Resistant Shigella Research Articles

"Molecular Characterization of Extended Spectrum Beta-Lactamase Resistance in Pediatric Shigella Isolates in Egypt".

Shigellosis is a major cause of morbidity and mortality among children, especially in developing countries. The increased extended-spectrum beta-lactamase (ESBL) resistance in Shigella poses a challenge for effective treatment. To examine the antibiotic resistance and ESBL profile of Shigella isolates from children with acute diarrhea. Shigella was isolated from stool cultures from pediatric patients suffering from acute diarrhea. The isolates were identified by bacteriological tests, serotyping, and multiplex polymerase chain reaction (PCR). The antimicrobial resistance was examined by disc diffusion. Phenotypic tests and PCR examined the ESBLs and CTX-M, SHV, and TEM genes. A total of 100 Shigella (10% prevalence rate) were isolated. The S. sonnei and S. dysenteries were the most prevalent species (33% and 31%, respectively), followed by S. flexneri (27%), and only 9% were S. boydii. The isolates had complete resistance (100%) to ampicillin. There was lower resistance to ciprofloxacin (24%), and no resistance to imipenem. By phenotypic tests, 54% of isolates had ESBL. By PCR, bla-CTX-M gene was the most prevalent (50%), followed by bla-TEM (48.1%). Only one isolate (1.9%) had the bla-SHV gene. The alarmingly high rates of antibiotic resistance and ESBL resistance among Shigella spp highlight the urgent need to restrict the unguided use of these drugs. Continuous monitoring of local and global antibiotic resistance patterns is required to prevent the spread of resistance.

Epidemiology and antimicrobial resistance rates for Shigella species in a resource-rich setting

Shigellosis is an acute, often dysenteric, diarrhoeal illness that is responsible for much morbidity and mortality worldwide. Increasing rates of multidrug-resistant (MDR) and extensively drug-resistant (XDR) ​Shigella spp. have been detected worldwide and a regular review of local epidemiological and resistance rates is necessary to help guide empirical antibiotic choice. This retrospective laboratory study of faecal isolates between 2013 and 2023 demonstrates increasing rates of resistance to third-generation cephalosporins, azithromycin and ciprofloxacin, alongside an overall increase in MDR and XDR isolates.

Study of Antimicrobial Resistance (AMR) in Shigella spp. in India.

Antimicrobial agents are essential in reducing illness and mortality brought on by infectious diseases in both humans and animals. However, the therapeutic effect of antibiotics has diminished due to an increase in antimicrobial drug resistance (AMR). This article provides a retrospective analysis of AMR in Shigella infections in India, showing a rise in resistance that has contributed to a global burden. Shigella spp. are widespread and the second-leading cause of diarrheal death in people of all ages. The frequency and mortality rates of Shigella infections are decreased by antibiotic treatment. However, the growth of broad-spectrum antibiotic resistance is making it more difficult to treat many illnesses. Reduced cell permeability, efflux pumps, and the presence of enzymes that break down antibiotics are the causes of resistance. AMR is a multifaceted and cross-sectoral problem that affects humans, animals, food, and the environment. As a result, there is a growing need for new therapeutic approaches, and ongoing surveillance of Shigella spp. infections which should definitely be improved for disease prevention and management. This review emphasizes on the epidemiological data of India, and antimicrobial resistance in Shigella spp.

Prevalence of Salmonella spp., Shigella spp., and intestinal parasites among food handlers working in University of Gondar student's cafeteria, Northwest Ethiopia.

