Imperial College London

ProfessorShiraneeSriskandan

Faculty of MedicineDepartment of Infectious Disease

Professor of Infectious Diseases
 
 
 
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Contact

 

s.sriskandan

 
 
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Assistant

 

Ms Teyanna Gaeta +44 (0)20 3313 1943

 
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Location

 

8N21ACWBHammersmith HospitalHammersmith Campus

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Summary

 

Publications

Publication Type
Year
to

190 results found

Herdman MT, Cordery R, Karo B, Purba AK, Begum L, Lamagni T, Kee C, Balasegaram S, Sriskandan Set al., 2021, Clinical management and impact of scarlet fever in the modern era: findings from a cross-sectional study of cases in London, 2018-2019, BMJ Open, Vol: 12, Pages: 1-9, ISSN: 2044-6055

Objectives In response to increasing incidence of scarlet fever and wider outbreaks of group A streptococcal infections in London, we aimed to characterise the epidemiology, symptoms, management and consequences of scarlet fever, and to identify factors associated with delayed diagnosis.Design and setting Cross-sectional community-based study of children with scarlet fever notified to London’s three Health Protection Teams, 2018–2019.Participants From 2575 directly invited notified cases plus invitations via parental networks at 410 schools/nurseries with notified outbreaks of confirmed/probable scarlet fever, we received 477 responses (19% of those directly invited), of which 412 met the case definition. Median age was 4 years (range <1 to 16), 48% were female, and 70% were of white ethnicity.Outcome measures Preplanned measures included quantitative description of case demographics, symptoms, care-seeking, and clinical, social, and economic impact on cases and households. After survey completion, secondary analyses of factors associated with delayed diagnosis (by logistic regression) and consequences of delayed diagnosis (by Cox’s regression), and qualitative analysis of free text comments were added.Results Rash was reported for 89% of cases, but followed onset of other symptoms for 71%, with a median 1-day delay. Pattern of onset varied with age: sore throat was more common at onset among children 5 years and older (OR3.1, 95% CI 1.9 to 5.0). At first consultation, for 28%, scarlet fever was not considered: in these cases, symptoms were frequently attributed to viral infection (60%, 64/106). Delay in diagnosis beyond first consultation occurred more frequently among children aged 5+ who presented with sore throat (OR 2.8 vs 5+without sore throat; 95% CI 1.3 to 5.8). Cases with delayed diagnosis took, on average, 1 day longer to return to baseline activities.Conclusions Scarlet fever may be initially overlooked, es

Journal article

Siggins MK, Sriskandan S, 2021, Bacterial lymphatic metastasis in infection and immunity, Cells, Vol: 11, ISSN: 2073-4409

Lymphatic vessels permeate tissues around the body, returning fluid from interstitial spaces back to the blood after passage through the lymph nodes, which are important sites for adaptive responses to all types of pathogens. Involvement of the lymphatics in the pathogenesis of bacterial infections is not well studied. Despite offering an obvious conduit for pathogen spread, the lymphatic system has long been regarded to bar the onward progression of most bacteria. There is little direct data on live virulent bacteria, instead understanding is largely inferred from studies investigating immune responses to viruses or antigens in lymph nodes. Recently, we have demonstrated that extracellular bacterial lymphatic metastasis of virulent strains of Streptococcus pyogenes drives systemic infection. Accordingly, it is timely to reconsider the role of lymph nodes as absolute barriers to bacterial dissemination in the lymphatics. Here, we summarise the routes and mechanisms by which an increasing variety of bacteria are acknowledged to transit through the lymphatic system, including those that do not necessarily require internalisation by host cells. We discuss the anatomy of the lymphatics and other factors that influence bacterial dissemination, as well as the consequences of underappreciated bacterial lymphatic metastasis on disease and immunity.

Journal article

Wan Y, Mills E, Leung RCY, Vieira A, Zhi X, Croucher NJ, Woodford N, Jauneikaite E, Ellington MJ, Sriskandan Set al., 2021, Alterations in chromosomal genes nfsA, nfsB, and ribE are associated with nitrofurantoin resistance in escherichia coli from the UK, Microbial Genomics, Vol: 7, Pages: 1-19, ISSN: 2057-5858

Antimicrobial resistance in enteric or urinary Escherichia coli is a risk factor for invasive E. coli infections. Due to widespread trimethoprim resistance amongst urinary E. coli and increased bacteraemia incidence, a national recommendation to prescribe nitrofurantoin for uncomplicated urinary tract infection was made in 2014. Nitrofurantoin resistance is reported in <6% urinary E. coli isolates in the UK, however, mechanisms underpinning nitrofurantoin resistance in these isolates remain unknown. This study aimed to identify the genetic basis of nitrofurantoin resistance in urinary E. coli isolates collected from north west London and then elucidate resistance-associated genetic alterations in available UK E. coli genomes. As a result, an algorithm was developed to predict nitrofurantoin susceptibility.Deleterious mutations and gene-inactivating insertion sequences in chromosomal nitroreductase genes nfsA and/or nfsB were identified in genomes of nine nitrofurantoin-resistant urinary E. coli isolates, as well as all further 11 E. coli isolates that were experimentally validated to be nitrofurantoin resistant. Eight categories of allelic changes in nfsA, nfsB, and the associated gene ribE were detected in 12,412 E. coli genomes from the UK. Evolutionary analysis of these three genes revealed homoplasic mutations and explained the previously reported order of stepwise mutations. The mobile gene complex oqxAB, which is associated with reduced nitrofurantoin susceptibility, was identified in only one of the 12,412 genomes.In conclusion, mutations and insertion sequences in nfsA and nfsB were leading causes of nitrofurantoin resistance in UK E. coli. As nitrofurantoin exposure increases in human populations, the prevalence of nitrofurantoin resistance in carriage E. coli isolates and those from urinary and bloodstream infections should be monitored.

