Human Salmonellosis Research Articles

Resistance of Salmonella spp. isolated from poultry meat to antimicrobial drugs

Uncontrolled use of antimicrobials in the prophylaxis and treatment of human and animal diseases leads to the appearance of residues in the environment and food. The use of antimicrobials as growth promoters in breeding affirms the importance of their residual finding in foods of animal origin. Bacteria of the genus Salmonella are one of the most common causes of food poisoning. All species of this genus are pathogenic to humans and cause various diseases known as salmonellosis. Humans can become infected through the faecal-oral route by consuming contaminated food and water or by direct contact with an animal. Salmonella that are resistant to antimicrobial drugs can transfer resistance genes to other microorganisms. In this work, the resistance of 10 Salmonella isolates from poultry meat to 8 different antimicrobial substances was examined by the disk diffusion method. All Salmonella isolates were sensitive to trimethoprim-sulfamethoxazole and chloramphenicol. All isolates were resistant to amoxicillin and significant percentages were resistant to other antimicrobial drugs. Also, multi-drug resistance of Salmonella isolates was found. The best prevention of salmonellosis in humans is constant and comprehensive control of this hazard in food products during production, processing, storage, and sale.

English

Chicken meat, which could be a healthy and nutritionally food, is regrettably incriminated as a source of Salmonella typhimurium which has a great ability to cause human salmonellosis. This study aimed to assess the prevalence of multidrug-resistant S. typhimurium in chicken meat and the effects of essential oils on its viability. A total of 300 chicken meat and its products samples were streaked on XLD agar plates, which was followed by identification of the isolates based on biochemical and serological tests. Ten isolates were serotyped as S. typhimurium then assayed for susceptibility to 14 antimicrobials by the single diffusion method. Eight isolates (80%) showed multiple antimicrobial resistance (MAR) for 3 or more antimicrobials with MAR index of 0.4857 in average. Serotyped S. typhimurium strain with the highest antimicrobial resistance, confirmed by 16s RNA sequencing, was selected for studying the effects of thyme, oregano, and lemon essential oils with concentrations of 0.5, and 1% on its viability after inoculating into chicken fillets by intensity of 3.0×106 and on sensory traits of chicken fillets on 2nd, 4th, 6th, and 8th days of inoculation during cold storage (4ºC). All results showed a significant reduction of S. typhimurium counts with highest inhibition obtained using 1% lemon essential oil. The sensory properties of treated chicken fillets were improved by all used essential oils, compared to the control samples after 6th day, and 8th day of the storage period. The samples treated with 0.5, and 1% lemon essential oil revealed the highest improvement of sensory attributes. This study proved that the majority of S. typhimurium existing in chicken meat are Multidrug-resistant and have no negative effect on sensory traits, hence, posing a public health hazard. Natural essential oils have, also, great antimicrobial effect on S. typhimurium, thus it could replace chemical antimicrobials.

Prevalence, serovar, and antimicrobial resistance of Salmonella isolated from meat and minced meat used for production smoked sausage

The objective of this study was to research the prevalence, serovars, and antimicrobial resistance profiles of Salmonella isolated from meat and minced meat used for the production of fermented sausage. A total of 116 samples were tested, and among them, 20 (17.2%) were positive. Salmonella was detected in 3 (10.3%) beef samples, 5 (19.2%) pork samples, and 6 (20.7%) poultry samples. In minced meat, the Salmonella prevalence was 18.8%. Salmonella enterica serovar Agama (5.2%) was the most commonly identified serovar, followed by S. Enteritidis (4.3%), S. Typhimurium (3.4%), S. Infantis (2.6%), and S. Lindenburg (1.7%). Most of the serovars identified in the present study are recognized as frequent causes of human salmonellosis. Thus, the presence of these serovars means foods with these meats are a likely source of human infections. We found the Salmonella isolates exhibited high rates of resistance to antimicrobials tetracycline, ampicillin, streptomycin, and ciprofloxacin. The highest level of resistance was to tetracycline (75%), followed by resistance to ampicillin (50%), streptomycin (30%), ciprofloxacin (20%), gentamicin (20%), and neomycin (10%). The high-level resistance observed for some of the serovars calls for concern. Salmonella with multidrug resistance in meat used to produce fermented sausages is considered a high additional risk for human health.

