Microdiversity of Salmonella Kentucky During Long-Term Colonization of a Dairy Herd.

Salmonella enterica subsp. enterica serovar Kentucky was repeatedly isolated from a commercial dairy herd that was enrolled in a longitudinal study where feces of asymptomatic dairy cattle were sampled intensively over an 8-year period. The genomes of 5 Salmonella Kentucky isolates recovered from the farm 2 years before the onset of the long-term colonization event and 13 isolates collected during the period of endemicity were sequenced. A phylogenetic analysis inferred that the Salmonella Kentucky strains from the farm were distinct from poultry strains collected from the same region, and three subclades (K, A1, and A2) were identified among the farm isolates, each appearing at different times during the study. Based on the phylogenetic analysis, three separate lineages of highly similar Salmonella Kentucky were present in succession on the farm. Genomic heterogeneity between the clades helped identify regions, most notably transcriptional regulators, of the Salmonella Kentucky genome that may be involved in competition among highly similar strains. Notably, a region annotated as a hemolysin expression modulating protein (Hha) was identified in a putative plasmid region of strains that colonized a large portion of cows in the herd, suggesting that it may play a role in asymptomatic persistence within the bovine intestine. A cell culture assay of isolates from the three clades with bovine epithelial cells demonstrated a trend of decreased invasiveness of Salmonella Kentucky isolates over time, suggesting that clade-specific interactions with the animals on the farm may have played a role in the dynamics of strain succession. Results of this analysis further demonstrate an underappreciated level of genomic diversity within strains of the same Salmonella serovar, particularly those isolated during a long-term period of asymptomatic colonization within a single dairy herd.

[Genetic characterization and drug resistance analysis of Salmonella Kentucky ST314 in Shenzhen in 2010-2021].

OBJECTIVE: To understand the prevalence, genetic characteristics and drug resistance features of Salmonella Kentucky ST314 in Shenzhen. METHODS: Whole genome sequencing of 14 strains of Salmonella Kentucky ST314 collected from 2010-2021 by the Foodborne Disease Surveillance Network of Shenzhen Center for Disease Control and Prevention for phylogenetic evolutionary analysis, drug resistance gene and plasmid detection; drug susceptibility experiments were performed by micro-broth dilution method. RESULTS: A total of 57 strains of Salmonella Kentucky were collected from the foodborne disease surveillance network, 14 of which were ST314. The Shenzhen isolates were clustered with isolates from Southeast Asian countries such as Vietnam and Thailand on clade 314.2, and the single nucleotide polymorphism distance between local strains in Shenzhen was large, indicating dissemination. In this study, a total of 17 drug resistance genes/mutations in 9 categories were detected in the genome of Salmonella Kentucky ST314, carrying 3 extended spectrum beta-lactamases(ESBLs), including bla_(CTX-M-24)(14.3%, 2/14), bla_(CTX-M-55)(7.1%, 1/14), and bla_(CTX-M-130)(14.3%, 2/14), all located on plasmids. Regarding quinolone resistance factors, two plasmid-mediated quinolone resistance(PMQR) genes were identified in the genome: qnrB6(71.4%, 10/14) and aac(6')Ib-cr(78.6%, 11/14), a quinolone resistance quinolone resistance-determining regions(QRDR) mutation T57 S(100%, 14/14). The multi-drug resistance rate of Salmonella Kentucky ST314 in Shenzhen was 92.86%(13/14)with the highest rate of resistance to tetracycline and cotrimoxazole(100%, 14/14), followed by chloramphenicol(92.86%, 13/14), cefotaxime and ampicillin(78.57%, 11/14), ciprofloxacin and nalidixic acid(71.43%, 10/14), and ampicillin-sulbactam had the lowest resistance rate(21.43%, 3/14). CONCLUSION: ST314 is the second most prevalent ST type among Salmonella Kentucky in Shenzhen, mainly isolated from food, especially poultry; phylogenetic analysis suggests that ST314 is a disseminated infection and the genome shows a highly genetically conserved phenotype. Drug resistance of Salmonella Kentucky ST314 is very serious, especially QRDR mutation, PMQR gene co-mediated quinolone resistance and plasmid-mediated cephalosporin resistance are prominent and deserve extensive attention.

Inhibitory effects of vorinostat (SAHA) against food-borne pathogen Salmonella enterica serotype Kentucky mixed culture biofilm with virulence and quorum-sensing relative expression.

