Characterization of virulence factors of Salmonella isolated from human stools and street food in urban areas of Burkina Faso.

BACKGROUND: This study was undertaken to identify and functionally characterize virulence genes from Salmonella isolates in street food and stool cultures. From February 2017 to May 2018, clinical and food Salmonella strains were isolated in three regions in Burkina Faso. Salmonella was serotyped according to the White-Kauffmann-Le Minor method, and polymerase chain reaction (PCR) was used to detec invA, spvR, spvC, fimA and stn virulence genes commonly associated with salmonellosis in Sub-Saharan Africa. RESULTS: A total of 106 Salmonella isolates (77 human stools; 14 sandwiches) was analyzed using a serological identification with an O-group test reagent. The presence of Salmonella was confirmed in 86% (91/106) of the samples were reactive (OMA-positive/OMB-positive). Salmonella serogroup O:4,5 was the most common serogroup detected (40%; 36/91). Salmonella Enteritidis and Typhimurium represented 5.5% (5/91) and 3.3% (3/91), respectively and were identified only from clinical isolates. Furthermore, 14 serotypes of Salmonella (12/91 human strains and 2/15 sandwich strains) were evocative of Kentucky/Bargny serotype. For the genetic profile, 66% (70/106) of the Salmonella had invA and stn genes; 77.4% (82/106) had the fimA gene. The spvR gene was found in 36.8% (39/106) of the isolates while 48.1% (51/106) had the spvC gene. Among the identified Salmonella Enteritidis and Salmonella Typhimurium isolated from stools, the virulence genes detected were invA (3/5) versus (2/3), fimA (4/5) versus (3/3), stn (3/5) versus (2/3), spvR (4/5) versus (2/3) and spvC (3/5) versus (2/3), respectively. CONCLUSION: This study reports the prevalence of Salmonella serotypes and virulence genes in clinical isolates and in street foods. It shows that food could be a significant source of Salmonella transmission to humans. Our results could help decision-making by the Burkina Faso health authority in the fight against street food-related diseases, in particular by training restaurateurs in food hygiene.

[Analysis on epidemiological characteristics of multidrug-resistant Salmonella Kentucky in Beijing, 2010-2020].

Objective: To investigate the epidemiological, drug resistance and molecular characteristics of Salmonella (S.) Kentucky strains isolated from diarrheal patients in Beijing. Methods: The drug susceptibility of 22 S. Kentucky strains isolated in Beijing during 2010-2020 was tested by using the micro broth dilution method. The multilocus sequence typing (MLST), drug resistance genes and Salmonella genomic island (SGI) identifications of the strains were performed by whole-genome sequencing (WGS).The pulsed field gel electrophoresis (PFGE) was performed to analyze the molecular epidemiological characteristics of the isolates. Results: The 22 strains were highly resistant to 8-22 kinds of antibiotics, especially to ciprofloxacin, cephalosporins and azithromycin, etc., showing a super high level of multidrug resistance and 21 strains were positive for extended-spetrum beta-lactamase (ESBL). The WGS analysis revealed that all the isolates belonged to ST198, carrying SGI1-K. The drug resistance genes tetA, sul1 and qacE were identified in all strains and Quinolone resistance-determining regions (QRDRs) showed 2 mutations in gyrA (S83F, D87 N) and 3 mutations in the parC gene (T57S, S80I, T255S). The resistance genes associated with ß-lactam antibiotics (blaCTX-M-55, blaCTX-M-14b, blaTEM-141, blaTEM-206, blaTEM-209, blaTEM-214, blaTEM-1B), resistance genes associated with aminoglycosides [aac(3)-Id, aac(3)-IId, aac(6')-Iaa, aadA7, aadA17, aph(3')-Ia, aph(3'')-Ib, aph(6)-Id,rmtB] as well as floR, dfrA14, mphA and qnrS1 had significant differences in the strains of different years, which were highly consistent with the drug-resistant phenotype. Furthermore, phylogenetic analysis showed that the similarity of the 22 strains was more than 85%, and the strains were highly homologous to CIP-resistant ST198-X1 circulating in the world. In the process of spread, the drug resistance and PFGE spectrums had changed, two clusters had formed. Conclusions: The S. Kentucky strains isolated in Beijing shared high homology with the multidrug-resistant strain ST198-X1-SGI-1K isolated in the world, which has maintained a low level of spread since 2016, causing sporadic infections and clusters of diarrhea, and has serious resistances to fluoroquinolones, ESBLs and azithromycin. The surveillance for multidrug-resistant S. Kentucky should be strengthened.