Relevance of food bacterial zoonoses in the Dnipropetrovsk Region (Ukraine) during 2020

When the world is facing an unprecedented COVID-19 pandemic, the importance of animal disease surveillance has become apparent. A significant proportion of new and existing human diseases are zoonoses. Microbiological researches remain relevant today. They guarantee the quality of food raw materials and products, as well as identify sources of infection. The aim of our work was to study the spread of foodborne bacterial zoonoses in the Dnipropetrovsk region during 2020. The study used the methods provided by DSTU ISO 6887-2:2005, DSTU ISO 4833:2006, DSTU ISO 4832:2015, DSTU EN 12824:2004, DSTU ISO 11290-1:2003, DSTU 7444:2013, DSTU ISO 6888-2:2003, DSTU ISO 7937:2006. As a result of the study of the epidemic situation regarding outbreaks of acute intestinal infectious diseases and food poisoning in 2020 in Ukraine, 52 cases were investigated, including cases in which children have been affected (43.8%). In the etiological structure, the largest share of outbreaks caused by salmonella (34.6%) and outbreaks of viral etiology (25%) was observed. The registration of outbreaks of human salmonellosis in 82% of regions in Ukraine proves that geographical conditionality, climatic conditions, species structure of farm animals and the level of socio-economic status of the population are important factors in the development of the disease. The presence of positive for animal salmonellosis localities also demonstrates the constant spread of this zoonosis in Ukraine, which causes contamination by these bacteria of food products of animal origin and environmental objects. The dominance of the Dnipropetrovsk Region in 2020 in the number of outbreaks of acute intestinal infectious diseases contributed to a detailed investigation of bacteriological studies of raw materials of animal origin and food products, which revealed 2.56% of non-compliant samples, where the highest percentage of violations of safety criteria was poultry products. Thus, high-risk products included semi-finished products and culinary products from meat, in particular poultry; minced meat and mechanically rolled meat, as well as ready-to-eat meat products — sausages, namely poultry, and eggs. Poultry products of seven types (n = 3,226) were analyzed for the presence of sanitary-indicative microflora (coliform bacteria, mesophilic aerobic and facultative-anaerobic microorganisms), opportunistic microflora (coagulase-positive staphylococci, Proteus, sulfite-reducing clostridia), and pathogenic microflora (bacteria of the genera Salmonella, Listeria). The percentage of samples that did not meet the requirements of regulatory documentation by indicators was: mesophilic aerobic and facultative anaerobic microorganisms up to 10.92%; coliform bacteria — up to 3.90%. Pathogenic contaminants of poultry products of domestic Ukrainian production were: Salmonella Enteritidis (up to 4.20%), Listeria monocytogenes — 12.50%. The paper shows problematic in 2020 nosological forms in the structure of pathogens of food bacterial zoonoses and identifies their potential sources. Microbiological studies have shown that the contaminants of poultry products of domestic Ukrainian production in the Dnipropetrovsk Region were sanitary-indicative (coliform bacteria, mesophilic aerobic and facultative-anaerobic microorganisms), opportunistic pathogens (Staphylococcus aureus, sulfite-reducing clostridia), and pathogenic microflora (bacteria of the genera Salmonella, Listeria). The author has monitored the geographical serotypic predisposition of Salmonella, which is due to the prevalence of O-group D in the Dnipropetrovsk Region, and the possibility of their passage through the food chain. It was found that minced meat and meat of mechanical deboning from poultry is one of the factors of transmission of a potentially pathogenic for humans and animals species of Listeria — L. monocytogenes in the region

Coverage of the national surveillance system for human Salmonella infections, Belgium, 2016-2020.

The surveillance of human salmonellosis in Belgium is dependent on the referral of human Salmonella isolates to the National Reference Center (NRC). Knowledge of current diagnostic practices and the coverage of the national Salmonella surveillance system are important to correctly interpret surveillance data and trends over time, to estimate the true burden of salmonellosis in Belgium, and to evaluate the appropriateness of implementing whole-genome sequencing (WGS) at this central level. The coverage of the NRC was defined as the proportion of all diagnosed human Salmonella cases in Belgium reported to the NRC and was assessed for 2019 via a survey among all licensed Belgian medical laboratories in 2019, and for 2016-2020 via a capture-recapture study using the Sentinel Network of Laboratories (SNL) as the external source. In addition, the survey was used to assess the impact of the implementation of culture-independent diagnostic tests (CIDTs) at the level of peripheral laboratory sites, as a potential threat to national public health surveillance programs. The coverage of the NRC surveillance system was estimated to be 83% and 85%, based on the results of the survey and on the two-source capture-recapture study, respectively. Further, the results of the survey indicated a limited use of CIDTs by peripheral laboratories in 2019. Given the high coverage and the limited impact of CIDTs on the referral of isolates, we may conclude that the NRC can confidently monitor the epidemiological situation and identify outbreaks throughout the country. These findings may guide the decision to implement WGS at the level of the NRC and may improve estimates of the true burden of salmonellosis in Belgium.

