Search Results (340)

Background: Salmonellosis is a major global public health concern, commonly caused by serovars such as Salmonella enterica serovar Typhimurium and Salmonella enterica serovar Enteritidis. Rare serovars, however, may represent underrecognized links between environmental reservoirs and human infection. Salmonella enterica serovar Haifa is a sporadic serotype primarily associated with livestock and environmental sources and has previously been reported in Indian poultry but not in human clinical cases to date. Case Presentation: A 70-year-old male with a history of type 2 diabetes, presented with acute watery diarrhea and dehydration. One week prior to symptom onset, the patient reported direct contact with cattle and poultry in a rural setting. Laboratory investigations revealed leucopenia and elevated procalcitonin (3.73 ng/mL). Stool culture yielded non-lactose fermenting colonies on MacConkey agar and H₂S-producing colonies on Hektoen enteric agar. The isolate was identified via VITEK 2 and confirmed as Salmonella enterica serovar Haifa by the National Institute for Research in Bacterial Infections (NIRBI). Antimicrobial susceptibility testing (AST) revealed that the isolate showed resistance to ampicillin, ceftriaxone, and ciprofloxacin. The patient was successfully treated with a three-day course of intravenous Azithromycin (1 g) and achieved rapid clinical recovery. Conclusions: To the best of our knowledge, this case represents the first reported human infection caused by S. Haifa in India. The finding highlights the potential zoonotic risk of rare non-typhoidal Salmonella serovars and emphasizes the importance of surveillance, routine serotyping, and antimicrobial resistance monitoring within a One Health framework. Full article

Background/Objectives: Salmonella is a major foodborne pathogen commonly associated with poultry products and poses a significant public health concern worldwide. This study aimed to determine the distribution of Salmonella serotypes isolated from retail chicken meat and to evaluate their quinolone resistance profiles, along with selected virulence and antimicrobial resistance genes. Methods: A total of 53 Salmonella isolates recovered from retail chicken meat were serotyped and subjected to quinolone susceptibility testing and PCR-based detection of class 1 integrons, antimicrobial resistance genes, and virulence-associated genes. Results: Of these, 41 (77.35%) were identified as Salmonella Infantis (S. Infantis) and 12 (22.65%) as Salmonella Enteritidis (S. Enteritidis). Antimicrobial susceptibility testing revealed that 47 (88.67%) isolates were resistant to enrofloxacin, 32 (60.37%) to ciprofloxacin, 26 (49.05%) to moxifloxacin, and 24 (45.28%) to norfloxacin. All S. Enteritidis isolates were susceptible to ciprofloxacin, moxifloxacin, and norfloxacin. Broth microdilution results showed that 20.75% of isolates were susceptible and 77.35% were intermediate to ciprofloxacin, with minimum inhibitory concentration values ranging between 0.02 and 1 µg/mL. The class 1 integron gene (int1) was detected in 83.01% of isolates. The mcr1, mcr2, mcr3, mcr4, mcr5, qnrA, and qnrC genes were not detected in any isolates. Among S. Infantis isolates, 2 (4.88%) and 9 (21.95%) were positive for qnrB and qnrSm genes, respectively, while all S. Enteritidis isolates were negative for these genes. Virulence gene analysis showed that sitC was detected in 100% of isolates and sopE in 98.11%. The spvC and pefA genes were detected in 13.2% of isolates. Conclusions: The findings suggest that S. Infantis was the predominant serotype and that quinolone resistance was common among Salmonella isolates from retail chicken meat. The virulence gene profiles indicated that these isolates harbored a wide range of markers associated with host invasion, intracellular survival, and adaptation within the host environment. Moreover, the high prevalence of the int1 gene highlights the need for further investigation of integron-associated resistance determinants and their potential role in the dissemination of antimicrobial resistance through chicken products and the associated risk of transmission to humans. Full article

