Global population structure and genotyping framework for genomic surveillance of the major dysentery pathogen, Shigella sonnei.

Shigella sonnei is the most common agent of shigellosis in high-income countries, and causes a significant disease burden in low- and middle-income countries. Antimicrobial resistance is increasingly common in all settings. Whole genome sequencing (WGS) is increasingly utilised for S. sonnei outbreak investigation and surveillance, but comparison of data between studies and labs is challenging. Here, we present a genomic framework and genotyping scheme for S. sonnei to efficiently identify genotype and resistance determinants from WGS data. The scheme is implemented in the software package Mykrobe and tested on thousands of genomes. Applying this approach to analyse >4,000 S. sonnei isolates sequenced in public health labs in three countries identified several common genotypes associated with increased rates of ciprofloxacin resistance and azithromycin resistance, confirming intercontinental spread of highly-resistant S. sonnei clones and demonstrating the genomic framework can facilitate monitoring the spread of resistant clones, including those that have recently emerged, at local and global scales.

Comparative genome analysis of 12 Shigella sonnei strains: virulence, resistance, and their interactions.

Shigellosis is a highly infectious disease that is mainly transmitted via fecal-oral contact of the bacteria Shigella. Four species have been identified in Shigella genus, among which Shigella flexneri is used to be the most prevalent species globally and commonly isolated from developing countries. However, it is being replaced by Shigella sonnei that is currently the main causative agent for dysentery pandemic in many emerging industrialized countries such as Asia and the Middle East. For a better understanding of S. sonnei virulence and antibiotic resistance, we sequenced 12 clinical S. sonnei strains with varied antibiotic-resistance profiles collected from four cities in Jiangsu Province, China. Phylogenomic analysis clustered antibiotic-sensitive and resistant S. sonnei into two distinct groups while pan-genome analysis reveals the presence and absence of unique genes in each group. Screening of 31 classes of virulence factors found out that type 2 secretion system is doubled in resistant strains. Further principle component analysis based on the interactions between virulence and resistance indicated that abundant virulence factors are associated with higher levels of antibiotic resistance. The result present here is based on statistical analysis of a small sample size and serves basically as a guidance for further experimental and theoretical studies.

Phylogenetic and Evolutionary Analysis Reveals the Recent Dominance of Ciprofloxacin-Resistant Shigella sonnei and Local Persistence of S. flexneri Clones in India.

Shigella is the second leading cause of bacterial diarrhea worldwide. Recently, Shigella sonnei seems to be replacing Shigella flexneri in low- and middle-income countries undergoing economic development. Despite this, studies focusing on these species at the genomic level remain largely unexplored. Here, we compared the genome sequences of S. flexneri and S. sonnei isolates from India with the publicly available genomes of global strains. Our analysis provides evidence for the long-term persistence of all phylogenetic groups (PGs) of S. flexneri and the recent dominance of the ciprofloxacin-resistant S. sonnei lineage in India. Within S. flexneri PGs, the majority of the study isolates belonged to PG3 within the predominance of serotype 2. For S. sonnei, the current pandemic involves globally distributed multidrug-resistant (MDR) clones that belong to Central Asia lineage III. The presence of such epidemiologically dominant lineages in association with stable antimicrobial resistance (AMR) determinants results in successful survival in the community.IMPORTANCEShigella is the second leading cause of bacterial diarrhea worldwide. This has been categorized as a priority pathogen among enteric bacteria by the Global Antimicrobial Resistance Surveillance System (GLASS) of the World Health Organization (WHO). Recently, S. sonnei seems to be replacing S. flexneri in low- and middle-income countries undergoing economic development. Antimicrobial resistance in S. flexneri and S. sonnei is a growing international concern, specifically with the international dominance of the multidrug-resistant (MDR) lineage. Genomic studies focusing on S. flexneri and S. sonnei in India remain largely unexplored. This study provides information on the introduction and expansion of drug-resistant Shigella strains in India for the first time by comparing the genome sequences of S. flexneri and S. sonnei isolates from India with the publicly available genomes of global strains. The study discusses the key differences between the two dominant species of Shigella at the genomic level to understand the evolutionary trends and genome dynamics of emerging and existing resistance clones. The present work demonstrates evidence for the long-term persistence of all PGs of S. flexneri and the recent dominance of a ciprofloxacin-resistant S. sonnei lineage in India.

