Prevalence of Salmonella Isolates and Their Distribution Based on Whole-Genome Sequence in a Chicken Slaughterhouse in Jiangsu, China

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

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

Distribution and genetic characterization of fluoroquinolone resistance gene qnr among Salmonella strains from chicken in China

The prevalence and dissemination of the plasmid-mediated fluoroquinolone (FQ) resistance gene qnr in Salmonella are considered serious public health concerns worldwide. So far, no comprehensive large-scale studies have focused on the prevalence and genetic characteristics of the qnr gene in Salmonella isolated from chickens. Herein, this study aimed to investigate the prevalence, antimicrobial resistance (AMR) patterns, and molecular characteristics of chicken-originated qnr-positive Salmonella strains from chicken farms, slaughterhouses, and markets in 12 provinces of China in 2020-2021. The overall prevalence of the qnr gene was 21.13% (56/265), with the highest prevalence in markets (36.11%, 26/72), followed in farms (17.95%, 21/117), and slaughterhouses (10.53%, 9/76). Only the qnrS and qnrB genes were detected, and the prevalence rate of the qnrS gene (19.25%, 51/265) was higher than that of the qnrB gene (1.89%, 5/265). Whole genome sequencing identified 37 distinct AMR genes and 15 plasmid replicons, and the most frequent mutation in quinolone resistance determining regions was parC (T57S; 91.49%, 43/47). Meanwhile, four different qnrS and two qnrB genetic environments were discovered among 47 qnr-positive Salmonella strains. In total, 21.28% (10/47) of the strains were capable of conjugative transfer, and all were qnrS1-positive strains, with the majority of transferable plasmids being IncHI2 types (n = 4). Overall, the prevalence of qnr-positive Salmonella strains from chickens in China and their carriage of multiple resistance and virulence genes and transferable plasmids is a major concern, which calls for continuous surveillance of qnr-positive Salmonella and the development of measures to control its prevalence and transmission.IMPORTANCESalmonella is a common foodborne pathogen responsible for 155,000 deaths annually worldwide. Fluoroquinolones (FQs) are used as first-line drugs for the treatment of Salmonella infections in several countries and regions. However, the emergence and increasing prevalence of the FQ-resistant gene qnr in Salmonella isolated from chickens have been widely reported. Gaining insight into the genetic mechanisms of AMR genes in chicken could lead to the development of preventive measures to control and reduce the risk of drug resistance. In this study, we identified qnr-positive Salmonellae isolated from chickens in different regions of China and their AMR patterns and genome-wide characteristics, providing a theoretical basis for further control of their prevalence and transmission.

Antimicrobial resistance and genomic investigation of Salmonella isolated from retail foods in Guizhou, China

Introduction

Salmonella is a major foodborne pathogen worldwide that causes severe morbidity and mortality. It is mainly caused by consuming contaminated food, with retail food considered the primary source.

Methods

In Guizhou, China, 102 Salmonella strains isolated from 2016 to 2021 underwent phenotypic antimicrobial resistance testing and whole-genome sequencing (WGS) to understand Salmonella diversity, including serotypes, sequencing types (STs), antimicrobial genes, virulence genes, plasmid types, multi-locus sequence types (MLST), and core genome MLST (cgMLST).

Results and discussion

S.Typhimurium was the dominant serotype, and O:4(B) was the leading serogroup. The most prevalent genotype was ST40. Phenotypic antimicrobial resistance identified 66.7% of the sampled isolates as multi-drug resistant (MDR). S.Enteritidis (n = 7), S.Typhimurium (n = 1), S.Indiana (n = 1), S.Kentucky (n = 1), S.Uganda (n = 1), all of which were MDR, were resistant to Colistin. Resistance rates varied significantly across different strains and food types, particularly meat products exhibiting higher resistance. Notably, significant increases in resistance were observed from 2016 to 2021 for the following: ≥ 1 resistant (P = 0.001), MDR (P = 0.001), ampicillin (P = 0.001), tetracycline (P < 0.001), chloramphenicol (P = 0.030), and trimethoprim/sulfamethoxazole (P = 0.003). The marked escalation in drug resistance over the recent years, coupled with the varying resistance rates among food sources, underscores the growing public health concern. Our findings highlight the need for a coordinated approach to effectively monitor and respond to Salmonella infections in Guizhou, China.

Persistence of microbiological hazards in food and feed production and processing environments

Listeria monocytogenes (in the meat, fish and seafood, dairy and fruit and vegetable sectors), Salmonella enterica (in the feed, meat, egg and low moisture food sectors) and Cronobacter sakazakii (in the low moisture food sector) were identified as the bacterial food safety hazards most relevant to public health that are associated with persistence in the food and feed processing environment (FFPE). There is a wide range of subtypes of these hazards involved in persistence in the FFPE. While some specific subtypes are more commonly reported as persistent, it is currently not possible to identify universal markers (i.e. genetic determinants) for this trait. Common risk factors for persistence in the FFPE are inadequate zoning and hygiene barriers; lack of hygienic design of equipment and machines; and inadequate cleaning and disinfection. A well-designed environmental sampling and testing programme is the most effective strategy to identify contamination sources and detect potentially persistent hazards. The establishment of hygienic barriers and measures within the food safety management system, during implementation of hazard analysis and critical control points, is key to prevent and/or control bacterial persistence in the FFPE. Once persistence is suspected in a plant, a 'seek-and-destroy' approach is frequently recommended, including intensified monitoring, the introduction of control measures and the continuation of the intensified monitoring. Successful actions triggered by persistence of L. monocytogenes are described, as well as interventions with direct bactericidal activity. These interventions could be efficient if properly validated, correctly applied and verified under industrial conditions. Perspectives are provided for performing a risk assessment for relevant combinations of hazard and food sector to assess the relative public health risk that can be associated with persistence, based on bottom-up and top-down approaches. Knowledge gaps related to bacterial food safety hazards associated with persistence in the FFPE and priorities for future research are provided.

