sampling sources across the slaughter procedures (600 samples) as well as at retail outlets supplied by these processors (45 samples). The prevalence was 18.9 % among all the samples, with the highest prevalence observed in feces (40.0 %), lairage pens (38.0 %), and hides (34.0 %). A total of 6 serotypes were identified, with S. Rissen (46.3 %) and S. typhimurium (32.0 %) found to be the most prevalent serotypes. 86.8 % of Salmonella isolates were multi-drug resistant, with the majority of strains resistant to erythromycin, sulfisoxazole, and ampicillin. The multilocus sequence typing analysis revealed 6 STs were obtained from 45 isolates, with the dominant type ST469 accounting for 40.0 % of the total, which suggested a high possibility of cross-contamination between the plant processing chain and retail outlets. This work reveals the prevalence and correlation of Salmonella isolates between pork slaughter and retail outlets and acts as a case-study for stakeholders wishing to improve pork supply chain hygiene, control cross-contamination between the various slaughtering processes, and obtain continuous updates on Salmonella surveillance.

Efficiency, cytotoxicity, and survivability evaluation of Salmonella phage cocktail against Salmonella derived from broiler sources

Background and Aim

Salmonella is a leading cause of foodborne illnesses worldwide, often linked to poultry products. Antibiotic resistance among Salmonella strains has increased the need for alternative decontamination strategies, such as bacteriophage (phage) therapy. This study evaluates the lytic efficiency, cytotoxicity, and survivability of a Salmonella phage cocktail derived from wastewater sources.

Materials and Methods

A total of 251 Salmonella enterica isolates from broiler production chains were tested against two selected phages (WP109 and WP128). The phages were characterized for lytic ability, cytotoxicity on Caco-2 cells, and survivability under simulated gastrointestinal and harsh environmental conditions. A cocktail of the phages was further tested for efficiency at different multiplicities of infection (MOIs) against representative Salmonella strains.

Results

Phage WP109 lysed 91.2% of Salmonella isolates, while WP128 lysed 78.2%. The phage cocktail exhibited a significant reduction of Salmonella counts at MOI 104, achieving up to a 4.4 log CFU/mL reduction in vitro. The cocktail maintained 99.9% survivability in simulated gastric conditions and displayed no cytotoxic effects on Caco-2 cells. Moreover, it was resistant to various ionic sanitizers and pH levels ranging from 2 to 11.

Conclusion

The developed phage cocktail demonstrated high lytic efficacy, stability, and safety under simulated conditions, highlighting its potential as a biocontrol agent in the broiler production chain. These findings support its application in reducing Salmonella contamination while addressing the challenges posed by antibiotic resistance.

Isolation, characterization and liposome-loaded encapsulation of a novel virulent Salmonella phage vB-SeS-01

Introduction

Salmonella is a common foodborne pathogenic bacterium, displaying facultative intracellular parasitic behavior, which can help the escape against antibiotics treatment. Bacteriophages have the potential to control both intracellular and facultative intracellular bacteria and can be developed as antibiotic alternatives.

Methods

This study isolated and characterized vB-SeS-01, a novel Guernseyvirinae phage preying on Salmonella enterica, whose genome is closely related to those of phages SHWT1 and vB-SenS-EnJE1. Furthermore, nine phage-carrying liposome formulations were developed by film hydration method and via liposome extruder.

Results and Discussion

Phage vB-SeS-01 displays strong lysis ability against 9 out of 24 tested S. enterica strains (including the pathogenic "Sendai" and "Enteritidis" serovars), high replicability with a burst size of 111 ± 15 PFU/ cell and a titre up to 2.1 × 1011 PFU/mL, and broad pH (4.0 ~ 13.0) and temperature (4 ~ 80°C) stabilities. Among the nine vB-SeS-01 liposome-carrying formulations, the one encapsulated with PC:Chol:T80:SA = 9:1:2:0.5 without sonication displayed the optimal features. This formulation carried up to 1011 PFU/mL, with an encapsulation rate of 80%, an average size of 172.8 nm, and a polydispersity index (PDI) of 0.087. It remained stable at 4°C and 23°C for at least 21 days and at 37°C for 7 days. Both vB-SeS-01 and vB-SeS-01-loaded liposomes displayed intracellular antimicrobial effects and could reduce the transcription level of some tested intracellular inflammatory factors caused by the infected S. enterica sv. Sendai 16,226 and Enteritidis 50041CMCC.

Isolation, characterization and therapeutic efficacy of lytic bacteriophage ZK22 against Salmonella Typhimurium in mice

BACKGROUND

Salmonella enterica serovar Typhimurium is one of the most common serovars of Salmonella associated with clinical cases. It not only leads to diarrhea and mortality raised in livestock and poultry farming, but also poses a risk to food safety.

RESULTS

In this study, a lytic bacteriophage named ZK22 was isolated and identified from sewage. It exhibited favorable capability against 20 strains of S. Typhimurium. The genome of ZK22 consisted of a double-stranded DNA with a total length of 47,066 base pairs and a GC content of 45.71%. A total of 78 coding sequences were predicted, with no virulence genes or drug resistance genes predicted. Based on blastn similarity analysis, ZK22 belongs to the genus Skatevirus of the class Caudoviricetes, as a long-tailed Siphovirus. Biological characteristics of ZK22 indicated that the optimal multiplicity of infection (MOI) of bacteriophage ZK22 to S. Typhimurium was 10- 2 (PFU/cell), with an incubation period of around 10 min and the burst size of 393 PFU/cell. The physicochemical resistance results of ZK22 demonstrated that it maintained stability under temperatures ranging from 4 °C to 70 °C and under pH conditions ranging from 3 to 12. After inoculating S. Typhimurium at 37 °C, co-culture mixed with the optimal multiplicity of infection exhibited the lowest OD600 within 12 h, demonstrating the exceptional antibacterial effect. Inoculation of phage ZK22 in mice infected with S. Typhimurium was performed to assess its therapeutic efficacy in vivo. The results showed that phage ZK22 at a dose of 108 PFU/mL increased the survival rates of infected mice, effectively suppressed the dissemination and colonization of the host bacteria in the mice, and alleviated the inflammatory response caused by the infection.

CONCLUSIONS

In summary, bacteriophage ZK22 presents favorable application prospects as a potential biological agent for the control of Salmonella infections in livestock and poultry farming.

Inhibitory effects of nafcillin and diosmin on biofilm formation by Salmonella Typhimurium

OBJECTIVE

The foodborne pathogen Salmonella enterica serovar Typhimurium causes self-limiting gastroenteritis in humans and is difficult to eliminate due to its ability to adhere to surfaces and form biofilms that exhibit high resistance to antimicrobial agents. To explore alternative strategies for biofilm treatment, it is essential to investigate novel agents that inhibit Salmonella biofilms.

METHOD

In this study, we investigated the minimum biofilm inhibitory concentrations (MBICs) and minimum biofilm eradication concentrations (MBECs) of nafcillin and diosmin, both previously identified as Lon protease inhibitors, against biofilms formed by S. Typhimurium. Furthermore, we examined the expression of genes associated with the type II toxin-antitoxin system to enhance our understanding of the impact of these inhibitors.

RESULTS

The findings indicated a strong antibiofilm effect of nafcillin, with MBIC and MBEC values of 8 µg/mL and 32 µg/mL, respectively. These results were confirmed by field emission scanning electron microscopy (FE-SEM), which showed that biofilm formation was reduced in the presence of nafcillin. Additionally, it revealed morphological changes in the bacteria within the nafcillin-treated biofilms. Furthermore, gene expression analyses demonstrated a significant reduction in the expression of type II TA system genes following treatment with nafcillin and diosmin.

CONCLUSION

This study highlights the effectiveness of nafcillin in disrupting the biofilms of S. Typhimurium. These results suggest promising avenues for the development of novel therapeutic strategies targeting biofilms associated with S. Typhimurium.

