Cases Of Salmonellosis Research Articles

Serotypes, antibiotic resistance, and molecular characterization of non-typhoidal salmonella isolated from diarrheic patients in Guangxi Zhuang Autonomous Region, China, 2014–2017

The serotype, antimicrobial resistance, and molecular typing of 843 Salmonella isolates recovered from diarrheic patients in Guangxi Zhuang Autonomous Region (Guangxi), China from 2014 to 2017 were investigated. Among these 843 isolates, a total of 67 Salmonella serotypes and four un-typable isolates were detected by the slide agglutination method. The most prevalence serotype was Salmonella 1,4,[5],12:i:- (27.4%, 231/843), followed by S. Enteritidis (20.8%) and S. Typhimurium (16.1%). Many of these isolates (86.2%, 727/843) were resistant to more than one antibiotic. The rate of resistance to early generation antimicrobial agents was high (AMP [73.8%], TET [65.5%], and NAL [43.2%]). Moreover, the rate of resistance to clinically important antimicrobial agents was of great concern (CIP [21.6%], CTX [12.9%], and AZM [5.7%]). Importantly, 34 (4.0%) isolates of nine serovars were resistant to both CIP and CTX, which included 14 (1.7%) that were also resistant to AZM. In addition, 74.9% (631/843) of nontyphoidal Salmonella isolates demonstrated decreased susceptibility to ciprofloxacin with S. Enteritidis as the dominant serovar. Overall, 393 (46.6%) isolates were identified as multidrug resistance (MDR) with resistance to three or more classes of antimicrobials, of which MDR S. 1,4,[5],12:i:- accounted for the highest proportion (31.6%, 124/393). Genotypic analyses by pulsed-field gel electrophoresis of 447 isolates containing the three most common serotypes revealed a high diversity, suggesting that the majority human salmonellosis cases are attributed to sporadic events. These results highlighted the diversity of Salmonella serotypes and the high prevalence of emerging MDR Salmonella. 1,4,[5],12:i:- isolates in Guangxi. Therefore, surveillance of these emerging MDR isolates should be enhanced to monitor antimicrobial resistant Salmonella in the food chain and to inform risk-based decisions to protect public health.

Application of Whole-Genome Sequences and Machine Learning in Source Attribution of Salmonella Typhimurium.

Prevention of the emergence and spread of foodborne diseases is an important prerequisite for the improvement of public health. Source attribution models link sporadic human cases of a specific illness to food sources and animal reservoirs. With the next generation sequencing technology, it is possible to develop novel source attribution models. We investigated the potential of machine learning to predict the animal reservoir from which a bacterial strain isolated from a human salmonellosis case originated based on whole‐genome sequencing. Machine learning methods recognize patterns in large and complex data sets and use this knowledge to build models. The model learns patterns associated with genetic variations in bacteria isolated from the different animal reservoirs. We selected different machine learning algorithms to predict sources of human salmonellosis cases and trained the model with Danish Salmonella Typhimurium isolates sampled from broilers (n = 34), cattle (n = 2), ducks (n = 11), layers (n = 4), and pigs (n = 159). Using cgMLST as input features, the model yielded an average accuracy of 0.783 (95% CI: 0.77–0.80) in the source prediction for the random forest and 0.933 (95% CI: 0.92–0.94) for the logit boost algorithm. Logit boost algorithm was most accurate (valid accuracy: 92%, CI: 0.8706–0.9579) and predicted the origin of 81% of the domestic sporadic human salmonellosis cases. The most important source was Danish produced pigs (53%) followed by imported pigs (16%), imported broilers (6%), imported ducks (2%), Danish produced layers (2%), Danish produced cattle and imported cattle (<1%) while 18% was not predicted. Machine learning has potential for improving source attribution modeling based on sequence data. Results of such models can inform risk managers to identify and prioritize food safety interventions.