Journal article

Herdman MT, Cordery R, Karo B, Purba AK, Begum L, Lamagni T, Kee C, Balasegaram S, Sriskandan Set al., 2021, Clinical management and impact of scarlet fever in the modern era: findings from a cross-sectional study of cases in London, 2018-2019, BMJ OPEN, Vol: 11, ISSN: 2044-6055

Journal article

Cordery R, Purba A, Begum L, Mills E, Mosavie M, Vieira A, Jauneikaite E, Leung RCY, Siggins M, Ready D, Hoffman P, Lamagni T, Sriskandan Set al., 2021, Frequency of Transmission, asymptomatic shedding, and airborne spread of Streptococcus pyogenes among school children exposed to scarlet fever: a longitudinal multi-cohort molecular epidemiology contact tracing study, The Lancet Microbe, ISSN: 2666-5247

Background: Despite recommendations regarding prompt treatment of cases and enhanced hygiene measures, scarlet fever outbreaks increased in England between 2014-2018. Methods: We undertook a prospective, intensive contact tracing study in schools with consecutive scarlet fever cases to assess the impact of standard interventions on transmission of Streptococcus pyogenes between cases, classroom contacts, households, and classroom environments over 4 weeks using genome sequencing. Findings: Six classes, comprising 12 scarlet fever cases, 17 household contacts, and 278 classroom contacts were recruited. Prevalence of the outbreak strain in asymptomatic classroom contacts was high, increasing from 9.6% in week 1, to 26.9% in week 2, 23.9% in week 3, then 14.3% in week 4. Colonisation with non-outbreak strains was 0 - 7.5%. Genome sequencing showed clonality of isolates within each of six classes, confirming recent transmission accounted for high carriage. Of asymptomatic classroom contacts with S. pyogenes -positive throat swabs who were tested for transmissibility, 6/28 (21%) had positive cough plates and/or hand swabs, of whom three remained S. pyogenes -positive for 3 weeks. Only 1/60 surface swabs taken in 3 classrooms yielded S. pyogenes . In contrast, settle plates placed in elevated locations were S. pyogenes -positive in both classrooms tested. Interpretation: S. pyogenes transmission in schools is intense and may occur prior to, or in spite of reported treatment of cases, underlining a need for rapid case management. Despite guideline adherence, heavy shedding of S. pyogenes by small numbers of classroom contacts may perpetuate outbreaks, and airborne transmission has a plausible role in spread. Funding: Action Medical Research, UKRI, NIHR

Journal article

Seethalakshmi PS, Charity OJ, Giakoumis T, Kiran GS, Sriskandan S, Voulvoulis N, Selvin Jet al., 2021, Delineating the impact of COVID-19 on antimicrobial resistance: An Indian perspective., Science of the Total Environment, ISSN: 0048-9697

The COVID-19 pandemic has shattered millions of lives globally and continues to be a challenge to public health due to the emergence of variants of concern. Fear of secondary infections following COVID-19 has led to an escalation in antimicrobial use during the pandemic, while some antimicrobials have been repurposed as treatments for SARS-CoV-2, further driving antimicrobial resistance. India is one of the largest producers and consumers of antimicrobials globally, hence the task of curbing antimicrobial resistance is a huge challenge. Practices like empirical antimicrobial prescription and repurposing of drugs in clinical settings, self-medication and excessive use of antimicrobial hygiene products may have negatively impacted the prevalence of antimicrobial resistance in India. However, the expanded production of antimicrobials and disinfectants during the pandemic in response to increased demand may have had an even greater impact on the threat of antimicrobial resistance through major impacts on the environment. The review provides an outline of the impact COVID-19 can have on antimicrobial resistance in clinical settings and the possible outcomes on the environment. This review calls for the upgrading of existing antimicrobial policies and emphasizes the need for research studies to understand the impact of the pandemic on antimicrobial resistance in India.