Synthesis and pharmacological evaluation of Andrographolide and Ajwain as promising alternatives to antibiotics for treating Salmonella gallinarum infection in chicken

The emergence of antibiotic resistance in pathogenic bacteria, including Salmonella gallinarum, poses a significant challenge to poultry health and food safety. In response, alternative strategies are urgently needed to mitigate bacterial infections without exacerbating antibiotic resistance. Phytoremediation, a sustainable and environmentally friendly approach, harnesses the natural detoxification capabilities of plants to remediate contaminants. This study explores the potential of combined phytoremediation using Andrographolide, derived from Andrographis paniculata, and Ajwain derived from Trachyspermum ammi as promising alternatives to antibiotics for treating Salmonella gallinarum infection in poultry. Andrographolide, known for its potent antimicrobial properties, exhibits inhibitory effects while Ajwain, rich in bioactive compounds, possesses antimicrobial and immunomodulatory properties. By leveraging their combined phytoremediation potential, Andrographolide and Ajwain offer a multifaceted approach to combat Salmonella gallinarum within the poultry environment. The study employed a rigorous experimental design, including in vitro assessments of antimicrobial susceptibility, cytotoxicity, and optimal concentration determination. Following this, in vivo experiments were conducted using a chicken model infected with Salmonella gallinarum. Results demonstrated that the selected combinations effectively reduced mortality rates, alleviated clinical symptoms, and mitigated gross pathological signs associated with Salmonella infection. Gene expression studies indicated a downregulation of proinflammatory cytokines, underscoring potential implications of a combined phytoremediation strategy as an innovative and sustainable solution to address Salmonella gallinarum infections in poultry production systems.

Geography, Antimicrobial Resistance, and Genomics of Salmonella enterica (Serotypes Newport and Anatum) from Meat in Mexico (2021-2023)

Salmonella enterica non-typhoidal is a major contributor to diarrheal diseases, with over 2600 serovars identified across diverse environments. In Mexico, serovars Newport and Anatum have shown a marked increase, especially in foodborne disease, posing a public health problem. We conducted a cross-sectional study from 2021 to 2023 using active epidemiological surveillance to assess contamination in ground beef and pork at butcher shops nationwide. It involved isolation, phenotypic antimicrobial resistance, comparative genomics, spatial distribution, antimicrobial-resistance genes, and pangenome analysis. A total of 402 non-typhoidal S. enterica strains were isolated, including 59 Newport and 50 Anatum. After curating for redundancy, 45 Newport and 32 Anatum strains remained. We found that 75% of Newport strains exhibited multidrug resistance (MDR), compared to 25% of Anatum strains. Salmonella Newport also showed a broader distribution and stronger antibiotic-resistance capacity, particularly due to genes such as mphA and ramA. Our pangenome analysis showed a predominance of cell maintenance and survival-process genes in the accessory genome of both serotypes. Considering unique genes, Salmonella Anatum and Newport showed a notorious abundance of genes with functions related to replication, recombination, and repair. The substantial rise of Anatum and Newport strains in meat samples for human consumption presents an epidemiological alert, highlighting the critical need for stringent surveillance programs to mitigate human and ecosystem health risks.

Salmonella enterica Serovar Infantis in Broiler Chickens: A Systematic Review and Meta-Analysis

Salmonella enterica subsp. enterica serovar Infantis poses a growing threat to public health, due to its increasing prevalence worldwide and its association with high levels of antimicrobial resistance. Among livestock, S. Infantis is especially isolated from broilers. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic review was conducted by searching in three databases (Web of Science, Scopus, and PubMed) for English-language studies (1957-2023) that reported the prevalence of S. Infantis in broiler farms. Eligible studies included epidemiological investigations conducted in broiler chickens by sampling the house environment (flock-level prevalence) or the birds (individual-level prevalence). A random-effect model was applied to calculate S. Infantis pooled prevalence estimates with 95% confidence intervals (CIs). Furthermore, to assess between-study heterogeneity, the inconsistency index statistic (I2) was calculated. Among 537 studies retrieved, a total of 9 studies reporting flock-level prevalence of S. Infantis and 4 reporting individual-level prevalence were retained for analysis. The flock-level pooled prevalence was estimated to be 9% (95% CI: 1-26%) and a high between-study heterogeneity was found (I2 = 99%, p < 0.01). Concerning individual-level prevalence, a meta-analysis was not performed due to the scarcity of eligible studies. The data presented underscore the significant occurrence of S. Infantis in broilers at the farm level. By summarizing the existing literature, this work provides useful insights for conducting future surveys of Salmonella spp. in live broiler chickens as a preliminary step for developing more efficient control strategies.

Prevalence and serotype of poultry salmonellosis in Africa: a systematic review and meta-analysis

Salmonellosis represents a significant economic and public health concern for the poultry industry in Africa, leading to substantial economic losses due to mortality, reduced productivity, and food safety problems. However, comprehensive information on the burden of poultry salmonellosis at the continental level is scarce. To address this gap, a systematic review and meta-analysis were conducted to consolidate information on the prevalence and circulating serotypes of poultry salmonellosis in African countries. This involved the selection and review of 130 articles published between 1984 and 2021. A detailed systematic review protocol was structured according to Cochrane STROBE and PRISMA statement guideline. From the 130 selected articles from 23 different African countries, the overall pooled prevalence estimate (PPE) of poultry salmonellosis in Africa was found to be 14.4% (95% CI = 0.145-0.151). Cameroon reported the highest PPE at 71.9%. The PPE was notably high in meat and meat products at 23%. The number of research papers reporting poultry salmonellosis in Africa has shown a threefold increase from 1984 to 2021. Salmonella Enteritidis and Typhimurium were the two most prevalent serotypes reported in 18 African countries. Besides, Salmonella Kentucky, Virchow, Gallinarum, and Pullorum were also widely reported. Western Africa had the highest diversity of reported Salmonella serotypes (141), in contrast to southern Africa, which reported only 27 different serotypes. In conclusion, poultry salmonellosis is highly prevalent across Africa, with a variety of known serotypes circulating throughout the continent. Consequently, it is crucial to implement strategic plans for the prevention and control of Salmonella in Africa.RESEARCH HIGHLIGHTS The pooled sample prevalence of poultry salmonellosis in Africa is high (14.4%).The highest PPE was recorded in meat and meat products.Salmonella serotypes of zoonotic importance were found in all sample types.Salmonella Enteritidis and Typhimurium are common serotypes spreading in Africa.

Multidrug-Resistant Proteus mirabilis and Other Gram-Negative Species Isolated from Native Egyptian Chicken Carcasses

Poultry carcasses may be reservoirs for the zoonotic transmission of antimicrobial-resistant bacteria to humans and pose a major public health hazard. During the isolation of Salmonella from poultry and other foods, many of the presumptive typical Salmonella colonies on xylose lysine deoxycholate (XLD) agar were found to lack the invA gene, which is the specific target gene for Salmonella spp. Therefore, the current study aimed to estimate the prevalence and antimicrobial resistance profiles of extensively drug-resistant invA-negative non-Salmonella isolates recovered from native Egyptian chicken carcasses as presumptive Salmonella colonies on XLD agar. The non-Salmonella isolates were detected in 84% (126/150) of the examined native Egyptian chicken carcasses and classified into five genera, with prevalence rates of 64% (96/150), 14% (21/150), 6.7% (10/150), 3.3% (5/150), and 1.3% (2/150) for Proteus, Citrobacter, Shigella, Pseudomonas, and Edwardsiella, respectively. One hundred and ninety-five invA-negative, non-verified presumptive Salmonella isolates were recovered and classified at the species level into Proteus mirabilis (132/195; 67.7%), Proteus vulgaris (11/195; 5.6%), Citrobacter freundii (26/195; 13.3%), Shigella flexneri (8/195; 4.1%), Shigella sonnei (6/195; 3.1%), Shigella dysenteriae (3/195; 1.5%), Pseudomonas fluorescens (6/195; 3.1%), and Edwardsiella tarda (3/195; 1.5%). All (195/195; 100%) of these isolates showed resistance against cefaclor and fosfomycin. Additionally, these isolates showed high resistance rates of 98%, 92.8%, 89.7%, 89.2%, 89.2%, 86.7%, 80%, 78.5%, 74.4%, and 73.9% against cephalothin, azithromycin, vancomycin, nalidixic acid, tetracycline, sulfamethoxazole/trimethoprim, cefepime, gentamicin, cefotaxime, and ciprofloxacin, respectively. Interestingly, all (195/195; 100%) of the identified isolates were resistant to at least five antibiotics and exhibited an average MAR (multiple antibiotic resistance) index of 0.783. Furthermore, 73.9% of the examined isolates were classified as extensively drug-resistant, with an MAR index equal to 0.830. The high prevalence of extensively drug-resistant foodborne Proteus, Citrobacter, Shigella, Pseudomonas, and Edwardsiella isolated from native chicken carcasses poses a great hazard to public health and necessitates more monitoring and concern about the overuse and misuse of antibiotics in humans and animals. This study also recommends the strict implementation of GHP (good hygienic practices) and GMP (good manufacturing practices) in the chicken meat supply chain to protect consumer health.