A systemic review of literatures on human Salmonella enterica serovars in Nigeria (1999-2018).

INTRODUCTION: Salmonella infections are endemic in Nigeria. There is lack of reliable data on culture-positive Salmonella with national coverage. This systemic review of literatures was undertaken to aggregate data on culture proven cases of human Salmonellae and to determine the prevailing serotypes for disease burden estimations. METHODOLOGY: This involved comprehensive search engines of Pubmed, Google Scholar, Google and Embase for the literatures on culture positive human Salmonellae from 1999-2018. This review documented the prevalence, common Salmonella serotypes. antibiotic resistance and risk factors associated with human Salmonella infections. RESULTS: This study revealed that 21out of 36 States in Nigeria reported Salmonella-associated diseases, spanning the six geopolitical zones. Our study revealed prevalence of 1.9% (2,732/143,756) Salmonella-bacteraemia and 16.3% (1,967/12,081) Salmonella-associated gastroenteritis. Fifty-three 53 Salmonella serotypes were identified. 39 serotypes were associated with Salmonella-bacteraemia and 31 serotypes with Salmonella-gastroenteritis. Salmonella typhi remains the commonest serotype accounting for 85.2% for Salmonella-bacteraemia and 73.1% Salmonella-gastroenteritis. S. typhimurium (3.8%) was mostly implicated invasive non-typhoidal serotype followed S. enteritidis (2.8%) among others. Human Immunodeficiency Virus-infected individuals, malnutrition was among factors predisposing Salmonella infections. Over 60% of the reported Salmonella isolates developed resistance to two or more of 23 antibiotics recorded, mostly ampicillin, cotrimoxazole, tetracycline and amoxicillin. CONCLUSIONS: This study revealed 39 Invasive and 31 non-invasive Salmonella serotypes. Ampicillin, cotrimoxazole, amoxicillin-clavulanate and tetracycline are the most frequently reported antibiotics resisted by Salmonella isolates. This antimicrobial resistance exhibited poses a threat to public health. Data generated from this review would serve as a baseline information for future surveillance studies.

Epidemiological Analysis of Salmonella enterica subsp. enterica Serovar Dublin in German Cattle Herds Using Whole-Genome Sequencing.

Salmonella enterica subsp. enterica serovar Dublin is a cattle-adapted serovar that causes enteritis and systemic diseases in animals. In Germany, S. Dublin is not detected or is very rarely detected in some federal states but is endemic in certain regions. Information on detailed genetic characteristics of S. Dublin is not available. An understanding of the paths and spreading of S. Dublin within and between regions and over time is essential to establish effective control strategies. Whole-genome sequencing (WGS) and bioinformatic analysis were used to explore the genetic traits of S. Dublin and to determine their epidemiological context. Seventy-four S. Dublin strains collected in 2005 to 2018 from 10 federal states were studied. The phylogeny was analyzed using core-genome single-nucleotide polymorphisms (cgSNPs) and core-genome multilocus sequence typing. Genomic clusters at 100 cgSNPs, 40 cgSNPs, and 15 cgSNPs were selected for molecular epidemiology. WGS-based genoserotyping confirmed serotyping. Important specific virulence determinants were detected in all strains, but multidrug resistance in German S. Dublin organisms is uncommon. Use of different thresholds for cgSNP analysis enabled a broad view and also a detailed view of the occurrence of S. Dublin in Germany. Genomic clusters could be allocated nationwide, to a limited number of federal states, or to special regions only. Results indicate both persistence and spread of S. Dublin within and between federal states in short and longer time periods. However, to detect possible routes of infection or persistence of S. Dublin indicated by genomic analysis, information on the management of the cattle farms and contacts with corresponding farms are essential. IMPORTANCE Salmonella enterica subsp. enterica serovar Dublin is a bovine host-adapted serovar that causes up to 50% of all registered outbreaks of salmonellosis in cattle in Germany. S. Dublin is not detected or is only rarely detected in some federal states but has been endemic in certain regions of the country for a long time. Information on genetic traits of the causative strains is essential to determine routes of infection. WGS and bioinformatic analysis should be used to explore the genetic characteristics of S. Dublin. Combining the genomic features of S. Dublin strains with information on the management of the cattle farms concerned should enable the detection of possible routes of infection or persistence of S. Dublin. This approach is regarded as a prerequisite to developing effective intervention strategies.