Poultry production as the main reservoir of ciprofloxacin- and tigecycline-resistant extended-spectrum β-lactamase (ESBL)-producing Salmonella enterica serovar Kentucky ST198.2-2 causing human infections in China

Salmonella enterica serovar Kentucky (S. Kentucky) has been regarded as a common serotype causing human nontyphoidal salmonellosis, frequently associated with the consumption of contaminated poultry products. Recently, multidrug-resistant (MDR) S. Kentucky ST198 with strong resistance to cefotaxime, ciprofloxacin, and tigecycline has emerged and been frequently detected in both poultry and humans in Europe and Asia. In this study, whole-genome sequencing (WGS) analysis divided 327 S. Kentucky ST198 isolates into two clades, of which ST198.2 is more prevalent than ST198.1 worldwide. We further compared the genomic characteristics of 70 ST198 isolates from animals and humans during 2019-2022 plus previously reported 38 isolates from 2013 to 2019 in China. One hundred five of the 108 isolates were ST198.2, which could be differentiated into two subclades. ST198.2-1 was prevalent in isolates during 2013-2019, while ST198.2-2 has increased to be the predominant subclade in isolates since 2019. CRISPR typing can differentiate the clade ST198.1 isolates from clade ST198.2 ones but cannot differentiate the two subclade isolates. The acquisition of a large multi-drug resistant region in ST198.2-2 enhanced bacterial resistance to β-lactam, aminoglycoside, amphenicol, and fosfomycin. In addition, compared with the extended-spectrum β-lactamase (ESBL)-encoding gene blaCTX-M-14b in ST198.2-1, co-existence of blaCTX-M-55 and blaTEM-1B was detected in most of the ST198.2-2 isolates. The emergence of ciprofloxacin- and tigecycline-resistant ESBL-producing S. Kentucky ST198.2-2 strains highlight the necessity for Salmonella surveillance. It is imperative to implement more effective measures to prevent and control transmission of these strains from poultry to humans. IMPORTANCE Salmonella enterica serovar Kentucky (S. Kentucky) can cause human infections through consumption of contaminated food of animal origin, and the emergence of multidrug-resistant (MDR) ST198-S. Kentucky strains are of concern for human and animal health. Based on whole-genome sequencing (WGS) analysis, this study revealed that the clade ST198.2-2 S. Kentucky has increased to the predominant group in both chickens and humans in China since 2019, which is different to previous studies of the prevalent ST198.2-1 S. Kentucky before 2019. Acquirement of a multidrug resistance region (MRR) makes the ST198.2-2 S. Kentucky to be extensively drug-resistant (XDR) isolate compared with ST198.2-1 S. Kentucky. Besides, the ST198.2-2 S. Kentucky was mainly detected in chickens (chicken meat, intestinal contents, and slaughterhouse) and humans, indicating chicken is the main reservoir for these XDR S. Kentucky isolates. Therefore, it is necessary to implement continuous Salmonella surveillance and effective measures, such as the development of phages and novel antibiotics/compounds, to prevent the transmission of XDR ST198.2-2 S. Kentucky from chickens to humans across China.

Emergence of chromosomally located blaCTX-M-14b and qnrS1 in Salmonella enterica serotype Kentucky ST198 in China

Highly fluoroquinolone-resistant Salmonella enterica serotype Kentucky has become widespread in recent years, largely associated with the spread of sequence type 198 (ST198), which often leads to multidrug resistance. Research on the genomic epidemiology of Salmonella Kentucky in China is currently uncommon. In this study, we analysed the genomic epidemiology and antimicrobial resistance characteristics of Salmonella Kentucky ST198 collected from foodborne disease surveillance in Shenzhen, China, during 2010-2021, using whole-genome sequencing and antibiotic susceptibility testing. In addition, 158 global Salmonella Kentucky ST198 genomes were included for comparison. Among 8559 Salmonella isolates, 43 Salmonella Kentucky ST198 isolates were detected during 2010-2021. The global Salmonella Kentucky ST198 evolutionary tree was divided into five clades, with Shenzhen isolates distributed in clades 198.1, 198.2-1 and 198.2-2, mainly clustered with Chinese strains. Strains in clade 198.2 dominated in Shenzhen and all of them showed multidrug resistance. Nine strains showed high resistance to ceftriaxone, which was associated with blaCTX-M-14b in clade 198.2-1, which was demonstrated to be located on the chromosome. Fifteen strains showed high resistance to ciprofloxacin, which was associated with carriage of qnrS1 in clade 198.2-2. qnrS1 was first located on an IncHI2 plasmid and then transferred into the chromosome. Here we report the genomic and antimicrobial resistance characterisation of Salmonella Kentucky ST198 in Shenzhen. Of particular concern, we identified for the first time a clade 198.2-1 isolate carrying blaCTX-M-14b as well as chromosomally located qnrS1 in clade 198.2-2 of Salmonella Kentucky ST198 in China, highlighting the necessity of surveillance of clade 198.2.