Colistin-, cefepime-, and levofloxacin-resistant Salmonella enterica serovars isolated from Egyptian chicken carcasses

OBJECTIVES

The emergence of multidrug-resistant (MDR) Salmonella strains, especially resistant ones toward critically important antimicrobial classes such as fluoroquinolones and third- and fourth-generation cephalosporins, is a growing public health concern. The current study, therefore, aimed to determine the prevalence, and existence of virulence genes (invA, stn, and spvC genes), antimicrobial resistance profiles, and the presence of β-lactamase resistance genes (blaOXA, blaCTX-M1, blaSHV, and blaTEM) in Salmonella strains isolated from native chicken carcasses in Egypt marketed in Mansoura, Egypt, as well as spotlight the risk of isolated MDR, colistin-, cefepime-, and levofloxacin-resistant Salmonella enterica serovars to public health.

METHODS

One hundred fifty freshly dressed native chicken carcasses were collected from different poultry shops in Mansoura City, Egypt between July 2022 and November 2022. Salmonella isolation was performed using standard bacteriological techniques, including pre-enrichment in buffered peptone water (BPW), selective enrichment in Rappaport Vassiliadis broth (RVS), and cultivating on the surface of xylose-lysine-desoxycholate (XLD) agar. All suspected Salmonella colonies were subjected to biochemical tests, serological identification using slide agglutination test, and Polymerase Chain Reaction (PCR) targeting the invasion A gene (invA; Salmonella marker gene). Afterward, all molecularly verified isolates were screened for the presence of virulence genes (stn and spvC). The antimicrobial susceptibility testing for isolated Salmonella strains towards the 16 antimicrobial agents tested was analyzed by Kirby-Bauer disc diffusion method, except for colistin, in which the minimum inhibition concentration (MIC) was determined by broth microdilution technique. Furthermore, 82 cefotaxime-resistant Salmonella isolates were tested using multiplex PCR targeting the β-lactamase resistance genes, including blaOXA, blaCTX-M1, blaSHV, and blaTEM genes.

RESULTS

Salmonella enterica species were molecularly confirmed via the invA Salmonella marker gene in 18% (27/150) of the freshly dressed native chicken carcasses. Twelve Salmonella serotypes were identified among 129 confirmed Salmonella isolates with the most predominant serotypes were S. Kentucky, S. Enteritidis, S. Typhimurium, and S. Molade with an incidence of 19.4% (25/129), 17.1% (22/129), 17.1% (22/129), and 10.9% (14/129), respectively. All the identified Salmonella isolates (n = 129) were positive for both invA and stn genes, while only 31.8% (41/129) of isolates were positive for the spvC gene. One hundred twenty-one (93.8%) of the 129 Salmonella-verified isolates were resistant to at least three antibiotics. Interestingly, 3.9%, 14.7%, and 75.2% of isolates were categorized into pan-drug-resistant, extensively drug-resistant, and multidrug-resistant, respectively. The average MAR index for the 129 isolates tested was 0.505. Exactly, 82.2%, 82.2%, 63.6%, 51.9%, 50.4%, 48.8%, 11.6%, and 10.1% of isolated Salmonella strains were resistant to cefepime, colistin, cefotaxime, ceftazidime/clavulanic acid, levofloxacin, ciprofloxacin, azithromycin, and meropenem, respectively. Thirty-one out (37.8%) of the 82 cefotaxime-resistant Salmonella isolates were β-lactamase producers with the blaTEM as the most predominant β-lactamase resistance gene, followed by blaCTX-M1 and blaOXA genes, which were detected in 21, 16, and 14 isolates respectively).

CONCLUSION

The high prevalence of MDR-, colistin-, cefepime-, and levofloxacin-resistant Salmonella serovars among Salmonella isolates from native chicken is alarming as these antimicrobials are critically important in treating severe salmonellosis cases and boost the urgent need for controlling antibiotic usage in veterinary and human medicine to protect public health.

Deciphering Microbiome, Transcriptome, and Metabolic Interactions in the Presence of Probiotic Lactobacillus acidophilus against Salmonella Typhimurium in a Murine Model

Salmonella enterica serovar Typhimurium (S. Typhimurium), a foodborne pathogen that poses significant public health risks to humans and animals, presents a formidable challenge due to its antibiotic resistance. This study explores the potential of Lactobacillus acidophilus (L. acidophilus 1.3251) probiotics as an alternative strategy to combat antibiotic resistance associated with S. Typhimurium infection. In this investigation, twenty-four BALB/c mice were assigned to four groups: a non-infected, non-treated group (CNG); an infected, non-treated group (CPG); a group fed with L. acidophilus but not infected (LAG); and a group fed with L. acidophilus and challenged with Salmonella (LAST). The results revealed a reduction in Salmonella levels in the feces of mice, along with restored weight and improved overall health in the LAST compared to the CPG. The feeding of L. acidophilus was found to downregulate pro-inflammatory cytokine mRNA induced by Salmonella while upregulating anti-inflammatory cytokines. Additionally, it influenced the expression of mRNA transcript, encoding tight junction protein, oxidative stress-induced enzymes, and apoptosis-related mRNA expression. Furthermore, the LEfSe analysis demonstrated a significant shift in the abundance of critical commensal genera in the LAST, essential for maintaining gut homeostasis, metabolic reactions, anti-inflammatory responses, and butyrate production. Transcriptomic analysis revealed 2173 upregulated and 506 downregulated differentially expressed genes (DEGs) in the LAST vs. the CPG. Functional analysis of these DEGs highlighted their involvement in immunity, metabolism, and cellular development. Kyoto Encyclopedia of Genes and Genome (KEGG) pathway analysis indicated their role in tumor necrosis factor (TNF), mitogen-activated protein kinase (MAPK), chemokine, Forkhead box O (FOXO), and transforming growth factor (TGF-β) signaling pathway. Moreover, the fecal metabolomic analysis identified 929 differential metabolites, with enrichment observed in valine, leucine, isoleucine, taurine, glycine, and other metabolites. These findings suggest that supplementation with L. acidophilus promotes the growth of beneficial commensal genera while mitigating Salmonella-induced intestinal disruption by modulating immunity, gut homeostasis, gut barrier integrity, and metabolism.