Prevalence, typing and antimicrobial resistance of Salmonella isolates from commercial shellfish in the North coast of Morocco.

Salmonellosis is one of the most common foodborne illnesses in the world. The irrational use of antibiotics in medicine and in animal nutrition has greatly favored the emergence and spread of resistant strains of non-typhoid Salmonella. This study aims the determination of the prevalence of Salmonella in bivalve mollusks in Northern Morocco, as well as the molecular typing and antibiotic susceptibility testing of the strains isolated from positive samples. In total, 150 samples from shellfish composed of mussels (Mytilus galloprovincialis), clams (Callista chione and Ruditapes descussatus) and oysters (Magallana gigas). Isolated Salmonella were characterized by Molecular techniques PCR, MLST and MLVA, phylogenetically grouped by MLSA, and susceptibilities were determined for 30 antimicrobial drugs using microdilution method by the BD Phoenix Automated Microbiology System. Prevalence of Salmonella enterica subsp. enterica was 12.67%, grouped in four serovars identified as Chester, Hadar, Typhimurium and Kentucky. Five different MLST STs (sequence types) were detected, ST1954 being the most common, which was mostly found in Chester isolates. Forty-two percent of the isolates showed resistance to more than one antibiotic, especially trimethoprim, sulfa drugs, quinolones and ß-lactam. There was a marked change in the serovars and antimicrobial resistance profiles of the Salmonella isolates in this study compared to those in previous studies.

Genome-wide analysis provides a deeper understanding of the population structure of the Salmonella enterica serotype Paratyphi B complex in Bangladesh.

The Salmonella enterica serotype Paratyphi B complex causes a wide range of diseases, from gastroenteritis to paratyphoid fever, depending on the biotypes Java and sensu stricto. The burden of Paratyphi B biotypes in Bangladesh is still unknown, as these are indistinguishable by Salmonella serotyping. Here, we conducted the first whole-genome sequencing (WGS) study on 79 Salmonella isolates serotyped as Paratyphi B that were collected from 10 nationwide enteric disease surveillance sites in Bangladesh. Placing these in a global genetic context revealed that these are biotype Java, and the addition of these genomes expanded the previously described PG4 clade containing Bangladeshi and UK isolates. Importantly, antimicrobial resistance (AMR) genes were scarce amongst Bangladeshi S. Java isolates, somewhat surprisingly given the widespread availability of antibiotics without prescription. This genomic information provides important insights into the significance of S. Paratyphi B biotypes in enteric disease and their implications for public health.

Pullorum Disease: Evolution of the Eradication Strategy.

The history of pullorum disease is closely intertwined with the history of avian health research and that of the poultry industry. The seriousness of the disease galvanized the attention and brought together, for the first time, the pioneers of poultry health research to work cooperatively on different aspects of the disease. Control of the disease made it possible for intensive poultry production to develop as the basis for the modern poultry industry. During the early 1900s, bacillary white diarrhea (BWD) was a devastating disease of young chickens threatening the developing poultry industry. Dr. Leo F. Rettger isolated and described the bacterial pathogen, Salmonella enterica serotype Pullorum, for the first time in 1900. BWD was renamed pullorum disease in 1929. In subsequent years, Rettger and coworkers were able to reproduce the disease and fulfill Koch's postulates. Rettger et al. also showed that Salmonella Pullorum was vertically transmitted, which was the first time that a pathogen was shown to be vertically transmitted. The development of serologic tests was of crucial importance because it led to the development of effective eradication methods to identify carrier birds and to exclude these birds from the breeder flocks. The negative impact of pullorum disease on the poultry industry ultimately was one of the major reasons that the National Poultry Improvement Plan (NPIP) was developed by scientists, the poultry industry, and the United States Department of Agriculture (USDA). Needless to say, the work of the pioneering researchers formed the basis for the control of the disease. The NPIP started in 1935, with 34 states participating in testing 4 million birds representing 58.2% of the birds hatched. The program rapidly expanded to 47 states by 1948 and tested more than 30 million birds. In 1967, all commercial chicken hatcheries participating in the NPIP were 100% free of pullorum and typhoid disease caused by Salmonella enterica serotype Gallinarum. This historical overview of pullorum disease describes in some detail the progress made, especially during the early years, toward controlling this disease using methodologies that were often very basic but nonetheless effective. One has to admire the ingenuity and persistence of the early researchers leading to their achievements considering the research tools that were available at the time.

