Burden and risk factors of Shigella sonnei shigellosis among children aged 0-59 months in hyperendemic communities in Israel

Twenty-five years of sentinel laboratory-based surveillance of shigellosis in a high-income country endemic for the disease, Israel, 1998 to 2022

BackgroundShigella is a leading cause of moderate-to-severe diarrhoea worldwide and diarrhoeal deaths in children in low- and-middle-income countries.AimWe investigated trends and characteristics of shigellosis and antimicrobial resistance of Shigella sonnei in Israel.MethodsWe analysed data generated by the Sentinel Laboratory-Based Surveillance Network for Enteric Pathogens that systematically collects data on detection of Shigella at sentinel laboratories, along with the characterisation of the isolates at the Shigella National Reference Laboratory. Trends in the shigellosis incidence were assessed using Joinpoint regression and interrupted time-series analyses.ResultsThe average incidence of culture-confirmed shigellosis in Israel declined from 114 per 100,000 population (95% confidence interval (CI): 112-115) 1998-2004 to 80 per 100,000 population (95% CI: 79-82) 2005-2011. This rate remained stable 2012-2019, being 18-32 times higher than that reported from the United States or European high-income countries. After decreasing to its lowest values during the COVID-19 pandemic years (19/100,000 in 2020 and 5/100,000 in 2021), the incidence of culture-confirmed shigellosis increased to 39 per 100,000 population in 2022. Shigella sonnei is the most common serogroup, responsible for a cyclic occurrence of propagated epidemics, and the proportion of Shigella flexneri has decreased. Simultaneous resistance of S. sonnei to ceftriaxone, ampicillin and sulphamethoxazole-trimethoprim increased from 8.5% (34/402) in 2020 to 92.0% (801/876) in 2022.ConclusionsThese findings reinforce the need for continuous laboratory-based surveillance and inform the primary and secondary prevention strategies for shigellosis in Israel and other endemic high-income countries or communities.

Shigella Vaccines: The Continuing Unmet Challenge

Shigellosis is a severe gastrointestinal disease that annually affects approximately 270 million individuals globally. It has particularly high morbidity and mortality in low-income regions; however, it is not confined to these regions and occurs in high-income nations when conditions allow. The ill effects of shigellosis are at their highest in children ages 2 to 5, with survivors often exhibiting impaired growth due to infection-induced malnutrition. The escalating threat of antibiotic resistance further amplifies shigellosis as a serious public health concern. This review explores Shigella pathology, with a primary focus on the status of Shigella vaccine candidates. These candidates include killed whole-cells, live attenuated organisms, LPS-based, and subunit vaccines. The strengths and weaknesses of each vaccination strategy are considered. The discussion includes potential Shigella immunogens, such as LPS, conserved T3SS proteins, outer membrane proteins, diverse animal models used in Shigella vaccine research, and innovative vaccine development approaches. Additionally, this review addresses ongoing challenges that necessitate action toward advancing effective Shigella prevention and control measures.

Pathogenicity and virulence of Shigella sonnei: A highly drug-resistant pathogen of increasing prevalence

Shigella spp. are the causative agent of shigellosis (or bacillary dysentery), a diarrhoeal disease characterized for the bacterial invasion of gut epithelial cells. Among the 4 species included in the genus, Shigella flexneri is principally responsible for the disease in the developing world while Shigella sonnei is the main causative agent in high-income countries. Remarkably, as more countries improve their socioeconomic conditions, we observe an increase in the relative prevalence of S. sonnei. To date, the reasons behind this change in aetiology depending on economic growth are not understood. S. flexneri has been widely used as a model to study the pathogenesis of the genus, but as more research data are collected, important discrepancies with S. sonnei have come to light. In comparison to S. flexneri, S. sonnei can be differentiated in numerous aspects; it presents a characteristic O-antigen identical to that of one serogroup of the environmental bacterium Plesiomonas shigelloides, a group 4 capsule, antibacterial mechanisms to outcompete and displace gut commensal bacteria, and a poorer adaptation to an intracellular lifestyle. In addition, the World Health Organization (WHO) have recognized the significant threat posed by antibiotic-resistant strains of S. sonnei, demanding new approaches. This review gathers knowledge on what is known about S. sonnei within the context of other Shigella spp. and aims to open the door for future research on understanding the increasing spread of this pathogen.

Shigella sonnei, an emerging multidrug-resistant sexually transmitted pathogen in Franche-Comté, France

Shigella sonnei (S. sonnei) is sometimes sexually transmitted. Men, who have sex with men (MSM), may have sexual behaviours different from heterosexual population, and thus may be at risk for S. sonnei infection. We describe three cases of multidrug-resistant S. sonnei in MSM (one HIV-infected patient and two patients receiving pre-exposure prophylaxis against HIV). S. sonnei was isolated from stool specimens and all patients were successfully treated with parenteral third-generation cephalosporins following laboratory confirmation that the isolates were resistant to azithromycin. Two men (patients 2 and 3) were linked epidemiologically. These cases highlight the emergence of this pathogen and its association with some sexual behaviours among MSM in Franche-Comté, France.