Food-borne infections continue to be a major public health problem at the international level. The issue becomes more serious in developing countries like Ethiopia. This study aimed to examine the prevalence of Salmonella and Shigella species and intestinal parasites, as well as antimicrobial resistance patterns and associated factors among food handlers at the University of Gondar cafeteria in northwest Ethiopia. An institutional-based cross-sectional study was conducted from February to June 2021 in the University of Gondar cafeterias. Data related to the socio-demographic characteristics and hygienic practices of study participants were collected using structured questionnaires. A total of 290 stool samples were collected from food handlers. Culture and conventional biochemical tests were used to isolate the Salmonella and the Shigella species. Wet mount, Formol-ether concentration, and Kato Katz techniques were applied to identify intestinal parasites. Additionally, drug susceptibility tests were performed using the disk diffusion method. Statistical analysis was done using SPSS version 26. Of 290 food handlers' stool samples analyzed, Twenty-seven 27 (9.3%) were positive for both Salmonella and Shigella species. The prevalence of Salmonella and Shigella species was 16 (5.5%) and 11 (3.8%), respectively. Most of the isolated pathogens were resistant to tetracycline 19 (70.4%), and trimethoprim/sulphamethoxazole 19 (70.4%). The overall rate of multi-drug resistant Shigella and Salmonella isolate was 59.3%. Besides, Fifty-seven 57 (19.7%) of the participants were positive for one or more intestinal parasites. The most prevalent intestinal Parasitosis was E. histolytica/dispar 22 (7.6%), followed by G. lamblia 13 (4.5%), and Ascaris lumbricoides 11 (3.8) not washing hands after using the toilet (AOR: 4.42, 95% CI: 1.57, 10.56), and consuming unpasteurized milk (AOR: 3.14, 95% CI: 1.65, 3.96), were factors significantly associated with the prevalence of Salmonella, and Shigella infection. Similarly, not washing hands after using the toilet (AOR: 2.19, 95% CI: 1.0, 1.4), and consuming unpasteurized milk (AOR: 10.4, 95% CI: 3.8, 28.8), were factors significantly associated with the prevalence of intestinal parasites infection. The prevalence of intestinal parasites, Salmonella, and Shigella species was high. Therefore, it is imperative to implement a public health policy that includes ongoing microbiological surveillance.

Multidrug-resistant conjugative plasmid carrying mphA confers increased antimicrobial resistance in Shigella

Shigellosis remains a common gastrointestinal disease mostly in children < 5 years of age in developing countries. Azithromycin (AZM), a macrolide, is currently the first-line treatment for shigellosis in Bangladesh; ciprofloxacin (CIP) and ceftriaxone (CRO) are also used frequently. We aimed to evaluate the current epidemiology of antimicrobial resistance (AMR) and mechanism(s) of increasing macrolide resistance in Shigella in Bangladesh. A total of 2407 clinical isolates of Shigella from 2009 to 2016 were studied. Over the study period, Shigella sonnei was gradually increasing and become predominant (55%) over Shigella flexneri (36%) by 2016. We used CLSI-guided epidemiological cut-off value (ECV) for AZM in Shigella to set resistance breakpoints (zone-diameter ≤ 15 mm for S. flexneri and ≤ 11 mm for S. sonnei). Between 2009 and 2016, AZM resistance increased from 22% to approximately 60%, CIP resistance increased by 40%, and CRO resistance increased from zero to 15%. The mphA gene was the key macrolide resistance factor in Shigella; a 63MDa conjugative middle-range plasmid was harboring AZM and CRO resistance factors. Our findings show that, especially after 2014, there has been a rapid increase in resistance to the three most effective antibiotics. The rapid spread of macrolide (AZM) resistance genes among Shigella are driven by horizontal gene transfer rather than direct lineage.

Isolation, Genomic Characterization of Shigella prophage fPSFA that effectively infects multi-drug resistant Shigella isolates from the Indian Poultry Sector

Because of uncontrolled use of antibiotics, emergence of multidrug-resistant Shigella species poses a huge potential of zoonotic transfer from poultry sector. With increasing resistance to current antibiotics, there is a critical need to explore antibiotic alternatives. Using a Shigella flexneri reference strain, we isolated a novel fPSFA phage after inducing with mitomycin C. The phage was found to be stable for wide ranges of temperature −20 °C–65 °C and pH 3 to 11. fPSFA shows a latent period that ranges from 20 to 30 min and generation times of 50–60 min. The genome analysis of phage reveals two major contigs of 23788 bp and 23285 bp with 50.16 % and 39.33 % G + C content containing a total of 80 CDS and 2 tRNA genes. The phage belongs to Straboviridae family and lacks any virulence or antimicrobial resistance gene, thus making it a suitable candidate for treatment of drug-resistant infections. To confirm lytic ability of novel phage, we isolated 54 multidrug-resistant Shigella species from thirty-five poultry fecal samples that shows multiple antibiotic resistance index ranging from 0.15 to 0.75 (from 3 Indian states). The fPSFA showed lytic activity against multidrug-resistant Shigella isolates (73.08 %) (MARI≥0.50). The wide host ranges of fPSFA phage demonstrate its potential to be used as a biocontrol agent.