Journal article

Li HK, Kaforou M, Rodriguez-Manzano J, Channon-Wells S, Monir A, Habgood-Coote D, Gupta RK, Mills EA, Lin J, Chiu Y-H, Pennisi I, Miglietta L, Mehta R, Obaray N, Herberg JA, Wright VJ, Georgiou P, Shallcross LJ, Mentzer AJ, Levin M, Cooke GS, Noursadeghi M, Sriskandan Set al., 2021, Discovery and validation of a 3-gene signature to distinguish COVID-19 and other viral infections in emergency infectious disease presentations; a case-control then observational cohort study, The Lancet Microbe, Vol: 2, Pages: 594-603, ISSN: 2666-5247

Background: Emergency admissions for infection often lack initial diagnostic certainty. COVID-19 has highlighted a need for novel diagnostic approaches to indicate likelihood of viral infection in a pandemic setting. We sought to derive and validate a blood transcriptional signature to detect viral infections including COVID-19 among adults with suspected infection presenting to the Emergency Department (ED).Methods: Blood RNA sequencing was performed on a discovery cohort of adults attending the ED with suspected infection who had subsequently-confirmed viral, bacterial, or no infection diagnoses. Differentially expressed host genes were subjected to feature selection to derive the most parsimonious discriminating signature. RT-qPCR validation of the signature was then performed in a prospective cohort of ED patients presenting with undifferentiated fever, and a second case-control cohort of ED patients with COVID-19 or bacterial infection. Signature performance was assessed by calculating area under receiver-operating characteristic curves (AUC-ROCs), sensitivities, and specificities.Findings: A 3-gene transcript signature was derived from the discovery cohort of 56 bacterial and 27 viral infection cases. In the validation cohort of 200 cases, the signature differentiated bacterial from viral infections with an AUC-ROC of 0.976 (95% CI: 0.919-1.000), sensitivity 97.3% and specificity of 100%. The AUC-ROC for C-reactive protein (CRP) and leucocyte count (WCC) was 0.833 (95% CI: 0.694-0.944) and 0.938 (95% CI: 0.840-0.986) respectively. The signature achieved higher net benefit in decision curve analysis than either CRP or WCC for discriminating viral infections from all other cases. In the second validation analysis the signature discriminated 35 bacterial infections from 34 SARS-CoV-2 positive COVID-19 infections with AUC-ROC of 0.953 (95% CI: 0.893-0.992), sensitivity 88.6% and specificity of 94.1%.Interpretation: This novel 3-gene signature discriminates viral i

Journal article

McKenna S, Huse KK, Giblin S, Pearson M, Majid Al Shibar MS, Sriskandan S, Matthews S, Pease JEet al., 2021, The role of streptococcal cell-envelope proteases in bacterial evasion of the innate immune system, Journal of Innate Immunity, Pages: 1-20, ISSN: 1662-811X

Bacteria possess the ability to evolve varied and ingenious strategies to outwit the host immune system, instigating an evolutionary arms race. Proteases are amongst the many weapons employed by bacteria, which specifically cleave and neutralize key signalling molecules required for a coordinated immune response. In this article, we focus on a family of S8 subtilisin-like serine proteases expressed as cell-envelope proteases (CEPs) by group A and group B streptococci. Two of these proteases known as Streptococcus pyogenes CEP (SpyCEP) and C5a peptidase cleave the chemokine CXCL8 and the complement fragment C5a, respectively. Both CXCL8 and C5a are potent neutrophil-recruiting chemokines, and by neutralizing their activity, streptococci evade a key defence mechanism of innate immunity. We review the mechanisms by which CXCL8 and C5a recruit neutrophils and the characterization of SpyCEP and C5a peptidase, including both in vitro and in vivo studies. Recently described structural insights into the function of this CEP family are also discussed. We conclude by examining the progress of prototypic vaccines incorporating SpyCEP and C5a peptidase in their preparation. Since streptococci-producing SpyCEP and C5a peptidase are responsible for a considerable global disease burden, targeting these proteases by vaccination strategies or by small-molecule antagonists should provide protection from and promote the resolution of streptococcal infections.

Journal article

Gibson JF, Pidwill GR, Carnell OT, Surewaard BGJ, Shamarina D, Sutton JAF, Jeffery C, Derré-Bobillot A, Archambaud C, Siggins MK, Pollitt EJG, Johnston SA, Serror P, Sriskandan S, Renshaw SA, Foster SJet al., 2021, Commensal bacteria augment Staphylococcus aureus infection by inactivation of phagocyte-derived reactive oxygen species, PLoS Pathogens, Vol: 17, ISSN: 1553-7366

Staphylococcus aureus is a human commensal organism and opportunist pathogen, causing potentially fatal disease. The presence of non-pathogenic microflora or their components, at the point of infection, dramatically increases S. aureus pathogenicity, a process termed augmentation. Augmentation is associated with macrophage interaction but by a hitherto unknown mechanism. Here, we demonstrate a breadth of cross-kingdom microorganisms can augment S. aureus disease and that pathogenesis of Enterococcus faecalis can also be augmented. Co-administration of augmenting material also forms an efficacious vaccine model for S. aureus. In vitro, augmenting material protects S. aureus directly from reactive oxygen species (ROS), which correlates with in vivo studies where augmentation restores full virulence to the ROS-susceptible, attenuated mutant katA ahpC. At the cellular level, augmentation increases bacterial survival within macrophages via amelioration of ROS, leading to proliferation and escape. We have defined the molecular basis for augmentation that represents an important aspect of the initiation of infection.