Conserved CRISPR arrays in Salmonella enterica serovar Infantis can serve as qPCR targets to detect Infantis in mixed serovar populations.

Salmonellosis is a leading bacterial cause of foodborne illness, and numerous Salmonella enterica serovars have been responsible for foodborne outbreaks. In the United States outbreaks are often linked to poultry and poultry-related products. The prevalence of Salmonella serovar Infantis has been increasing in poultry processing facilities over the past few years and in 2018 was identified as the causative agent for a large multistate outbreak linked to raw chicken. CRISPR-typing is a subtyping approach based on PCR and the sequencing of two Salmonella loci, CRISPR1 and CRISPR2. CRISPR-typing was used to interrogate 138 recent (2018-2019) isolates and genomes of ser. Infantis. Results show that the CRISPR elements are remarkably conserved in this serovar. The most conserved spacers, and those also unique to ser. Infantis, were used as targets to develop a ser. Infantis-specific qPCR assay. This assay was able to detect ser. Infantis in mixed serovar cultures of Salmonella, down to 0·1% of the population, highlighting the utility of this molecular approach in improving surveillance sensitivity for this important food safety pathogen. SIGNIFICANCE AND IMPACT OF THE STUDY: The incidence of human salmonellosis cases caused by Salmonella enterica serovar Infantis (ser. Infantis) has been increasing, as has its prevalence in broiler chickens, which are a frequent reservoir of Salmonella. A cluster of ser. Infantis genetically linked to an outbreak strain have been identified in numerous processing facilities. A qPCR assay targeting CRISPR elements that are unique to ser. Infantis has been developed and can detect this serovar directly from mixed cultures. This assay is sensitive enough to reveal ser. Infantis within a mixed Salmonella population where it constitutes only 0·1% of the population. The rapid nature of qPCR lends this assay to high-throughput screening of poultry samples to detect this important pathogen.

Prevalence, antibiotic resistance, PFGE and MLST characterization of Salmonella in swine mesenteric lymph nodes

This study evaluated 250 animals from 25 different processing lots, processed in four slaughterhouses in São Paulo state, Brazil for the presence of Salmonella in the mesenteric lymph nodes (10 g sample of each animal) and characterized the antibiotics resistance profile, the Pulsed Field Gel Electrophoresis – PFGE and Multi Locus Sequence Typing – MLST profiles of selected strains. The pathogen was present in 36.4% (n = 91, CL 95% 30.4–43.4) of samples and 72% (n = 18, CL 95% 50.6–87.9%) of the analyzed lots. The main serovars were S. Typhimurium (n = 23), Salmonella enterica subsp. enterica 1.4,5,12:i:- (n = 17), followed by S. Infantis (n = 12) and S. Havana (n = 11). Twenty-eight strains (30%) were classified as other serovars. Sixty-eight percent of the strains were resistant to Streptomycin and tetracycline, followed by ampicillin and sulphonamides (62.6%), chloramphenicol (56.0%), trimethoprim-sulfamethoxazole (41.8%) and nalidixic acid (40.7%). The antibiotics with lower resistance rates were cephalothin and aztreonam (both with 3.3% resistant), and ceftriaxone and cefepime (both with 7.7%). Multidrug-resistant strains (MDR) accounted for 70.3% of the isolates. Eight strains were submitted to MLST: four S. Typhimurium and one S.1.4,5,12:i:-, all belonging to the ST 19, two Salmonella Infantis, belonging to the ST 32 and one S. Derby, belonging to ST 40. Twenty-one isolates with different antibiotics resistance profiles from the most prevalent serovars were selected for PFGE analysis. Serovar S. Typhimurium (n = 11) revealed 4 pulsotypes and 1 cluster and S. 1.4,5,12:i:- (n = 10) revealed 5 pulsotypes and 4 clusters. The high prevalence of the pathogen, with its high rates of antibiotics resistance and belonging to genetic groups that are often associated with disease in humans, shows that the production chain of pork is a potential source of infection in salmonellosis cases. Therefore, effective preventive measures for pathogen control are needed to reduce the risk of foodborne diseases.