Lactiplantibacillus plantarum postbiotic protects against Salmonella infection in broilers via modulating NLRP3 inflammasome and gut microbiota

Salmonella infection is a major concern in poultry production which poses potential risks to food safety. Our previous study confirmed that Lactiplantibacillus plantarum (LP) postbiotic exhibited a strong antibacterial capacity on Salmonella in vitro. This study aimed to investigate the beneficial effects and underlying mechanism of LP postbiotic on Salmonella-challenged broilers. A total of 240 one-day-old male yellow-feathered broilers were pretreated with 0.8% deMan Rogosa Sharpe (MRS) medium or 0.8% LP postbiotic (LP cell-free culture supernatant, LPC) in drinking water for 28 d, and then challenged with 1×109 CFU Salmonella enterica serovar Enteritidis (SE). Birds were sacrificed 3 d postinfection. Results showed that LPC maintained the growth performance by increasing body weight (BW), average daily gain (ADG), and average daily feed intake (ADFI) in broilers under SE challenge. LPC significantly attenuated SE-induced intestinal mucosal damage. Specifically, it decreased the intestinal injury score, increased villus length and villus/crypt, regulated the expression of intestinal injury-related genes (Villin, matrix metallopeptidase 3 [MMP3], intestinal fatty acid-binding protein [I-FABP]), and enhanced tight junctions (zona occludens-1 [ZO-1] and Claudin-1). SE infection caused a dramatic inflammatory response, as indicated by the up-regulated concentrations of interleukin (IL)-1β, IL-6, TNF-α, and the downregulation of IL-10, while LPC pretreatment markedly reversed this trend. We then found that LPC inhibited the activation of NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome by decreasing the gene expression of Caspase-1, IL-lβ, and IL-18. Furthermore, LPC suppressed NLRP3 inflammasome activation by inhibiting nuclear factor-kappa B (NF-κB) signaling pathway (the reduced levels of toll-like receptor 4 [TLR4], myeloid differentiation factor 88 [MyD88], and NF-κB). Finally, our results showed that LPC regulated gut microbiota by enhancing the percentage of Ligilactobacillus and decreasing Alistipes and Barnesiella. In summary, we found that LP postbiotic was effective to protect broilers against Salmonella infection, possibly through suppressing NLRP3 inflammasome and optimizing gut microbiota. Our study provides the potential of postbiotics on prevention of Salmonella infection in poultry.

Extensively drug-, ciprofloxacin-, cefotaxime-, and azithromycin-resistant Salmonella enterica serovars isolated from camel meat in Egypt

Given the great importance of Salmonella as a leading foodborne pathogen of global concern and the few available data regarding its prevalence in camel meat, the present study aimed to determine the prevalence, antimicrobial resistance (AMR) profile, virulence genes, β-lactamase genes of Salmonella enterica serovars isolated from camel meat marketed in Egypt. Forty-five (29.6 %) of the 152 camel meat samples examined were positive for Salmonella spp. Among the 432 Salmonella presumptive colonies isolated, 128 were molecularly verified as Salmonella after confirmation by PCR targeting the Salmonella marker (invA) gene. Virulence genes, encompassing stn, spvC, and hilA genes, were detected in 91.4 % (117/128), 20.3 % (26/128), and 80.5 % (103/128) of the isolates, respectively. S. Enteritidis, S. Typhimurium, S. Cerro, and S. Montevideo were the most prevalent serovars with incidences of 25 % (32/128), 15.6 % (20/128), 15.6 % (20/128), and 12.5 % (16/128), respectively. Interestingly, 56.3 %, 53.1 %, 37.5 %, 28.1 %, 21.9 %, 18.8 %, 12.5 %, and 3.1 % of the isolates tested showed resistance to cefepime, ciprofloxacin, levofloxacin, cefotaxime, gentamicin, colistin, meropenem, and azithromycin, respectively. Salmonella isolates showed resistance to at least one antibiotic, with a mean multiple antibiotic resistance (MAR) index of 0.472. Interestingly, 59.4 %, 15.6 %, and 3.1 % of the isolates were categorized into multidrug-resistant, extensively drug-resistant, and pan-drug-resistant, respectively. Only 23 (25 %) of the 92 ampicillin-resistant isolates were proven to be Extended Spectrum Beta-Lactamase (ESBL)-producing Salmonella, in which β-lactamase (bla) genes were detected. The blaOXA-2 was the most existing gene where it was detected lonely in 10 of the ampicillin-resistant isolates and coexisted with blaCMY-1 in 4 isolates and with blaCMY-2 in a single isolate. The blaCMY-1, however, existed in 11 isolates, whereas the blaCMY-2 gene was only detected in 3 isolates tested. The present findings affirm that camel meat could be a leading reservoir for multi- and extensively-drug-resistance β-lactamase-producing Salmonella, representing a global public health challenge. Therefore, further research is necessary to detect the prevalence and AMR of Salmonella serovars from camel meat in Egypt and other countries to put camel meat as a source of Salmonella in foods of animal origin.

Genomic characterization of Salmonella isolated from retail chicken and humans with diarrhea in Qingdao, China

Salmonella, especially antimicrobial resistant strains, remains one of the leading causes of foodborne bacterial disease. Retail chicken is a major source of human salmonellosis. Here, we investigated the prevalence, antimicrobial resistance (AMR), and genomic characteristics of Salmonella in 88 out of 360 (24.4%) chilled chicken carcasses, together with 86 Salmonella from humans with diarrhea in Qingdao, China in 2020. The most common serotypes were Enteritidis and Typhimurium (including the serotype I 4,[5],12:i:-) among Salmonella from both chicken and humans. The sequence types were consistent with serotypes, with ST11, ST34 and ST19 the most dominantly identified. Resistance to nalidixic acid, ampicillin, tetracycline and chloramphenicol were the top four detected in Salmonella from both chicken and human sources. High multi-drug resistance (MDR) and resistance to third-generation cephalosporins resistance were found in Salmonella from chicken (53.4%) and humans (75.6%). In total, 149 of 174 (85.6%) Salmonella isolates could be categorized into 60 known SNP clusters, with 8 SNP clusters detected in both sources. Furthermore, high prevalence of plasmid replicons and prophages were observed among the studied isolates. A total of 79 antimicrobial resistant genes (ARGs) were found, with aac(6')-Iaa, blaTEM-1B, tet(A), aph(6)-Id, aph(3″)-Ib, sul2, floR and qnrS1 being the dominant ARGs. Moreover, nine CTX-M-type ESBL genes and the genes blaNMD-1, mcr-1.1, and mcr-9.1 were detected. The high incidence of MDR Salmonella, especially possessing lots of mobile genetic elements (MGEs) in this study posed a severe risk to food safety and public health, highlighting the importance of improving food hygiene measures to reduce the contamination and transmission of this bacterium. Overall, it is essential to continue monitoring the Salmonella serotypes, implement the necessary prevention and strategic control plans, and conduct an epidemiological surveillance system based on whole-genome sequencing.

Prevalence of Campylobacter spp., Salmonella spp., and Listeria monocytogenes, and Population Levels of Food Safety Indicator Microorganisms in Retail Raw Chicken Meat and Ready-To-Eat Fresh Leafy Greens Salads Sold in Greece

The presence of microbial pathogens in foods compromises their safety resulting in foodborne illnesses, public health disorders, product recalls, and economic losses. In this work, 60 samples of chilled raw chicken meat and 40 samples of packaged ready-to-eat (RTE) fresh leafy greens salads, sold in Greek retail stores (butchers and supermarkets), were analyzed for the presence of three important foodborne pathogenic bacteria, i.e., Campylobacter spp., Salmonella spp., and Listeria monocytogenes, following the detection protocols of the International Organization for Standardization (ISO). In parallel, the total aerobic plate count (APC), Enterobacteriaceae, total coliforms, Escherichia coli, and staphylococci were also enumerated as hygiene (safety) indicator organisms. When present, representative typical colonies for each pathogen were biochemically verified, following the ISO guidelines. At the same time, all the Campylobacter isolates from chicken (n = 120) were identified to the species level and further phylogenetically discriminated through multiplex and repetitive sequence-based (rep) polymerase chain reaction (PCR) methods, respectively. Concerning raw chicken, Campylobacter spp. were recovered from 54 samples (90.0%) and Salmonella spp. were recovered from 9 samples (15.0%), while L. monocytogenes was present in 35 samples (58.3%). No Campylobacter was recovered from salads, and Salmonella was present in only one sample (2.5%), while three salads were found to be contaminated with L. monocytogenes (7.5%). The 65% of the Campylobacter chicken isolates belonged to C. jejuni, whereas the rest, 35%, belonged to C. coli. Alarmingly, APC was equal to or above 106 CFU/g in 53.3% and 95.0% of chicken and salad samples, respectively, while the populations of some of the other safety indicators were in some cases also high. In sum, this study unravels high occurrence percentages for some pathogenic and food safety indicator microorganisms in raw chicken meat and RTE fresh leafy greens salads sold in Greek retail, highlighting the need for more extensive microbiological control throughout the food production chain (from the farm/field to the market).