Salmonella is a food-borne microorganism that is also a zoonotic bacterial hazard in the food sector. This study determined how well a mixed culture of Salmonella Kentucky formed biofilms on plastic (PLA), silicon rubber (SR), rubber gloves (RG), chicken skin and eggshell surfaces. In vitro interactions between the histone deacetylase inhibitor-vorinostat (SAHA)-and S. enterica serotype Kentucky were examined utilizing biofilms. The minimum inhibitory concentration (MIC) of SAHA was 120 µg mL-1. The addition of sub-MIC (60 µg mL-1) of SAHA decreased biofilm formation for 24 h on PLA, SR, RG, Chicken skin, and eggshell by 3.98, 3.84, 4.11, 2.86 and 3.01 log (p < 0.05), respectively. In addition, the initial rate of bacterial biofilm formation was higher on chicken skin than on other surfaces, but the inhibitory effect was reduced. Consistent with this conclusion, virulence genes expression (avrA, rpoS and hilA) and quorum-sensing (QS) gene (luxS) was considerably downregulated at sub-MIC of SAHA. SAHA has potential as an anti-biofilm agent against S. enterica serotype Kentucky biofilm, mostly by inhibiting virulence and quorum-sensing gene expression, proving the histone deacetylase inhibitor could be used to control food-borne biofilms in the food industry.

Antimicrobial-Resistant Escherichia coli, Enterobacter cloacae, Enterococcus faecium, and Salmonella Kentucky Harboring Aminoglycoside and Beta-Lactam Resistance Genes in Raw Meat-Based Dog Diets, USA.

The practice of feeding raw meat-based diets to dogs has grown in popularity worldwide in recent years. However, there are public health risks in handling and feeding raw meat-based dog diets (RMDDs) to dogs since there are no pathogen reduction steps to reduce the microbial load, which may include antimicrobial-resistant pathogenic bacteria. A total of 100 RMDDs from 63 suppliers were sampled, and selective media were used to isolate bacteria from the diets. Bacterial identification, antimicrobial susceptibility testing, and whole-genome sequencing (WGS) were conducted to identify antimicrobial resistance (AMR). The primary meat sources for RMDDs included in this study were poultry (37%) and beef (24%). Frozen-dry was the main method of product production (68%). In total, 52 true and opportunistic pathogens, including Enterobacterales (mainly Escherichia coli, Enterobacter cloacae) and Enterococcus faecium, were obtained from 30 RMDDs. Resistance was identified to 19 of 28 antimicrobials tested, including amoxicillin/clavulanic acid (23/52, 44%), ampicillin (19/52, 37%), cephalexin (16/52, 31%), tetracycline (7/52, 13%), marbofloxacin (7/52, 13%), and cefazolin (6/52, 12%). All 19 bacterial isolates submitted for WGS harbored at least one type of AMR gene. The identified AMR genes were found to mediate resistance to aminoglycoside (gentamicin, streptomycin, amikacin/kanamycin, gentamicin/kanamycin/tobramycin), macrolide, beta-lactam (carbapenem, cephalosporin), tetracycline, fosfomycin, quinolone, phenicol/quinolone, and sulfonamide. In conclusion, the results of this study suggest that feeding and handling RMDDs may pose a significant public health risk due to the presence of antimicrobial-resistant pathogens, and further research and intervention may be necessary to minimize these risks.

Genomic Diversity, Antimicrobial Resistance, and Virulence Gene Profiles of Salmonella Serovar Kentucky Isolated from Humans, Food, and Animal Ceca Content Sources in the United States.