Artículo histórico­Pulorosis: Evolución de las estrategias de erradicación La historia de la pulorosis está estrechamente relacionada con la historia de la investigación en salud aviar y de la industria avícola. La severidad de la enfermedad despertó la atención y reunió, por primera vez a los pioneros de la investigación en salud avícola para trabajar de manera cooperativa en diferentes aspectos de la enfermedad. El control de la enfermedad hizo posible que la producción avícola intensiva se desarrollara como base de la industria avícola moderna. A principios de la década de los 1900, la diarrea blanca bacilar (con las siglas en inglés BWD) era una enfermedad devastadora de pollos jóvenes que amenazaba la industria avícola en desarrollo. El Dr. Leo F. Rettger aisló y describió el patógeno bacteriano, Salmonella enterica serotipo Pullorum, por primera vez en 1900. La diarrea blanca bacilar pasó a llamarse pulorosis (pullorum disease) en 1929. En los años siguientes, Rettger y sus colaboradores pudieron reproducir la enfermedad y cumplir los postulados de Koch. Rettger y col. también mostraron que Salmonella Pullorum se transmitía verticalmente, y fue la primera vez que se demostró que un patógeno se transmitía verticalmente. El desarrollo de pruebas serológicas fue de crucial importancia porque condujo al desarrollo de métodos de erradicación efectivos para identificar aves portadoras y eliminar a estas aves de las parvadas reproductoras. El impacto negativo de la pulorosis en la industria avícola fue, en última instancia, una de las principales razones por las que los científicos, la industria avícola y el Departamento de Agricultura de los Estados Unidos (USDA) desarrollaron el Plan Nacional de Mejoramiento Avícola (NPIP). Es importante decir que el trabajo de los investigadores pioneros formó la base para el control de la enfermedad. El Plan Nacional de Mejoramiento Avícola comenzó en año 1935, con 34 estados participando en el análisis de 4 millones de aves que representaban el 58.2% de las aves producidas. El programa se expandió rápidamente a 47 estados en 1948 y evaluó a más de 30 millones de aves. En 1967, todas las plantas incubadoras de pollos comerciales que participaban en el Plan Nacional de Mejoramiento Avícola estaban 100% libres de pulorosis y tifoidea aviar causada por Salmonella enterica serotipo Gallinarum. Esta reseña histórica de la pulorosis describe con cierto detalle el progreso realizado, especialmente durante los primeros años, hacia el control de esta enfermedad utilizando metodologías que a menudo eran muy básicas no obstante efectivas. Es admirable el ingenio y la persistencia de los primeros investigadores que los llevaron a sus logros considerando las herramientas de investigación que estaban disponibles en ese momento.

Multilocus sequence typing of multidrug-resistant Salmonella strains circulating in poultry farms of Bangladesh.

Salmonella is one of the most important foodborne zoonotic pathogens, and becoming multidrug-resistant (MDR), which represents a serious public health concern worldwide. This study aimed to identify the circulating MDR strains of Salmonella through cutting edge molecular techniques including gene specific PCR, RAPD-PCR, ribosomal gene sequencing, and multilocus sequence types (MLST) in the poultry industry of Bangladesh. Two hundred Salmonella isolates were retrieved from 154 samples comprising droppings (n = 60), cloacal swabs (n = 60), feeds (n = 14), feeding water (n = 14), and handler's swab (n = 6) from 14 commercial layer farms of Bangladesh. The isolates were confirmed as Salmonella through invA gene specific PCR, and further genotyping was done by RAPD-PCR, and 16S rRNA sequencing. The isolates were distributed into 18 different genotypes according to RAPD typing. The phylogenetic analysis identified three diverging phylogroups such as S. enterica Litchfield, S. enterica Enteritidis and S. enterica Kentucky with 11, 8, and 6 strains, respectively. The in vitro antibiogram profiling the Salmonella isolates through disc diffusion method using 13 commercially available antibiotics revealed highest resistance against doxycycline (91.5%) followed by tetracycline and ampicillin (86.0%, in each), and 72.0% isolates as MDR, being resistant to ≥ 5 antibiotics. The MLST typing was carried out based on the PCR amplification of seven housekeeping genes (aroC, hisD, hemD, purE, secA, thrA, and dnaN). MLST typing also revealed three sequence types (STs) such as ST11, ST198, and ST214 in these isolates, and eBURST analysis showed ST11 as the founder genotype. The three STs were highly resistant to tetracyclines and quinolone group of antibiotics, and all of the isolates harboring S. enterica Litchfield showed the highest resistance. Circulating common MLSTs with MDR properties in different farms confirmed the possibility of a common route of intra-farm transmission. We report for the first time of the association serovar Litchfield (ST11) in avian salmonellosis with MDR properties which is an urgent public health concern in Bangladesh.