Assessment of the Risk of Salmonellosis Linked to the Consumption of Liquid Egg Products Made from Internally Contaminated Shell Eggs Initially Stored at 65°F (18°C) Compared with Eggs Stored at 45°F (7°C)

According to the U.S. Food and Drug Administration's (FDA's) rule on "Prevention of Salmonella Enteritidis in Shell Eggs during Production, Storage, and Transportation," shell eggs intended for human consumption are required to be held or transported at or below 45°F (7.2°C) ambient temperature beginning 36 h after time of lay. Meanwhile, eggs in hatcheries are typically stored at a temperature of 65°F (18.3°C). Although most of those eggs are directed to incubators for hatching, excess eggs have the potential to be diverted for human consumption as egg products through the "breaker" market if these eggs are refrigerated in accordance with FDA's requirement. Combining risk assessment models developed by the U.S. Department of Agriculture's Food Safety and Inspection Service for shell eggs and for egg products, we quantified and compared Salmonella Enteritidis levels in eggs held at 65°F versus 45°F, Salmonella Enteritidis levels in the resulting egg products, and the risk of human salmonellosis from consumption of those egg products. For eggs stored 5 days at 65°F (following 36 h at 75°F [23.9°C] in the layer house), the mean level of Salmonella Enteritidis contamination is 30-fold higher than for eggs stored at 45°F. These increased levels of contamination lead to a 47-fold increase in the risk of salmonellosis from consumption of egg products made from these eggs, with some variation in the public health risk on the basis of the egg product type (e.g., whole egg versus whole egg with added sugar). Assuming that 7% of the liquid egg product supply originates from eggs stored at 65°F versus 45°F, this study estimates an additional burden of 3,562 cases of salmonellosis per year in the United States. A nominal range uncertainty analysis suggests that the relative increase in the risk linked to the storage of eggs at higher temperature estimated in this study is robust to the uncertainty surrounding the model parameters. The diversion of eggs from broiler production to human consumption under the current storage practices of 65°F (versus 45°F) would present a substantive overall increase in the risk of salmonellosis.

Atypical Salmonella enterica Serovars in Murine and Human Macrophage Infection Models.

Nontyphoidal Salmonella species are globally disseminated pathogens and are the predominant cause of gastroenteritis. The pathogenesis of salmonellosis has been extensively studied using in vivo murine models and cell lines, typically challenged with Salmonella enterica serovar Typhimurium. Although S. enterica serovars Enteritidis and Typhimurium are responsible for most of the human infections reported to the Centers for Disease Control and Prevention (CDC), several other serovars also contribute to clinical cases of salmonellosis. Despite their epidemiological importance, little is known about their infection phenotypes. Here, we report the virulence characteristics and genomes of 10 atypical S. enterica serovars linked to multistate foodborne outbreaks in the United States. We show that the murine RAW 264.7 macrophage model of infection is unsuitable for inferring human-relevant differences in nontyphoidal Salmonella infections, whereas differentiated human THP-1 macrophages allowed these isolates to be further characterized in a more human-relevant context.

Four European Salmonella Typhimurium datasets collected to develop WGS-based source attribution methods

Zoonotic Salmonella causes millions of human salmonellosis infections worldwide each year. Information about the source of the bacteria guides risk managers on control and preventive strategies. Source attribution is the effort to quantify the number of sporadic human cases of a specific illness to specific sources and animal reservoirs. Source attribution methods for Salmonella have so far been based on traditional wet-lab typing methods. With the change to whole genome sequencing there is a need to develop new methods for source attribution based on sequencing data. Four European datasets collected in Denmark (DK), Germany (DE), the United Kingdom (UK) and France (FR) are presented in this descriptor. The datasets contain sequenced samples of Salmonella Typhimurium and its monophasic variants isolated from human, food, animal and the environment. The objective of the datasets was either to attribute the human salmonellosis cases to animal reservoirs or to investigate contamination of the environment by attributing the environmental isolates to different animal reservoirs.