Trend of Salmonella enterica occurrence and serotypes in Sardinian pig slaughterhouses.

The aim of this study was to evaluate Salmonella prevalence and serotypes in four Sardinian pig slaughterhouses. Moreover, a population study was conducted with pulsed field gel electrophoresis (PFGE). The results were compared with previous investigations carried out during years 2008 and 2014. A total of 147 samples were collected, 117 from slaughtered pigs (lymph nodes, colon content and carcass surface) and 30 from the slaughterhouse environment (surfaces in contact and not in contact with meat). Salmonella was isolated from 3.4% pig samples and was not detected from environmental samples. Comparing the results with those of previous investigations, occurrence showed a sharp decrease through the years in both animals (18.8% in 2008, 10% in 2014 and 3.4% in 2020) and environmental samples (34.1% in 2008, 3.7 in 2014, and 0% in 2020). At the same time, prevalence of carriers (pigs positive at lymph nodes and/or colon content level) showed a reduction through the years and was always lower in animals coming from local farms rather than those coming from other European Member States, probably indicating the role of stressful factors as transport in increasing Salmonella susceptibility and shedding.Salmonella serotypes were monophasic Typhimurium, Rissen and Muenchen. Overall, 13 different Salmonella serotypes were identified during the three surveys with the most prevalent being serotypes often isolated from slaughtered pigs and during human salmonellosis cases: S. Derby and S. Typhimurium in 2008, S. Anatum and S. Rissen in 2014, monophasic S. Typhimurium in 2020. Population study with pulsed field gel electrophoresis showed a high similarity between Salmonella strains belonging to the same serotype. The results of the investigations showed a decrease of Salmonella occurrence during twelve years in Sardinia, probably due to the improvement in the application of correct GMPs and GHPs at slaughterhouse and also to a reduction of the rate of carrier pigs at farm level.

Genomic and phenotypic comparison of two Salmonella Typhimurium strains responsible for consecutive salmonellosis outbreaks in New Zealand

Salmonella enterica serovar Typhimurium DT160 was the predominant cause of notified human salmonellosis cases in New Zealand from 2000 to 2010, before it was superseded by another S. Typhimurium strain, DT56 variant (DT56v). Whole genome sequencing and phenotypic testing were used to compare 109 DT160 isolates with eight DT56v isolates from New Zealand animal and human sources. Phylogenetic analysis provided evidence that DT160 and DT56v strains were distantly related with an estimated date of common ancestor between 1769 and 1821. The strains replicated at different rates but had similar antimicrobial susceptibility profiles. Both strains were resistant to the phage expressed from the chromosome of the other strain, which may have contributed to the emergence of DT56v. DT160 contained the pSLT virulence plasmid, and the sseJ and sseK2 genes that may have contributed to the higher reported prevalence compared to DT56v. A linear pBSSB1-family plasmid was also found in one of the DT56v isolates, but there was no evidence that this plasmid affected bacterial replication or antimicrobial susceptibility. One of the DT56v isolates was also sequenced using long-read technology and found to contain an uncommon chromosome arrangement for a Typhimurium isolate. This study demonstrates how comparative genomics and phenotypic testing can help identify strain-specific elements and factors that may have influenced the emergence and supersession of bacterial strains of public health importance.

Diversity and Resistance Profiles of Human Non-typhoidal Salmonella spp. in Greece, 2003–2020

Salmonella spp. is one of the most common foodborne pathogens in humans. Here, we summarize the laboratory surveillance data of human non-typhoidal salmonellosis in Greece for 2003–2020. The total number of samples declined over the study period (p < 0.001). Of the 193 identified serotypes, S. Enteritidis was the most common (52.8%), followed by S. Typhimurium (11.5%), monophasic S. Typhimurium 1,4,[5],12:i:- (4.4%), S. Bovismorbificans (3.4%) and S. Oranienburg (2.4%). The isolation rate of S. Enteritidis declined (p < 0.001), followed by an increase of the less common serotypes. Monophasic S. Typhimurium has been among the five most frequently identified serotypes every year since it was first identified in 2007. Overall, Salmonella isolates were resistant to penicillins (11%); aminoglycosides (15%); tetracyclines (12%); miscellaneous agents (sulphonamides, trimethoprim, chloramphenicol and streptomycin) (12%) and third-generation cephalosporins (2%). No isolate was resistant to carbapenems. In total, 2070 isolates (24%) were resistant to one or two antimicrobial classes and 903 (10%) to three and more. Out of the 1166 isolates resistant to fluoroquinolones (13%), 845 (72%) were S. Enteritidis. S. Enteritidis was also the most frequently identified serotype with a resistance to third-generation cephalosporins (37%, 62/166), followed by S. Typhimurium (12%, 20/166). MDR was most frequently identified for S. Typhimurium and its monophasic variant (resistant phenotype of ampicillin, streptomycin, tetracycline and sulphamethoxazole with or without chloramphenicol or trimethoprim).