Salmonella serovar Kentucky is frequently isolated from chickens and dairy cattle, but recovery from humans is comparatively low based on the U.S. National Antimicrobial Resistance Monitoring System (NARMS) reports. We aimed to better describe the genetic diversity, antimicrobial resistance, and virulence determinants of Salmonella Kentucky isolates from humans, food animal ceca, retail meat and poultry products, imported foods and food products, and other samples. We analyzed the genomes of 774 Salmonella Kentucky isolates and found that 63% (54/86) of human isolates were sequence type (ST)198, 33% (29/86) were ST152, and 3.5% (3/86) were ST314. Ninety-one percent (570/629) of cecal isolates and retail meat and poultry isolates were ST152 or ST152-like (one allele difference), and 9.2% (58/629) were ST198. Isolates from imported food were mostly ST198 (60%, 22/37) and ST314 (29.7%, 11/37). ST198 isolates clustered into two main lineages. Clade ST198.2 comprised almost entirely isolates from humans and imported foods, all containing triple mutations in the quinolone resistance-determining region (QRDR) that confer resistance to fluoroquinolones. Clade ST198.1 contained isolates from humans, ceca, retail meat and poultry products, and imported foods that largely lacked QRDR mutations. ST152 isolates from cattle had a lineage (Clade 2) distinct from ST152 isolates from chicken (Clade 4), and half of ST152 human isolates clustered within two other clades (Clades 1 and 3), largely distinct from Clades 2 and 4. Although clinical illness associated with Salmonella Kentucky is low, ST198 appears to account for most human infections in the Unites States but is uncommon among ceca of domestic food animals and retail meat and poultry products. These findings, combined with human exposure data, suggest that fluoroquinolone-resistant ST198 infections may be linked to the consumption of food products that are imported or consumed while traveling. We also found unique differences in the composition of virulence genes and antimicrobial resistance genes among the clades, which may provide clues to the host specificity and pathogenicity of Salmonella Kentucky lineages.

Antimicrobial Resistance and Whole-Genome Characterisation of High-Level Ciprofloxacin-Resistant Salmonella Enterica Serovar Kentucky ST 198 Strains Isolated from Human in Poland.

BACKGROUND: Salmonella Kentucky belongs to zoonotic serotypes that demonstrate that the high antimicrobial resistance and multidrug resistance (including fluoroquinolones) is an emerging problem. To the best of our knowledge, clinical S. Kentucky strains isolated in Poland remain undescribed. METHODS: Eighteen clinical S. Kentucky strains collected in the years 2018-2019 in Poland were investigated. All the strains were tested for susceptibility to 11 antimicrobials using the disc diffusion and E-test methods. Whole genome sequences were analysed for antimicrobial resistance genes, mutations, the presence and structure of SGI1-K (Salmonella Genomic Island and the genetic relationship of the isolates. RESULTS: Sixteen of 18 isolates (88.9%) were assigned as ST198 and were found to be high-level resistant to ampicillin (>256 mg/L) and quinolones (nalidixic acid MIC ≥ 1024 mg/L, ciprofloxacin MIC range 6-16 mg/L). All the 16 strains revealed three mutations in QRDR of GyrA and ParC. The substitutions of Ser83 → Phe and Asp87 → Tyr of the GyrA subunit and Ser80→Ile of the ParC subunit were the most common. One S. Kentucky isolate had qnrS1 in addition to the QRDR mutations. Five of the ST198 strains, grouped in cluster A, had multiple resistant determinants like blaTEM1-B, aac(6')-Iaa, sul1 or tetA, mostly in SGI1 K. Seven strains, grouped in cluster B, had shorter SGI1-K with deletions of many regions and with few resistance genes detected. CONCLUSION: The results of this study demonstrated that a significant part of S. Kentucky isolates from humans in Poland belonged to ST198 and were high-level resistant to ampicillin and quinolones.

Non-molecular characterization of pellicle formation by poultry Salmonella Kentucky strains and other poultry-associated Salmonella serovars in Luria Bertani broth.

There is limited research concerning the biofilm-forming capabilities of Salmonella Kentucky, a common poultry isolate. The objective was to quantitate pellicle formation of S. Kentucky versus better-characterized Salmonella strains of Enteritidis and Heidelberg. In separate experiments, Salmonella strains and serovars were tested for their biofilm-forming abilities in different Luria-Bertani (LB) broths (1); pellicle formation in different volumes of LB without salt (2); and the potential priming effects on formation after pellicles were transferred three consecutive times (3). Data were analyzed using One-Way ANOVA with means separated using Tukey's HSD (P ≤ 0.05). In the first experiment, there was no significant effect between strain and serovars (P > 0.05), but media type affected pellicle formation significantly with LB Miller and LB minus NaCl plus 2% glucose resulting in no pellicle formation (P < 0.001). When grown in 50 mL, Kentucky 38-0085 produced larger pellicles than Kentucky 38-0055, and Heidelberg strain 38-0127 (P < 0.0001). Serial transfers of pellicles did not significantly affect pellicle formation (P > 0.05); however, Kentucky 38-0084, 38-0085 and 38-0086 produced larger pellicles than Kentucky 38-0055 and 38-0056 and Heidelberg 38-0126, 38-0127 and 38-0152. The current study demonstrates the consistent biofilm forming capabilities of Kentucky and may explain why Kentucky is frequently isolated in poultry processing facilities.