Extracts from Cardiospermum grandiflorum and Blighia welwitschii (Sapindaceae) reveal antibacterial activity against Shigella species

Shigellosis is a disease condition caused by various species of the genus Shigella. Drug resistant Shigella has been identified as a pathogen for which there is a priority to develop antimicrobials. Cardiospermum grandiflorum and Blighia welwitschii are plants that have been used in ethnomedicine to treat diarrheal conditions. Scientific validation of the antibacterial efficacy of these plants is proven valuable. The present work aimed to investigate the antibacterial activity of extracts from C. grandiflorum and B. welwitschii against Shigella species. The antibacterial activity was evaluated against four species of Shigella using the broth microdilution method, whereas antioxidant activity was performed via colorimetric methods. Cytotoxicity test was carried out using Vero cells. Moreover, the phytochemical analysis of the active extracts was estimated using standard methods. Upon in vitro studies, extracts from C. grandiflorum and B. welwitschii inhibited the growth of three strains of Shigella species viz. Shigella flexneri, Shigella boydii and Shigella sonnei, with minimum inhibitory concentrations (MICs) less than 1000 µg/mL. Remarkably, cytotoxicity studies of the most promising extracts (B. welwitschii extracts) on Vero cells showed no toxicity. Concentration and time dependent antimicrobial test revealed the bactericidal orientation of B. welwitschii extracts at 4MIC. The phytochemical analysis showed that B. welwitschii extracts are rich in phenolics, flavonoids, tannins, etc. Overall, extracts from C. grandiflorum and B. welwitschii exhibited moderate to high and selective anti-Shigella activity. The present work demonstrated that B. welwitschii extracts are selective bactericidal and antioxidant extracts that can be further exploited as a source of potential anti-Shigella compounds. Nonetheless, isolation of antishigellosis compounds from B. welwitschii extracts, and their mechanistic studies are warranted.

Vaccinomics-aided next-generation novel multi-epitope-based vaccine engineering against multidrug resistant Shigella Sonnei: Immunoinformatics and chemoinformatics approaches.

Shigella sonnei is a gram-negative bacterium and is the primary cause of shigellosis in advanced countries. An exceptional rise in the prevalence of the disease has been reported in Asia, the Middle East, and Latin America. To date, no preventive vaccine is available against S. sonnei infections. This pathogen has shown resistances towards both first- and second-line antibiotics. Therefore, an effective broad spectrum vaccine development against shigellosis is indispensable. In the present study, vaccinomics-aided immunoinformatics strategies were pursued to identify potential vaccine candidates from the S. sonnei whole proteome data. Pathogen essential proteins that are non-homologous to human and human gut microbiome proteome set, are feasible candidates for this purpose. Three antigenic outer membrane proteins were prioritized to predict lead epitopes based on reverse vaccinology approach. Multi-epitope-based chimeric vaccines was designed using lead B- and T-cell epitopes combined with suitable linker and adjuvant peptide sequences to enhance immune responses against the designed vaccine. The SS-MEVC construct was prioritized based on multiple physicochemical, immunological properties, and immune-receptors docking scores. Immune simulation analysis predicted strong immunogenic response capability of the designed vaccine construct. The Molecular dynamic simulations analysis ensured stable molecular interactions of lead vaccine construct with the host receptors. In silico restriction and cloning analysis predicted feasible cloning capability of the SS-MEVC construct within the E. coli expression system. The proposed vaccine construct is predicted to be more safe, effective and capable of inducing robust immune responses against S. sonnei infections and may be worthy of examination via in vitro/in vivo assays.