Prevalence and Characterization of Salmonella Isolated from Chickens in Anhui, China

Salmonella is one of the most important zoonotic pathogens that can cause both acute and chronic illnesses in poultry flocks, and can also be transmitted to humans from infected poultry. The purpose of this study was to investigate the prevalence, antimicrobial resistance, and molecular characteristics of Salmonella isolated from diseased and clinically healthy chickens in Anhui, China. In total, 108 Salmonella isolates (5.66%) were successfully recovered from chicken samples (n = 1908), including pathological tissue (57/408, 13.97%) and cloacal swabs (51/1500, 3.40%), and S. Enteritidis (43.52%), S. Typhimurium (23.15%), and S. Pullorum (10.19%) were the three most prevalent isolates. Salmonella isolates showed high rates of resistance to penicillin (61.11%), tetracyclines (47.22% to tetracycline and 45.37% to doxycycline), and sulfonamides (48.89%), and all isolates were susceptible to imipenem and polymyxin B. In total, 43.52% isolates were multidrug-resistant and had complex antimicrobial resistance patterns. The majority of isolates harbored cat1 (77.78%), blaTEM (61.11%), and blaCMY-2 (63.89%) genes, and the antimicrobial resistance genes in the isolates were significantly positively correlated with their corresponding resistance phenotype. Salmonella isolates carry high rates of virulence genes, with some of these reaching 100% (invA, mgtC, and stn). Fifty-seven isolates (52.78%) were biofilm-producing. The 108 isolates were classified into 12 sequence types (STs), whereby ST11 (43.51%) was the most prevalent, followed by ST19 (20.37%) and ST92 (13.89%). In conclusion, Salmonella infection in chicken flocks is still serious in Anhui Province, and not only causes disease in chickens but might also pose a threat to public health security.

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.

Genetic Relationship between Salmonella Isolates Recovered from Calves and Broilers Chickens in Kafr El-Sheikh City Using ERIC PCR

A prevalent bacterial intestinal infection with severe economic damage is salmonellosis. Our study was carried out to diagnose Salmonella from chickens and calves, to determine its resistance to antimicrobials' phenotypic and genotypic characterization of integrons and β lactamase genes in the multidrug resistance of different Salmonella serotypes, and to detect the genetic relationship between Salmonella isolates collected from different origins using an ERIC PCR. In total, 200 samples from diseased chicken and diarrheic calves were obtained from 50 various farms from Kafr El-sheikh, Egypt. Salmonella poultry isolates were characterized as S. Typhimurium (3/8), S. Enteritidis (3/8), and S. Kentucky (2/8), but Salmonella isolates from cattle were S. Enteritidis (1/2) and S. Kentucky (1/2). When antibiotic susceptibility testing was completed on all of the isolates, it showed that there was multidrug resistance present (MDR). A PCR was applied for identifying the accompanying class 1 integrons and ESBLs from MDR Salmonella isolates (two isolates of S. Kentucky were divided as one from calf and one from poultry). Our results detected blaTEM and class 1 integron, but were negative for bla IMP, bla VIM, and bla SHV. An ERIC PCR was conducted for understanding the clonal relation between various β-lactamase-producing MDR Salmonella isolates. The same four previously mentioned isolates were also tested. The two isolates of S. Enteritidis isolated from poultry and calves had 100% similarity despite indicating that there were interactions between broilers and calves living on the same farm that caused infection from the same Salmonella strains, while the other two isolates of S. Kentucky showed only 33% serovarities.

Genomic Characterization of Antimicrobial-Resistant Salmonella enterica in Duck, Chicken, and Pig Farms and Retail Markets in Eastern China

Antimicrobial-resistant Salmonella enterica poses a significant public health concern worldwide. However, the dissemination of Salmonella enterica among food animals in eastern China has not been fully addressed. Here, we demonstrated the antimicrobial resistance (AMR) patterns and the whole-genome characterization of 105 S. enterica isolates from 1,480 fecal samples and anal swabs collected from 22 different farms (chickens, ducks, and pigs) and two live animal markets located in Zhejiang and Fujian Provinces in eastern China in 2019. The prevalence of isolates in duck farms (19.17%, 23/120) was statistically significantly higher (P < 0.001) than that in chicken farms (6.61%, 37/523) and pig farms (3.50%, 7/200). Among these isolates, 75.26% (79/105) were multidrug resistant, with the highest rates of resistance to tetracycline (76.20%) and ampicillin (67.62%) and the lowest resistance rate to meropenem (0.00%). The serotypes were consistent with sequence types and were closely related to the sampling animal species and sites. S. enterica serotype Kentucky (20.95%, 22/105) was the most frequent serotype and harbored more AMR patterns and genes than others. Furthermore, IncFII(S) and IncHI2 were the most prevalent replicons. A total of 44 acquired AMR genes were found. Among those genes, aac(6')-Iaa, blaTEM-1B, floR, dfrA14, fosA7, mph(A), qnrS1, sul1, tet(A), and ARR-3 were the dominant AMR genes mediating the AMR toward aminoglycosides, β-lactams, phenicol, trimethoprim, fosfomycin, macrolide, quinolone, sulfonamides, tetracycline, and rifampin, respectively. The consistency of acquired AMR genes with AMR phenotypes for ampicillin, ceftiofur, ceftazidime, meropenem, sulfamethoxazole-trimethoprim, and tetracycline was >90%. Together, our study highlights the application of whole-genome sequencing to assess veterinary public health threats. IMPORTANCE Public health is a significant concern in China, and the foodborne pathogen Salmonella, which is spread via the animal-borne food chain, plays an important role in the overall disease burden in China annually. The development of advanced sequencing technologies has introduced a new way of understanding emerging pathogens. However, the routine surveillance application of this method in China remains in its infancy. Here, we applied a pool of all isolates from the prevalence data in Zhejiang and Fujian for whole-genome sequencing and combined these data with the cutting-edge bioinformatic analysis pipeline for one-step determination of the complete genetic makeup for all 105 genomes. The illustrated method could provide a cost-effective approach, without labor-intensive laboratory characterization, for predicting serotypes, genotypes, plasmid types, antimicrobial resistance genes, and virulence genes, and thus would provide essential knowledge for emerging pathogens. Our findings and perspectives are essential for delivering updated knowledge on foodborne pathogens in an understudied region in China.

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.