CRISPR Typing and Antibiotic Resistance Correlates with Polyphyletic Distribution in Human Isolates of Salmonella Kentucky.

Although infrequently associated with reported salmonellosis in humans, Salmonella enterica, subsp. enterica serovar Kentucky (ser. Kentucky) is the most common nonclinical, nonhuman serovar reported in the United States. The goal of this study was to use Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-multi-virulence-locus sequence typing (MVLST) to subtype a collection of human clinical isolates of ser. Kentucky submitted to the Pennsylvania Department of Health and to determine the extent of antibiotic resistance in these strains. This analysis highlighted the polyphyletic nature of ser. Kentucky, and separated our isolates into two groups, Group I and Group II, which were equally represented in our collection. Furthermore, antimicrobial susceptibility testing on all isolates using a National Antimicrobial Resistance Monitoring System (NARMS) panel of antibiotics demonstrated that resistance profiles could be divided into two groups. Group I isolates were resistant to cephems and penicillins, whereas Group II isolates were resistant to quinolones, gentamicin, and sulfisoxazole. Collectively, 50% of isolates were resistant to three or more classes of antibiotics and 30% were resistant to five or more classes. The correlation of antibiotic resistance with the two different lineages may reflect adaptation within two distinct reservoirs of ser. Kentucky, with differential exposure to antimicrobials.

Molecular characterization of antibiotic resistant Salmonella Typhimurium and Salmonella Kentucky isolated from pre- and post-chill whole broilers carcasses.

There is conflicting data regarding whether commercial chilling has any effect on persistence of Salmonella serovars, including antibiotic resistant variants, on chicken carcasses. A total of 309 Salmonella Typhimurium and Salmonella Kentucky isolates recovered from pre- and post-chill whole broiler carcasses were characterized for genetic relatedness using Pulsed Field Gel Electrophoresis (PFGE) and for the presence of virulence factors (invA, pagC, spvC) by PCR and for aerobactin and colicin production by bioassays. A subset of these isolates (n = 218) displaying resistance to either sulfisoxazole and/or ceftiofur [S. Typhimurium (n = 66) and S. Kentucky (n = 152)] were further tested for the presence of associated antibiotic resistance elements (class-I integrons and blaCMY genes) by PCR. All 145 ceftiofur resistant S. Kentucky and S. Typhimurium isolates possessed blaCMY genes. Class-I integrons were only detected in 6.1% (n = 4/66) of sulfisoxazole resistant S. Typhimurium isolates. The PFGE analysis revealed the presence of genetically diverse populations within the recovered isolates but clusters were generally concordant with serotypes and antimicrobial resistance profiles. At a 100% pattern similarity index, thirty-six percent of the undistinguishable S. Typhimurium and 22% of the undistinguishable S. Kentucky isolates were recovered from the same chilling step. All isolates possessed the invA and pagC genes, but only 1.4%possessed spvC. Irrespective of the chilling step, there was a significant difference (P < 0.05) in the production of aerobactin and colicin between S. Typhimurium and S. Kentucky isolates. Taken together, these results indicate that chilling impacted the recovery of particular Salmonella clonal groups but had no effect on the presence of class-I integrons, blaCMY genes, and tested virulence factors.

Phenotypic and genomic characterization of a multidrug-resistant Salmonella enterica serovar Kentucky ST198 isolated from a patient in China.

OBJECTIVES: The objective of this study was to investigate the resistance mechanisms of a multidrug-resistant Salmonella Kentucky ST198 FJ-2064 isolated from a patient in China. METHODS: The antimicrobial susceptibility of FJ-2064 was determined by the standard disc dilution and broth microdilution methods. The complete genome of FJ-2064 was sequenced using PacBio and Illumina MiSeq platforms. Polymerase chain reaction (PCR) and S1-PFGE were utilized to confirm the mutation sites and the genomic plasmids, respectively. RESULTS: Isolate FJ-2064 belongs to sequence type ST198 and harboured no visible large plasmids, but was concurrent resistant to 22 detected antimicrobial agents including cefotaxime, ciprofloxacin, and azithromycin. The complete genome sequence identified 20 acquired antibiotic resistance genes (ARGs) and five chromosomal mutations in the gyrA and parC genes of the quinolone resistance determining regions (QRDRs) in FJ-2064. In addition, PCR sequencing confirmed that most of the ARGs were clustered on one multidrug-resistant region and a variant of SGI1-K. In particular, the bla-TEM-1 and bla-CTX-M-55, qnrS1, mph(A) genes, which confer resistance to cephalosporins, quinolones, and macrolides respectively, were all located on the multidrug-resistant region. CONCLUSIONS: We have demonstrated one multidrug-resistant region and a variant of SGI1-K in a Salmonella Kentucky ST198 that is co-resistant to cefotaxime, ciprofloxacin, and azithromycin.