Research Note: Changes in pathogenic characteristics and drug resistance of Salmonella in poultry meat in Jiading District, Shanghai from 2019 to 2021

To investigate the contamination status, serotype distribution, and drug resistance of Salmonella in poultry sold in Jiading District, Shanghai. Four types of raw poultry meats (chickens, ducks, geese, and pigeons) have been sampled from commercial markets, and potential Salmonella contamination has also been isolated and identified via serotype analysis. Furthermore, resistance of isolated Salmonella toward 14 commonly used antibiotics has also been conducted. Ninety-two Salmonella strains were isolated from 236 commercial poultry samples. The detection rates of Salmonella in pigeon, goose, duck, and chicken were 28.89, 44.44, 39.34, and 38.30%, respectively. The detection rate of Salmonella exhibits considerable variation across different years. The serotype composition of Salmonella in poultry demonstrates annual variability, undergoing significant changes from year to year. The majority serotypes of Salmonella have been revealed as S. Typhimurium, S. Enteritidis, and S. Agona. Relatively higher drug resistance was discovered with nalidixic acid, tetracycline, ampicillin and chloramphenicol, with drug resistance rate as 58.70, 53.25, 44.57, and 38.04%, respectively. Low drug resistance was revealed with cefotaxime, and completely sensitive to imipenem. Significant difference in drug resistance was noted in the Salmonella isolated from meats. Different serotypes of Salmonella strains have also revealed as difference in drug resistance. A total of 15.22% of Salmonella strains were nonresistant to any tested drugs. Multidrug-resistant strains accounted for 36.96% of isolated strains. The highest number of resistant antibiotics can reach 12 kinds of different antibiotics, Salmonella resistance is exhibiting a consistent upward trend overall. AMP-TET or CHL-CFZ drug resistance pattern suggested that the strain was multidrug resistant. The contamination of Salmonella in raw poultry meat samples in Jiading District, Shanghai is serious, and the drug resistance is increasing. The measures taken for epidemic prevention and control have a certain impact on the contamination of Salmonella in poultry meat. Therefore, monitoring and control should be strengthened.

Isolation, antimicrobial resistance and virulence characterization of Salmonella spp. from fresh foods in retail markets in Hangzhou, China

Salmonella can cause severe foodborne diseases. This study investigated the prevalence of Salmonella spp. in fresh foods in Hangzhou market and their harborage of antibiotic resistance and virulence genes, antibiotic susceptibility, and pathogenicity. A total of 500 samples (pork, n = 140; chicken, n = 128; vegetable, n = 232) were collected over a one-year period. Salmonella was found in 4.2% (21) of samples with the detection rate in pork, chicken and vegetables as 4.3% (6), 6.3% (8), and 3% (7), respectively. One Salmonella strain was recovered from each positive sample. The isolates were identified as six serotypes, of which S. Enteritidis (n = 7) and S. Typhimurium (n = 6) were the most predominant serotypes. The majority of isolates showed resistance to tetracycline (85.7%) and/or ciprofloxacin (71.4%). Tetracycline resistance genes showed the highest prevalence (90.5%). The occurrence of resistance genes for β-lactams (blaTEM-1, 66.7%; and blaSHV, 9.5%) and aminoglycosides (aadA1, 47.6%; Aac(3)-Ia, 19%) was higher than sulfonamides (sul1, 42.9%) and quinolones (parC, 38.1%). The virulence gene fimA was detected in 57.1% of isolates. Gene co-occurrence analysis implied that resistance genes were associated with virulence genes. Furthermore, selected S. Typhimurium isolates (n = 4) carrying different resistance and virulence genes up-regulated the secretions of cytokines IL-6 and IL-8 by Caco-2 cells in different degrees, suggesting that virulence genes may play a role in inflammatory transcription. In in vivo virulence test, microbiological counts in mouse feces and tissues showed that all included S. Typhimurium were able to infect mice, with one strain showing significantly higher virulence than others. In conclusion, this study indicates Salmonella contamination in fresh foods in Hangzhou market poses a risk to public health and it should be closely monitored to prevent and control foodborne diseases.

Molecular genotyping of Salmonella spp. isolated from cheese samples of local stores in Al-Diwaniyah city, Iraq

Background

Food safety is an important subject that the global cheese industry increases awareness of. This urges these economic sectors to elevate the level of research to minimize cheese contamination with pathogenic bacteria, such as Salmonella.

Aim

Based on these merits, this study was conducted to genotype Salmonella spp. isolated from cheese samples of local stores in Al-Diwaniyah City, Iraq.

Methods

The study used 41 samples of local fresh unsalted white cheese in a selective-growth-based isolation of Salmonella. These isolates were confirmed utilizing a slide-agglutination (SA) test and VITEK® 2 system (V2S). Then, the isolates were subjected to conventional PCR and sequencing techniques that both targeted the 16S rRNA gene. For subtyping, the Salmonella isolates were subjected to a random amplified polymorphic DNA (RAPD)-PCR method.

Results

The results of both SA and V2S revealed the presence of 14 (34.2%) isolates of Salmonella spp. in the cheese samples. The PCR confirmed 6 (42.9%) of these isolates, which further were defined with close nucleotide similarity (98.03%) and (97.88%) to different world isolates, such as Salmonella enterica subsp. Arizonae and Salmonella enterica subsp. enterica serovar Typhi, respectively. The RAPD-PCR findings showed different fragments for all the tested isolates.

Conclusion

The present study indicates that the samples of the local fresh unsalted white cheese contain different Salmonella genotypes, which could be originated from different contamination sources.

An Overview of Antimicrobial Resistance Profiles of Publicly Available Salmonella Genomes with Sufficient Quality and Metadata

Salmonella enterica (S. enterica) is a commensal organism or pathogen causing diseases in animals and humans, as well as widespread in the environment. Antimicrobial resistance (AMR) has increasingly affected both animal and human health and continues to raise public health concerns. A decade ago, it was estimated that the increased use of whole genome sequencing (WGS) combined with sharing of public data would drastically change and improve the surveillance and understanding of Salmonella epidemiology and AMR. This study aimed to evaluate the current usefulness of public WGS data for Salmonella surveillance and to investigate the associations between serovars, antibiotic resistance genes (ARGs), and metadata. Out of 191,306 Salmonella genomes deposited in European Nucleotide Archive and NCBI databases, 47,452 WGS with sufficient minimum metadata (country, year, and source) of S. enterica were retrieved from 116 countries and isolated between 1905 and 2020. For in silico analysis of the WGS data, KmerFinder, SISTR, and ResFinder were used for species, serovars, and AMR identification, respectively. The results showed that the five common isolation sources of S. enterica are human (29.10%), avian (22.50%), environment (11.89%), water (9.33%), and swine (6.62%). The most common ARG profiles for each class of antimicrobials are β-lactam (blaTEM-1B; 6.78%), fluoroquinolone [(parC[T57S], qnrB19); 0.87%], folate pathway antagonist (sul2; 8.35%), macrolide [mph(A); 0.39%], phenicol (floR; 5.94%), polymyxin B (mcr-1.1; 0.09%), and tetracycline [tet(A); 12.95%]. Our study reports the first overview of ARG profiles in publicly available Salmonella genomes from online databases. All data sets from this study can be searched at Microreact.