Multidrug-Resistant Shigella sonnei Bacteremia among Persons Experiencing Homelessness, Vancouver, British Columbia, Canada.

Increased invasive bloodstream infections caused by multidrug resistant Shigella sonnei were noted in Vancouver, British Columbia, Canada, during 2021-2023. Whole-genome sequencing revealed clonal transmission of genotype 3.6.1.1.2 (CipR.MSM5) among persons experiencing homelessness. Improvements in identifying Shigella species, expanding treatment options for multidrug resistant infections, and developing public health partnerships are needed.

Concordance between Genotypic and Phenotypic Drug-Resistant Profiles of Shigella Isolates from Taiyuan City, Shanxi Province, China, 2005 to 2016.

Antimicrobial resistance in Shigella spp. is a global public health concern. In this study, the AMR phenotypic profiles of 10 kinds of antibiotics were compared with the genotypic profiles using genomic analysis of 218 Shigella isolates from Taiyuan City, Shanxi Province, China, 2005 to 2016. Core genome Multilocus Sequence Typing (cgMLST) based on the EnteroBase Escherichia/Shigella scheme was used to obtain the genetic relatedness of Shigella isolates. Multiple-drug resistance was observed in 96.79% Shigella spp., and the resistance to antimicrobial agents varied between S. flexneri and S. sonnei. The genotypic results correlated well with the phenotypic profiles with concordance rates of 96.42% and 94.50% in S. flexneri and S. sonnei isolates, respectively, from Taiyuan City, Shanxi Province. The sensitivity and specificity of the genotypic antimicrobial susceptibility testing (AST) were 97.56% and 95.34% for S. flexneri, and 95.65% and 93.31% for S. sonnei isolates, respectively. A discrepancy of genotypic and phenotypic AST results existed in some cephalosporin- and azithromycin-resistant Shigella isolates; there were no clear resistance patterns to predict ciprofloxacin resistance. There were major discrepancies between genotypic and phenotypic AST in the genotypically resistant but phenotypically susceptible isolates. The drug-resistance patterns and essential drug-resistance genes to predict the phenotypic drug-resistant profiles were the discrepancies between S. flexneri and S. sonnei isolates. Phylogenetic analysis showed that isolates of the same cluster but with different antibiotic-resistance gene patterns occurred because of the loss or gain of antibiotic-resistance genes located in the plasmids and multidrug-resistance islands. IMPORTANCE Antimicrobial resistance in Shigella spp. has become a global public health concern. In this study, we identified the antimicrobial susceptibility testing (AST) characteristics based on genomic sequences of 218 Shigella isolates and analyzed the correlation between genotypic and phenotypic antibiotic resistance profiles of Shigella spp., especially for fluoroquinolone, macrolides, and third-generation cephalosporins. Our results show that the genotypic results correlated with the phenotypic profiles with concordance rates of 96.42% and 94.50% in S. flexneri and S. sonnei isolates, respectively. The drug-resistance patterns and essential drug-resistance genes to predict the phenotypic drug-resistant profiles of S. flexneri and S. sonnei isolates in Taiyuan city were distinct. The discrepancy between genotypic and phenotypic AST was considerable in the genotypically resistant but phenotypically susceptible isolates. The information on drug resistance and resistance genes in this study can offer more details on the prevalence of drug resistance of Shigella spp.

The evolution and international spread of extensively drug resistant Shigella sonnei

Shigella sonnei causes shigellosis, a severe gastrointestinal illness that is sexually transmissible among men who have sex with men (MSM). Multidrug resistance in S. sonnei is common including against World Health Organisation recommended treatment options, azithromycin, and ciprofloxacin. Recently, an MSM-associated outbreak of extended-spectrum β-lactamase producing, extensively drug resistant S. sonnei was reported in the United Kingdom. Here, we aimed to identify the genetic basis, evolutionary history, and international dissemination of the outbreak strain. Our genomic epidemiological analyses of 3,304 isolates from the United Kingdom, Australia, Belgium, France, and the United States of America revealed an internationally connected outbreak with a most recent common ancestor in 2018 carrying a low-fitness cost resistance plasmid, previously observed in travel associated sublineages of S. flexneri. Our results highlight the persistent threat of horizontally transmitted antimicrobial resistance and the value of continuing to work towards early and open international sharing of genomic surveillance data.