Shigella sonnei Outbreak Investigation During a Municipal Water Crisis-Genesee and Saginaw Counties, Michigan, 2016.

Objectives. To investigate a shigellosis outbreak in Genesee County, Michigan (including the City of Flint), and Saginaw County, Michigan, in 2016 and address community concerns about the role of the Flint water system.Methods. We met frequently with community members to understand concerns and develop the investigation. We surveyed households affected by the outbreak, analyzed Shigella isolate data, examined the geospatial distribution of cases, and reviewed available water quality data.Results. We surveyed 83 households containing 158 cases; median age was 10 years. Index case-patients from 55 of 83 households (66%) reported contact with a person outside their household who wore diapers or who had diarrhea in the week before becoming ill; results were similar regardless of household drinking water source. Genomic diversity was not consistent with a point source. In Flint, no space-time clustering was identified, and average free chlorine residual values remained above recommended levels throughout the outbreak period.Conclusions. The outbreak was most likely caused by person-to-person contact and not by the Flint water system. Consistent community engagement was essential to the design and implementation of the investigation.

Commensal Escherichia coli are a reservoir for the transfer of XDR plasmids into epidemic fluoroquinolone-resistant Shigella sonnei.

Despite the sporadic detection of fluoroquinolone-resistant Shigella in Asia in the early 2000s and the subsequent global spread of ciprofloxacin-resistant (cipR) Shigella sonnei from 2010, fluoroquinolones remain the recommended therapy for shigellosis1-7. The potential for cipR S. sonnei to develop resistance to alternative second-line drugs may further limit future treatment options8. Here, we aim to understand the evolution of novel antimicrobial resistant (AMR) S. sonnei variants after introduction into Vietnam. We found that cipR S. sonnei displaced the resident ciprofloxacin-susceptible (cipS) lineage while rapidly acquiring additional resistance to multiple alternative antimicrobial classes. We identified several independent acquisitions of extensively drug-resistant/multidrug-resistant-inducing plasmids, probably facilitated by horizontal transfer from commensals in the human gut. By characterizing commensal Escherichia coli from Shigella-infected and healthy children, we identified an extensive array of AMR genes and plasmids, including an identical multidrug-resistant plasmid isolated from both S. sonnei and E. coli in the gut of a single child. We additionally found that antimicrobial usage may impact plasmid transfer between commensal E. coli and S. sonnei. These results suggest that, in a setting with high antimicrobial use and a high prevalence of AMR commensals, cipR S. sonnei may be propelled towards pan-resistance by adherence to outdated international treatment guidelines.

Use of whole genome sequencing in surveillance for antimicrobial-resistant Shigella sonnei infections acquired from domestic and international sources.

Shigella species are a major cause of gastroenteritis worldwide, and Shigella sonnei is the most common species isolated within the United States. Previous surveillance work in Pennsylvania documented increased antimicrobial resistance (AMR) in S. sonnei associated with reported illnesses. The present study examined a subset of these isolates by whole genome sequencing (WGS) to determine the relationship between domestic and international isolates, to identify genes that may be useful for identifying specific Global Lineages of S. sonnei and to test the accuracy of WGS for predicting AMR phenotype. A collection of 22 antimicrobial-resistant isolates from patients infected within the United States or while travelling internationally between 2009 and 2014 was chosen for WGS. Phylogenetic analysis revealed both international and domestic isolates were one of two previously defined Global Lineages of S. sonnei, designated Lineage II and Lineage III. Twelve of 17 alleles tested distinguish these two lineages. Lastly, genome analysis was used to identify AMR determinants. Genotypic analysis was concordant with phenotypic resistance for six of eight antibiotic classes. For aminoglycosides and trimethoprim, resistance genes were identified in two and three phenotypically sensitive isolates, respectively. This article contains data hosted by Microreact.