Distribution-based maximum likelihood estimation methods are preferred for estimating Salmonella concentration in chicken when contamination data are highly left-censored

Salmonella is a common chicken-borne pathogen that causes human infections. Data below the detection limit, referred to as left-censored data, are frequently encountered in the detection of pathogens. The approach of handling the censored data was regarded to affect the estimation accuracy of microbial concentration. In this study, a set of Salmonella contamination data was collected from chilled chicken samples using the most probable number (MPN) method, which consisted of 90.42% (217/240) non-detect values. Two simulated datasets with fixed censoring degrees of 73.60% and 90.00% were generated based on the real-sampling Salmonella dataset for comparison. Three methodologies were applied for handling left-censored data: (i) substitution with different alternatives, (ii) the distribution-based maximum likelihood estimation (MLE) method, and (iii) the multiple imputation (MI) method. For each dataset, the negative binomial (NB) distribution-based MLE and zero-modified NB distribution-based MLE were preferable for highly censored data and resulted in the least root mean square error (RMSE). Replacing the censored data with half the limit of quantification was the next best method. The mean concentration of Salmonella monitoring data estimated by the NB-MLE and zero-modified NB-MLE methods was 0.68 MPN/g. This study provided an available statistical method for handling bacterial highly left-censored data.

Comparison of Antibiotic Resistance Profiles of Salmonella Isolates from Retail Meats in Nanchang, China, in Two Periods

Salmonella is one of the most important foodborne pathogens. In this article, a total of 160 Salmonella isolates recovered from retail meats in June-July 2018 (before COVID-19 outbreak) and December 2020-April 2021 (after COVID-19 outbreak) in Nanchang, China, were characterized for serotyping, antimicrobial susceptibility, and specific resistance gene screening. The prevalence of Salmonella Typhimurium increased from 5.4% in 2018 to 19.1% in 2021, and Salmonella Enteritidis increased from 3.3% in 2018 to 8.8% in 2021. Compared with those in June-July 2018, Salmonella isolates in December 2020-April 2021 demonstrated a significant increase in resistance to 13 tested antibiotics except for doxycycline and nitrofurantoin (p < 0.05). The Salmonella isolates in December 2020-April 2021 showed a higher presence of plasmid-mediated quinolone resistance genes (qnrA, qnrB, and qnrS), and mutations in the quinolone resistance-determining region (gyrA Asp87Asn, gyrA Asp87Tyr, parC Thr57Ser, and parC Ser80Ile). Whole-genome sequencing was used to analyze four polymyxin B-resistant strains. Some common mutation sites in eptC and micA were found in the four strains. Based on the data in this article, it indicated that antibiotic resistance was facilitated and more gene mutations related to quinolone resistance were developed.

A Potential Adhesin/Invasin STM0306 Participates in Host Cell Inflammation Induced by Salmonella enterica Serovar Typhimurium

Salmonella enterica serovar typhimurium (S. Typhimurium) is a common Gram-negative foodborne pathogenic bacterium that causes gastrointestinal disease in humans and animals. It is well known that adhesins and invasins play crucial roles in the infection mechanism of S. Typhimurium. S. Typhimurium STM0306 has been denoted as a putative protein and its functions have rarely been reported. In this study, we constructed the STM0306 gene mutant strain of S. Typhimurium and purified the recombinant STM0306 from Escherichia coli. Deletion of the STM0306 gene resulted in reduced adhesion and invasion of S. Typhimurium to IPEC-J2, Caco-2, and RAW264.7 cells. In addition, STM0306 could bind to intestinal epithelial cells and induced F-actin modulation in IPEC-J2 cells. Furthermore, we found that STM0306 activated the nuclear factor kappa B (NF-κB) signaling pathway and increased the mRNA expression of pro-inflammatory cytokines such as IL-1β, TNF-α, as well as chemokine CXCL2, thus resulting in cellular inflammation in host cells. In vivo, the deletion of the STM0306 gene led to reduced pathogenicity of S. Typhimurium, as evidenced by lower fecal bacterial counts and reduced body weight loss in S. Typhimurium infected mice. In conclusion, the STM0306 of S. Typhimurium is an important adhesin/invasin involved in the pathogenic process and cellular inflammation of the host.

Genome-based risk assessment for foodborne Salmonella enterica from food animals in China: A One Health perspective

Salmonella is one of the most common causes of foodborne bacterial disease. Animal-borne foods are considered the primary sources of Salmonella transmission to humans. However, genomic assessment of antimicrobial resistance (AMR) and virulence of Salmonella based on One Health approach remains obscure in China. For this reason, we analyzed the whole genome sequencing data of 134 Salmonella isolates recovered from different animal and meat samples in China. The 134 Salmonella were isolated from 2819 samples (4.75 %) representing various sources (pig, chicken, duck, goose, and meat) from five Chinese provinces (Zhejiang, Guangdong, Jiangxi, Hunan, and Qinghai). AMR was evaluated by the broth dilution method using 13 different antimicrobial agents, and results showed that 85.82 % (115/134) of isolates were resistant to three or more antimicrobial classes and were considered multidrug-resistant (MDR). Twelve sequence types (STs) were detected, with a dominance of ST469 (29.85 %, 40/134). The prediction of virulence genes showed the detection of cdtB gene encoding typhoid toxins in one isolate of S. Muenster recovered from chicken, while virulence genes associated with type III secretion systems were detected in all isolates. Furthermore, plasmid-type prediction showed the abundance of IncFII(S) (13/134; 9.7 %) and IncFIB(S) (12/134; 8.95 %) in the studied isolates. Together, this study demonstrated the ability to use whole-genome sequencing (WGS) as a cost-effective method to provide comprehensive knowledge about foodborne Salmonella isolates in One Health surveillance approach.

Mobile genetic elements drive the multidrug resistance and spread of Salmonella serotypes along a poultry meat production line

The presence of mobile genetic elements in Salmonella isolated from a chicken farm constitutes a potential risk for the appearance of emerging bacteria present in the food industry. These elements contribute to increased pathogenicity and antimicrobial resistance through genes that are related to the formation of biofilms and resistance genes contained in plasmids, integrons, and transposons. One hundred and thirty-three Salmonella isolates from different stages of the production line, such as feed manufacturing, hatchery, broiler farm, poultry farm, and slaughterhouse, were identified, serotyped and sequenced. The most predominant serotype was Salmonella Infantis. Phylogenetic analyses demonstrated that the diversity and spread of strains in the pipeline are serotype-independent, and that isolates belonging to the same serotype are very closely related genetically. On the other hand, Salmonella Infantis isolates carried the pESI IncFIB plasmid harboring a wide variety of resistance genes, all linked to mobile genetic elements, and among carriers of these plasmids, the antibiograms showed differences in resistance profiles and this linked to a variety in plasmid structure, similarly observed in the diversity of Salmonella Heidelberg isolates carrying the IncI1-Iα plasmid. Mobile genetic elements encoding resistance and virulence genes also contributed to the differences in gene content. Antibiotic resistance genotypes were matched closely by the resistance phenotypes, with high frequency of tetracycline, aminoglycosides, and cephalosporins resistance. In conclusion, the contamination in the poultry industry is described throughout the entire production line, with mobile genetic elements leading to multi-drug resistant bacteria, thus promoting survival when challenged with various antimicrobial compounds.

Prevalence and resistance to antibacterial agents in Salmonella enterica strains isolated from poultry products in Northern Kazakhstan

Background and Aim: Salmonella is one of the main causative agents of foodborne infections. The source of the pathogen, in most cases, is poultry products. The intensification of poultry farming and the constant and uncontrolled use of antimicrobials has led to an increase in the level of antibiotic resistance, especially in developing countries. This study aimed to determine the level of sensitivity to antimicrobial agents in Salmonella enterica strains isolated from poultry products in Northern Kazakhstan, as well as to determine the genetic mechanisms of resistance and the presence of integrons. Materials and Methods: In total, 398 samples of poultry products sold in Northern Kazakhstan were selected. Salmonella strains were isolated from product samples using microbiological methods. Salmonella was identified based on morphological, biochemical, and serological methods, as well as polymerase chain reaction (PCR). Sensitivity testing for antimicrobial agents was performed using the disk diffusion method. The detection of resistance genes was performed using PCR and gel electrophoresis. Results: Out of 398 samples of poultry products, a total of 46 Salmonella isolates were obtained. Most of the isolates belong to the serovar Salmonella Enteritidis (80.4%). The assessment of sensitivity to antibacterial agents showed that Salmonella was mainly resistant to nalidixic acid (63%), furadonin (60.9%), ofloxacin (45.6%), and tetracycline (39.1%). In 64.3% of cases, Salmonella was resistant to three or more groups of antibacterial agents. Resistance genes such as tetA, tetB, blaTEM, aadA, sul3, and catII, as well as integrons of two classes (teg1 and teg2), were identified. Conclusion: Poultry products contain antimicrobial-resistant strains of Salmonella, as well as genes encoding resistance mechanisms. The results emphasize the need for constant monitoring of not only pathogenic microorganisms but also their sensitivity to antimicrobial agents. The potential threat to human health requires a unified approach to the problem of antibiotic resistance from representatives of both public health and the agroindustrial complex. Keywords: antibiotic resistance, food safety, poultry, resistance genes, Salmonella.