Discovery of a novel sub-lineage of multi-drug resistant Shigella flexneri in Southern California

Clustered outbreaks of multi-drug resistant (MDR) Shigella are on the rise among men who have sex with men (MSM). Identification of MDR sub-lineages is critical for clinical management and public health interventions. Here, we describe a novel MDR sub-lineage of Shigella flexneri isolated from an MSM patient without a travel history in Southern California. Detailed genomic characterization of this novel strain would serve as a reference to aid monitoring and future outbreak investigation of MDR Shigella among MSM.

Increasing trend of antimicrobial resistance in Shigella associated with MSM transmission in Barcelona, 2020-21: outbreak of XRD Shigella sonnei and dissemination of ESBL-producing Shigella flexneri.

Several countries have recently reported the detection of ESBL-producing Shigella sonnei associated with transmission among MSM. In a previous study by our group, 2.8% of Shigella spp. obtained from MSM in Barcelona between 2015 and 2019 were ESBL producers. To describe and characterize the emerging ESBL-producing Shigella spp. associated with sexual transmission among MSM detected from 2020 to 2021 in Barcelona, elucidating their connectivity with contemporaneous ESBL-producing Shigella spp. from other countries. From 2020 to 2021, we identified that among MSM, 68% of S. sonnei were XDR harbouring blaCTX-M-27 and 14% of Shigella flexneri were MDR harbouring blaCTX-M-27. WGS analysis showed that the ESBL-producing S. sonnei were part of a monophyletic cluster, which included isolates responsible for the prolonged outbreak occurring in the UK. Our data also reveal the first emergence and clonal dissemination of ESBL-producing and fluoroquinolone-resistant S. flexneri 2a among MSM. We report an increasing trend of antimicrobial resistance in Shigella spp. among MSM in Barcelona since 2021, mainly as a consequence of the dissemination of XDR ESBL-producing S. sonnei, previously reported in the UK. These results highlight the importance of international collaborative surveillance of MDR/XDR S. sonnei and S. flexneri for rapid identification of their emergence and the prevention of the transmission of these pathogens.

2004. Contemporary Clinical Epidemiology of Pediatric Shigella spp. Infections in Houston, TX, 2016-2021

Abstract Background Infections due to Gram-negative pathogens that cause gastrointestinal illnesses are a significant cause of morbidity in children. The contemporary clinical and epidemiological features of pediatric Shigella spp. infections in urban cities in the United States are not well described. Methods We used a retrospective cohort of patients (0-18 years of age) from a network of hospitals in Houston, TX. Only patients with Shigella spp. isolated from clinical samples dated from 2016 to 2021 were included in the study. Demographic, clinical, and microbiological data and susceptibility profile were extracted from the medical record. Results We identified a total of 73 pediatric patients with Shigella spp. Infections. The median age at presentation was 5 years. Hospital admission occurred in 32 % of infections with a median length of stay of 1 day (Table 1). Of cases with available clinical data, 80% of patients with Shigella spp. infections reported fever (Table 2). Of note, 62% of patients developed bloody diarrhea (Table 2). The majority of patients infected with Shigella flexneri (4/7) reported a history of international travel. Seizures were observed in 5 patients. No episodes of bacteremia were identified. Among patients with an identified exposure, daycare attendance and contact with individuals experiencing similar symptoms were the most common (Table 2). The majority of Shigella species were S. sonnei (90.4%) (Table 3). Resistance to trimethoprim-sulfamethoxazole (TMP-SMX) was common (45/68, 66%) among Shigella spp. isolates tested. No resistance to third generation cephalosporins was observed. (Table 3). Although azithromycin was the most common antibiotic used for treatment, susceptibility testing for this antibiotic was not performed in any of the cases. Conclusion Infections due to Shigella spp. are a significant burden among pediatric patients in a major metropolitan health care system (Houston, TX). Bloody diarrhea was the most common presentation, although the presence of Shiga-toxin-positive isolates was unknown. The observed high frequency of resistance to TMP-SMX and emergence of multi-drug resistant Shigella spp. in other countries warrants continued surveillance. Disclosures Cesar A. Arias, MD, PhD, Entasis Phramceuticals: Grant/Research Support|MeMed Diagnostics: Grant/Research Support|Merck: Grant/Research Support.