Multilocus sequence typing analysis and second-generation sequencing analysis of Salmonella Wandsworth.

BACKGROUND: Salmonella Wandsworth is a rare serotype of Salmonella. This study analyzed the genotyping, genome structure, and molecular biological functions of Salmonella Wandsworth based on the results of multilocus sequence typing and next-generation sequencing genome assembly analysis. METHODS: Serological typing was performed using the slide-agglutination method. The micro broth dilution method was used to test antibiotic susceptibility. Multilocus sequence typing (MLST) was used to perform the homology analysis, while the second-generation sequencing genome analysis was used to analyze the whole genome of the bacteria. RESULTS: Salmonella Wandsworth is Group Q Salmonella. The MLST of this strain was ST1498. Salmonella Wandsworth was sensitive to antibiotics, such as ceftriaxone, imipenem, chloramphenicol, and colistin, but was resistant to ampicillin, cefalotin, gentamicin, and ciprofloxacin. The second-generation sequencing results showed that the genome sequence length of the bacteria was 5109457bp. Annotated COG library analysis generated 3,746 corresponding genes. After the comparison with the KEGG library, 1,340 genes, which participate in 19 types of metabolic pathways, were obtained. A total of 249 pathogenic factors and 2 disease islands were predicted. 2 CRISPR sites and 8 Cas sites were predicted. It can be seen from the evolutionary tree that Salmonella Wandsworth MLST1498 and Paratyphi B str.SPB7 are gathered together. We identified one resistance gene, namely, aac(6')-Iaa accounting for aminoglycoside resistance. CONCLUSION: Salmonella Wandsworth isolated in this study is Salmonella group Q. Consequently, it is necessary to strengthen the understanding of clinical infections of Salmonella Wandsworth and carry out continuous monitoring and research.

Investigation of Salmonella Phage-Bacteria Infection Profiles: Network Structure Reveals a Gradient of Target-Range from Generalist to Specialist Phage Clones in Nested Subsets.

Bacteriophages that lyse Salmonella enterica are potential tools to target and control Salmonella infections. Investigating the host range of Salmonella phages is a key to understand their impact on bacterial ecology, coevolution and inform their use in intervention strategies. Virus-host infection networks have been used to characterize the "predator-prey" interactions between phages and bacteria and provide insights into host range and specificity. Here, we characterize the target-range and infection profiles of 13 Salmonella phage clones against a diverse set of 141 Salmonella strains. The environmental source and taxonomy contributed to the observed infection profiles, and genetically proximal phages shared similar infection profiles. Using in vitro infection data, we analyzed the structure of the Salmonella phage-bacteria infection network. The network has a non-random nested organization and weak modularity suggesting a gradient of target-range from generalist to specialist species with nested subsets, which are also observed within and across the different phage infection profile groups. Our results have implications for our understanding of the coevolutionary mechanisms shaping the ecological interactions between Salmonella phages and their bacterial hosts and can inform strategies for targeting Salmonella enterica with specific phage preparations.

Characterization of Salmonella serotypes prevalent in asymptomatic people and patients.