Journal article

Taylor E, Bal AM, Balakrishnan I, Brown NM, Burns P, Clark M, Diggle M, Donaldson H, Eltringham I, Folb J, Gadsby N, Macleod M, Ratnaraja NVDV, Williams C, Wootton M, Sriskandan S, Woodford N, Hopkins KLet al., 2021, A prospective surveillance study to determine the prevalence of 16S rRNA methyltransferase-producing Gram-negative bacteria in the UK, Journal of Antimicrobial Chemotherapy, Vol: 76, Pages: 2428-2436, ISSN: 0305-7453

OBJECTIVES: To determine the prevalence of 16S rRNA methyltransferase- (16S RMTase-) producing Gram-negative bacteria in patients in the UK and to identify potential risk factors for their acquisition. METHODS: A 6 month prospective surveillance study was conducted from 1 May to 31 October 2016, wherein 14 hospital laboratories submitted Acinetobacter baumannii, Enterobacterales and Pseudomonas aeruginosa isolates that displayed high-level amikacin resistance according to their testing methods, e.g. no zone of inhibition with amikacin discs. Isolates were linked to patient travel history, medical care abroad, and previous antibiotic exposure using a surveillance questionnaire. In the reference laboratory, isolates confirmed to grow on Mueller-Hinton agar supplemented with 256 mg/L amikacin were screened by PCR for 16S RMTase genes armA, rmtA-rmtH and npmA, and carbapenemase genes (blaKPC, blaNDM, blaOXA-48-like and blaVIM). STs and total antibiotic resistance gene complement were determined via WGS. Prevalence was determined using denominators for each bacterial species provided by participating hospital laboratories. RESULTS: Eighty-four isolates (44.7%), among 188 submitted isolates, exhibited high-level amikacin resistance (MIC >256 mg/L), and 79 (94.0%) of these harboured 16S RMTase genes. armA (54.4%, 43/79) was the most common, followed by rmtB (17.7%, 14/79), rmtF (13.9%, 11/79), rmtC (12.7%, 10/79) and armA + rmtF (1.3%, 1/79). The overall period prevalence of 16S RMTase-producing Gram-negative bacteria was 0.1% (79/71 063). Potential risk factors identified through multivariate statistical analysis included being male and polymyxin use. CONCLUSIONS: The UK prevalence of 16S RMTase-producing Gram-negative bacteria is low, but continued surveillance is needed to monitor their spread and inform intervention strategies.

Journal article

Jauneikaite E, Pichon B, Mosavie M, Fallowfield JL, Davey T, Thorpe N, Nelstrop A, Sriskandan S, Lamb LEet al., 2021, Staphylococcus argenteus transmission among healthy Royal Marines: a molecular epidemiology case-study, Journal of Infection, Vol: 83, ISSN: 0163-4453

Objectives: During a prospective study of S. aureus carriage in Royal Marines recruits, six S. argenteus strains were identified in four recruits. As S. argenteus sepsis leads to mortality similar to S. aureus, we determined the potential for within same troop transmission, to evaluate future outbreak risk.Methods: We used whole-genome sequencing to characterise S. argenteus and investigate phylogenetic relationships between isolates.Results: S. argenteus strains (t5078, ST2250) were detected in 4/40 recruits in the same troop (training cohort) in weeks 1, 6 or 15 of training. No mec, tsst or LukPV genes were detected. We identified differences of 1-17 core SNPs between S. argenteus from different recruits. In two recruits, two S. argenteus strains were isolated; these could be distinguished by 2 and 15 core SNPs.Conclusions: The identification of S. argenteus within a single troop from the total recruit population suggests a common source for transmission, though high number of SNPs were identified, both within-host and within-cluster. The high number of SNPs between some isolates may indicate a common source of diverse isolates or a high level of S. argenteus mutation in carriage. S. argenteus is newly recognised species; and understanding of the frequency of genetic changes during transmission and transition from asymptomatic carriage to disease is required.

Journal article

Jauneikaite E, Honeyford K, Blandy O, Mosavie M, Pearson M, Ramzan FA, Ellington MJ, Parkhill J, Costelloe CE, Woodford N, Sriskandan Set al., 2021, Bacterial genotypic and patient risk factors for adverse outcomes in Escherichia coli bloodstream infections: a prospective molecular-epidemiological study

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p><jats:italic>Escherichia coli</jats:italic> bloodstream infections have increased rapidly in the UK, for reasons that are unclear. The relevance of highly fit, or multi-drug resistant lineages such as ST131 to overall <jats:italic>E. coli</jats:italic> disease burden remains to be fully determined. We set out to characterise the prevalence of <jats:italic>E. coli</jats:italic> multi-locus sequence types (MLST) and determine if these were associated with adverse outcomes in an urban population of <jats:italic>E. coli</jats:italic> bacteraemia patients.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We undertook whole genome sequencing of <jats:italic>E. coli</jats:italic> blood isolates from all patients with diagnosed <jats:italic>E. coli</jats:italic> bacteraemia in north-west London from July 2015 to August 2016 and assigned multi-locus sequence types to all isolates. Isolate sequence types were linked to routinely collected antimicrobial susceptibility, patient demographic, and clinical outcome data to explore relationships between the <jats:italic>E. coli</jats:italic> sequence types, patient factors, and outcomes.</jats:p></jats:sec><jats:sec><jats:title>Findings</jats:title><jats:p>A total of 551 <jats:italic>E. coli</jats:italic> genomes were available for analysis. More than half of these cases were caused by four <jats:italic>E. coli</jats:italic> sequence types: ST131 (21%), ST73 (15%), ST69 (9%) and ST95 (8%). <jats:italic>E. coli</jats:italic> genotype ST131-C2 was associated with non-susceptibility to quinolones and third-generation cephalosporins, and also to amoxicillin, augmentin, gentamicin and trimethoprim. An associat