Abundance of Multidrug resistant Shigella flexneri in avian environment in District Haripur, Khyberpakhtunkhwa, Pakistan

Abundance of Multidrug resistant Shigella flexneri in avian environment in District Haripur, Khyberpakhtunkhwa, Pakistan

Isolation, Identification and Evaluation of Antibiotic Sensitivity and Resistance of Shigella Dysenteriae Isolated from Food, Water and Soil

Background: Shigella is a genus of gram negative, facultative anerobic rod shaped bacteria divided into four species that are Shigella dysenteriae (serogroup A), Shigella flexneri (serogroup B), Shigella boydii (serogroup C) and Shigella sonnei (serogroup D). Shigella species are the etiological agent of shigellosis and most serious illnesses are caused by Shigella dysenteriae. Aim: The aim of this study was to determine antibiotic sensitivity and resistance of Shigella dysenteriae isolates to ensure that severe diarrhea infection remain treatable. Method: A total of 75 samples from different environmental sources were collected, processed and tested for the identification of Shigella dysenteriae after observing the cultural, morphological and biochemical characteristics. Antibiotic sensitivity and resistance pattern of these isolates were also studied by disk diffusion method. Results: It was observed that out of 75 samples, 42 samples were positive for Shigella dysenteriae. All Shigella isolates were highly resistant to Penicillin (100%), Vancomycin (100%), Aztreonam (100%), Ertapenem (100%) followed by Ceftriaxone (78%) and aAmikacin (74%) whereas highly sensitive to Imipenem (72%) followed by Ciproflaxin (67%) and Meropenem (47%). Conclusion: Resistance of Shigella dysenteriae to antibiotics that are commonly used for treatment of shigellosis is increasing at alarming rate. Multipronged strategies should be adopted to ensure that severe diarrhea infection remain treatable.

MORE ON THE GLOBAL BURDEN OF SHIGELLOSIS

The article “Shigellosis outbreaks-an update” by Gabriela Loredana Popa and Mircea Ioan Popa provides an overview of recent shigellosis outbreaks worldwide after scrutinizing ProMed communications of the last years [1]. A special review section is dedicated to Shigella spp. associated outbreaks in the European region. As background, the authors reiterate the clinical and epidemiological characteristics of the disease. The paper highlights the continuing burden of shigellosis worldwide including the rise of antibiotic-resistant Shigella isolates and the emerging epidemic transmission of multi-drug resistant Shigella spp. among MSM communities. The authors recommend that shigellosis should not be neglected in the global efforts to prevent and control infectious diseases of public health importance. The comments below reinforce the message of this review with additional evidence from recent studies on the importance of Shigella as the leading cause of moderate to severe diarrhea (MSD) and dysentery globally and on the urgent need for licensed vaccines to reduce the burden of shigellosis primarily in children under 5 years of age in lowand-middle-income-countries (LMICs).

Identification of MHC Class II Immunopeptidomes from Shigella flexneri 2a-infected Macrophages as Potential Vaccine Candidates