Therapeutic target identification via differential genome analysis of antibiotic resistant Shigella sonnei and inhibitor evaluation against a selected drug target

Shigella sonnei has been implicated in bloody diarrhea (accompanied by abdominal pain and fever) and is an emerging pathogen of concern, especially in developing countries. The major means of transmission is the fecal-oral route while sexual transmission has also been reported. In children, the impact might be stunted growth due to life-threatening illness. Resistance has been reported in this species for several types of antibiotics. In this study, we retrieved the antibiotic-resistant labeled whole genome sequences of the species from the PATRIC database and performed a pan-genome analysis to filter out core genes. Antibiotic resistance was studied in the core, accessory and unique genome. Core genes were utilized as seed substance for essentiality analysis and drug candidate assignment. Product of the gene aroG, i.e. chorismate biosynthetic process 3-deoxy-7-phosphoheptulonate synthase enzyme, responsible for aromatic amino acid family biosynthetic process, was taken for further downstream processing. Natural product libraries of flavonoids (n = 178), ZINC database derived inhibitor compounds of the 3-deoxy-7-phosphoheptulonate synthase enzyme (n = 112), and streptomycin compounds (n = 737) were docked to find out potent inhibitors, followed by dynamics simulation of 50 ns each for top compounds.. Physicochemical and ADMET profiling of the top compounds was done to analyze their safety for consumption. We propose that the top compounds: Phytoene from Streptomycin library and ZINC000036444158 (synonym:1,16-bis[(dihydroxyphosphinyl)oxy]hexadecane) from 3-deoxy-7-phosphoheptulonate synthase inhibitor library of ZINC database (and used as a control in this study) should be tested in vitro against Shigella sonnei, to fully determine their efficacy. This could add to the drying pipeline of potent drug molecules against emerging pathogens.

A Significant Decrease in the Incidence of Shigellosis in Israel during COVID-19 Pandemic

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) causes COVID-19 and is mostly person-to-person transmitted through respiratory droplets. The implications of the strategies implemented to prevent COVID-19 transmission on other infectious diseases are unclear. We aimed to appraise trends in the incidence of salmonellosis, shigellosis and campylobacteriosis in Israel during COVID-19 pandemic. Positive stool samples for Salmonella, Shigella and Campylobacter are reported on a monthly basis to the Israel Center for Disease Control from sentinel laboratories, within the framework of a surveillance network of bacterial culture-proven enteric diseases. Age-adjusted incidence rates per 100,000 of shigellosis, salmonellosis and campylobacteriosis were calculated. Mean rates before and after the local onset of COVID-19 pandemic in Israel were compared and Relative Risk Reduction (RRR) was calculated. Joinpoint was used to evaluate secular trends. The mean age-adjusted incidence rate of shigellosis in March–July 2020 was lower than the rate observed in March–July 2018–2019 (RRR = 86.6%), but also decreased for salmonellosis (RRR = 33.0%) and campylobacteriosis (RRR = 30.0%). Using Joinpoint we have shown that the decrease observed for shigellosis was significantly sharper (Annual Percent Change (APC) = −77.7) between February 2020 and May 2020 than for salmonellosis (APC = −14.0) between July 2019 and April 2020 and for campylobacteriosis (APC = −1.1) between January 2018 and July 2020. The preventive measures applied to reduce transmission of COVID-19, including social distancing and hand washing, were ecologically associated with a decreased risk of bacterial enteric diseases in Israel. The association was strongest for shigellosis, a disease that is mostly person-to-person transmitted, as compared to salmonellosis and campylobacteriosis which are mostly foodborne transmitted.

Persistent Transmission of Shigellosis in England Is Associated with a Recently Emerged Multidrug-Resistant Strain of Shigella sonnei

Whole-genome sequencing has enhanced surveillance and facilitated detailed monitoring of the transmission of Shigella species in England. We undertook an epidemiological and phylogenetic analysis of isolates from all cases of shigellosis referred to Public Health England between 2015 and 2018 to explore recent strain characteristics and the transmission dynamics of Shigella species. Of the 4,950 confirmed cases of shigellosis identified during this period, the highest proportion of isolates was Shigella sonnei (54.4%), followed by S. flexneri (39.2%), S. boydii (4.1%), and S. dysenteriae (2.2%). Most cases were adults (82.9%) and male (59.5%), and 34.9% cases reported recent travel outside the United Kingdom. Throughout the study period, diagnoses of S. flexneri and S. sonnei infections were most common in men with no history of recent travel abroad. The species prevalence was not static, with cases of S. flexneri infection in men decreasing between 2015 and 2016 and the number of cases of S. sonnei infection increasing from 2017. Phylogenetic analysis showed this recent increase in S. sonnei infections was attributed to a novel clade that emerged from a Central Asia sublineage exhibiting resistance to ciprofloxacin and azithromycin. Despite changes in species prevalence, diagnoses of Shigella infections in England are persistently most common in adult males without a reported travel history, consistent with sexual transmission among men who have sex with men. The trend toward increasing rates of ciprofloxacin resistance in S. sonnei, in addition to plasmid-mediated azithromycin resistance, is of significant public health concern with respect to the transmission of multidrug-resistant gastrointestinal pathogens and the risk of treatment failures.

Serum IgG antibodies to Shigella lipopolysaccharide antigens - a correlate of protection against shigellosis

Shigella is a leading cause of diarrhea among children globally and of diarrheal deaths among children under 5 years of age in low- and middle-income countries. To date, no licensed Shigella vaccine exists. We review evidence that serum IgG antibodies to Shigella LPS represent a good correlate of protection against shigellosis; this could support the process of development and evaluation of Shigella vaccine candidates. Case-control and cohort studies conducted among Israeli soldiers serving under field conditions showed significant serotype-specific inverse associations between pre-exposure serum IgG antibodies to Shigella LPS and shigellosis incidence. The same serum IgG fraction showed a dose-response relationship with the protective efficacy attained by vaccine candidates tested in phase III trials of young adults and children aged 1-4 years and in Controlled Human Infection Model studies and exhibited mechanistic protective capabilities. Identifying a threshold level of these antibodies associated with protection can promote the development of an efficacious vaccine for infants and young children.