Shifting national surveillance of Shigella infections toward geno-serotyping by the development of a tailored Luminex assay and NGS workflow.

The phylogenetically closely related Shigella species and enteroinvasive Escherichia coli (EIEC) are responsible for millions of episodes of bacterial dysenteriae worldwide. Given its distinct epidemiology and public health relevance, only Shigellae are subject to mandatory reporting and follow-up by public health authorities. However, many clinical laboratories struggle to differentiate non-EIEC, EIEC, and Shigella in their current workflows, leading to inaccuracies in surveillance and rising numbers of misidentified E. coli samples at the National Reference Centre (NRC). In this paper, we describe two novel tools to enhance Shigella surveillance. First, we developed a low-cost Luminex-based multiplex assay combining five genetic markers for species identification with 11 markers for serotype prediction for S. sonnei and S. flexneri isolates. Using a test panel of 254 clinical samples, this assay has a sensitivity of 100% in differentiation of EIEC/Shigella pathotype from non-EIEC strains, and 68.7% success rate in distinction of Shigella and EIEC. A novel, and particularly successful marker was a Shigella-specific deletion in the spermidine acetyltransferase gene speG, reflecting its metabolic decay. For Shigella serotype prediction, the multiplex assay scored a sensitivity and specificity of 96.6% and 98.4%, respectively. All discrepancies were analyzed with whole-genome sequencing and shown to be related to causative mutations (stop codons, indels, and promoter mutations) in glycosyltransferase genes. This observation spurred the development of an in silico workflow which extracts the Shigella serotype from Next-Generation Sequencing (NGS) data, taking into account gene functionality. Both tools will be implemented in the workflow of the NRC, and will play a major role in the shift from phenotypic to genotyping-based surveillance of shigellosis in Belgium.

Detection and discrimination of Shigella sonnei and Shigella flexneri based on vacuolar responses in Saccharomyces cerevisiae.

This study provided a system for bacteria detection based on a lysosome-like-vacuole response in the yeast Saccharomyces cerevisiae. Vacuoles are factors known to activate the immune system in the presence of foreign substances. Here, Shigella sonnei and Shigella flexneri were exposed to yeast to analyze the alteration of vacuolar enzymes. The ability to detect the bacteria was evaluated by confocal microscopy after exposing and staining vacuoles with LysoTracker. Results showed that the treatment of yeast with these bacteria increased the number of red vacuole-like organelles surrounding yeast nuclei. Thus, vacuole alteration can be used as a biomarker for bacteria detection. Next, the expression of vacuolar enzymes under the influence of bacteria was examined using two-dimensional gel electrophoresis (2-DE) method for screening specific biomarkers for each Shigella strain. Finally, the recombinant yeasts that contained biomarkers fused to different fluorescent proteins confirmed the ability of yeast to detect these two Shigella strains at concentrations ranging from 10 to 100 CFU/mL.

Microevolution and Patterns of Transmission of Shigella sonnei within Cyclic Outbreaks Shigellosis, Israel.

Whole-genome sequencing unveiled host and environment-related insights to Shigella sonnei transmission within cyclic epidemics during 2000-2012 in Israel. The Israeli reservoir contains isolates belonging to S. sonnei lineage III but of different origin, shows loss of tetracycline resistance genes, and little genetic variation within the O antigen: highly relevant for Shigella vaccine development.

[Etiologic characteristics of Shigella sonnei strains isolated from some areas of Guangdong province and Guangxi Zhuang Autonomous Region of China, 2014-2016].