Consumers's willingness to pay for avoiding Salmonella infection

Salmonellosis is a widely known infectious disease in Hungary that played dominant role between 1960 and 1996 and remained one of the top food-borne illnesses to these days with an estimated total number of 96 048 cases (2019). Beside direct costs of treatment, indirect costs are also significant on the level of population. Among indirect costs, consumer well-being losses are difficult to be estimated. For this purpose, the willingness to pay (WTP) method is used most frequently that measures the cost an individual would undertake to avoid a certain harm. For the well-being loss estimation, the data of National Food Chain Safety Authority's annual consumer survey was used, in which 323 respondents gave evaluable answer to the open-ended WTP question. Results indicate that an average respondent would pay 18.6 EUR to avoid salmonellosis. Main factors affecting WTP were size of family and number of children. The numbers indicate that the consumer well-being loss could be about 1 786 060 EUR annually, resulting from the multiplication of the estimated number of annual salmonellosis cases and the average WTP value. It can be concluded that consumer well-being losses alone would call for further interventions in Salmonella eradication, not to mention other – more direct – cost elements.

Factors associated with Salmonella infection in patients with gastrointestinal complaints seeking health care at Regional Hospital in Southern Highland of Tanzania

BackgroundSalmonellosis remains an important public health problem globally. The disease is among the leading causes of morbidity and mortality in developing countries that experience poor hygiene and lack of access to clean and safe water. There was an increase in reported cases of Salmonellosis in Njombe Region, Southern Highland of Tanzania between 2015 and 2016 based on clinical diagnosis. Nevertheless, little is known about the factors contributing to the transmission of this disease in the region. This study was conducted to determine the prevalence, antimicrobial susceptibility, and factors associated with Salmonella infection among patients who report gastrointestinal complaints.MethodsA cross-sectional study was conducted from December 2017 to February 2018 among patients with gastrointestinal complaints at Kibena Regional Hospital. Stool samples were submitted for isolation of Salmonella spp. Identification was based on conventional biochemical tests and serotyping to differentiate typhoid and non-typhoid Salmonella (NTS). Antimicrobial susceptibility was performed using the Kirby-Bauer disc diffusion method. Multivariable logistic regression analysis was performed to examine the factors independently associated with Salmonella infection.ResultsThe prevalence of Salmonella infection among participants with gastrointestinal complaints was 16.5% (95% CI: 12.7–21.1) of them, 83.7, 95% CI: 70.9–91.5 were NTS while 16.3, 95% CI: 8.5–29.0 were Typhoid Salmonella species.All isolates were sensitive to ceftriaxone and ciprofloxacin, whereas 27.8 and 100% were resistant to co-trimoxazole and ampicillin respectively. The odd of Salmonella infection was fourfold higher among participants with formal employment (AOR 3.8, 95% CI, 1.53–9.40). Use of water from wells/rivers (AOR 2.2, 95% CI, 1.07–4.45), drinking untreated water (AOR 2.6, 95% CI, 1.21–5.48) and often eating at a restaurant (AOR 3.4, 95% CI, 1.28–8.93) had increased odds of Salmonella infection. Likewise, having abdominal pain (AOR 8.5, 95% CI, 1.81–39.78) and diarrhea (AOR 2.3, 95% CI, 1.12–4.68) were independent symptoms that predict Salmonella infection.ConclusionThere is a high prevalence of Salmonella infection among people who report gastrointestinal complaints and it is clinically predicated by diarhoea and abdominal pain. Employed participants and those eating at restaurant and drinking unsafe water had higher risk of infection. Salmonella spp. causing gastroenteritis has developed resistance to commonly used antibiotics.