Journal article

Rawson TM, Hernandez B, Moore L, Herrero P, Charani E, Ming D, Wilson R, Blandy O, Sriskandan S, Toumazou C, Georgiou P, Holmes Aet al., 2021, A real-world evaluation of a case-based reasoning algorithm to support antimicrobial prescribing decisions in acute care, Clinical Infectious Diseases, Vol: 72, Pages: 2103-2111, ISSN: 1058-4838

BackgroundA locally developed Case-Based Reasoning (CBR) algorithm, designed to augment antimicrobial prescribing in secondary care was evaluated.MethodsPrescribing recommendations made by a CBR algorithm were compared to decisions made by physicians in clinical practice. Comparisons were examined in two patient populations. Firstly, in patients with confirmed Escherichia coli blood stream infections (‘E.coli patients’), and secondly in ward-based patients presenting with a range of potential infections (‘ward patients’). Prescribing recommendations were compared against the Antimicrobial Spectrum Index (ASI) and the WHO Essential Medicine List Access, Watch, Reserve (AWaRe) classification system. Appropriateness of a prescription was defined as the spectrum of the prescription covering the known, or most-likely organism antimicrobial sensitivity profile.ResultsIn total, 224 patients (145 E.coli patients and 79 ward patients) were included. Mean (SD) age was 66 (18) years with 108/224 (48%) female gender. The CBR recommendations were appropriate in 202/224 (90%) compared to 186/224 (83%) in practice (OR: 1.24 95%CI:0.392-3.936;p=0.71). CBR recommendations had a smaller ASI compared to practice with a median (range) of 6 (0-13) compared to 8 (0-12) (p<0.01). CBR recommendations were more likely to be classified as Access class antimicrobials compared to physicians’ prescriptions at 110/224 (49%) vs. 79/224 (35%) (OR: 1.77 95%CI:1.212-2.588 p<0.01). Results were similar for E.coli and ward patients on subgroup analysis.ConclusionsA CBR-driven decision support system provided appropriate recommendations within a narrower spectrum compared to current clinical practice. Future work must investigate the impact of this intervention on prescribing behaviours more broadly and patient outcomes.

Journal article

Jauneikaite E, Pichon B, Mosavie M, Fallowfield JL, Davey T, Thorpe N, Nelstrop A, Sriskandan S, Lamb LEet al., 2021, Characterisation of Staphylococcus argenteus carried by healthy Royal Marines: a molecular epidemiology case-study

<jats:title>Abstract</jats:title><jats:sec><jats:title>Objectives</jats:title><jats:p>During a prospective study of <jats:italic>S. aureus</jats:italic> carriage in Royal Marines (RM) recruits, six <jats:italic>S. argenteus</jats:italic> strains were identified in four recruits undertaking military training together. As <jats:italic>S. argenteus</jats:italic> sepsis leads to mortality similar to <jats:italic>S. aureus</jats:italic>, we determined the potential for person-to-person transmission, to evaluate future outbreak risk.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We used whole-genome sequencing to characterise <jats:italic>S. argenteus</jats:italic> and investigate phylogenetic relationships between isolates. Participant colonisation with <jats:italic>S. aureus</jats:italic> and skin and soft tissue infection acquisition were recorded.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>All six <jats:italic>S. argenteus</jats:italic> strains were <jats:italic>spa</jats:italic>-type t5078, ST2250. Strains were detected in 4/40 recruits in the same troop (training cohort) in weeks 1, 6 or 15 of training. No <jats:italic>mec, tsst</jats:italic> or <jats:italic>LukPV</jats:italic> genes were detected. We identified differences of 10-35 core SNPs between <jats:italic>S. argenteus</jats:italic> from different recruits. In two recruits, two <jats:italic>S. argenteus</jats:italic> strains were isolated; these could be distinguished by 3 and 15 core SNPs in each case. <jats:italic>S. argenteus</jats:italic> was not identified in any one of the other 21 participating troops (1,012 recruits).</jats:p></jats:sec><jats:sec><jats:title>Conclusions&

Journal article

Collin SM, Groves N, O' Sullivan C, Jauneikaite E, Patel D, CUnney R, Meehan M, Reynolds A, Smith A, Lindsay D, Doherty L, Davies E, Chalker V, Lamb P, Afshar B, Balasegaram S, Coelho J, Ready D, Brown CS, Efstratiou A, Le Doare K, Sriskandan S, Heath PT, Lamagni Tet al., 2021, Uncovering infant group B streptococcal (GBS) disease clusters in the UK and Ireland through genomic analysis: a population-based epidemiological study, Clinical Infectious Diseases, Vol: 72, Pages: e296-e302, ISSN: 1058-4838