Salmonella Yoruba: a rare serotype revealed through genomic sequencing along the farm-to-fork continuum of an intensive poultry farm in KwaZulu-Natal, South Africa

Salmonella enterica is a zoonotic pathogen of worldwide public health importance. We characterised Salmonella isolates from poultry along the farm-to-fork continuum using whole genome sequencing (WGS) and bioinformatics analysis. Three multilocus sequence types (MLSTs), i.e., ST15 (1.9%), ST152 (5.9%) and ST1316 (92.2%) and three serotypes, i.e., S. Heidelberg (1.9%), Kentucky (5.9%) and Yoruba (92.2%) were detected. The rare serotype, S. Yoruba, was detected among the farm and abattoir isolates and contained resistance and virulence determinants. Resistome analysis revealed the presence of the aac(6')-Iaa gene associated with aminoglycoside resistance, a single point mutation in the parC gene associated with fluoroquinolone and quinolone resistance, and a single isolate contained the fosA7 gene responsible for fosfomycin resistance. No antibiotic resistance genes (ARGs) were identified for isolates phenotypically non-susceptible to azithromycin, cephalosporins, chloramphenicol and nitrofurantoin and resistance was thought to be attributable to other resistance mechanisms. The fully susceptible profiles observed for the wastewater isolates suggest that the poultry environment may receive antibiotic-resistant strains and resistance determinants from poultry with the potential of becoming a pathway of Salmonella transmission along the continuum. Six plasmids were identified and were only carried by 92.2% of the S. Yoruba isolates in varying combinations. Four plasmids were common to all S. Yoruba isolates along the continuum; isolates from the litter and faeces on the farm contained two additional plasmids. Ten Salmonella pathogenicity islands (SPIs) and 177 virulence genes were identified; some were serotype-specific. Phylogenetic analysis of S. Heidelberg and Kentucky showed that isolates were related to animal and human isolates from other countries. Phylogenetic analysis among the S. Yoruba isolates revealed four clades based on the isolate sources along the farm-to-fork continuum. Although the transmission of Salmonella strains along the farm-to-fork continuum was not evident, pathogenic, resistant Salmonella present in the poultry production chain poses a food safety risk. WGS analysis can provide important information on the spread, resistance, pathogenicity, and epidemiology of isolates and new, rare or emerging Salmonella strains to develop intervention strategies to improve food safety.

Characterisation of Salmonella Enteritidis ST11 and ST1925 Associated with Human Intestinal and Extra-Intestinal Infections in Singapore

Salmonella Enteritidis is a major foodborne pathogen worldwide. In this study, a total of 276 S. enteritidis isolates, collected between 2016 and 2017 from human, food and farm/slaughterhouse samples, were studied to enhance the understanding of the epidemiology of human salmonellosis in Singapore. Results showed all 276 isolates belonged either to ST1925 (70.3%) or ST11 (29.7%), with ST11 being significantly more frequent in extra-intestinal isolates and chicken isolates. Food isolates, most of which were from poultry, showed the highest prevalence of resistance (33–37%) against beta-lactams or beta-lactams/beta-lactamase inhibitor combination (ampicillin, piperacillin and ampicillin/sulbactam). The analysis showed the detection of genes associated with resistance to aminoglycoside genes (99.6%), tetracycline (55.1%), and beta-lactams (14.9%) of all isolates. Nine types of plasmids were found in 266 isolates; the most common incompatibility group profiles were IncFIB(S)-IncFII(S)-IncX1 (72.2%) and IncFIB(S)-IncFII(S) (15.8%). Most plasmid harbouring isolates from chicken (63.6%, 14/22) and from human (73.8%, 175/237) shared the same plasmid profile (IncFIB(S)-IncFII(S)-IncX1). SNP analysis showed clustering of several isolates from poultry food products and human isolates, suggesting phylogenetic relatedness among these isolates. Lastly, this study provides important epidemiological insights on the application of phenotypic and next-generation sequencing (NGS) tools for improved food safety and public health surveillance and outbreak investigation of S.enteritidis.

Assessing Salmonella Prevalence and Complexity Through Processing Using Different Culture Methods

Conventional Salmonella surveillance requires a week for isolation, confirmation, and subsequent serotyping. We previously showed that this could be reduced by 24 h by combining the pre-enrichment and enrichment steps into a single selective pre-enrichment step and was tested on directly after picking. The goal of this study was 2-fold: 1) to evaluate the use of selective pre-enrichment through each step of processing, including postintervention when the Salmonella load is reduced, and 2) to assess any changes in serovar populations in Salmonella positive samples. Duplicate carcass drip samples, each representative of 500 broiler carcasses, were collected by catching processing water drip under moving carcass shackle lines in each of three commercial broiler slaughter plants. Samples were collected post-pick, post-inside-outside bird wash (IOBW), and post-chill; duplicate wing rinses were performed pre- and post-antimicrobial parts dip. Each processing plant was sampled 6 times for a total of 180 samples collected. The number of Salmonella positives identified with selective pre-enrichment conditions (48/180) was similar to traditional selective enrichment culture conditions (52/180), showed good concordance in recovery rate between the 2 culture methods (Fisher's exact test, P = 0.72). We also found that the incidence of Salmonella reduced dramatically after antimicrobial intervention (post-pick 66.7% vs. post chill 8.3%). When serovar populations were evaluated in Salmonella positive samples using CRISPR-SeroSeq, we detected four different Salmonella serovars, Kentucky, Infantis, Schwarzengrund, and Typhimurium, and their incidence rose between post-pick and post-IOBW. The relative abundance of Infantis within individual samples increased between post-pick and post-IOBW while the relative abundance of the other 3 serovars decreased. These results suggest that a selective pre-enrichment step reduces the time required for Salmonella isolation without negatively affecting detection and serovar profiles in culture positive samples were not altered between culture conditions used.