Seroprevalence of Toxoplasma gondii and Salmonella in Hunted Wild Boars from Two Different Regions in Switzerland.

Simple SummaryWild boars are widely distributed in the northern and southern wooded regions of Switzerland and are popular for their meat. Wild boars can carry a variety of parasites, bacteria, and viruses that could infect humans and domestic animals. In this study, we focused on two important pathogens, the parasite Toxoplasma gondii and the bacterium Salmonella. We used enzyme-linked immunosorbent assay (ELISA) tests to detect antibodies to these pathogens in diaphragm tissue samples from hunted wild boars from two different regions of Switzerland. While the seroprevalence of T. gondii antibodies was similar for animals from the northern and southern region (29% and 37%, respectively), Salmonella seropositivity was very much higher in wild boars from the northern area (52%) than among animals from the south (5%). This may be related to the wild boar density, which may in turn be a risk factor for domestic animals and humans living in the same area. Pathogens in wild boars are of public health significance as a potential source of meat-borne diseases in humans.Toxoplasma gondii and Salmonella are zoonotic foodborne pathogens that may be transmitted to humans through the consumption of raw or undercooked meat, including game. The aim of this study was to determine the seroprevalence of T. gondii and Salmonella antibodies in wild boars in two different regions in Switzerland. During the hunting season of 2020, a total of 126 diaphragm muscle samples of hunted wild boars were collected and the meat juice of these samples was analysed for pathogen-specific IgG antibodies using commercial enzyme-linked immunosorbent assay (ELISA) kits. The overall seroprevalences were 35% for T. gondii and 17% for Salmonella, respectively. In general, seropositivity increased with the age of the animals. Seroprevalences of T. gondii were similar for animals from the northern region (29%) to those from the southern region (36.8%), indicating that T. gondii is widespread in the sylvestrian environment. By contrast, Salmonella seropositivity was remarkably higher in wild boars from the north (52%) compared with those from the south (5.3%). The high occurrence of Salmonella may represent a risk of transmission to compatriot domestic animals such free-range farmed pigs as well as to humans. Further, meat of hunted wild boars may present a source of human toxoplasmosis or salmonellosis.

Free-Living Aquatic Turtles as Sentinels of Salmonella spp. for Water Bodies.

Reptile-associated human salmonellosis cases have increased recently in the United States. It is not uncommon to find healthy chelonians shedding Salmonella enterica. The rate and frequency of bacterial shedding are not fully understood, and most studies have focused on captive vs. free-living chelonians and often in relation to an outbreak. Their ecology and significance as sentinels are important to understanding Salmonella transmission. In 2012–2013, Salmonella prevalence was determined for free-living aquatic turtles in man-made ponds in Clarke and Oconee Counties, in northern Georgia (USA) and the correlation between species, basking ecology, demographics (age/sex), season, or landcover with prevalence was assessed. The genetic relatedness between turtle and archived, human isolates, as well as, other archived animal and water isolates reported from this study area was examined. Salmonella was isolated from 45 of 194 turtles (23.2%, range 14–100%) across six species. Prevalence was higher in juveniles (36%) than adults (20%), higher in females (33%) than males (18%), and higher in bottom-dwelling species (31%; common and loggerhead musk turtles, common snapping turtles) than basking species (15%; sliders, painted turtles). Salmonella prevalence decreased as forest cover, canopy cover, and distance from roads increased. Prevalence was also higher in low-density, residential areas that have 20–49% impervious surface. A total of 9 different serovars of two subspecies were isolated including 3 S. enterica subsp. arizonae and 44 S. enterica subsp. enterica (two turtles had two serotypes isolated from each). Among the S. enterica serovars, Montevideo (n = 13) and Rubislaw (n = 11) were predominant. Salmonella serovars Muenchen, Newport, Mississippi, Inverness, Brazil, and Paratyphi B. var L(+) tartrate positive (Java) were also isolated. Importantly, 85% of the turtle isolates matched pulsed-field gel electrophoresis patterns of human isolates, including those reported from Georgia. Collectively, these results suggest that turtles accumulate Salmonella present in water bodies, and they may be effective sentinels of environmental contamination. Ultimately, the Salmonella prevalence rates in wild aquatic turtles, especially those strains shared with humans, highlight a significant public health concern.