BackgroundThe true frequency of hospital outbreaks of invasive group B streptococcal (iGBS; Streptococcus agalactiae) disease in infants is unknown. We used whole genome sequencing (WGS) of iGBS isolates collected during a period of enhanced surveillance of infant iGBS disease in the UK and Ireland to determine the number of clustered cases.MethodsPotentially linked iGBS cases from infants with early (<7 days of life) or late-onset (7–89 days) disease were identified from WGS data (HiSeq 2500 platform, Illumina) from clinical sterile site isolates collected between 04/2014 and 04/2015. We assessed time and place of cases to determine a single-nucleotide polymorphism (SNP) difference threshold for clustered cases. Case details were augmented through linkage to national hospital admission data and hospital record review by local microbiologists.ResultsAnalysis of sequences indicated a cutoff of ≤5 SNP differences to define iGBS clusters. Among 410 infant iGBS isolates, we identified 7 clusters (4 genetically identical pairs with 0 SNP differences, 1 pair with 3 SNP differences, 1 cluster of 4 cases with ≤1 SNP differences) of which 4 clusters were uncovered for the first time. The clusters comprised 16 cases, of which 15 were late-onset (of 192 late-onset cases with sequenced isolates) and 1 an early-onset index case. Serial intervals between cases ranged from 0 to 59 (median 12) days.ConclusionsApproximately 1 in 12 late-onset infant iGBS cases were part of a hospital cluster. Over half of the clusters were previously undetected, emphasizing the importance of routine submission of iGBS isolates to reference laboratories for cluster identification and genomic confirmation.

Journal article

Tan LKK, Reglinski M, Teo D, Reza N, Lamb LEM, Nageshwaran V, Turner CE, Wikstrom M, Frick I-M, Bjorck L, Sriskandan Set al., 2021, Vaccine-induced, but not natural immunity, against the Streptococcal Inhibitor of complement protects against invasive disease, npj Vaccines, Vol: 6, Pages: 1-9, ISSN: 2059-0105

Highly pathogenic emm1 Streptococcus pyogenes strains secrete the multidomain Streptococcal inhibitor of complement (SIC) that binds and inactivates components of the innate immune response. We aimed to determine if naturally occurring or vaccine-induced antibodies to SIC are protective against invasive S. pyogenes infection. Immunisation with full-length SIC protected mice against systemic bacterial dissemination following intranasal or intramuscular infection with emm1 S. pyogenes. Vaccine-induced rabbit anti-SIC antibodies, but not naturally occurring human anti-SIC antibodies, enhanced bacterial clearance in an ex vivo whole-blood assay. SIC vaccination of both mice and rabbits resulted in antibody recognition of all domains of SIC, whereas naturally occurring human anti-SIC antibodies recognised the proline-rich region of SIC only. We, therefore, propose a model whereby natural infection with S. pyogenes generates non-protective antibodies against the proline-rich region of SIC, while vaccination with full-length SIC permits the development of protective antibodies against all SIC domains.

Journal article

Ellington MJ, Davies F, Jauneikaite E, Hopkins KL, Turton JF, Adams G, Pavlu J, Innes AJ, Eades C, Brannigan ET, Findlay J, White L, Bolt F, Kadhani T, Chow Y, Patel B, Mookerjee S, Otter JA, Sriskandan S, Woodford N, Holmes Aet al., 2020, A multi-species cluster of GES-5 carbapenemase producing Enterobacterales linked by a geographically disseminated plasmid, Clinical Infectious Diseases, Vol: 71, Pages: 2553-2560, ISSN: 1058-4838

BACKGROUND: Early and accurate treatment of infections due to carbapenem-resistant organisms is facilitated by rapid diagnostics but rare resistance mechanisms can compromise detection. One year after a GES-5 carbapenemase-positive Klebsiella oxytoca infection was identified by whole genome sequencing (WGS) (later found to be part of a cluster of three cases), a cluster of 11 patients with GES-5-positive K. oxytoca was identified over 18 weeks in the same hospital.METHODS: Bacteria were identified by MALDI-TOF, antimicrobial susceptibility testing followed EUCAST guidelines. Ertapenem-resistant isolates were referred to Public Health England for characterization using PCR detection of GES, pulse-field gel electrophoresis (PFGE) and WGS for the second cluster.RESULTS: The identification of the first GES-5 K. oxytoca isolate was delayed, being identified on WGS. A GES-gene PCR informed the occurrence of the second cluster in real-time. In contrast to PFGE, WGS phylogenetic analysis refuted an epidemiological link between the two clusters; it also suggested a cascade of patient-to-patient transmission in the later cluster. A novel GES-5-encoding plasmid was present in K. oxytoca,E. coli and E. cloacae isolates from unlinked patients within the same hospital group and in human and wastewater isolates from three hospitals elsewhere in the UK.CONCLUSIONS: Genomic sequencing revolutionized the epidemiological understanding of the clusters, it also underlined the risk of covert plasmid propagation in healthcare settings and revealed the national distribution of the resistance-encoding plasmid. Sequencing results also informed and led to the ongoing use of enhanced diagnostic tests for detecting carbapenemases locally and nationally.