Prevalence of Salmonella in Chinese Food Commodities: A Meta-Analysis

ABSTRACT

The objective of the present study was to analyze the prevalence of Salmonella in multiple food commodities in the People's Republic of China by performing a meta-analysis. Accordingly, we screened studies that examined the prevalence of Salmonella in PubMed, Embase, and Web of Science databases. Methodological quality assessment and heterogeneity analyses were performed for included studies. The prevalence rate with the 95% confidence interval (CI) was selected as the effect size. Subgroup analyses for each food type were conducted and then stratified by regions, food chain processing points, and seasons. In total, 49 studies were included in the meta-analysis, among them, 8 (16.3%) studies were deemed "high risk," 13 (26.5%) studies were "unclear risk," and 28 (57.2%) studies were "low risk." The overall prevalence rate of Salmonella was 20.0% (95% CI: 15.9 to 24.4). The prevalence rate of Salmonella in raw meat products was 23.6% (95% CI: 19.8 to 27.6), which was higher than that in aquatic products, 13.7% (95% CI: 3.1 to 29.9), milk products, 0.9% (95% CI: 0.0 to 3.9), frozen convenience foods, 6.5% (95% CI: 4.4 to 8.9), ready-to-eat foods, 2.0% (95% CI: 1.1 to 3.2), vegetables and fruits, 0.9% (95% CI: 0.0 to 5.2), and shell eggs, 4.2% (95% CI: 3.0 to 5.7). Subgroup analyses revealed that prevalence rates of Salmonella in raw meat products from abattoirs, 26.3% (95% CI: 17.4 to 36.3) and retail stores, 30.0% (95% CI: 24.6 to 35.8) were higher than those determined from farms, 10.2% (95% CI: 7.0 to 13.9); P < 0.05); however, no significant difference was observed in the prevalence of Salmonella stratified by different geographical regions or seasons (P > 0.05). On the basis of these findings, high levels of Salmonella contamination could be detected in raw meat products in China, and the prevalence rate of Salmonella in raw meat products from abattoirs and retail stores was high.

HIGHLIGHTS

Diagnostic bias during the COVID-19. A rare case report of salmonella typhi

Introduction

In poor countries, due to the limited resources, mostly they prescribe medications without proper diagnosis. The aim of this report is to show diagnostic bias of COVID-19 case.

Case presentation

A 17-year-old male patient was presented to the Hospital with a fever up to 39 °C associated with rigor, sweating, generalized body pain, myalgia, fatigue, loss of appetite, headache, and multiple joint pain with no swelling and redness. The vital signs were steady on physical examination, except temperature which was 39 °C. The chest was clear, and the pulse rate was 90 beats per minute. The heart rate relative bradycardia and lungs were normal. Both a PCR test for COVID-19, and a viral assay ELISA were negative. After further investigations, the culture findings revealed the strong development of Gram-negative coccobacilli (Salmonella serotype Typhi) bacteria under the microscope, which was confirmed by using VITEK 2 to identify it. and treated with ciprofloxacin tab, two times per day for five days and amikacin ampule 500 mg IV every 24 hours for 10 days.

Discussion

Fever is a well-known sign of COVID-19 infection which has been observed in 83%–98% of patients with COVID19. As a result, it may be difficult to tell the difference between COVID-19 and other febrile infections, causing delays in diagnosis and treatment and may blind the physician from considering other febrile illnesses.

Conclusion

Physicians should construct more comprehensive differential diagnoses for people who experience fever, headache, or myalgia symptoms that are linked to a pandemic. COVID-19.

•

Differential diagnosis of patients with persistent Covid-19 sign should be considered.

•

lack awareness of typhoid fever can lead to diagnostic bias during the COVID-19.

•

Direct medical history and exposure can help clinicians to investigate of illnesses.

Florfenicol Enhances Colonization of a Salmonella enterica Serovar Enteritidis floR Mutant with Major Alterations to the Intestinal Microbiota and Metabolome in Neonatal Chickens

Florfenicol is an important antibiotic commonly used in poultry production to prevent and treat Salmonella infection. However, oral administration of florfenicol may alter the animals' natural microbiota and metabolome, thereby reducing intestinal colonization resistance and increasing susceptibility to Salmonella infection. In this study, we determined the effect of florfenicol (30 mg/kg of body weight) on gut colonization of neonatal chickens challenged with Salmonella enterica subsp. enterica serovar Enteritidis. We then analyzed the microbial community structure and metabolic profiles of cecal contents using microbial 16S amplicon sequencing and liquid chromatography-mass spectrometry (LC-MS) untargeted metabolomics, respectively. We also screened the marker metabolites using a multi-omics technique and assessed the effect of these markers on intestinal colonization by S. Enteritidis. Florfenicol administration significantly increased the loads of S. Enteritidis in cecal contents, spleen, and liver and prolonged the residence of S. Enteritidis. Moreover, florfenicol significantly affected cecal colony structures, with reduced abundances of Lactobacillus and Bacteroidetes and increased levels of Clostridia, Clostridium, and Dorea. The metabolome was greatly influenced by florfenicol administration, and perturbation in metabolic pathways related to linoleic acid metabolism (linoleic acid, conjugated linoleic acid [CLA], 12,13-EpOME, and 12,13-diHOME) was most prominently detected. We screened CLA and 12,13-diHOME as marker metabolites, which were highly associated with Lactobacillus, Clostridium, and Dorea. Supplementation with CLA maintained intestinal integrity, reduced intestinal inflammation, and accelerated Salmonella clearance from the gut and remission of enteropathy, whereas treatment with 12,13-diHOME promoted intestinal inflammation and disrupted intestinal barrier function to sustain Salmonella infection. Thus, these results highlight that florfenicol alters the intestinal microbiota and metabolism of neonatal chickens and promotes Salmonella infection mainly by affecting linoleic acid metabolism. IMPORTANCE Florfenicol is a broad-spectrum fluorine derivative of chloramphenicol frequently used in poultry to prevent/treat Salmonella. However, oral administration of florfenicol may lead to alterations in the microbiota and metabolome in the chicken intestine, thereby reducing colonization resistance to Salmonella infection, and the possible mechanisms linking antibiotics and Salmonella colonization in poultry have not yet been fully elucidated. In the current study, we show that increased colonization by S. Enteritidis in chickens administered florfenicol is associated with large shifts in the gut microbiota and metabolic profiles. The most influential linoleic acid metabolism is highly associated with the abundances of Lactobacillus, Clostridium, and Dorea in the intestine. The screened target metabolites in linoleic acid metabolism affect S. Enteritidis colonization, intestinal inflammation, and intestinal barrier function. Our findings provide a better understanding of the susceptibility of animal species to Salmonella after antibiotic intervention, which may help to elucidate infection mechanisms that are important for both animal and human health.