Prevalence and transmission of extensively drug-resistant Salmonella enterica serovar Kentucky ST198 based on whole-genome sequence in an intensive laying hen farm in Jiangsu, China.

Salmonella, which is widely distributed in nature, is an important zoonotic pathogen affecting humans, livestock, and other animals. Salmonella infection not only hinders the development of livestock and poultry-related industries but also poses a great threat to human health. In this study, we collected 1,537 samples including weak chicks, dead embryos, fecal samples and environmental samples from 2020 to 2023 (for a period of 1 to 2 months per year) to keep a long-term monitor the prevalence of Salmonella in an intensive laying hen farm, 105 Salmonella strains were isolated with an isolation rate of 6.83% (105/1,537). It revealed a significant decrease in prevalence rates of Salmonella over time (P < 0.001). Before 2020, the predominant serotype was S. Enteritidis. S. Kentucky was first detected in November 2020 and its proportion was gradually found to exceed that of S. Enteritidis since then. S. Kentucky isolates were distributed in various links of the four regions in the poultry farm. A total of 55 S. Kentucky strains, were assigned to ST198 based on whole genome sequencing. Among them, 54 strains were resistant to 12 to 16 antibiotics, indicating that they were extensively drug-resistant (XDR). Seventeen antimicrobial resistance genes were detected in 55 S. Kentucky isolates. For most of these isolates, antibiotic resistance phenotypes were concordant with their genotypes. All S. Kentucky strains isolated from this farm in 2020 to 2023 showed a high similarity based on their core-genome SNP-based phylogeny. The traceability analysis revealed that S. Kentucky was introduced to the farm through newly purchased flocks. The long-term existence of XDR S. Kentucky ST198 poses a substantial risk because of the multiage management and circulation of workers in this poultry farm. Thus, this study is the first to report extensively drug-resistant S. Kentucky ST198 detected in this intensive poultry farm in China.

A novel variant in Salmonella genomic island 1 of multidrug-resistant Salmonella enterica serovar Kentucky ST198.

Salmonella enterica serovar Kentucky ST198 is a major health threat due to its resistance to ciprofloxacin and several other drugs, including third-generation cephalosporins. Many drug-resistant genes have been identified in the Salmonella genomic island 1 variant K (SGI1-K). In this study, we investigated the antimicrobial resistance (AMR) profile and genotypic relatedness of two isolates of ciprofloxacin-resistant (CIPR) S. Kentucky ST198 from poultry in Northeastern Thailand. We successfully assembled the complete genomes of both isolates, namely SSSE-01 and SSSE-03, using hybrid de novo assembly of both short- and long-read sequence data. The complete genomes revealed their highly similar genomic structures and a novel variant of SGI1-K underlying multidrug-resistant (MDR) patterns, including the presence of blaTEM-1b, which confers resistance to beta-lactams, including cephalosporins and lnu(F) which confers resistance to lincomycin and other lincosamides. In addition, the chromosomal mutations in the quinolone resistance-determining region (QRDR) were found at positions 83 (Ser83Phe) and 87 (Asp87Asn) of GyrA and at positions 57 (Thr57Ser) and 80 (Ser80Ile) of ParC suggesting high resistance to ciprofloxacin. We also compared SSSE-01 and SSSE-03 with publicly available complete genome data and revealed significant variations in SGI1-K genetic structures and variable relationships to antibiotic resistance. In comparison to the other isolates, SGI1-K of SSSE-01 and SSSE-03 had a relatively large deletion in the backbone, spanning from S011 (traG∆) to S027 (resG), and the inversion of the IS26-S044∆-yidY segment. Their MDR region was characterized by the inversion of a large segment, including the mer operon and the relocation of IntI1 and several resistance genes downstream of the IS26-S044∆-yidY segment. These structural changes were likely mediated by the recombination of IS26. The findings broaden our understanding of the possible evolution pathway of SGI1-K in fostering drug resistance, which may provide opportunities to control these MDR strains.IMPORTANCEThe emergence of ciprofloxacin-resistant (CIPR) Salmonella Kentucky ST198 globally has raised significant concerns. This study focuses on two poultry isolates from Thailand, revealing a distinct Salmonella genomic island 1 variant K (SGI1-K) genetic structure. Remarkably, multiple antibiotic resistance genes (ARGs) were identified within the SGI1-K as well as other locations in the chromosome, but not in plasmids. Comparing the SGI1-K genetic structures among global and even within-country isolates unveiled substantial variations. Intriguingly, certain isolates lacked ARGs within the SGI1-K, while others had ARGs relocated outside. The presence of chromosomal extended-spectrum ß-lactamase (ESBL) genes and lincosamide resistance, lnu(F), gene, could potentially inform the choices of the treatment of CIPRS. Kentucky ST198 infections in humans. This study highlights the importance of understanding the diverse genetic structures of SGI1-K and emphasizes the role of animals and humans in the emergence of antimicrobial resistance.