BACKGROUND: Infection with Salmonella enterica usually results in diarrhea, fever, and abdominal cramps, but some people become asymptomatic or chronic carrier as a source of infection for others. This study aimed to analyze the difference in serotype, antimicrobial resistance, and genetic profiles between Salmonella strains isolated from patients and those from asymptomatic people in Nantong city, China. METHODS: A total of 88 Salmonella strains were collected from patients and asymptomatic people from 2017 to 2018. Serotyping, antimicrobial susceptibility testing, and PFGE analysis were performed to analyze the characteristics of these strains. RESULTS: Twenty serotypes belonging to 8 serogroups were identified in the 88 Salmonella strains. S. Typhimurium remained to be the predominant serotype in strains from both patients and asymptomatic people. Among the 27 strains from patients, S. Enteritidis and S. Rissen were shown as the other two major serotypes, while S. London, S. Derby, and S. Meleagridis were demonstrated as the other significant serotypes among the 61 strains from asymptomatic people. Antimicrobial resistance testing revealed that 84.1% of strains from both resources were multi-drug resistant. PFGE displayed a highly discriminative ability to differentiate strains belonging to S. Derby, S. Typhimurium, etc., but could not efficiently differentiate serotypes like S. Enteritidis. CONCLUSIONS: This study's results demonstrated that S. Typhimurium could cause human infection in both symptomatic and asymptomatic state; S. London, S. Derby, and S. Meleagridis usually cause asymptomatic infection, while S. Enteritidis infection mainly results in human diseases. The high multi-drug resistance rate detected in the antimicrobial resistance and diverse PFGE profiles of these strains implied that the strains were isolated from different sources, and the increased surveillance of Salmonella from both patients and asymptomatic people should be taken to control the disease.

Prevalence and Characteristics of Salmonella spp. from a Pig Farm in Shanghai, China.

Salmonella spp. is a major foodborne pathogen that is distributed among most pork production chains worldwide. This study aimed to investigate the dynamic changes in Salmonella spp. along the pig breeding process monthly from April 2018 to March 2019 in a pig farm in Shanghai, China, and identify the potential critical control points during the production. In total, 239 Salmonella spp. isolates were obtained from 1389 samples, in which Salmonella were detected from 26.3% (222/843) of fecal samples, 7.1% (17/240) of feed samples, and 0.0% (0/306) of both water and insect samples. Seven different serotypes were identified, with the predominant serotype being Salmonella Derby (21.8%), followed by Salmonella Typhimurium (18.8%), Salmonella Rissen (16.3%), Salmonella Mbandaka (12.6%), and Salmonella 1,4,[5],12:i:- (11.8%). Most probable number (MPN) analysis revealed that the load of Salmonella spp. gradually increased along the pig production chain, while the highest number of Salmonella spp. isolates was at the fattening stage (MPN value, 11-15 MPN/g). The pulsed-field gel electrophoresis showed that both Salmonella Typhimurium and Salmonella Derby isolates were grouped to six clusters. The antimicrobial resistance analyzed demonstrated that 80.0% of the isolates were of multidrug resistance and resistant to sulfamethoxazole (84.5%), lincomycin (89.4%), ampicillin (96.9%), oxytetracycline (93.8%), and tetracycline (95.1%). We further evaluated the Salmonella spp. Resistance to quaternary ammonium compounds (QACs) showed an increasing trend along with the testing period indicating that the use of QACs could induce the resistance of Salmonella spp. to QACs. Our study confirmed the dynamic changes in Salmonella spp. over time and space in this pig farm and identified feed and the fattening house as the key points for the prevention and control of Salmonella spp. contamination.

Development and evaluation of an outbreak surveillance system integrating whole genome sequencing data for non-typhoidal Salmonella in London and South East of England, 2016-17.

An outbreak surveillance system for Salmonella integrating whole genome sequencing (WGS) and epidemiological data was developed in South East and London in 2016-17 to assess local WGS clusters for triage and investigation. Cases genetically linked within a 5 single-nucleotide polymorphism (SNP) single linkage cluster were assessed using a set of locally agreed thresholds based on time, person and place, for reporting to local health protection teams (HPTs). Between September 2016 and September 2017, 230 unique 5-SNP clusters (442 weekly reports) of non-typhoidal Salmonella 5-SNP WGS clusters were identified, of which 208 unique 5-SNP clusters (316 weekly reports) were not reported to the HPTs. In the remaining 22 unique clusters (126 weekly clusters) reported to HPTs, nine were known active outbreak investigations, seven were below locally agreed thresholds and six exceeded local thresholds. A common source or vehicle was identified in four of six clusters that exceeded locally agreed thresholds. This work demonstrates that a threshold-based surveillance system, taking into account time, place and genetic relatedness, is feasible and effective in directing the use of local public health resources for risk assessment and investigation of non-typhoidal Salmonella clusters.

Infection dynamics of Salmonella Infantis strains displaying different genetic backgrounds - with or without pESI-like plasmid - vary considerably.