Outbreak investigation of septicemic salmonellosis in calves.

An early and accurate diagnosis of septicemic salmonellosis is critical for implementing timely and proper treatment, prevention, and control measures. Here, we report a study on three outbreaks of septicemic salmonellosis in calves from Midwestern Brazil. the morbidity, mortality and lethality rates were of 10.55%, 2.79%, and 26.4%, respectively. Higher susceptibility was detected in Bos taurus than in Bos indicus cattle. Clinical manifestations consisted of apathy, hyperthermia, difficulty breathing and panting, and pallor of the mucous membranes. Chronic cases had necrosis of the tail tip and ears. Gross findings included enlarged liver, non-collapsed edematous lungs and diphtheritic enteritis. Significant histopathological changes included paratyphoid nodules in the liver and acute interstitial pneumonia. Salmonella enterica subsp. enterica serotype Dublin was detected by culture and by PCR from the blood of live calves, and from the spleen, liver, bile, mesenteric lymph node and lung samples of necropsied calves. We suggest that in clinical cases of septicemic salmonellosis, blood samples are better than fecal samples for detection of the agent, being a sound test to identify animal carriers in the herd.

ЭПИДЕМИОЛОГИЯ ВСПЫШЕК САЛЬМОНЕЛЛЁЗА В ГРУЗИИ ЗА 2011-2018 гг.

The goal of the research was assessment of spread of salmonellosis in Georgia in 2012-2018. For the purpose of the research, we analyzed the data of confirmed and suspected cases of salmonellosis, obtained from the reports of the NCDC and the National Food Agency of Georgia. The results of the research prove that the analysis of outbreaks of given diseases in Georgia is not enough in most cases of outbreaks; risk factors are not always detected. Without completed data, it is impossible to develop and conduct targeted sanitary and hygienic measures. Our study also confirms that for the population it is necessary to create a guide to hygiene measures when buying, storing, preparing, processing food, since the consumers responsible for safety of food together with their producers at home.

Exposures Associated with Non-Typhoidal Salmonella Infections Caused by Newport, Javiana, and Mississippi Serotypes in Tennessee, 2013-2015: A Case-Case Analysis.

Non-typhoidal Salmonella (NTS) infection (salmonellosis) is one of the most prevalent gastrointestinal diseases throughout the world. Human infections caused by Salmonella Newport, Javiana, and Mississippi serotypes have been observed to occur at higher rates on an annual basis in western Tennessee. The reason for the increased rate of NTS infection by these three serotypes in this region is not known. We conducted a case-case analysis to identify potential risk factors associated with the three Salmonella serotypes using FoodNet data, obtained from the Tennessee Department of Health, consisting of 1578 culture-confirmed salmonellosis cases in Tennessee from 2013 through 2015. Among all the exposure variables tested (254 in total), we found contact with pet treats or chews in the seven days prior to illness was the factor that was significantly associated with these serotypes compared to other serotypes (odds ratio adjusted = 3.0 (95% confidence intervals 1.6, 5.5), P < 0.0005). This study highlights the need for further investigation of potential exposures (other than pet treats or chews), including several possible environmental sources of NTS infection in humans.

Salmonellosis in Saudi Arabia; an underestimated disease?