Salmonellosis is a significant zoonotic and foodborne disease caused by Salmonella. As a primary reservoir, poultry infections can result in decreased survival rates, diminished production performance and contamination of poultry products, thereby posing a serious threat to the sustainable development of poultry farming and human health. In this study, a total of 979 samples were collected from a laying hen production chain, and 84 Salmonella strains were isolated, with an isolation rate of 8.58% (84/979). Among these, 54 isolates (11.2%) were from commercial house samples, followed by nine isolates (10.8%) from market samples, 10 isolates (5.88%) from hatchery samples, and 11 isolates (4.55%) from breeder house samples. Six different serotypes were identified, with Salmonella enterica serovar Enteritidis (S. Enteritidis) being the predominant serotype (41.7%), followed by Salmonella enterica serovar Typhimurium (S. Typhimurium) (22.6%) and Salmonella enterica serovar Infantis (S. Infantis) (21.4%). The S. Enteritidis was distributed in various production stages in the laying hen production chain. Among the 16 antibiotics tested, 30 selected strains exhibited 100% resistance to nalidixic acid (NAL) and ciprofloxacin (CIP), attributed to mutations in the quinolone resistance-determining region (QRDR) of the gyrA gene. Following this, the resistance rates for ampicillin (AMP), amoxicillin–clavulanate (AMC), and streptomycin (STR) were 56.7%. Antimicrobial resistance genotypes were consistent with the drug resistance phenotype. Whole genome sequencing (WGS) phylogenetic analysis based on core genome single nucleotide polymorphism (cgSNP) revealed that Salmonella can spread across various stages of the laying hen production chain, posing a potential threat to human health. Furthermore, 165 virulence-associated genes were identified among the investigated isolates, indicating a highly conserved virulence repertoire. This study investigates the prevalence of Salmonella within a laying hen production chain, providing a scientific foundation for the effective prevention and control of Salmonella infection. Full article

This study aimed to identify circulating lineages of the most prevalent human-associated Salmonella serotypes identified through routine surveillance in Romania between 2023 and 2025 and assess their role in the spread of antimicrobial resistance (AMR). A total of 271 isolates (217 S. Enteritidis, 28 monophasic S. Typhimurium, and 26 S. Typhimurium) were investigated using Illumina short-read sequencing. The isolates were assigned to 9 MLST sequence types (STs) and 109 core genome MLST complex types. The predominant STs were ST11 (96% in S. Enteritidis), ST19 (77% in S. Typhimurium), and ST34 (79% in monophasic S. Typhimurium). Overall, 148 isolates carried at least one AMR determinant, including 28 acquired genes and 6 gene mutations, conferring resistance to ten antimicrobial classes. Four percent of all isolates were predicted to be multidrug-resistant, often associated with determinants conferring tolerances to biocides and/or heavy metals. The most prevalent resistance markers were GyrA_D87Y in S. Enteritidis ST11 (94/217) and bla_TEM-1 in S. Typhimurium ST19 (7/26). Among monophasic S. Typhimurium ST34 isolates, the co-occurrence of bla_TEM-1, aph(3”)-Ib, aph(6)-Id, sul2, and tet(B) genes was common (17/28). The 43 predicted AMR plasmids were not shared across serotypes, except among those carrying the qnrB19 gene. These results provide a genomic baseline for AMR surveillance in Romania and strengthen the human surveillance component of national One Health efforts to control resistant Salmonella. Full article

Cherry tomatoes are highly susceptible to Salmonella contamination during pre- and post-harvest handling, leading to foodborne illness outbreaks and significant economic losses. Edible coatings incorporating natural antimicrobials offer a promising alternative to conventional chemical treatments for enhancing food safety while maintaining produce quality. This study developed and evaluated a pectin-based edible coating enriched with zinc nanohydroxide-thymol nanohybrids (ZnNH-T) for controlling Salmonella contamination and extending shelf-life of cherry tomatoes. ZnNH-T nanohybrids were synthesized via precipitation, followed by thymol intercalation, and characterized by SEM. Four coating formulations were prepared: pectin alone (P), pectin-thymol (PT), pectin-ZnNH (PNH), and pectin-ZnNH-T (PNHT). Antibacterial activity of the four coatings was first screened in vitro by disc diffusion against six S. enterica serovars; three serovars (Typhimurium, Enteritidis, and Montevideo) showing a statistically significant, coating-dependent inhibition response were selected for the postharvest assay. Cherry tomatoes were coated and dip-inoculated with three Salmonella serotypes (Typhimurium, Enteritidis, and Montevideo) at approximately 10⁵ CFU/mL and stored at 25 °C for 12 days. Antimicrobial efficacy, antioxidant activity (ABTS assay), and physicochemical quality parameters (weight loss, color, pH, and total soluble solids) were evaluated. Zinc nanohydroxides were successfully synthesized, as observed in SEM morphology. ABTS radical scavenging activity of filmogenic solutions was highest for PT (92.4%) and moderate for PNHT (65.9%), while P and PNH showed minimal activity (20.1% and 17.8%, respectively). PNHT coating achieved an approximately 2-log CFU/g reduction in Salmonella populations compared to uncoated controls over 12 days of storage, demonstrating sustained antimicrobial efficacy. Coated tomatoes exhibited significantly reduced weight loss (8% for PNHT vs. 13% for control), better color retention, lycopene content, maintained firmness, and stable pH and TSS values compared to uncoated controls. The pectin-ZnNH-T coating system represents a novel multifunctional approach for enhancing cherry tomato safety and quality. The use of thymol from the layered hydroxide structure, combined with zinc ion antimicrobial effects, provides sustained pathogen reduction while maintaining desirable physicochemical properties. This natural, biodegradable coating technology has potential for commercial application in fresh produce preservation. Full article