Journal article

Siggins MK, Lynskey NN, Lamb L, Johnson L, Huse K, Pearson M, Banerji S, Turner CE, Woollard K, Jackson DG, Sriskandan Set al., 2020, Extracellular bacterial lymphatic metastasis drives Streptococcus pyogenes systemic infection, Nature Communications, Vol: 11, ISSN: 2041-1723

Unassisted metastasis through the lymphatic system is a mechanism of dissemination thus far ascribed only to cancer cells. Here, we report that Streptococcus pyogenes also hijack lymphatic vessels to escape a local infection site, transiting through sequential lymph nodes and efferent lymphatic vessels to enter the bloodstream. Contrasting with previously reported mechanisms of intracellular pathogen carriage by phagocytes, we show S. pyogenes remain extracellular during transit, first in afferent and then efferent lymphatics that carry the bacteria through successive draining lymph nodes. We identify streptococcal virulence mechanisms important for bacterial lymphatic dissemination and show that metastatic streptococci within infected lymph nodes resist and subvert clearance by phagocytes, enabling replication that can seed intense bloodstream infection. The findings establish the lymphatic system as both a survival niche and conduit to the bloodstream for S. pyogenes, explaining the phenomenon of occult bacteraemia. This work provides new perspectives in streptococcal pathogenesis with implications for immunity.

Journal article

Matthews S, McKenna S, Malito E, Rouse S, Abate F, Bensi G, Emiliano C, Micoli F, Mancini F, Gomes Moriel D, Grandi G, Mossakowska D, Pearson M, Xu Y, Pease J, Sriskandan S, Margarit I, Bottomley MJet al., 2020, Structure, dynamics and immunogenicity of a catalytically inactive CXC Chemokine-degrading Protease SpyCEP from Streptococcus pyogenes, Computational and Structural Biotechnology Journal, Vol: 18, Pages: 650-660, ISSN: 2001-0370

Over 18 million disease cases and half a million deaths worldwide are estimated to be caused annually by Group A Streptococcus. A vaccine to prevent GAS disease is urgently needed. SpyCEP (Streptococcus pyogenes Cell-Envelope Proteinase) is a surface-exposed serine protease that inactivates chemokines, impairing neutrophil recruitment and bacterial clearance, and has shown promising immunogenicity in preclinical models. Although SpyCEP structure has been partially characterized, a more complete and higher resolution understanding of its antigenic features would be desirable prior to large scale manufacturing. To address these gaps and facilitate development of this globally important vaccine, we performed immunogenicity studies with a safety-engineered SpyCEP mutant, and comprehensively characterized its structure by combining X-ray crystallography, NMR spectroscopy and molecular dynamics simulations. We found that the catalytically-inactive SpyCEP antigen conferred protection similar to wild-type SpyCEP in a mouse infection model. Further, a new higher-resolution crystal structure of the inactive SpyCEP mutant provided new insights into this large chemokine protease comprising nine domains derived from two non-covalently linked fragments. NMR spectroscopy and molecular simulation analyses revealed conformational flexibility that is likely important for optimal substrate recognition and overall function. These combined immunogenicity and structural data demonstrate that the full-length SpyCEP inactive mutant is a strong candidate human vaccine antigen. These findings show how a multi-disciplinary study was used to overcome obstacles in the development of a GAS vaccine, an approach applicable to other future vaccine programs. Moreover, the information provided may also facilitate the structure-based discovery of small-molecule therapeutics targeting SpyCEP protease inhibition.

Journal article

Jauneikaite E, Ferguson T, Mosavie M, Fallowfield JL, Davey T, Thorpe N, Allsopp A, Shaw AM, Fudge D, O'Shea MK, Wilson D, Morgan M, Pichon B, Kearns AM, Sriskandan S, Lamb LEet al., 2020, Staphylococcus aureus colonisation and acquisition of skin and soft tissue infection amongst Royal Marines recruits: A prospective cohort study, Clinical Microbiology and Infection, Vol: 26, Pages: 381.e1-381.e6, ISSN: 1198-743X

Objectives: Skin and soft tissue infections (SSTIs) are a serious health issue for military personnel. Of particular importance are those caused by MRSA and PVL-positive S. aureus (PVL-SA), as they have been associated with outbreaks of SSTIs. A prospective observational study was conducted in Royal Marines recruits to investigate the prevalence of PVL-SA carriage and any association with SSTIs.Methods: 1,012 RM recruits were followed through a 32-week training programme, with nose and throat swabs obtained at weeks 1, 6, 15 and 32. S. aureus isolates were characterised by antibiotic susceptibility testing, spa typing, presence of mecA/C and PVL genes. Retrospective review of the clinical notes for SSTI acquisition was conducted.Results: S. aureus colonisation decreased from week-1 to week-32 (41% to 26%, p<0.0001). Of 1,168 S. aureus isolates, 3/1168 (0.3%) were MRSA and 10/1168 (0.9%) PVL-positive (all MSSA) and 169/1168 (14.5%) were resistant to clindamycin. Isolates showed genetic diversity with 238 different spa types associated with 25 MLST clonal complexes. SSTIs were seen in 35% (351/989) of recruits with 3 training days lost per recruit. SSTI acquisition rate was reduced amongst persistent carriers (p<0.0283). Conclusions: Nose and throat carriage of MRSA and PVL-SA was low amongst recruits, despite a high incidence of SSTIs being reported particularly cellulitis. Carriage strains were predominantly MSSA with a marked diversity of genotypes. Persistent nose and/or throat carriage was not associated with SSTI acquisition. Putative person-to-person transmission within troops was identified based on spa typing requiring further research to confirm and explore potential transmission routes.