Salmonellosis is one of the most commonly reported foodborne diseases that affect human health with subsequent economic losses. Salmonellosis is considered a disease with public health burden globally. Efficient surveillance systems for disease monitoring and reporting are important for measuring health burden and planning controlled measures based. In this study, the characterization of salmonellosis in KSA from 2013-2017 is presented. Incidence data were obtained from the Ministry of Health’s (MoH) data for laboratory-confirmed cases. Extracted incidence data were analyzed according to the nationality of the patients (Saudi and non-Saudi), gender (male and female), age, health provinces (20 health provinces throughout KSA), and months. From 2013-2017, there were 5202 (mean; 1040.4) cases of salmonellosis reported. The average incidence rate over 5 years period per 100000 people (A.I.R/5YR) was 3.30. A.I.R/5YR was 3.451 for Saudi patients and 2.995 for non-Saudi patients (p-value: 0.0032). Among males and females, A.I.R/5YR was 3.429 for male and 3.316 for female (p-value; 0.014). Among < 15 and ≥ 15 age groups, A.I.R/5YRs were 6.04 and 2.221 for < 15 and ≥ 15 (p-value: 0.613), respectively. Salmonellosis highest A.I.R/5YR according to health provinces 14.13 in the Eastern province. The highest incidences by months were reported from August to October. In comparison to reported regional and global incidence rates for salmonellosis, reported rates in KSA are likely to be underestimated. In estimating salmonellosis incidence, and in where a country-specific multiplier is not available, it is possible to apply a multiplier of a neighbouring country or of the region to calculate a more accurate disease incidence. Thus, and by re-estimating incidence according to regional and global multipliers, the officially reported incidences of salmonellosis in KSA are likely to be underestimated by 37.6 to 345.36 folds.

Antimicrobial Resistance Patterns of &amp;lt;i&amp;gt;Salmonella&amp;lt;/i&amp;gt; in Ethiopia Since 2009/2010: A Review

<i>Salmonella</i> is one of the major and important foodborne pathogens of humans and animals causing salmonellosis, which have great medical and economical cost. Infections with <i>Salmonella</i> in food-producing animals present a serious public health concern, because food products of animal origin are considered to be a significant source of human infection. Most common sources of infection are eggs and related products, and meat from poultry and other food animal species. Milk and dairy products have also been associated with outbreaks of salmonellosis in people. Studies indicated the widespread occurrence of antimicrobial resistance in Ethiopia. The emergence and persistence of antimicrobial resistance is driven by varied factors including the indiscriminate use of antibiotics and variable drug efficacy and presents a major threat to the control of infectious diseases. In recent years, since the rate at which resistance occurs has outpaced the development of new drug replacements, it has become necessary to use the currently available agents, optimally and appropriately. Therefore, developing strategies in order to minimize the expansion of antimicrobial resistance is critically important. Performing drug susceptibility test for each salmonellosis case and Educating the community about <i>Salmonella</i> transmission is very important. Moreover, collaboration of different stakeholders like the public health, animal health, and animal agriculture communities plays a pivotal role.

Quantitative microbial risk assessment for Salmonella in eggs

The scope of this quantitative risk assessment model is to estimate the number of salmonellosis cases per million servings of table egg, as well as the probability of illness when ingesting a random serving of table egg. The model describes the potential egg contamination bySalmonellaEnteritidis from farm to fork according to time/temperature storage conditions, as well as consumption practices.

The European Union One Health 2018 Zoonoses Report.

This report of the European Food Safety Authority and the European Centre for Disease Prevention and Control presents the results of zoonoses monitoring activities carried out in 2018 in 36 European countries (28 Member States (MS) and 8 non‐MS). The first and second most commonly reported zoonoses in humans were campylobacteriosis and salmonellosis, respectively. The European Union (EU) trend for confirmed human cases of these two diseases was stable during 2014–2018. The proportion of human salmonellosis cases due to Salmonella Enteritidis was at the same level in 2018 as in 2017. Of the 27 reporting MS, 16 met all Salmonella reduction targets for poultry, whereas 11 MS failed meeting at least one. The EU flock prevalence of target Salmonella serovars in breeding hens, laying hens, broilers and fattening turkeys decreased during recent years but stalled in breeding turkeys. Salmonella results from Competent Authorities for pig carcasses and for poultry tested through National Control Programmes were more frequently positive compared with food business operators. Shiga toxin‐producing Escherichia coli (STEC) infections in humans were the third most commonly reported zoonosis in the EU and increased from 2014 to 2018. Yersiniosis was the fourth most frequently reported zoonosis in humans in 2018 with a stable trend in 2014–2018. The number of reported confirmed listeriosis cases further increased in 2018, despite Listeria rarely exceeding the EU food safety limit tested in ready‐to‐eat food. In total, 5,146 food‐ and waterborne outbreaks were reported. Salmonella was the most commonly detected agent with S. Enteritidis causing one in five outbreaks. Salmonella in eggs and egg products was the highest risk agent/food pair. A large increase of human West Nile virus infections was reported in 2018. The report further updates on bovine tuberculosis, Brucella, Trichinella, Echinococcus, Toxoplasma, rabies, Coxiella burnetii (Q fever) and tularaemia.