Historical microbiological collections linked to epidemiological and clinical metadata represent a valuable resource for retrospective investigation of long-term changes in pathogen populations. In this retrospective study, we analyzed the epidemiological, clinical, and microbiological information recorded in the datasheets accompanying Salmonella enterica isolates archived in a historical collection assembled in Lombardy, Italy, between 2001 and 2016. Overall, metadata associated with 6624 salmonellosis cases with confirmed serovar identification were included to describe serovar distribution, bloodstream infections, and antimicrobial resistance (AMR) patterns within the collection. Four serovars (S. Typhimurium, S. Enteritidis, S. 1,4,[5],12:i:-, S. Napoli) accounted for approximately 80% of all cases. The relative representation of S. Napoli increased over the study period, whereas S. Choleraesuis showed the highest proportion of bloodstream isolates and predominantly affected adults. Overall, resistance to penicillins (46.9%) and tetracyclines (48.0%) was common, whereas resistance to fluoroquinolones (2.9%) and third-generation cephalosporins (<2%) remained low. Among invasive non-typhoidal Salmonella (iNTS) infections, 69.3% of isolates were resistant to at least one antimicrobial class, and 34.7% exhibited multidrug resistance (MDR), with fluoroquinolone resistance increasing to 13.9%. These findings highlight the value of historical microbiological collections and their associated metadata for documenting long-term changes in serovar distribution, invasive infections, and AMR, while emphasizing their importance as a resource for future molecular epidemiology and One Health surveillance. Full article

Objectives: Increasing antimicrobial resistance among foodborne pathogens, particularly extended-spectrum β-lactamase (ESBL) and plasmid-mediated AmpC β-lactamase (pAmpC) production, has become a major public health concern worldwide. This study aimed to determine the presence of Salmonella Enteritidis, Salmonella Typhimurium, and Escherichia coli O157:H7 in bovine carcasses and to evaluate their antibiotic resistance profiles together with ESBL and pAmpC resistance characteristics. Methods: A total of 300 bovine carcasses were examined for the presence of Salmonella spp. and E. coli O157:H7 using culture-based isolation methods following ISO 6579-1 and FDA guidelines, respectively. The isolates were confirmed by molecular methods, and stx1, stx2, eae, and hly were investigated in E. coli O157:H7 isolates. Antimicrobial susceptibility testing was performed according to EUCAST guidelines. ESBL and pAmpC production were determined phenotypically and subsequently characterized by molecular methods. Results: A total of 25 Salmonella spp. (32% S. Enteritidis and 68% S. Typhimurium) and 20 E. coli O157:H7 isolates were recovered from different bovine carcasses. stx2 was the most frequently detected virulence gene. Of the 31 phenotypically ESBL-positive isolates, 29 carried at least one ESBL-associated gene. The predominant ESBL gene was bla_CTX-M (79.3%), followed by bla_TEM and bla_SHV (37.9%). Among CTX-M gene groups, CTX-M-25 was the most prevalent (94.4%). Phenotypic pAmpC production was detected in 13 isolates, while 17 isolates carried at least one pAmpC-associated gene, with FOX identified as the predominant gene group. All isolates were resistant to pefloxacin, followed by gentamicin (93.3%) and cefoxitin (55.5%). Multidrug resistance was detected in 34 (75.6%) isolates. Conclusions: The detection of ESBL-producing, pAmpC-positive, and multidrug-resistant Salmonella spp. and Escherichia coli O157:H7 isolates in bovine carcasses indicates the presence of antimicrobial-resistant foodborne pathogens in the beef production chain. These findings highlight the need for continued monitoring of antimicrobial resistance and effective control measures at the slaughterhouse level. Full article