Food-borne infections with Salmonella are among the most common causes of human diseases worldwide, and infections with the serovar Infantis are becoming increasingly important. So far, diverse phenotypes and genotypes of S. Infantis have been reported. Therefore, the present study aimed to investigate the infection dynamics of two different S. Infantis strains in broilers. For this purpose, 15 birds were infected on day 2 of life with 108 CFU/ml of a pESI+ or a pESI- S. Infantis strain, respectively. Ten uninfected birds served as in-contact birds to monitor transmission. In both groups, an increase of infection was observed from 7 days of age onwards, reaching its peak at 28 days. However, the pESI+ strain proved significantly more virulent being re-isolated from most cloacal swabs and organs by direct plating. In contrast, the pESI- strain could be re-isolated from cloacal swabs and caeca only when enrichment was applied. Although the excretion of this strain was limited, the transmission level to in-contact birds was similar to the pESI+ strain. Differences in infection dynamics were also reflected in the antibody response: whereas the pESI+ strain provoked a significant increase in antibodies, antibody levels following infection with the pESI- strain remained in the range of negative control birds. The actual findings provide for the first time evidence of S. Infantis strain-specific infectivity in broilers and confirm previous observations in the field regarding differences in persistence on farms and resistance against disinfectants.

Salmonella spp. profiles isolated from seabird samples from the Brazilian coast.

In view of growing concerns, in a One Health context, regarding the transport and dissemination of pathogenic microorganisms among seabirds and other vertebrate animals, including humans, the aim of this study was to identify Salmonella spp. in stranded and non-stranded resident and migratory wild seabirds from the Brazilian coast. Antimicrobial susceptibility and molecular profiles, quinolone resistance genes and antigenic characterization of the isolates were also carried out. Fresh faeces and cloacal swabs were obtained totaling 122 seabirds sampled throughout different Brazilian coast regions. At the laboratory, sample culturing, Salmonella spp. isolation and biochemical identification were performed, followed by antigenic profile identification by serum agglutination, susceptibility profile characterization by the agar disc diffusion technique, detection of quinolone resistance genes (qnrA, qnrB, qnrS) using the multiplex polymerase chain reaction technique (multiplex PCR) and, finally, isolates profiles identification by pulsed field gel electrophoresis (PFGE). Salmonella enterica subsp. enterica was identified in 7% of the studied birds, comprising three different serovars: Panama (63 %), Typhimurium (25 %) and Newport (13 %). The most important findings reported herein are the first description of Salmonella panama in seabirds and the totality of isolates being resistant (or intermediate) to at least one tested antimicrobial, with emphasis on quinolone resistance. The molecular results suggest that the observed resistance cannot be explained by the presence of plasmid-mediated quinolone resistance genes. The PFGE suggests that the Panama and Newport profiles detected herein are not yet widespread in Brazil, unlike Typhimurium, which is already well distributed throughout the country. Considering this finding, we suggest that seabirds are an important link in the epidemiological chain of this serovar. The monitoring of these bacteria in seabirds, as well as of their susceptibility profiles to antimicrobials, must be continuous, strengthening the role of these animals as environmental health indicators and sentinels.

Leafy greens as a potential source of multidrug-resistant diarrhoeagenic Escherichia coli and Salmonella.

A continued rise in leafy green-linked outbreaks of disease caused by pathogenic Escherichia coli or Salmonella, particularly strains exhibiting multidrug resistance (MDR), has emerged as a major threat to human health and food safety worldwide. Thus, the present study was conducted to examine antimicrobial resistance, including MDR, in diarrhoeagenic E. coli (DEC) and Salmonella isolates obtained from leafy greens from rural and urban areas of India. Of the collected samples (830), 14.1 and 6.5% yielded 117 E. coli (40 DEC and 77 non-DEC) and 54 Salmonella isolates, respectively. Among the DEC pathotypes, enteroaggregative E. coli was the most prevalent (10.2 %), followed by enteropathogenic E. coli (9.4 %), enteroinvasive E. coli (7.6 %) and enterohemorrhagic E. coli (6.8 %). Antimicrobial susceptibility testing of all bacterial isolates with respect to drugs categorized as critically or highly important in both human and veterinary medicine revealed moderate to high (30-90%) resistance for amoxicillin/clavulanic acid, ampicillin, gentamycin and colistin, but relatively low resistance (>30 %) for ciprofloxacin, trimethoprim/sulfamethoxazole and fosfomycin. Notably, all DEC and more than 90% non-DEC or Salmonella isolates were found to be multidrug-resistant to drugs of both human and animal importance. Overall, the results of the present study suggest that leafy greens are potential reservoirs or sources of multidrug-resistant DEC and Salmonella strains in the rural or urban areas of India.