Serotyping, MLST, and Core Genome MLST Analysis of Salmonella enterica From Different Sources in China During 2004-2019

Salmonella enterica (S. enterica) is an important foodborne pathogen, causing food poisoning and human infection, and critically threatening food safety and public health. Salmonella typing is essential for bacterial identification, tracing, epidemiological investigation, and monitoring. Serotyping and multilocus sequence typing (MLST) analysis are standard bacterial typing methods despite the low resolution. Core genome MLST (cgMLST) is a high-resolution molecular typing method based on whole genomic sequencing for accurate bacterial tracing. We investigated 250 S. enterica isolates from poultry, livestock, food, and human sources in nine provinces of China from 2004 to 2019 using serotyping, MLST, and cgMLST analysis. All S. enterica isolates were divided into 36 serovars using slide agglutination. The major serovars in order were Enteritidis (31 isolates), Typhimurium (29 isolates), Mbandaka (23 isolates), and Indiana (22 isolates). All strains were assigned into 43 sequence types (STs) by MLST. Among them, ST11 (31 isolates) was the primary ST. Besides this, a novel ST, ST8016, was identified, and it was different from ST40 by position 317 C → T in dnaN. Furthermore, these 250 isolates were grouped into 185 cgMLST sequence types (cgSTs) by cgMLST. The major cgST was cgST235530 (11 isolates), and only three cgSTs contained isolates from human and other sources, indicating a possibility of cross-species infection. Phylogenetic analysis indicated that most of the same serovar strains were putatively homologous except Saintpaul and Derby due to their multilineage characteristics. In addition, serovar I 4,[5],12:i:- and Typhimurium isolates have similar genomic relatedness on the phylogenetic tree. In conclusion, we sorted out the phenotyping and genotyping diversity of S. enterica isolates in China during 2004-2019 and clarified the temporal and spatial distribution characteristics of Salmonella from different hosts in China in the recent 16 years. These results greatly supplement Salmonella strain resources, genetic information, and traceability typing data; facilitate the typing, traceability, identification, and genetic evolution analysis of Salmonella; and therefore, improve the level of analysis, monitoring, and controlling of foodborne microorganisms in China.

Prevalence, Characterization, and Pathogenicity of Salmonella enterica Subspecies enterica Serovar Derby from Yaks in the Aba Tibetan Autonomous Prefecture, China

Simple Summary

Salmonella spp. is a very important pathogen in the livestock industry and public health, which poses a major threat to global public health. Yaks and their by-products have a significant economic status in the Qinghai–Tibetan Plateau. The aim of this study was to investigate the prevalence of salmonella in yak farms and to conduct a molecular characterization and tests on its pathogenicity in mice with the use of salmonella isolated from yaks with diarrhea as well as from drinking water samples. The prevalence of salmonella was 19.75% of 162 samples collected from yak farms, and all isolates were found to belong to the serovar of Salmonella Derby and ST40. All Salmonella Derby isolates from both fecal and drinking water samples from 13 farms were clonally related based on SNP alignment. Salmonella Derby was still detected positively in the feces of model mice on day 24 post-injection. This study reports the prevalence of Salmonella Derby in yaks with diarrhea and in their drinking water. In addition, the pathogenicity of the S. Derby in mice was investigated. Findings suggest that Salmonella Derby excreted by diarrheic yaks is a source of contamination for other yaks and the environment and is highly pathogenic to mice. Seeing that Salmonella Derby has become one of the most common Salmonella serovars, this situation gives rise to further risk from the potential spread of food-borne diseases.

Abstract

Salmonella enterica subsp. enterica serovar Derby (S. Derby) is one of the numerous non-typhoidal Salmonella serovars and has been recognized as a food-borne pathogen. In 2019, outbreaks of salmonellosis were reported in 13 yak farms in the Aba Tibetan Autonomous Prefecture, China. A total of 32 salmonella strains were isolated from 162 fecal samples of yaks with diarrhea as well as from drinking water samples. The isolates were subjected to serovar identification, animal experiments, and whole-genome sequencing (WGS) analyses. The serovar of all the isolates was S. Derby, and the sequence types (STs) were ST40. The analysis of the differences of single-nucleotide polymorphisms (SNPs) showed that the salmonella strains isolated from 13 farms were clonally related. Animal experiments showed that the lethal dose (LD₅₀) was 4.57 × 10⁷ CFU (colony-forming units); the shedding time of S. Derby in mice was 24 days; the bacterial loads in spleen were higher than those in other organs (ileum, liver, and cecum). Pathological analyses by hematoxylin and eosin (H&E) staining revealed obvious damage in the spleen, liver, and intestine. These results indicate that the S. Derby from yaks can cause infection in mice.