This study evaluated the microbiological quality, phenolic compound profile, antimicrobial activity against foodborne pathogens, and the presence of potential chemical markers associated with microplastic polymers in 35 commercial bee pollen samples obtained from the seven geographical regions of Türkiye. Microbiological analyses included the enumeration of total mesophilic aerobic bacteria, coliforms, yeasts and molds, lactobacilli, lactococci, and psychrophilic bacteria. Antimicrobial activity was determined against Escherichia coli O157:H7, Staphylococcus aureus, and Salmonella Enteritidis using the disk diffusion method. Phenolic compounds were analyzed by HPLC-DAD, while characteristic pyrolysis products associated with microplastics were analyzed by PY-GC/MS. The results indicated that the pollen samples generally exhibited low microbial contamination levels and variable antimicrobial activity, depending on their geographical origin. Quercetin was identified as the predominant phenolic compound, and samples with higher phenolic content tended to show stronger antimicrobial effects, particularly against S. aureus. PY-GC/MS analyses revealed the presence of several chemical markers potentially associated with plastic polymers in a considerable proportion of the samples. Spearman correlation analysis showed a positive correlation between total phenolic content and particularly S. aureus inhibition. These findings highlight the nutritional and functional value of bee pollen while also drawing attention to emerging food safety concerns related to possible exposure to plastic-associated environmental contaminants. Regular monitoring of bee pollen is therefore recommended to ensure product quality and consumer safety. Full article

Salmonella spp. is a pathogen of concern in the food industry. This study evaluated the effect of temperature (10 °C and 37 °C) on the biofilm formation of S. Enteritidis PT30 on stainless steel up to 50 h, assessing the biofilm index (BI). The main extracellular polymeric substances (EPS) such as carbohydrates, proteins and eDNA were quantified. Scanning electron microscopy (SEM) was used to evaluate the biofilm formation. Results showed the effect of temperature on biofilm formation and EPS production. After 5 h at 37 °C the growth of planktonic and biofilm cells considerably increased (~7 log); however, the BI was higher for biofilms at 10 °C. Carbohydrates reached a maximum concentration after 15 h at 37 °C (65.49 μg/mL). The protein concentration reached a peak after 24 h regardless of the temperature. eDNA production was similar between the two temperatures (α = 0.05) and through the incubation time, ranging from 1.65 to 2.21 ng/μL. SEM images showed three-dimensional structures of the biofilm formed at 37 °C composed of cells, filaments, excreted EPS and a network of fibers. These results can help to understand the biofilm formation from this pathogen and develop effective interventions to break down these complex structures and effectively sanitize food contact surfaces. Full article

Salmonella enterica is a significant Gram-negative bacterium possessing over 2500 serovars capable of affecting both animals and humans and disseminating widely due to its adaptability, genetic diversity, and ability to form biofilms. Different serovars, such as S. enterica Typhimurium (ST), Enteritidis (SE), and Infantis (SI), display varying traits and survival strategies in harsh environments. Biofilms, composed of proteins, lipids, and DNA, enable bacteria to survive stresses such as pH changes, nutrient shortages, temperature fluctuations, and disinfectants. Evaluating disinfectants on inert surfaces is crucial for understanding their effectiveness and impact on poultry. This study assessed the efficacy of chlorine dioxide (ClO₂) disinfectant against ST, SE, and SI growth, biofilm formation, and biofilm removal at varying concentrations in vitro. Results showed serotype-dependent and condition-specific responses, with SE and SI being more affected than ST, which may be associated with differences in oxidative stress response mechanisms, highlighting the need for tailored disinfection protocols. Full article