Prevalence and antimicrobial resistance of Salmonella enterica serovars Enteritidis and Typhimurium isolated from retail chicken meat in Wasit markets, Iraq

Background and Aim: Food poisoning caused by Salmonella enterica serovars is the most common type of foodborne illness. Tainted chicken meat is a major vector for spreading these serovars throughout the food supply chain. Salmonella isolates that developed resistance to commonly used antimicrobials pose a noteworthy risk to public health, yet there has been a lack of data on this issue in Iraq. Therefore, it is crucial to address these serious public health challenges with an adequate database on the occurrence and antibiotic resistance of these serovars. This study aimed to determine the frequency of occurrence of Salmonella enterica serovars Enteritidis and Typhimurium (S. Enteritidis and S. Typhimurium), antimicrobial resistance (AMR), and prevalence of multidrug resistance among S. Enteritidis and S. Typhimurium isolated from poultry meat collected in Wasit Province in Iraq. Materials and Methods: A total of 150 raw and frozen poultry meat samples were gathered from retail markets in various locales across the Wasit Governorate in Iraq. Salmonella spp. were successfully cultured and identified using the technique recommended by ISO 6579:2002, with minor modifications. The multiplex polymerase chain reaction approach was used to confirm Salmonella spp. (S. Enteritidis and S. Typhimurium). A disk diffusion test was performed to determine the susceptibility to particular antimicrobial agents, and 12 different antimicrobial agents were evaluated. Results: Only 19 of the 150 (12.7%) samples tested positive for Salmonella (16% and 11% were isolated from raw and frozen chicken meat, respectively). S. Enteritidis accounted for 63.2%, whereas S. Typhimurium accounted for 36.8%. Nalidixic acid resistance was the most common (73.7%), followed by sulfamethoxazole-trimethoprim (63.2%) and tetracycline (63.2%), but gentamicin and ciprofloxacin (up to 15.8%) only had modest resistance. Antibiogram of S. Enteritidis and S. Typhimurium yield 13 antibiotypes. Among the 19 Salmonella isolates, 12 of 19 (63.2%) established resistance to no less than three categories of antimicrobials. Conclusion: This study highlighted the necessity of limiting the utilization of antibiotics in animal production by providing vital information regarding the frequency and AMR of Salmonella at markets in Wasit Province. Therefore, risk assessment models could use these data to lessen the amount of Salmonella passed on to humans in Iraq from chicken meat. Keywords: antimicrobial resistance, chicken, food poisoning, serovars.

Epidemiology of foodborne diseases caused by Salmonella in Zhejiang Province, China, between 2010 and 2021

Objective

Salmonella infection is a common cause of bacterial foodborne diseases (FBDs) globally. In this study, we aimed to explore the epidemiological and etiological characteristics of Salmonella infection from 2012-2021 in Zhejiang Province, China.

Methods

Descriptive statistical methods were used to analyze the data reported by the Centers for Disease Control and Prevention at all levels in Zhejiang Province through the China National Foodborne Diseases Surveillance Network from 2012-2021.

Results

A total of 11,269 Salmonella cases were reported, with an average positive rate of 3.65%, including 1,614 hospitalizations. A significant seasonal trend was observed for Salmonella cases, with the highest rate over the summer period, peaking from May to October, accounting for 77.96%. The results indicated a higher positive rate among respondents aged 0-4 years, especially for the scattered children (P < 0.05). The highest number of Salmonella infections were caused due to contaminated fruit and fruit products. Households (54.69%) had the most common exposure settings. Serotypes analysis revealed that Salmonella typhimurium (36.07%), Salmonella enteritidis (15.17%), and Salmonella london (6.05%) were the dominant strains among the 173 serotypes. Diarrhea, abdominal pain, fever, nausea, and vomiting were the main symptoms of these serotypes.

Conclusions

FBDs caused by Salmonella are important issues for public health in Zhejiang Province, and there is a need to focus on the epidemiological and etiological characteristics to control Salmonella infections.

A Meta-Analysis and Systematic Review of Listeria monocytogenes Response to Sanitizer Treatments

Listeria monocytogenes is a ubiquitous organism that can be found in food-related environments, and sanitizers commonly prevent and control it. The aim of this study is to perform a meta-analysis of L. monocytogenes response to sanitizer treatments. According to the principle of systematic review, we extracted 896 records on the mean log-reduction of L. monocytogenes from 84 publications as the dataset for this study. We applied a mixed-effects model to describe L. monocytogenes response to sanitizer treatment by considering sanitizer type, matrix type, biofilm status, sanitizer concentration, treatment time, and temperature. Based on the established model, we compared the response of L. monocytogenes under different hypothetical conditions using forest plots. The results showed that environmental factors (i.e., sanitizer concentration, temperature, and treatment time) affected the average log-reduction of L. monocytogenes (p < 0.05). L. monocytogenes generally exhibited strong resistance to citric acid and sodium hypochlorite but had low resistance to electrolyzed water. The planktonic cells of L. monocytogenes were less resistant to peracetic acid and sodium hypochlorite than the adherent and biofilm cells. Additionally, the physical and chemical properties of the contaminated or inoculated matrix or surface also influenced the sanitizer effectiveness. This review may contribute to increasing our knowledge of L. monocytogenes resistance to sanitizers and raising awareness of appropriate safety precautions.

Salmonella spp. in Chicken: Prevalence, Antimicrobial Resistance, and Detection Methods

Multidrug-resistant Salmonella spp. is one of the leading causes of worldwide foodborne disease outbreaks. Animal-derived foods, particularly chicken and poultry products, are the most likely source of Salmonella transmission to humans. The increasing demand for chicken meat has raised a global food safety issue. This review aims to determine the prevalence and antimicrobial resistance of Salmonella spp. in chickens from various countries in Asia. The methods for detecting Salmonella will also be discussed in this review. The prevalence of Salmonella spp. in chicken and poultry products is lower in developed countries than in developing countries. In addition, the incidence of Salmonella spp. in chicken and poultry products from fresh markets is higher than those from supermarkets. Furthermore, this review also reported the presence of multidrug-resistant Salmonella strains in various Asian countries. Rapid Salmonella detection based on immunological assays, molecular-based assays, and biosensors can provide more accurate results with high sensitivity and specificity. These methods also require a shorter time than the cultural-based Salmonella detection method. The use of suitable detection methods to determine the presence of Salmonella spp. in chicken and poultry products is important to ensure food safety.