Genomic Investigation of Salmonella Isolates Recovered From a Pig Slaughtering Process in Hangzhou, China

The pig industry is the principal source of meat products in China, and the presence of pathogens in pig-borne meat is a crucial threat to public health. Salmonella is the major pathogen associated with pig-borne diseases. However, route surveillance by genomic platforms along the food chain is still limited in China. Here, we conducted a study to evaluate the dynamic prevalence of Salmonella in a pig slaughtering process in Hangzhou, Zhejiang Province, China. Fifty-five of 226 (24.37%) samples were positive for Salmonella; from them, 78 different isolates were selected and subjected to whole genome sequencing followed by bioinformatics analyses to determine serovar distribution, MLST patterns, antimicrobial resistance genes, plasmid replicons, and virulence factors. Moreover, phenotypic antimicrobial resistance was performed using the broth dilution method against 14 antimicrobial agents belonging to 10 antimicrobial classes. Our results showed that samples collected from the dehairing area (66.66%) and the splitting area (57.14%) were the most contaminated. Phenotypic antimicrobial resistance classified 67 of 78 isolates (85.90%) as having multidrug resistance (MDR), while the highest resistance was observed in tetracycline (85.90%; 67/78) followed by ampicillin (84.62%; 66/78), chloramphenicol (71.80%; 56/78), and nalidixic acid (61.54%; 48/78). Additionally, serovar prediction showed the dominance of Salmonella Typhimurium ST19 (51.28%; 40/78) among the 78 studied isolates, while plasmid prediction reported the dominance of IncHI2A_1 (20.51%; 16/78), followed by IncX1_1 (17.95%; 14/78) and IncHI2_1 (11.54%; 9/78). Virulence factor prediction showed the detection of cdtB gene encoding typhoid toxins in two Salmonella Goldcoast ST358 and one Salmonella Typhimurium ST19, while one isolate of Salmonella London ST155 was positive for genes encoding for the siderophore “yersiniabactin” and the gene senB encoding for enterotoxin production. From this study, we conclude that pig slaughterhouses are critical points for the dissemination of virulent and multidrug-resistant Salmonella isolates along the food chain which require the implementation of management systems to control the critical points. Moreover, there is an urgent need for the implementation of the whole genome sequencing platform to monitor the emergence of virulent and multidrug-resistant clones along the food chain.

Characterization of a Broad-Host-Range Lytic Phage SHWT1 Against Multidrug-Resistant Salmonella and Evaluation of Its Therapeutic Efficacy in vitro and in vivo

Inappropriate use of antibiotics has accelerated to the emergence of multidrug-resistant bacteria, becoming a major health threat. Moreover, bacterial biofilms contribute to antibiotic resistance and prolonged infections. Bacteriophage (phage) therapy may provide an alternative strategy for controlling multidrug-resistant bacterial infections. In this study, a broad-host-range phage, SHWT1, with lytic activity against multidrug-resistant Salmonella was isolated, characterized and evaluated for the therapeutic efficacy in vitro and in vivo. Phage SHWT1 exhibited specific lytic activity against the prevalent Salmonella serovars, such as Salmonella Pullorum, Salmonella Gallinarum, Salmonella Enteritidis, and Salmonella Typhimurium. Morphological analysis showed that phage SHWT1 was a member of the family Siphoviridae and the order Caudovirales. Phage SHWT1 had a latent period of 5 min and burst size of ~150 plaque-forming units (PFUs)/cell. The phage was stable from pH 3-12 and 4–65°C. Phage SHWT1 also showed capacity to lyse Salmonella planktonic cells and inhibit the biofilm formation at optimal multiplicity of infection (MOI) of 0.001, 0.01, 0.1, and 100, respectively. In addition, phage SHWT1 was able to lyse intracellular Salmonella within macrophages. Genome sequencing and phylogenetic analyses revealed that SHWT1 was a lytic phage without toxin genes, virulence genes, antibiotic resistance genes, or significant genomic rearrangements. We found that phage SHWT1 could successfully protect mice against S. enteritidis and S. typhimurium infection. Elucidation of the characteristics and genome sequence of phage SHWT1 demonstrates that this phage is a potential therapeutic agent against the salmonellosis caused by multidrug-resistant Salmonella.

Tracking Salmonella enterica by whole genome sequencing of isolates recovered from broiler chickens in a poultry production system

Salmonella enterica is a major cause of foodborne diseases, and is also an important pathogenic bacterium in poultry industry. Whole genome sequencing (WGS) has become a crucial molecular typing technology used for the surveillance of the pathogenic bacteria. In the present study, we adopted WGS for tracking transmission of S. enterica in the production chain of broiler chickens. A total of 74 S. enterica strains were isolated from the different steps of breeding and slaughtering in a large production enterprise in Sichuan Province, China. The isolation rate of Salmonella was the highest in procedure of defeathering (50.0%) and evisceration (36.7%). Serotype identification showed that 74 Salmonella isolates included 7 serotypes, among which Mbandaka accounted for the highest proportions (35.1%). WGS revealed that 74 strains belonged to 7 different sequence types (STs), as well as 7 different ribosomal STs and 35 core genome STs. cgMLST-based Minimum Spanning Trees and phylogenetic tree based on the SNPs indicated that three serotypes, Mbandaka, Indiana and Kentucky, could be clonally transmitted between broiler farm and slaughterhouse. Heterogeneous resistant phenotypes and genotypes were found in two serotypes, Indiana and Kentucky. Our study indicated WGS in an accurate tool for molecular typing of S. enterica. Routine surveillance of S. enterica in the production chain of broiler chickens is needed.

Salmonella Contamination of Broiler Chicken Carcasses at Critical Steps of the Slaughter Process and in the Environment of Two Slaughter Plants: Prevalence, Genetic Profiles, and Association with the Final Carcass Status