The formation of biofilms by Salmonella is of considerable interest to the food production and medical industries. This study investigated the effects of a carrier medium (Luria–Bertani, Mueller–Hinton II, Brain Heart Infusion or chicken meat juice), temperature (14 °C, 23 °C or 37 °C) and surface type (adhesive, non-adhesive or suspension plate) on biofilm formation in 16 different Salmonella isolates belonging to the serovars S. Enteritidis (five isolates), S. Infantis (five isolates) and S. Typhimurium (six isolates). Chicken meat juice was found to have a moderate yet balanced supportive effect, while Mueller–Hinton II (MH-II) medium drastically supported biofilm formation at low temperatures, albeit with significant variation among the isolates. Temperature and medium also affected the antibacterial, biofilm inhibitory and destructive effects of essential oils. At 14 °C and 23 °C, 35% of essential oils exhibited antibacterial activity against Salmonella serovars at a concentration of 0.1%, as determined by the drop plate method. Ajowan, thyme, orange, clove and oregano EOs completely inhibited biofilm formation at a concentration of 0.1%. More than half of the 60 essential oils tested reduced the optical density of mature biofilms (OD: 0.15–0.36) to below 0.05; ajowan, lime, palmarosa, thyme, oregano and clove were the most effective, exhibiting antibacterial, biofilm inhibitory and biofilm destructive effects on all of the investigated Salmonella isolates. Full article

The effective control of foodborne salmonellosis relies on the rapid and reliable detection and identification of the pathogen. Reliable detection tools for identifying the most common Salmonella serovars should translate to a considerable alleviation of the health burden attributed to Salmonella. We have developed a PCR assay for the rapid identification of colonies of Salmonella enterica serovar Thompson, a common serovar. Genomic analyses of publicly available sequences of Salmonella Thompson revealed the presence of a unique, Thompson-specific fragment, which we have used to design a pair of oligonucleotides, STho-F and STho-R, for the PCR amplification of an 808 bp DNA fragment. Using crude DNA extracts, the 808 bp fragment was detected in 77 out of 78 isolates of S. Thompson (sensitivity = 98.7% n = 78 isolates) but not in any of the non-Salmonella organisms tested (n = 100; 100% specificity) nor in non-Thompson Salmonella serovars (n = 100; 100% specificity). The sensitivity (inclusivity) and specificity (exclusivity) indices of the PCR assay for S. Thompson met the standard regulatory requirements. The Thompson primer pair was compatible with other primers pairs in a multiplex PCR designed for three other common Salmonella serovars. Colonies belonging to the Enteritidis serovar (n = 100), Heidelberg serovar (n = 100), Typhimurium serovar (n = 100), and Thompson serovar (n = 77) were correctly designated, indicating excellent inclusivity and exclusivity scores for all four Salmonella serovars tested in a single multiplex PCR. Full article

Multidrug-resistant (MDR) Salmonella enteritidis infections cause high mortality and devastating economic losses in poultry, pose severe threats to animal health and food safety, and create an urgent demand for effective antibiotic alternatives. Herein, we developed a cationic liposome-encapsulated bacteriophage endolysin Lys40 (designated Lys40-Lip), and systematically evaluated its therapeutic efficacy in a chick model challenged with Salmonella enteritidis strain S4. Recombinant Lys40 was encapsulated into cationic liposomes with an encapsulation efficiency (EE) of 34.83%. The resulting Lys40-Lip nanoparticles had a hydrodynamic diameter of 137.3 ± 4.1 nm, a high positive zeta potential of +42.5 ± 0.3 mV, and excellent stability, retaining 78.52% of its initial bactericidal activity after 56 days of storage at 4 °C. Following a three-day oral treatment in Salmonella enteritidis S4-infected chicks, Lys40-Lip significantly increased survival rates in a dose-dependent manner (72.22% to 88.89% for low-to-high dose vs. 44.44% in infected controls, p < 0.05) and reduced ileal Salmonella enteritidis S4 colonization by 28.8% compared to free Lys40. Histopathology revealed Lys40-Lip restored duodenal villus integrity and reduced jejunal and ileal inflammation. Serum cytokine analysis confirmed that Lys40-Lip effectively regulated the host inflammatory response, significantly downregulating the pro-inflammatory cytokines IL-1β and IL-6, and upregulating the anti-inflammatory cytokine IL-10. Crucially, liposomal encapsulation overcame the outer membrane barrier of Gram-negative bacteria via charge-driven fusion mediated by its high positive surface potential (+42.5 ± 0.3 mV), enabling targeted delivery of Lys40 without the need for EDTA or other outer membrane permeabilizers. Lys40-Lip significantly improved the therapeutic outcomes of avian salmonellosis via synergistic direct bactericidal activity, intestinal barrier protection and inflammatory response regulation, offering a promising nanotherapeutic strategy for the control of this disease in veterinary practice. Full article