Relationship Between Census Tract-Level Poverty and Domestically Acquired Salmonella Incidence: Analysis of Foodborne Diseases Active Surveillance Network Data, 2010-2016.

The relationships between socioeconomic status and domestically acquired salmonellosis and leading Salmonella serotypes are poorly understood. We analyzed surveillance data from laboratory-confirmed cases of salmonellosis from 2010-2016 for all 10 Foodborne Disease Active Surveillance Network (FoodNet) sites, having a catchment population of 47.9 million. Case residential data were geocoded, linked to census tract poverty level, and then categorized into 4 groups according to census tract poverty level. After excluding those reporting international travel before illness onset, age-specific and age-adjusted salmonellosis incidence rates were calculated for each census tract poverty level, overall and for each of the 10 leading serotypes. Of 52 821geocodable Salmonella infections (>96%), 48 111 (91.1%) were domestically acquired. Higher age-adjusted incidence occurred with higher census tract poverty level (P < .001; relative risk for highest [≥20%] vs lowest [<5%] census tract poverty level, 1.37). Children <5 years old had the highest relative risk (2.07). Although this relationship was consistent by race/ethnicity and by serotype, it was not present in 5 FoodNet sites or among those aged 18-49 years. Children and older adults living in higher-poverty census tracts have had a higher incidence of domestically acquired salmonellosis. There is a need to understand socioeconomic status differences for risk factors for domestically acquired salmonellosis by age group and FoodNet site to help focus prevention efforts.

Changing epidemiology of invasive non-typhoid Salmonella infection: a nationwide population-based registry study

ObjectivesNon-typhoid Salmonella (NTS) may invade beyond the intestine, causing bacteraemia, sepsis, and infection of normally sterile sites. The epidemiology of invasive NTS (iNTS) infection is under-researched. We determined trends, risk factors, serotype distribution, antimicrobial resistance (AMR), and attributable sources of iNTS infection in a high-income setting. Methods22,837 records of culture-confirmed human salmonellosis cases and 10,008 serotyped Salmonella isolates from five putative animal reservoirs (pigs, cattle, broilers, layers, reptiles) in the Netherlands during 2005–2018 were retrieved from national surveillance registries. Risk factors for iNTS infection were identified using logistic regression analysis. Source attribution modelling was based on serotyping, prevalence, and exposure data. ResultsThe average annual percentage of iNTS infections was 4.6% (range 3.5–5.7%). An increase in iNTS infections was observed since 2012 (odds ratio (OR) 1.09, 95% confidence interval (95% CI) 1.04–1.14). Increased iNTS infection risk was associated with wintertime (OR 1.37, 95% CI 1.12–1.66), male sex (OR 1.73, 95% CI 1.51–1.99), older age (ORs: 3.27 to 16.33, depending on age groups), and living in rural areas (OR 1.54, 95% CI 1.23–1.93). While 52% of iNTS infections (n = 950) were caused by serotypes Enteritidis and Typhimurium, those displaying the highest invasiveness relative to their occurrence were Dublin (32.9%, n = 163), Panama (21.6%, n = 106), and Poona (14.1%, n = 71). Cattle were a larger source of iNTS than non-iNTS infections (12.2% vs. 7.6%). Lower AMR and multi-resistance rates were observed among iNTS (37.9%) than non-iNTS isolates (48.6%). DiscussionThe increase in iNTS infections, which is reported also in other countries, is of public health and clinical concern. The underlying reasons seem to be multi-factorial in nature. iNTS infection risk depends more on the infecting serotypes and patient demographics, and less on the attributable reservoirs and AMR profiles.