Genomic and phenotypic characterization of Salmonella enterica serovar Kentucky.

Non-typhoidal Salmonella are extremely diverse and different serovars can exhibit varied phenotypes, including host adaptation and the ability to cause clinical illness in animals and humans. In the USA, Salmonella enterica serovar Kentucky is infrequently found to cause human illness, despite being the top serovar isolated from broiler chickens. Conversely, in Europe, this serovar falls in the top 10 serovars linked to human salmonellosis. Serovar Kentucky is polyphyletic and has two lineages, Kentucky-I and Kentucky-II; isolates belonging to Kentucky-I are frequently isolated from poultry in the USA, while Kentucky-II isolates tend to be associated with human illness. In this study, we analysed whole-genome sequences and associated metadata deposited in public databases between 2017 and 2021 by federal agencies to determine serovar Kentucky incidence across different animal and human sources. Of 5151 genomes, 90.3 % were from isolates that came from broilers, while 5.9 % were from humans and 3.0 % were from cattle. Kentucky-I isolates were associated with broilers, while isolates belonging to Kentucky-II and a new lineage, Kentucky-III, were more commonly associated with cattle and humans. Very few serovar Kentucky isolates were associated with turkey and swine sources. Phylogenetic analyses showed that Kentucky-III genomes were more closely related to Kentucky-I, and this was confirmed by CRISPR-typing and multilocus sequence typing (MLST). In a macrophage assay, serovar Kentucky-II isolates were able to replicate over eight times better than Kentucky-I isolates. Analysis of virulence factors showed unique patterns across these three groups, and these differences may be linked to their association with different hosts.

Ceftriaxone Resistant Salmonella enterica Serovar Kentucky as a Cause of Bacteremia and Gastroenteritis: A Case Report.

Salmonella enterica serovar Kentucky is an emerging human pathogen in developed countries and also a concern for public health in developing countries. Although genus Salmonella is usually susceptible to many antimicrobial agents, a recent increase in resistance has become a cause for concern. A case of ceftriaxone resistant Salmonella enterica serovar Kentucky causing bacteremia and acute gastroenteritis is reported in this paper. The Salmonella Kentucky isolate in this case was resistant to most classes of antibiotics. This is the first case report of Salmonella enterica serovar Kentucky resistant to ceftriaxone. Multidrug resistant patterns of Salmonella Kentucky are observed globally. Awareness of various nontyphoid Salmonella causing human infections is of utmost importance, because delayed identification, serotyping, and susceptibility testing may delay the administration of antibiotics leading to worsening outcomes.

Genomic characterization of multidrug-resistant Salmonella serovar Kentucky ST198 isolated in poultry flocks in Spain (2011-2017).