Necrotizing enteritis (NE) is an important intestinal disease threatening the poultry farming industry, and the ban on antibiotic growth promoters has created an urgent demand for safe and effective NE vaccines. Recombinant attenuated Salmonella vectors (RASVs) administered orally can induce mucosal immune responses against delivered antigens, thus showing great potential to elicit protective immunity against NE. The EntB protein is a newly discovered putative enterotoxin of Clostridium perfringens (C. perfringens). Bioinformatic predictions in this study revealed that EntB contains nineteen potential antigenic epitopes, two functional domains (NlpC and YgiM), and interacts with ten proteins, supporting its potential as a target antigen for NE vaccines. To optimize the immunogenicity of EntB-based vaccines, we constructed a novel recombinant attenuated Salmonella Enteritidis (S. Enteritidis) vector rSC0169 harboring a rhamnose-regulated delayed attenuation system, which was then used to deliver EntB to generate the recombinant strain rSC0169(pS-EntB). This system enhanced the immunogenicity of the Salmonella vector rSC0169 and further elicited robust mucosal immune responses against EntB, as well as humoral and cellular immune responses. Compared with the control strain rSC0169(pS0018), rSC0169(pS-EntB) candidate vaccine strain significantly alleviated NE symptoms, increased the intestinal villus height/crypt depth (VH/CD) ratio, upregulated tight junction protein expression, and reduced excessive pro-inflammatory cytokine production. In conclusion, this study provides a promising NE candidate vaccine and offers a valuable strategy for developing vaccines against other intestinal bacterial diseases. Full article

Non-typhoidal Salmonella (NTS) is an important poultry-associated pathogen with major One Health and economic impacts, but data on its epidemiology and antimicrobial resistance in Nigeria remain limited. This study investigated the prevalence, serovar distribution, clonal relatedness, and antimicrobial resistance of NTS along the poultry production chain in Enugu State, southeastern Nigeria. A total of 2400 samples were collected, comprising feces (cecal content)/cloacal swabs from chickens (n = 1100), eggs (n = 400), chicken meat (n = 600), and stool samples from poultry workers (n = 300). Isolation and identification were performed using standard bacteriological methods, with confirmation by serotyping and polymerase chain reaction (PCR) targeting the invA gene. Genetic relatedness was assessed using enterobacterial repetitive intergenic consensus (ERIC)-PCR, and antimicrobial susceptibility was determined by the disk diffusion method. Overall, 47 (2.0%) Salmonella enterica isolates were recovered from 2400 samples, with the highest prevalence observed in eggs (3.5%), followed by human stool (3.3%), chicken meat (1.8%), and chicken feces (1.1%). Only 35 (11.8%) of the 297 sampled farms were positive for Salmonella, and recovery rates differed significantly (p = 0.0065) among sample sources. Five serotypes were identified, dominated by S. Typhimurium (57.4%), followed by S. Enteritidis (14.9%), S. Anatum (12.8%), S. Stanley (8.5%), and S. Agona (6.3%). ERIC-PCR revealed multiple clonal clusters, many containing isolates from mixed sources, indicating circulation of related strains between poultry and humans. All isolates were resistant to ampicillin, with high resistance to tetracycline (76.6%), sulphamethoxazole–trimethoprim (51.1%), and fluoroquinolones. Overall, 80.9% of isolates were multidrug-resistant, with a mean Multiple Antibiotic Resistance Index of 0.29, highest among isolates from chicken feces. Although the prevalence of NTS was low, the presence of genetically related multidrug-resistant strains across the production chain underscores the role of poultry as a reservoir for zoonotic transmission and highlights the need for coordinated One Health surveillance and antimicrobial stewardship strategies in Nigeria. Full article