Intensive animal farming operations and outbreaks of zoonotic bacterial diseases in Ukraine

In Ukraine zoonoses are a permanent threat to human health, some of them are bacterial diseases associated with farm animals. Complete avoidance of outbreaks of bacterial zoonoses is not possible but it is appropriate to study them to reduce the risks of transmission of zoonosis pathogens from industrial farms to the human population and the environment. The article highlights the results of a literature review on the potential role of industrial livestock farms in the spread of major bacterial zoonoses in Ukraine. About half of all of the country’s farmed animals are kept on farms using industrial technology; more than half of the establishments are classified as medium and large. The technology of keeping animals on such farms contributes to the development of diseases of obligate hosts caused by fecal bacteria. The systematic search and selection of literary sources, which are relevant to the topic of the study were carried out. The vast majority of analyzed publications are published in Ukrainian in local peer-reviewed scientific journals. An analysis of open-access official statistics from the state authorities of Ukraine was also conducted. The authors analyzed statistics and scientific papers published over the last 10–15 years discussing the outbreaks of food-borne zoonoses among humans and the studying their pathogens (Campylobacter spp., Salmonella spp., Escherichia coli (STEC strains), Listeria spp.) on industrial livestock farms. The main source of Campylobacter spp. and Salmonella spp. distribution are industrial poultry, including broilers and chickens, respectively. The STEC strains E. coli carriers are various types of farm animals, including cattle and pigs. The majority of infections documented in Ukraine are cases of salmonellosis in humans and animals. Despite reports of a significant prevalence of campylobacteriosis, colibacillosis and listeriosis in livestock farms, their association with outbreaks of food-borne zoonoses in humans remains poorly understood. The concept of an industrial livestock farm involves a permanent presence of a risk of outbreaks of bacterial zoonoses and their rapid spreading to the human population. This is due to concentrated maintenance of animals, standardized feeding, the priority of achieving the highest productivity of animals and economic indicators. Under such conditions, disturbance of hygienic norms and technologies significantly increases the risk of bacterial zoonoses on industrial farms. It is important to enforce the continuous control of the level of microbial pollution of farms, animal health, hygiene of milk production and processing, meat, eggs, etc. Farms have a negative impact on the ecological welfare of the surrounding territories. The problem of spread of antibiotic-resistant strains of bacterial zoonoses is a very serious one. Efforts for the formation of a national system of epidemiological supervision over bacterial zoonoses, comprising epidemiological, epizootological, ecological, microbiological, serological and molecular genetic monitoring, as well as the development on this basis of effective prophylactic and anti-epidemic measures are relevant and necessary.

Isolation and antimicrobial resistance of motileSalmonella entericafrom the poultry hatchery environment.

Salmonella is a globally distributed major food-borne pathogen and poultry is one of the predominant sources of salmonellosis in humans. To investigate the presence of motile Salmonella in the poultry hatchery environment, we collected 97 fluff samples from four selected broiler breeder chicken hatcheries from Chattogram, Bangladesh during July-December 2015. To isolate motile Salmonella enterica, we used conventional bacteriological techniques followed by serological verification using anti-Salmonella Poly A-E serum and species confirmation by conventional PCR assay. Antimicrobial susceptibility testing by Kirby-Bauer disc diffusion method for 10 commonly used antibiotics was performed on all isolates. Isolates displaying phenotypic resistance to ampicillin were tested by PCR for blaTEM gene, whereas those resistant to tetracycline were tested for the presence of tetA, tetB and tetC genes. A total of 24 samples (24.7%; 95% CI: 16.5-34.5, N = 97) from 3 hatcheries were positive for motile Salmonella. Of them, 21 (87.5%) and 12 (50.0%) were resistant to ampicillin and tetracycline, respectively, 9 (37.5%) to nalidixic acid and sulphamethoxazole/trimethoprim. No resistance was detected to ceftriaxone, cefoxitin, gentamicin, neomycin, ciprofloxacin and colistin. Ten (42%) of 24 isolates from 2 hatcheries were multi-drug resistant (i.e. resistant to ≥ 3 antimicrobial classes). Six of 21 ampicillin resistant isolates contained blaTEM gene and 10 of 12 tetracycline resistant isolates contained tetA gene. This study highlights the circulation of multi-drug resistant motile Salmonella in the hatchery environment for the first time in Bangladesh. Further epidemiological and molecular studies are therefore needed to identify the serotypes and source of the bacteria in hatcheries.