BACKGROUND: Shigella is a Gram-negative rod-shaped intracellular bacterial pathogen that causes bacterial dysentery or shigellosis among children under five years old. Antibiotics have been less effective in treating shigellosis due to the multi-drug resistance of Shigella. Therefore, an effective vaccine is urgently needed to prevent this disease. The present study aims to determine the peptides presented by major histocompatibility complex (MHC) class II molecules of Shigella-infected macrophages using mass spectrometry-based immunopeptidomics approaches. The MHC class II-associated peptides derived from Shigella-infected macrophages are candidates for developing subunit-based Shigella vaccine.METHODS: THP-1-derived macrophages were infected with Shigella flexneri 2a at the multiplicity of infection equal to 10. The lysate was immunoprecipitated and analyzed by liquid chromatography–tandem mass spectrometry (LC-MS/MS). The sequences retrieved were analyzed using bioinformatics tools.RESULTS: The Shigella-infected THP-1-derived macrophages contained sample peptides from source proteins of almost all subcellular localizations. Eight peptides from S. flexneri 2a-infected macrophages were predicted to be localized at the outer membrane proteins (OMPs) of S. flexneri 2a by the PSORTb server. Two of the OMP-associated peptides were predicted as antigenic, non-allergenic, and non-toxic by respective bioinformatics tools.CONCLUSION: The findings in this study showed two selected OMPs have great potential for vaccine development against shigellosis.KEYWORDS: immunopeptidomics, mass spectrometry, vaccine development, Shigella, MHC peptides

Evolutionary histories and antimicrobial resistance inShigella flexneri and Shigella sonnei in Southeast Asia

Conventional disease surveillance for shigellosis in developing country settingsrelies on serotyping and low-resolution molecular typing, which fails to contextualise the evolutionary history of the genus. Here, we interrogated a collection of 1,804 Shigella whole genome sequences from organisms isolated in four continental Southeast Asian countries (Thailand, Vietnam, Laos, and Cambodia) over three decades to characterise the evolution of both S. flexneri and S. sonnei. We show that S. sonnei and each major S. flexneri serotype are comprised of genetically diverse populations, the majority of which were likely introduced into Southeast Asia in the 1970s-1990s. Intranational and regional dissemination allowed widespread propagation of both species across the region. Our data indicate that the epidemiology of S. sonnei and the major S. flexneri serotypes were characterised by frequent clonal replacement events, coinciding with changing susceptibility patterns against contemporaneous antimicrobials. We conclude that adaptation to antimicrobial pressure was pivotal to the recent evolutionary trajectory of Shigella in Southeast Asia.

The repurposing of Tebipenem pivoxil as alternative therapy for severe gastrointestinal infections caused by extensively drug-resistant Shigella spp.

Diarrhoea remains one of the leading causes of childhood mortality globally. Recent epidemiological studies conducted in low-middle income countries (LMICs) identified Shigella spp. as the first and second most predominant agent of dysentery and moderate diarrhoea, respectively. Antimicrobial therapy is often necessary for Shigella infections; however, we are reaching a crisis point with efficacious antimicrobials. The rapid emergence of resistance against existing antimicrobials in Shigella spp. poses a serious global health problem. Aiming to identify alternative antimicrobial chemicals with activity against antimicrobial resistant Shigella, we initiated a collaborative academia-industry drug discovery project, applying high-throughput phenotypic screening across broad chemical diversity and followed a lead compound through in vitro and in vivo characterisation. We identified several known antimicrobial compound classes with antibacterial activity against Shigella. These compounds included the oral carbapenem Tebipenem, which was found to be highly potent against broadly susceptible Shigella and contemporary MDR variants for which we perform detailed pre-clinical testing. Additional in vitro screening demonstrated that Tebipenem had activity against a wide range of other non-Shigella enteric bacteria. Cognisant of the risk for the development of resistance against monotherapy, we identified synergistic behaviour of two different drug combinations incorporating Tebipenem. We found the orally bioavailable prodrug (Tebipenem pivoxil) had ideal pharmacokinetic properties for treating enteric pathogens and was effective in clearing the gut of infecting organisms when administered to Shigella-infected mice and gnotobiotic piglets. Our data highlight the emerging antimicrobial resistance crisis and shows that Tebipenem pivoxil (licenced for paediatric respiratory tract infections in Japan) should be accelerated into human trials and could be repurposed as an effective treatment for severe diarrhoea caused by MDR Shigella and other enteric pathogens in LMICs. Tres Cantos Open Lab Foundation (projects TC239 and TC246), the Bill and Melinda Gates Foundation (grant OPP1172483) and Wellcome (215515/Z/19/Z).