Objective: To investigated the etiologic characteristics of Shigella (S.) sonnei strains causing outbreaks and sporadic cases in some areas of Guangdong province and Guangxi Zhuang Autonomous Region during 2014-2016. Methods: Fourteen S. sonnei strains isolated from outbreaks and 6 S. sonnei strains from sporadic cases from Guangdong and Liuzhou of Guangxi Zhuang Autonomous Region were tested for antimicrobial resistance and analyzed by pulsed-field gel electrophoresis (PFGE). Six typical strains were selected for whole genome sequencing typing and compared with 51 strains isolated both at home and abroad from NCBI genome database. Results: The antibiotic resistance test indicated the isolates had high resistance rate to ampicillin, tetracycline, gentamicin, trimethoprim/sulfamethoxazole and nalidixic acid, while sensitive to azithromycin, chloromycetin and imipenem. PFGE showed high similarity (93.2%) among the strains isolated from different areas. The whole genome sequencing analysis also revealed that all the typical strains were clustered into a same evolution branch, close to some strains from Korea. Conclusions: The S. sonnei strains isolated from some areas of Guangdong and Guangxi Zhuang Autonomous Region showed high resistance to commonly used antibiotics, but they were sensitive to azithromycin, chloramphenicol and imipenem. The isolates in this study also showed similar PFGE patterns and close phylogenic evolution.

Molecular typing and occurrence of beta-lactam resistance genes of Shigella sonnei strains isolated from 1983 to 2014 in the São Paulo state of Brazil.

Shigella sonnei, which has generally been associated with dysentery in developed countries, has recently been emerging in developing countries. Specifically, in Brazil few published studies have that molecularly characterized this species. The aims of this study were to analyze the efficacy of typing using multiple-locus variable-number tandem-repeat analysis (MLVA), study the phylogeny by multi-locus sequence typing (MLST) and assess the presence of some beta-lactam resistance genes in S. sonnei strains isolated from human diarrhoeic faeces in the São Paulo State in Brazil between 1983 and 2014. Seventy-two such S. sonnei strains were typed by MLVA and grouped into two clusters. The discrimination index of MLVA was found to be 0.996. Twenty strains were typed by MLST as ST152. In addition, the blaTEM gene was detected in eight (72.7%) of the 11 S. sonnei strains that had previously been shown to be resistant to ß-lactams. However, blaCTX-M-1group , blaCTX-M-9group and blaSHV genes were not found. MLVA results suggested the existence of two prevalent subtypes in the S. sonnei strains studied, confirming previous results. Moreover, MLVA efficiently discriminated monomorphic S. sonnei species. Because the S. sonnei strains studied belonged to clonal complex 152 and all isolates were typed as ST152, MLST is not a suitable method for studying the population structure of S. sonnei. Although, the rates of ß-lactam resistance were not high in the present study, the frequency of blaTEM may represent a risk for patients receiving antimicrobial treatment. Taken together, the results provide better molecular characterization of this globally clinically important pathogen.

Next generation sequencing-based multigene panel for high throughput detection of food-borne pathogens.

Contamination of food by chemicals or pathogenic bacteria may cause particular illnesses that are linked to food consumption, commonly referred to as foodborne diseases. Bacteria are present in/on various foods products, such as fruits, vegetables and ready-to-eat products. Bacteria that cause foodborne diseases are known as foodborne pathogens (FBPs). Accurate detection methods that are able to reveal the presence of FBPs in food matrices are in constant demand, in order to ensure safe foods with a minimal risk of causing foodborne diseases. Here, a multiplex PCR-based Illumina sequencing method for FBP detection in food matrices was developed. Starting from 25 bacterial targets and 49 selected PCR primer pairs, a primer collection called foodborne pathogen - panel (FPP) consisting of 12 oligonucleotide pairs was developed. The FPP allows a more rapid and reliable identification of FBPs compared to classical cultivation methods. Furthermore, FPP permits sensitive and specific FBP detection in about two days from food sample acquisition to bioinformatics-based identification. The FPP is able to simultaneously identify eight different bacterial pathogens, i.e. Listeria monocytogenes, Campylobacter jejuni, Campylobacter coli, Salmonella enterica subsp. enterica serovar enteritidis, Escherichia coli, Shigella sonnei, Staphylococcus aureus and Yersinia enterocolitica, in a given food matrix at a threshold contamination level of 101cell/g. Moreover, this novel detection method may represent an alternative and/or a complementary approach to PCR-based techniques, which are routinely used for FBP detection, and could be implemented in (parts of) the food chain as a quality check.