The occurrence of multidrug-resistant Salmonella nagoya and other serovars in healthy commercial layers in Ilorin, Nigeria

The occurrence of drug-resistant non-typhoidal Salmonella (NTS) in poultry has serious economic implications for the poultry industry and has the potential to cause human Salmonellosis. This study, therefore, aimed to determine the circulating serovars of NTS and their antibiotic susceptibility patterns in poultry in Ilorin. This cross-sectional study was conducted from January to March 2015. A total of 420 samples (cloacal, n=140; fecal, n=140; feed, n=70, and water, n=70) were aseptically collected from live adult birds from 14 farms using a systematic random sampling technique. Salmonella was isolated using the ISO 6579 method. Antibiotic sensitivity testing of NTS serovars was performed using the Kirby Bauer disc – diffusion method and interpreted using the epidemiological cut-off (ECOFF) values. The prevalence of NTS in poultry was 7.4% (n=31). Feed samples were the most contaminated samples (42%, n=13/31). Faecal sample (32%, n=10/31), cloacal swabs (19.5%, n= 6/31), and water samples (6.5%, n=2/31) also contained NTS. There was a significant difference between NTS isolation rates between farms (p&lt;0.05). Only 21 isolates purposively selected across farms and sample types were serotyped. Salmonella nagoya was the most prevalent (52%, n=11/21). Other serovars were Salmonella brijbhumi (5%, n=1/21); Salmonella enteritidis (5%, n=1/21); and Salmonella enterica subsp. enterica serovar 6, 8: z4 (19%, n=4/21). Four isolates (19%) were untypable. All isolates showed multidrug resistance. Most of the isolates were resistant to ampicillin (82.3%) and tetracycline (76.5%). Some isolates were resistant to cefotaxime (23.5%) and ciprofloxacin (29.4%). The occurrence of multidrug-resistant salmonella isolates is considered a critical public health threat that requires urgent global action. There is a need for a coordinated national salmonella surveillance program in Nigeria.

Characterisation of Salmonella enterica clones carrying mcr-1 plasmids in meat products and patients in Northern Thailand using long read sequencing

Salmonella spp. is an important foodborne pathogen associated with consumption of contaminated food, especially food of livestock origin. Antimicrobial resistance (AMR) in Salmonella has been reported globally and increasing AMR in food production is a major public health issue worldwide. The objective of this study was to describe the genetic relatedness among Salmonella enterica isolates, which displayed identical DNA fingerprint profiles. Ten S. enterica isolates were selected from meat and human cases with an identical rep-PCR profile of serovars Rissen (n = 4), Weltevreden (n = 4), and Stanley (n = 2). We used long-read whole genome sequencing (WGS) on the MinION sequencing platform to type isolates and investigate in silico the presence of specific AMR genes. Antimicrobial susceptibility testing was tested by disk diffusion and gradient diffusion method to corroborate the AMR phenotype. Multidrug resistance and resistance to more than one antimicrobial agent were observed in eight and nine isolates, respectively. Resistance to colistin with an accompanying mcr-1 gene was observed among the Salmonella isolates. The analysis of core genome and whole genome MLST revealed that the Salmonella from meat and human salmonellosis were genetically related. Hence, it could be concluded that meat is one of the important sources for Salmonella infection in human.

Identification of Differentially Expressed Non-coding RNA Networks With Potential Immunoregulatory Roles During Salmonella Enteritidis Infection in Ducks.

Salmonella enterica serovar Enteritidis (S. Enteritidis) is a pathogen that can colonize the preovulatory follicles of poultry, thereby causing both reduced egg production and an elevated risk of foodborne salmonellosis in humans. Although a few studies have revealed S. Enteritidis preferentially invades the granulosa cell layer within these follicles, it can readily persist and proliferate through mechanisms that are not well-understood. In this study, we characterized competing endogenous RNA (ceRNA) regulatory networks within duck granulosa cells following time-course of S. Enteritidis challenge. The 8108 long non-coding RNAs (lncRNAs), 1545 circular RNAs (circRNAs), 542 microRNAs (miRNAs), and 4137 mRNAs (fold change ≥2; P < 0.01) were differentially expressed during S. Enteritidis challenge. Also, eight mRNAs, eight lncRNAs and five circRNAs were selected and the consistent expression trend was found between qRT-PCR detection and RNA-seq. Moreover, the target genes of these differentially expressed ncRNAs (including lncRNAs, circRNAs and miRNAs) were predicted, and significantly enriched in the innate immune response and steroidogenesis pathways. Then, the colocalization and coexpression analyses were conducted to investigate relationships between ncRNAs and mRNAs. The 16 differentially expressed miRNAs targeting 60 differentially expressed mRNAs were identified in granulosa cells at 3 and 6 h post-infection (hpi) and enriched in the MAPK, GnRH, cytokine-cytokine receptor interaction, Toll-like receptor, endocytosis, and oxidative phosphorylation signaling pathways. Additionally, underlying lncRNA-miRNA-mRNA and circRNA-miRNA-mRNA ceRNA networks were then constructed to further understand their interaction during S. Enteritidis infection. Lnc_012227 and novel_circ_0004892 were identified as ceRNAs, which could compete with miR-let-7g-5p and thereby indirectly modulating map3k8 expression to control S. Enteritidis infection. Together, our data thus identified promising candidate ncRNAs responsible for regulating S. Enteritidis infection in the preovulatory follicles of ducks, offering new insights regarding the ovarian transmission of this pathogen.