Salmonella Kentucky is commonly found in poultry and rarely associated with human disease. However, a multidrug-resistant (MDR) S. Kentucky clone [sequence type (ST)198] has been increasingly reported globally in humans and animals. Our aim here was to assess if the recently reported increase of S. Kentucky in poultry in Spain was associated with the ST198 clone and to characterize this MDR clone and its distribution in Spain. Sixty-six isolates retrieved from turkey, laying hen and broiler in 2011-2017 were subjected to whole-genome sequencing to assess their sequence type, genetic relatedness, and presence of antimicrobial resistance genes (ARGs), plasmid replicons and virulence factors. Thirteen strains were further analysed using long-read sequencing technologies to characterize the genetic background associated with ARGs. All isolates belonged to the ST198 clone and were grouped in three clades associated with the presence of a specific point mutation in the gyrA gene, their geographical origin and isolation year. All strains carried between one and 16 ARGs whose presence correlated with the resistance phenotype to between two and eight antimicrobials. The ARGs were located in the Salmonella genomic island (SGI-1) and in some cases (blaSHV-12, catA1, cmlA1, dfrA and multiple aminoglycoside-resistance genes) in IncHI2/IncI1 plasmids, some of which were consistently detected in different years/farms in certain regions, suggesting they could persist over time. Our results indicate that the MDR S. Kentucky ST198 is present in all investigated poultry hosts in Spain, and that certain strains also carry additional plasmid-mediated ARGs, thus increasing its potential public health significance.

Genomic diversity and resistome profiles of Salmonella enterica subsp. enterica serovar Kentucky isolated from food and animal sources in Ireland.

Salmonella enterica subsp. enterica serovar Kentucky is frequently isolated from poultry, dairy and beef cattle, the environment and people with clinical salmonellosis globally. However, the sources of this serovar and its diversity and antimicrobial resistance capacities remain poorly described in many regions. To further understand the genetic diversity and antimicrobial sensitivity patterns among S. Kentucky strains isolated from non-human sources in Ireland, we sequenced and analysed the genomes of 61 isolates collected from avian, bovine, canine, ovine, piscine, porcine, environmental and vegetation sources between 2000 and 2016. The majority of isolates (n = 57, 93%) were sequence type (ST) 314, while only three isolates were ST198 and one was ST152. Several isolates were multidrug-resistant (MDR) and 14 carried at least one acquired antimicrobial resistance gene. When compared to a database of publicly available ST314, four distinct clades were identified (clades I-IV), with the majority of isolates from Ireland clustering together in Clade I. Two of the three ST198 isolates were characteristic of those originating outside of the Americas (Clade ST198.2), while one was distantly clustered with isolates from South and North America (Clade ST198.1). The genomes of the two clade ST198.2 isolates encoded Salmonella Genomic Island 1 (SGI1), were multidrug-resistant and encoded polymorphisms in the DNA gyrase (gyrA) and DNA topoisomerase (parC) known to confer resistance to fluoroquinolones. The single ST152 isolate was from raw beef, clustered with isolates from food and bovine sources in North America and was pan-susceptible. Results of this study indicate that most S. Kentucky isolates from non-human sources in Ireland are closely related ST314 and only a few isolates are antimicrobial-resistant. This study also demonstrates the presence of multidrug-resistant ST198 in food sources in Ireland.

Genomic characterization of Salmonella enterica serovar Kentucky and London recovered from food and human salmonellosis in Zhejiang Province, China (2016-2021).

Increasing human salmonellosis caused by Salmonella enterica serovar Kentucky and London has raised serious concerns. To better understand possible health risks, insights were provided into specific genetic traits and antimicrobial resistance of 88 representative isolates from human and food sources in Zhejiang Province, China, during 2016-2021. Phylogenomic analysis revealed consistent clustering of isolates into the respective serovar or sequence types, and identified plausible interhost transmission via distinct routes. Each serovar exhibited remarkable diversity in host range and disease-causing potential by cgMLST analyses, and approximately half (48.6%, 17/35) of the food isolates were phylogenetically indistinguishable to those of clinical isolates in the same region. S. London and S. Kentucky harbored serovar-specific virulence genes contributing to their functions in pathogenesis. The overall resistance genotypes correlated with 97.7% sensitivity and 60.2% specificity to the identified phenotypes. Resistance to ciprofloxacin, cefazolin, tetracycline, ampicillin, azithromycin, chloramphenicol, as well as multidrug resistance, was common. High-level dual resistance to ciprofloxacin and cephalosporins in S. Kentucky ST198 isolates highlights evolving threats of antibiotic resistance. These findings underscored the necessity for the development of effective strategies to mitigate the risk of food contamination by Salmonella host-restricted serovars.

The Use of Star Anise-Cinnamon Essential Oil as an Alternative Antibiotic in Prevention of Salmonella Infections in Yellow Chickens.