The challenging task to select Salmonella target serovars in poultry: the Italian point of view.

According to the European Food Safety Authority (EFSA) and European Centre for Disease Prevention and Control (ECDC) annual report, human salmonellosis is mostly related to consumption of contaminated poultry products. Since 2003 in Europe, the Salmonella serovars considered relevant for human health and subject to control in breeding hens of Gallus gallus are: S. Enteritidis, S. Typhimurium (including the monophasic variant), S. Infantis, S. Hadar and S. Virchow. Herein, we investigated the Italian epidemiological situation from 2016 to 2018, comparing Salmonella serovar distributions in humans and poultry, in order to identify the target Salmonella serovars that, if controlled, would potentially have the largest public health impact in Italy. The results showed that control of S. Virchow and S. Hadar does no longer seem to be a priority in Italy and that S. Napoli and S. Derby, which are not included in the group of EU target serovars, are among the most frequent serovars isolated from humans in Italy. While S. Derby has its main reservoir in pigs, S. Napoli does not have a specific reservoir. However, because this serovar is frequently isolated from breeding poultry flocks and is characterised by causing severe human illness, it is a potential target Salmonella serovar in breeding hens of Gallus gallus in Italy.

Detection of spatial and spatio-temporal Salmonella Heidelberg and Salmonella Typhimurium human case clusters focused around licensed abattoirs in Ontario in 2015, and their potential relation to known outbreaks.

Salmonellosis is one of several zoonotic diseases for which individuals with occupational animal contact, including abattoir workers, are at an increased risk. If meat is contaminated during slaughter, this can increase the risk of enteric illness for consumers. In this study, we investigated whether reported cases of Salmonella Heidelberg and Typhimurium were clustered around abattoirs in Ontario in 2015 and whether there was any evidence (laboratory/exposure) to suggest an abattoir at the centre of a cluster might be the source of exposure. Data for each reported case of S. Heidelberg and S. Typhimurium in Ontario in 2015 were collected. Multi-focused and non-focused spatial and space-time cluster detection tests were performed for each serotype, with and without cases linked to known outbreaks, using Poisson and space-time permutation models. Focused tests included the location of abattoirs operational in all or part of 2015. Laboratory data and exposure information were used to explore the relatedness of cases within identified clusters. Focused spatial tests identified clusters of S. Heidelberg and S. Typhimurium around abattoirs. Focused space-time permutation tests identified 2 significant space-time clusters of S. Heidelberg; one cluster (n = 11 cases) included 8 of 9 cases associated with a known outbreak and the other cluster (n = 18 cases) was not part of a previously identified outbreak. Review of laboratory and risk factor information suggested that cases within each cluster shared a common exposure. Cases were not asked about goat or sheep meat consumption. The focused cluster test, particularly with the space-time permutation model, could assist in identifying outbreaks associated with a particular physical location, such as an abattoir. Improvements to the current case investigation process, such as consistent collection and reporting of high-risk occupation information and more detailed food consumption history, could assist in outbreak identification when coupled with this statistic.

Rapid identification of pathogens by using surface-enhanced Raman spectroscopy and multi-scale convolutional neural network.

Salmonella is a prevalent pathogen causing serious morbidity and mortality worldwide. There are over 2600 serovars of Salmonella. Among them, Salmonella Enteritidis, Salmonella Typhimurium, and Salmonella Paratyphi were reported to be the most common foodborne pathogenic serovars in the EU and China. In order to provide a more efficient approach to detect and distinguish these serovars, a new analytical method was developed by combining surface-enhanced Raman spectroscopy (SERS) with multi-scale convolutional neural network (CNN). We prepared 34-nm gold nanoparticles (AuNPs) as the label-free Raman substrate, measured 1854 SERS spectra of these three Salmonella serovars, and then proposed a multi-scale CNN model with three parallel CNNs to achieve multi-dimensional extraction of SERS spectral features. We observed the impact of the number of iterations and training samples on the recognition accuracy by changing the ratio of the number of the training and testing sets. By comparing the calculated data with experimental one, it was shown that our model could reach recognition accuracy more than 97%. These results indicate that it was not only feasible to combine SERS spectroscopy with multi-scale CNN for Salmonella serotype identification, but also for other pathogen species and serovar identifications.