ABSTRACT

Salmonella is a foodborne pathogen commonly associated with poultry products. The aims of this work were to (i) estimate the impact of critical steps of the slaughter process on Salmonella detection from broiler chicken carcasses in two commercial poultry slaughter plants in Quebec, Canada; (ii) investigate the presence of Salmonella in the slaughter plant environment; (iii) describe, using a high-resolution melting (HRM) approach, the HRM Salmonella profiles and serotypes present on carcasses and in the slaughter plant environment; and (iv) evaluate whether the HRM flock status after chilling could be predicted by the flock status at previous steps of the slaughter process, the status of previous flocks, or the status of the processing environment, for the same HRM profile. Eight visits were conducted in each slaughter plant over a 6-month period. In total, 379 carcass rinsates from 79 flocks were collected at five critical steps of the slaughter process. Environmental samples were also collected from seven critical sites in each slaughter plant. The bleeding step was the most contaminated, with >92% positive carcasses. A decrease of the contamination along the slaughtering process was noted, with carcasses sampled after dry-air chilling showing ≤2.5% Salmonella prevalence. The most frequently isolated serotypes were Salmonella Heidelberg, Kentucky, and Schwarzengrund. The detection of the Salmonella Heidelberg 1-1-1 HRM profile on carcasses after chilling was significantly associated with its detection at previous steps of the slaughter process and in previously slaughtered flocks from other farms during a same sampling day. Results highlight the importance of the chilling step in the control of Salmonella on broiler chicken carcasses and the need to further describe and compare the competitive advantage of Salmonella serotypes to survive processing. The current study also illustrates the usefulness of HRM typing in investigating Salmonella contamination along the slaughter process.

HIGHLIGHTS

Prevalence, Antibiotic Susceptibility Profile, and Associated Risk Factors of Salmonella Isolate among Diarrheal Patients Visiting Dessie Referral Hospital, Northeast Ethiopia

Salmonellosis remains an important public health problem worldwide, particularly in the developing countries such as Ethiopia. A cross-sectional study was conducted to determine the prevalence, antibiotic susceptibility profile, and associated risk factors of Salmonella isolate among diarrheal patients who were visiting Dessie Referral Hospital, Dessie, Northeast Ethiopia, from November 2016 to January 2017. 384 stool samples were collected using sterile stool cups. Out of these, 20 (5.21%) were found to be positive for Salmonella species. The distribution of positive samples among the three age groups indicated that Salmonella species were predominantly prevalent in the age group of three months (0.25 years) to 4 years old patients. Abdominal pain, vomiting, watery consistency of stool, and 1–5 days of diarrhea were the clinical features that were significantly associated with salmonellosis. Eating raw vegetables and fruits, consumption of street-vended foods, cohabitation of animals, using water from the unprotected source, absence of latrine, and consumption of raw products of animals such as eggs and raw milk were the risk factors that were significantly associated with the prevalence of Salmonella species. The antibiotic sensitivity test was performed for the isolated Salmonella species against 5 currently recommended antibiotics. The antimicrobial sensitivity study carried out using the Kirby–Bauer disk diffusion method showed that 100% of Salmonella isolates were sensitive to ciprofloxacin and 80% sensitive to nalidixic acid, respectively. Among them, twenty isolated Salmonella species resistant to ampicillin, tetracycline, and trimethoprim-sulfamethoxazole were 100%, 85%, and 80%, respectively. This study revealed that Salmonella species were prevalent among diarrheal patients who were visiting Dessie Referral Hospital, and therefore, routine diagnosis of patients with diarrhea cases is required, and drugs must be prescribed after performing the sensitivity test, or checking the updated information on the local antibiotics pattern is always necessary.

Antimicrobial resistance and molecular characterization of Salmonella enterica serovar Corvallis isolated from human patients and animal source foods in China

In this study, 205 Salmonella enterica serovar Corvallis strains were obtained from humans and foods from Guangdong, Guangxi, and Shanghai in China from 2009 to 2017 to assess drug resistance and molecular epidemiology. These isolates displayed high rates of resistance to sulfisoxazole (94.15%) and tetracycline (77.56%). Surprisingly, the rate of resistance to ciprofloxacin reached 21.46%. Moreover, 63.9% of the strains displayed multidrug resistance. Detection of quinolone genes showed that 97.56% of the strains had single mutations (T57S) in parC. The plasmid-mediated quinolone resistance (PMQR) genes qnrS, aac(6')-Ib-cr, and qnrB, were also detected. The extended spectrum β-lactamase (ESBLS) gene that was most common among the isolates was bla_TEM-1 (18.05%). These S. Corvallis isolates are the first to date, that have been reported to possess bla_CTX-M-55 or bla_NDM-5. Additionally, 95.61% of isolates were biofilm producers. The streptomycin resistance rate was higher in strong biofilm producers (87.50%) than in moderate (37.93%) and weak (26.49%) biofilm producers. Pulsed-field gel electrophoresis (PFGE) showed that some strains from different sources had the same genotype. These isolates may be transmitted to humans through food and therefore the monitoring of these isolates should be strengthened in China.

Non-Typhoidal Salmonella at the Human-Food-of-Animal-Origin Interface in Australia

Non-typhoidal Salmonella is a major zoonotic pathogen that plays a significant role in foodborne human salmonellosis worldwide through the consumption of contaminated foods, particularly those of animal origin. Despite a considerable reduction in human salmonellosis outbreaks in developed countries, Australia is experiencing a continuous rise of such outbreaks in humans. This review of the literature highlights the reported non-typhoidal Salmonella outbreaks in humans as well as the occurrence of the pathogen in foods from animal sources throughout Australia. Non-typhoidal Salmonella infections from food animals are more often associated with at-risk people, such as immunocompromised and aged people or children. Although several animal-sourced foods were recognised as the catalysts for salmonellosis outbreaks in Australia, egg and egg-based products remained the most implicated foods in the reported outbreaks. This review further highlights the antimicrobial resistance trends of non-typhoidal Salmonella isolates at the human-food interface, with a focus on clinically important antimicrobials in humans, by collating evidence from previous investigations in Australia. The rise in antimicrobial-resistant Salmonella, especially to antimicrobials commonly prescribed to treat human salmonellosis, has become a significant global public health concern. However, the overall prevalence of antimicrobial resistance in Australia is considerably lower than in other parts of the world, particularly in terms of critically important antimicrobials for the treatment of human salmonellosis. The present review adds to our understanding of the global epidemiology of non-typhoidal Salmonella with emphasis on the past few decades in Australia.