Salmonella is capable of harming human and animal health, and its multidrug resistance (MDR) has always been a public health problem. In addition, antibiotic-free or antibiotic-reduced policies have been implemented in poultry production. Therefore, the search for antibiotic alternatives is more urgent than ever before. The aim of this study was to assess the antibacterial activity of star anise-cinnamon essential oil (SCEO) in vitro and its prophylactic effect against the infections of Salmonella pullorum, Salmonella give, and Salmonella kentucky in vivo. The results demonstrated that SCEO is effective against Salmonella pullorum, Salmonella give, and Salmonella kentucky in vitro. Supplementation with SCEO could significantly decrease the infections of Salmonella pullorum and Salmonella give, whereas it could slightly but not significantly decrease the infection of Salmonella kentucky, while also significantly alleviating the body weight (BW) loss caused by the infections of Salmonella pullorum, Salmonella give, and Salmonella kentucky in Yellow chickens. The SCEO had the best prophylactic effect against the infection of Salmonella give in Yellow chickens, followed by the infection of Salmonella pullorum and the infection of Salmonella kentucky. The SCEO, used as an antibiotic alternative, could be an effective prevention strategy against the infections of Salmonella pullorum, Salmonella give, and Salmonella kentucky in Yellow chickens.

Effects of environmental conditions (temperature, pH, and glucose) on biofilm formation of Salmonella enterica serotype Kentucky and virulence gene expression.

Salmonella is a foodborne pathogen and an emerging zoonotic bacterial threat in the food industry. The aim of this study was to evaluate the biofilm formation by a cocktail culture of 3 wild isolates of Salmonella enterica serotype Kentucky on plastic (PLA), silicon rubber (SR), and chicken skin surfaces under various temperatures (4, 10, 25, 37, and 42°C) and pH values (4.0, 5.0, 6.0, 7.0, and 8.0). Then, at the optimum temperature and pH, the effects of supplementation with glucose (0, 0.025, 0.05, and 0.4% w/v) on biofilm formation were assessed on each of the surfaces. The results indicated that higher temperatures (25 to 42°C) and pH values (7.0 and 8.0) led to more robust biofilm formation than lower temperatures (4 and 10°C) and lower pH levels (4.0 to 6.0). Moreover, biofilm formation was induced by 0.025% glucose during incubation at the optimum temperature (37°C) and pH (7.0) but inhibited by 0.4% glucose. Consistent with this finding, virulence related gene (rpoS, rpoH, hilA, and avrA) expression was increased at 0.025% glucose and significantly reduced at 0.4% glucose. This results also confirmed by field emission scanning electron microscope, confocal laser scanning microscopy, and autoinducer-2 determination. This study concluded that optimum environmental conditions (temperature 37°C, pH 7.0, and 0.25% glucose) exhibited strong biofilm formation on food and food contract surfaces as well as increased the virulence gene expression levels, indicating that these environmental conditions might be threating conditions for food safety.

Characterization of the emerging multidrug-resistant Salmonella enterica serotype Kentucky ST314 in China.

Salmonella enterica serotype Kentucky (S. Kentucky) is an important Salmonella serotype with multiple sequence types (ST) with a worldwide incidence. We identified 8 STs from 180 strains of S. Kentucky, and ST314 emerged as the most commonly encountered ST. Drug susceptibility testing revealed that ST314 had multiple resistance properties, and 75.5% of the strains were resistant to three or more classes of antimicrobials. The rate of resistance to chloramphenicol, florfenicol, sulfafurazole and tetracycline were greater than 60%. The rates of ST314 resistance to quinolones were as follows: ciprofloxacin, 32.1%; nalidixic acid, 16%; and ofloxacin, 7.5%. Investigating the mechanism of quinolone resistance of ST314 revealed that mutations in the quinolone resistance-determining regions were rare, and resistance mainly occurred due to the resistance genes carried by plasmids. Only 1.9% (2/106) of ST314 strains had mutations in the quinolone resistance-determining regions (QRDR). The drug resistance genes of ST314 were primarily of plasmid-mediated quinolone resistance (PMQR). The detection rate of Salmonella genomic island 1 (SGI1) in ST314 was 12.3%. XbaI-pulsed-field gel electrophoresis revealed that S. enterica Kentucky ST314 was capable of cross-regional and cross-host transmission in China. We found ST314 to be the dominant S. Kentucky ST in China, and it carried multidrug resistance. This is the first report about the emergence of quinolone-resistant S. enterica Kentucky ST314 in China, which is different from previous reports, and the findings of the present study suggest that the mechanism of quinolone resistance in these strains are plasmid-mediated. Notably, plasmids carrying resistance genes may promote the rapid spread of ciprofloxacin resistance.