Comparison of phenotypic and WGS-derived antimicrobial resistance profiles of Shigella sonnei isolated from cases of diarrhoeal disease in England and Wales, 2015.

Objectives: Phenotypic and genotypic methods for the detection of antimicrobial resistance (AMR) in Shigella sonnei in England and Wales were compared and evaluated. Methods: WGS data from 341 isolates of S. sonnei isolated between June 2015 and January 2016 were mapped to genes known to be associated with phenotypic AMR. Antimicrobial susceptibility testing was performed on all viable isolates (n = 335). Results: Fifteen of 335 isolates had a discrepancy between phenotypic and genotypic testing for 1 of the 10 antimicrobial classes tested, equating to 15 (0.45%) discordant results out of a possible 3350 isolate/antimicrobial combinations. All 15 mismatched results were genotypically resistant but phenotypically susceptible. Eleven of the 15 discrepancies were observed in streptomycin resistance profiles. The most common resistance profile was trimethoprim, sulphonamides, tetracyclines and streptomycin, occurring in 97 (28.4%) isolates. Resistances to ciprofloxacin and the third-generation cephalosporins, not detected in England and Wales prior to 2002, were identified in 18.2% and 12% of isolates, respectively. Three hundred and four (89.1%) isolates were MDR. There was no significant association between any of the AMR determinants tested and recent foreign travel in male or female cases. The number of isolates of S. sonnei harbouring blaTEM-1 and ermB/mphA was significantly higher in men who reported no recent travel outside the UK. Conclusions: The use of WGS for routine public health surveillance is a reliable method for rapid detection of emerging AMR in isolates of S. sonnei.

Detecting and Discriminating Shigella sonnei Using an Aptamer-Based Fluorescent Biosensor Platform.

In this paper, a Whole-Bacteria SELEX (WB-SELEX) strategy was adopted to isolate specific aptamers against Shigella sonnei. Real-time PCR amplification and post-SELEX experiment revealed that the selected aptmers possessed a high binding affinity and specificity for S. sonnei. Of the 21 aptamers tested, the C(t) values of the SS-3 and SS-4 aptamers (Ct = 13.89 and Ct = 12.23, respectively) had the lowest value compared to other aptamer candidates. The SS-3 and SS-4 aptamers also displayed a binding affinity (KD) of 39.32 ± 5.02 nM and 15.89 ± 1.77 nM, respectively. An aptamer-based fluorescent biosensor assay was designed to detect and discriminate S. sonnei cells using a sandwich complex pair of SS-3 and SS-4. The detection of S. sonnei by the aptamer based fluorescent biosensor platform consisted of three elements: (1) 5'amine-SS-4 modification in a 96-well type microtiter plate surface (N-oxysuccinimide, NOS) as capture probes; (2) the incubation with S. sonnei and test microbes in functionalized 96 assay wells in parallel; (3) the readout of fluorescent activity using a Cy5-labeled SS-3 aptamer as the detector. Our platform showed a significant ability to detect and discriminate S. sonnei from other enteric species such as E. coli, Salmonella typhimurium and other Shigella species (S. flexneri, S. boydii). In this study, we demonstrated the feasibility of an aptamer sensor platform to detect S. sonnei in a variety of foods and pave the way for its use in diagnosing shigellosis through multiple, portable designs.

An 11-year study of shigellosis and Shigella species in Taiyuan, China: Active surveillance, epidemic characteristics, and molecular serotyping.