Genome-Wide Searching Single Nucleotide-Polymorphisms (SNPs) and SNPs-Targeting a Multiplex Primer for Identification of Common Salmonella Serotypes

A rapid and high-quality single-nucleotide polymorphisms (SNPs)-based method was developed to improve detection and reduce salmonellosis burden. In this study, whole-genome sequence (WGS) was used to investigate SNPs, the most common genetic marker for identifying bacteria. SNP-sites encompassing 15 sets of primers (666–863 bp) were selected and used to amplify the target Salmonella serovar strains, and the amplified products were sequenced. The prevalent Salmonella enterica subspecies enterica serovars, including Typhimurium; Enteritidis, Agona, enterica, Typhi, and Abony, were amplified and sequenced. The amplified sequences of six Salmonella serovars with 15 sets of SNP-sites encompassing primers were aligned, explored SNPs, and SNPs-carrying primers (23 sets) were designed to develop a multiplex PCR marker (m-PCR). Each primer exists in at least two SNPs bases at the 3′ end of each primer, such as one was wild, and another was a mismatched base by transition or transversion mutation. Thus, twenty-three sets of SNP primers (242–670 bp), including 13 genes (SBG, dedA, yacG, mrcB, mesJ, metN, rihA/B, modA, hutG, yehX, ybiY, moeB, and sopA), were developed for PCR confirmation of target Salmonella serovar strains. Finally, the SNPs in four genes, including fliA gene (S. Enteritidis), modA (S. Agona and S. enterica), sopA (S. Abony), and mrcB (S. Typhimurium and S. Typhi), were used for detection markers of six target Salmonella serotypes. We developed an m-PCR primer set in which Salmonella serovars were detected in a single reaction. Nevertheless, m-PCR was validated with 21 Salmonella isolates (at least one isolate was taken from one positive animal fecal, and n = 6 reference Salmonella strains) and non-Salmonella bacteria isolates. The SNP-based m-PCR method would identify prevalent Salmonella serotypes, minimize the infection, and control outbreaks.

Antimicrobial resistance of Salmonella Indiana from retail chickens in China and emergence of an mcr-1-harboring isolate with concurrent resistance to ciprofloxacin, cefotaxime, and colistin

Salmonella enterica serotype Indiana (S. Indiana) in Chinese poultry meat has aroused widespread concern because of its high prevalence and strong antimicrobial resistance. In consideration of the relationship in our previous study between S. Indiana and co-resistance to ciprofloxacin and cefotaxime (CIP-CTX), which were the first-line drug which were used in Salmonella infection in clinical, the antimicrobial resistance (AMR) of 224 CIP-CTX co-resistant S. Indiana isolated from retail chicken samples in China were investigated, with the aim of characterizing the AMR profiles and related resistance mechanisms to ciprofloxacin and cefotaxime among these CIP-CTX co-resistant S. Indiana isolates, all of which showed multi-drug-resistant (MDR) phenotypes. GyrA (S83F and D87N/G) with ParC (T57S and S80R) were the dominant amino acid substitution types, with oqxA, oqxB, and aac (6′)-Ib-cr identified as common plasmid-mediated quinolone resistance (PMQR)-encoding genes. Five bla_CTX-M gene subtypes were identified with bla_CTX-M-65 ranking at the top. Equally important, we obtained one isolate CFSA664 harboring the mcr-1 gene was ESBL producer with co-resistance to nine in ten classes of tested drugs inclduing colistin. A single circular chromosome and 3 circular plasmids were found in its genome. Among the 26 AMR genes identified, 24 were located on plasmid pCFSA664-1, including three ESBL genes, while plasmid pCFSA664-3 owning only the mcr-1 gene and sharing the same backbone structure with plasmids from Enterobacteriaceae. No insertion sequences were found near the mcr-1 gene but a relaxase-encoding gene in the flank, which could transfer into E. coli J53 at a relatively high frequency. S. Indiana in this study exhibited highly drug-resistant phenotypes, contributing to the acceleration of the dissemination and emergence of this pathogen among different sources. Surveillance and a One Health strategy are needed to limit the emergence of S. Indiana along the food chain.

Prevalence, Serotypes, and Antimicrobial Resistance Patterns of Non-Typhoid Salmonella in Food in Northern Taiwan

Salmonella is one of the most common bacteria causing food poisoning worldwide. We evaluated the prevalence, the serotypes, and the antimicrobial resistance (AMR) of Salmonella isolates from many kinds of food, particularly pork and chicken in retail, in Taiwan between January 2017 and December 2019. The E-test was used to assess antimicrobial susceptibility and a polymerase chain reaction was performed for serotyping. A total of 459 different foods were investigated, and 117 Salmonella strains were isolated. Retail pork and chicken were the most common Salmonella-contaminated foods (64.1% and 29.1%, respectively). Of the 117 isolates, 23 serotypes were identified. The serotypes Derby (16.2%), Anatum (13.7%), and Agona (8.5%) were the most prevalent. The resistance rates to ciprofloxacin, ceftriaxone, and carbapenem were 41.9%, 11.1%, and 1.7%, respectively. The Derby and Anatum serotypes were prevalent in chicken and pork; the Anatum serotype had significantly higher ciprofloxacin and ceftriaxone resistance rates and was highly prevalent in 2017 and 2018. Multi-locus sequence typing analysis revealed that the 58 randomly chosen Salmonella isolates belonged to 18 sequence types (STs). ST64 (Anatum, 16 out of 58, 27.6%) was the most common, followed by ST321 (Muenster, 6/58, 10.3%), ST831 (Give, 5/58, 8.6%), ST155 (London, 4/58, 6.9%) and ST314 (Kentucky, 4/58, 6.9%). Multidrug-resistant Salmonella strains were remarkably observed in the serotypes Anatum (ST64) and Goldcoast (ST358). This study revealed that retail pork was commonly contaminated with antimicrobial-resistant Salmonella. Thus, periodic investigations of Salmonella serotypes and AMR are needed.

An Online Pattern Recognition-Oriented Workshop to Promote Interest among Undergraduate Students in How Mathematical Principles Could Be Applied within Veterinary Science

Knowing the importance of mathematics and its relationship with veterinary medicine plays an important role for students. To promote interest in this relationship, we developed the workshop “Math in Nature” that utilizes the surrounding environment for stimulating pattern-recognition and observational skills. It consisted of four sections: A talk by a professional researcher, a question-and-answer section, a mathematical pattern identification session, and a discussion of the ideas proposed by students. The effectiveness of the program to raise interest in mathematics was evaluated using a questionnaire applied before and after the workshop. Following the course, a higher number of students agreed with the fact that biological phenomena can be explained and predicted by applying mathematics, and that it is possible to identify mathematical patterns in living beings. However, the students’ perspectives regarding the importance of mathematics in their careers, as well as their interest in deepening their mathematical knowledge, did not change. Arguably, “Math in Nature” could have exerted a positive effect on the students’ interest in mathematics. We thus recommend the application of similar workshops to improve interests and skills in relevant subjects among undergraduate students.

Prevalence of Antibiotic Resistance in Salmonella Serotypes Concurrently Isolated from the Environment, Animals, and Humans in South Africa: A Systematic Review and Meta-Analysis

One of the main global concerns is the usage and spread of antibiotic resistant Salmonella serovars. The animals, humans, and environmental components interact and contribute to the rapid emergence and spread of antimicrobial resistance, directly or indirectly. Therefore, this study aimed to determine antibiotic resistance (AR) profiles of Salmonella serotypes isolated from the environment, animals, and humans in South Africa by a systematic review and meta-analysis. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were followed to search four databases for studies published from 1980 to 2021, that reported the antibiotic resistance profiles of Salmonella serotypes isolated in South Africa. The AR was screened from 2930 Salmonella serotypes which were isolated from 6842 samples. The Western Cape province had high pooled prevalence estimates (PPE) of Salmonella isolates with AR profiles followed by North West, Gauteng, and Eastern Cape with 94.3%, 75.4%, 59.4%, and 46.2%, respectively. The high PPE and heterogeneity were observed from environmental samples [69.6 (95% CI: 41.7−88.3), Q = 303.643, I² = 98.353, Q-P = 0.045], animals [41.9 (95% CI: 18.5–69.5), Q = 637.355, I² = 98.745, Q-P = 0.577], as well as animals/environment [95.9 (95% CI: 5.4−100), Q = 55.253, I² = 96.380, Q-P = 0.300]. The majority of the salmonella isolates were resistant to sulphonamides (92.0%), enrofloxacin and erythromycin (89.3%), oxytetracycline (77.4%), imipenem (72.6%), tetracycline (67.4%), as well as trimethoprim (52.2%), among the environment, animals, and humans. The level of multidrug-resistance recorded for Salmonella isolates was 28.5% in this review. This study has highlighted the occurrence of AR by Salmonella isolates from animals, humans, and environmental samples in South Africa and this calls for a consolidated “One Health” approach for antimicrobial resistance epidemiological research, as well as the formulation of necessary intervention measures to prevent further spread.