Salmonella Typhimurium Adhesin OmpV Activates Host Immunity To Confer Protection against Systemic and Gastrointestinal Infection in Mice.

Salmonella enterica Typhimurium is a rod-shaped Gram-negative bacterium that mostly enters the human body through contaminated food. It causes a gastrointestinal disorder called salmonellosis in humans and typhoid-like systemic disease in mice. OmpV, an outer membrane protein of S. Typhimurium, helps in adhesion and invasion of bacteria to intestinal epithelial cells and thus plays a vital role in the pathogenesis of S. Typhimurium. In this study, we have shown that intraperitoneal immunization with OmpV is able to induce high IgG production and protection against systemic disease. Further, oral immunization with OmpV-incorporated proteoliposome (OmpV-proteoliposome [PL]) induces production of high IgA antibody levels and protection against gastrointestinal infection. Furthermore, we have shown that OmpV induces Th1 bias in systemic immunization with purified OmpV, but both Th1 and Th2 polarization in oral immunization with OmpV-proteoliposome (PL). Additionally, we have shown that OmpV activates innate immune cells, such as monocytes, macrophages, and intestinal epithelial cells, in a Toll-like receptor 2 (TLR2)-dependent manner. Interestingly, OmpV is recognized by the TLR1/2 heterodimer in monocytes, but by both TLR1/2 and TLR2/6 heterodimers in macrophages and intestinal epithelial cells. Further, downstream signaling involves MyD88, interleukin-1 receptor-associated kinase (IRAK)-1, mitogen-activated protein kinase (MAPK) (both p38 and Jun N-terminal protein kinase (JNK)), and transcription factors NF-κB and AP-1. Due to its ability to efficiently activate both the innate and adaptive immune systems and protective efficacy, OmpV can be a potential vaccine candidate against S. Typhimurium infection. Further, the fact that OmpV can be recognized by both TLR1/2 and TLR2/6 heterodimers increases its potential to act as good adjuvant in other vaccine formulations.

Prevalence, Serovars, and Factors Associated with Salmonella Contamination of Chicken Carcasses Sold in Outlets of the Informal Market in Gauteng Province, South Africa

Salmonella has been linked to many foodborne illnesses and epidemics in both humans and animals. This cross-sectional study determined the prevalence, serovars, and factors associated with Salmonella contamination of chickens slaughtered in informal market outlets in Gauteng Province, South Africa. A total of 151 chicken carcasses were randomly collected from 47 outlets. Standard bacteriological and molecular methods were used to isolate, identify, and determine the serovar of Salmonella isolates. The prevalence of Salmonella in carcass swabs, cloacal swabs, and carcass drips was 29.1% (44 of 151), 27.2% (41 of 151), and 43.7% (66 of 151), respectively, and the differences were statistically significant (P = 0.004). Only 5 (township locations of outlet, throughput, carcass evisceration, location of carcass for sale, and outlet sanitation) of 10 factors investigated for the contamination of carcasses by Salmonella were statistically significantly (P < 0.05) associated with the isolation of Salmonella. Of the 268 isolates of Salmonella, 157 (58.6%) were typeable using a limited molecular PCR technique, and nine serovars were identified. The predominant Salmonella enterica serovars were Bovismorbificans (31.0%), Enteritidis (7.5%), and Hadar (6.7%). The five important factors found to be significantly associated with the isolation of Salmonella at these outlets offer opportunities for the reduction of Salmonella contamination. There is a need for further investigation of the probable causes of the predominant isolation of Salmonella serovar Bovismorbificans in chickens and its potential implications for human infections in South Africa. It is concluded that chickens purchased from the informal market in Gauteng Province can be a source for salmonellosis in humans if improperly cooked before consumption.

Salmonella Derby: A Comparative Genomic Analysis of Strains From Germany.