A hospital-based surveillance of shigellosis was conducted in Taiyuan from 2005 to 2015. A total of 2655 stool cultures were collected from patients with diarrhea, 115 were identified as S. flexneri and 107 were S. sonnei. The highest infection rates were found among children under 5 years of age (34.2 %), and during the summer (61.0 %). ​Six serotypes were identified among S. flexneriisolates:1a, 2a, 2b, Xv, X and Y. Serotype 2a and Xv were the dominant serotypes in two periods, 2012-2015 and 2005-2008, respectively. High shigellosis rates over the past decade highlight shigellosis is still a major public health problem in Taiyuan.

[SONNEI DYSENTERY MORBIDITY IN KHABAROVSK AND KHABAROVSK REGION DUE TO ATYPICAL MANNITOL-NEGATIVE CAUSATIVE AGENT].

AIM: Determine features of epidemic process (EP) of Sonnei dysentery in Khabarovsk Region in 2012 - 2014 due to atypical causative agent. MATERIALS AND METHODS: Detailed characteristics of 161 cultures of Shigella sonnei isolated from 81 patients from epidemic focus in children boarding school in Bikin as well as from 22 patients from sporadic and group foci of dysenteryin Khabarovsk (biochemical type, colicin-genotype, spectrum of drug resistance) is given. Molecular-biologic subtyping was carried out for 11 strains by Pulsed Field Gel Electrophoresis method (PFGE). RESULTS: Materials of observation of a prolonged foci of Sonnei dysentery with contact-domestic transmission route of the infection in children boarding house for disabled (October 2012 - September 2014) are presented. The diseases are etiologically connected with atypical mannitol- negative types of shigella isolated for the first time in 40 years of observation in Khabarovsk region. Epidemic process of shigellosis was supported by prolonged carriership of the causative agent in patients and special contingent ofthe nursing home. Shigella cultures isolated in the focus belonged to the same colicin-genotype and 2 distinct drug resistance clones, but a single genotype established by PFGE method. CONCLUSION: Results of the studies give evidence on the importance of determi- nation of traditional phenotypic and contemporary genotypic variants of shigella and the neces- sity of search for arguments, additional methodic approaches for establishing similarities and differences of shigella isolates from within the same outbreak of the diseases as well as for com- parison of strains circulating in different territories.

Multiple- locus variable-number tandem-repeat analysis (MLVA) of Shigella sonnei isolates of 2012 outbreak I. R. Iran.

Shigella sonnei is a major cause of diarrhea especially in children. Molecular study can help to determine the outbreak of this bacterium. Multiple-Locus Variable number tandem repeat Analysis (MLVA) will largely influence the public health field by introducing newer, faster, safer, and effective procedure for typing of microorganisms. A total of fifty shigella isolates were collected between November 2012 to October 2013 in Tehran, Iran. The strains were identified base on biochemical and molecular tests. Subsequently, all shigella species were confirmed by species-specific polymerase chain reaction (PCR). Virulence factors were detected using PCR for ial, set1A, and set1B genes. The strains were genotyped by MLVA typing method. All of the isolates were identified as S. sonnei by biochemical and molecular (PCR) methods. Virulence genes identified among all isolates included ial, and set1A genes in 20% and 5% of all isolates, respectively. On the other hand, none of isolates were positive for set1B gene. Using MLVA method 22 MLVA types were identified. MLVA type 11 accounted for 32% of isolates. Moreover, all virulence factors were only detected in MLVA type 11, 9, 5, 4. The results of this study indicate that the Iranian 2012-2013 S. sonnei outbreak isolates were virulent and clonaly related. Furthermore, this study showed that MLVA can be used as useful method for S. sonnei genotyping in epidemiological investigations.

ESBL-Producing and Macrolide-Resistant Shigella sonnei Infections among Men Who Have Sex with Men, England, 2015.

In England in 2015, Shigella sonnei isolates from men who have sex with men produced extended-spectrum ß-lactamases and exhibited macrolide resistance. Whole-genome sequencing showed a close relationship among the isolates, which harbored a plasmid that was previously identified in a shigellosis outbreak among this population but has acquired a mobile element.