WGS based study of the population structure of Salmonella enterica serovar Infantis

BackgroundSalmonella Infantis (S. Infantis) is one of the most frequent Salmonella serovars isolated from human cases of salmonellosis and the most detected serovar from animal and food sources in Europe. The serovar is commonly associated with poultry and there is increasing concern over multidrug resistant clones spreading worldwide, as the dominating clones are characterized by presence of large plasmids carrying multiple resistance genes. Increasing the knowledge of the S. Infantis population and evolution is important for understanding and preventing further spread.In this study, we analysed a collection of strains representing different decades, sources and geographic locations. We analysed the population structure and the accessory genome, in particular we identified prophages with a view to understand the role of prophages in relation to the evolution of this serovar.ResultsWe sequenced a global collection of 100 S. Infantis strains. A core-genome SNP analysis separated five strains in e-Burst Group (eBG) 297 with a long branch. The remaining strains, all in eBG31, were divided into three lineages that were estimated to have separated approximately 150 years ago. One lineage contained the vast majority of strains. In five of six clusters, no obvious correlation with source or geographical locations was seen. However, one cluster contained mostly strains from human and avian sources, indicating a clone with preference for these sources. The majority of strains within this cluster harboured a pESI-like plasmid with multiple resistance genes. Another lineage contained three genetic clusters with more rarely isolated strains of mainly animal origin, possibly less sampled or less infectious clones.Conserved prophages were identified in all strains, likely representing bacteriophages which integrated into the chromosome of a common ancestor to S. Infantis. We also saw that some prophages were specific to clusters and were probably introduced when the clusters were formed.ConclusionsThis study analysed a global S. Infantis population and described its genetic structure. We hypothesize that the population has evolved in three separate lineages, with one more successfully emerging lineage. We furthermore detected conserved prophages present in the entire population and cluster specific prophages, which probably shaped the population structure.

METHODICAL ASPECTS OF ANTIMICROBIAL SUSCEPTIBILITY TESTING OF SALMONELLA (REVIEW OF LITERATURE)

Salmonella is one of the leading food-borne infection pathogen: annually in the Russian Federation about 50 thousand cases of salmonellosis are registered. Antimicrobial therapy is necessary in the case of severe infection in children under 6 years and persons over 50 years, in patients with severe accompanying disease, as well as in the case of generalization of the infection. Beta-lactam antibiotics, quinolones and azithromycin are included in the list of drugs recommended for antimicrobial therapy of salmonellosis, including typhoid fever. The effectiveness of therapy largely depends on the appropriate antimicrobial susceptibility testing: the choice of testing method, indicator antibiotics and result interpretation. Salmonella belong to the Enterobacteriacae family and are characterized by common mechanisms of resistance to quinolones and beta-lactams, but antimicrobial susceptibility testing of Salmonella to these groups of antibiotics has a number of features. The article presents current data on the susceptibility of Salmonella, including S. Typhi, to antibiotics and leading clinically significant resistance mechanisms. The methodical aspects of Salmonella antimicrobial susceptibility testing of the drugs used for the treatment of salmonellosis (quinolones, beta-lactams and azithromycin) are described in detail. Interpretation of Salmonella testing results according the modern international and Russian recommendations are presented. The authors propose the algorithms for Salmonella antimicrobial susceptibility testing of quinolones, cephalosporins and carbapenems, as well as criteria for result interpretation, allowing the detection of clinically significant mechanisms of resistance to beta-lactams (production of beta-lactamases of different molecular classes) and quinolones (chromosomal mutations and acquired resistance genes).