Salmonella enterica subspecies enterica serovar Derby (S. Derby) is one of the most frequent causes for salmonellosis in humans and animals. Understanding the genetic diversity of S. Derby, as well as the nature and origin of its resistance to antimicrobial treatment are thus the key to epidemiological control and surveillance. Here, we report an analysis of 15 S. Derby strains isolated from pig and cattle in slaughterhouses across Germany (2000–2015), which belonged to multilocus sequence types (ST) ST39, ST40 and ST682. Strains were compared to publicly available S. Derby sequence data of these three STs from Germany, comprising 65 isolates collected between 2004 and 2018 from different sources (i.e., pigs, humans, cattle, wild boar, and poultry). A total of 80 sequences (ST39 = 34, ST40 = 21, and ST682 = 25) were analyzed to assess genetic diversity, to identify virulence-associated and antimicrobial resistance genes (ARGs), and to characterize plasmid content. Strains belonging to all three STs were identified in each source examined. Strains with the same ST were closely related regardless of origin. Altogether, 72.5% of the isolates carried at least one resistance gene, furthermore ST40 carried most of the ARGs and the plasmid replicons. The IncI1 replicon was detected in eleven isolates, four of them carried IncI1 plasmid ST26 with clonal complex 2. The comparison of these four isolates with an IncI1 ST26 plasmid reported in 2010 from a German pig (JX566770), showed only variations in a region carrying different ARGs and mobile genetic elements. The strains of our collection had similar genetic diversity as the strains taken from the public database. Moreover, we found that strains harboring multidrug resistant IncI plasmid were found in different animal species, indicating that S. Derby may be implicated in the spread of antimicrobial resistance among animal species. Results may contribute to the knowledge about the diversity in S. Derby in Germany, which may be useful for the future surveillance and antimicrobial resistance of this serovar.

Prevalence, virulence factor and antimicrobial resistance analysis of Salmonella Enteritidis from poultry and egg samples in Iran

BackgroundSalmonella enterica serovar Enteritidis (S. Enteritidis) is one of the most common serovars, associated with human salmonellosis. The food-borne outbreak of this bacterium is mainly related to the consumption of contaminated poultry meat and poultry products, including eggs. Therefore, rapid and accurate detection, besides investigation of virulence characteristics and antimicrobial resistance profiles of S. Enteritidis in poultry and poultry egg samples is essential. A total of 3125 samples (2250 poultry and 875 poultry egg samples), sent to the administrative centers of veterinary microbiology laboratories in six provinces of Iran, were examined for Salmonella contamination, according to the ISO 6579 guideline. Next, duplex PCR was conducted on 250 presumptive Salmonella isolates to detect invA gene for identification of the genus Salmonella and sdf gene for identification of S. Enteritidis. Subsequently, the S. Enteritidis isolates were examined for detection of important virulence genes (pagC, cdtB, msgA, spaN, tolC, lpfC, and spvC) and determination of antibiotic resistance patterns against nalidixic acid, trimethoprim-sulfamethoxazole, cephalothin, ceftazidime, colistin sulfate, and kanamycin by the disk diffusion method.ResultsOverall, 8.7 and 2.3% of poultry samples and 6.3 and 1.3% of eggs were contaminated with Salmonella species and S. Enteritidis, respectively. The invA and msgA genes (100%) and cdtB gene (6.3%) had the highest and the lowest prevalence rates in S. Enteritidis isolates. The spvC gene, which is mainly located on the Salmonella virulence plasmid, was detected in 50.8% of S. Enteritidis isolates. The S. Enteritidis isolates showed the highest and the lowest resistance to nalidixic acid (87.3%) and ceftazidime (11.1%), respectively. Unfortunately, 27.0% of S. Enteritidis isolates were multidrug-resistant (MDR).ConclusionThe rate of contamination with Salmonella in the poultry and egg samples, besides the presence of antimicrobial resistant and MDR Salmonella isolates harboring the virulence genes in these samples, could significantly affect food safety and subsequently, human health. Therefore, continuous monitoring of animal-source foods, enhancement of poultry farm control measures, and limiting the use of antibiotics for prophylactic purposes in food producing animals, are essential for reducing the zoonotic risk of this foodborne pathogen for consumers and also choosing effective antibiotics for the treatment of salmonellosis.

Draft Genome Sequences of Salmonella enterica subsp. diarizonae Serotype IIIb_61:I,v:1,5,(7) Strains Isolated from Wheat Grains.

Salmonella enterica subsp. diarizonae serotypes are primarily involved in reptile-associated salmonellosis in humans. Here, we report the draft genome sequences of three S. enterica subsp. diarizonae strains belonging to the serotype IIIb_61:1,v:1,5,(7), isolated from wheat grains collected at the time of harvest. Strains of serotype IIIb_61:1,v:1,5,(7) have been isolated from feces of reptiles, cattle, and sheep and from infections in humans.