Journal article

Parks T, Elliot K, Lamagni T, Auckland K, Mentzer AJ, Guy R, Cartledge D, Strakova L, O'Connor D, Pollard AJ, Neville MJ, Mahajan A, Ashrafian H, Chapman SJ, Hill AVS, Sriskandan S, Knight JCet al., 2020, Elevated risk of invasive group a streptococcal disease and host genetic variation in the human leukocyte antigen locus, Genes and Immunity, Vol: 21, Pages: 63-70, ISSN: 1466-4879

Invasive group A streptococcal (GAS) disease is uncommon but carries a high casefatality rate relative to other infectious diseases. Given the ubiquity of mild GASinfections, it remains unclear why healthy individuals will occasionally develop lifethreatening infections, raising the possibility of host genetic predisposition. Here, wepresent the results of a case-control study including 43 invasive GAS cases and1,540 controls. Using HLA imputation and linear mixed-models, we find each copy ofthe HLA-DQA1*01:03 allele associates with a two-fold increased risk of disease(odds ratio 2.3, 95% confidence interval 1.3-4.4, P=0.009), an association whichpersists with classical HLA typing of a subset of cases and analysis with analternative large control dataset with validated HLA data. Moreover, we propose theassociation is driven by the allele itself rather than the background haplotype. Overallthis finding provides impetus for further investigation of the immunogenetic basis ofthis devastating bacterial disease.

Journal article

Collin SM, Lamb P, Jauneikaite E, Le Doare K, Creti R, Berardi A, Heath PT, Sriskandan S, Lamagni Tet al., 2019, Hospital clusters of invasive Group B Streptococcal disease: a systematic review, Journal of Infection, Vol: 79, Pages: 521-527, ISSN: 0163-4453

Objectives: To characterize outbreaks of invasive Group B Streptococcal (iGBS) disease in hospitals.Methods: Systematic review using electronic databases to identify studies describing iGBS outbreaks/clusters or cross-infection/acquisition in healthcare settings where ‘cluster’ was defined as ≥2 linked cases. PROSPERO CRD42018096297.Results: Twenty-five references were included describing 30 hospital clusters (26 neonatal, 4 adult) in 11 countries from 1966 to 2019. Cross-infection between unrelated neonates was reported in 19 clusters involving an early-onset (<7 days of life; n = 3), late-onset (7–90 days; n = 13) index case or colonized infant (n = 3) followed by one or more late-onset cases (median serial interval 9 days (IQR 3–17, range 0–50 days, n = 45)); linkage was determined by phage typing in 3 clusters, PFGE/MLST/PCR in 8, WGS in 4, non-molecular methods in 4. Postulated routes of transmission in neonatal clusters were via clinical personnel and equipment, particularly during periods of crowding and high patient-to-nurse ratio. Of 4 adult clusters, one was attributed to droplet spread between respiratory cases, one to handling of haemodialysis catheters and two unspecified.Conclusions: Long intervals between cases were identified in most of the clusters, a characteristic which potentially hinders detection of GBS hospital outbreaks without enhanced surveillance supported by genomics.

Journal article

Herbert R, Hatcher J, Jauneikaite E, Gharbi M, d'Arc S, Obaray N, Rickards T, Rebec M, Blandy O, Hope R, Thomas A, Bamford K, Jepson A, Sriskandan Set al., 2019, Two-year analysis of Clostridium difficile ribotypes associated with increased severity, Journal of Hospital Infection, Vol: 103, Pages: 388-394, ISSN: 0195-6701

BackgroundCertain Clostridium difficile ribotypes have been associated with complex disease phenotypes including recurrence and increased severity, especially the well-described hypervirulent ribotype RT027. In this study we set out to determine the pattern of ribotypes causing infection and association if any with severity.MethodsAll faecal samples submitted to a large diagnostic laboratory for C. difficile testing between 2011 and 2013 were subject to routine testing and cultured. All C. difficile isolates were ribotyped and associated clinical and demographic patient data were retrieved then linked to ribotyping data.ResultsA total of 86 distinct ribotypes were identified from 705 isolates of C. difficile. Ribotypes RT002 and RT015 were the most prevalent (22.5%, n=159). Only five isolates (0.7%) were the hypervirulent RT027. Ninety of 450 (20%) patients with clinical information available died within 30-days of C. difficile isolation. Ribotype RT220, one of the ten commonest ribotypes, was associated with elevated median C-reactive protein and significantly increased 30-day all-cause mortality when compared with ribotypes RT002 and RT015, and with all other ribotypes found in the study.ConclusionsA wide range of C. difficile ribotypes were responsible for C. difficile infection presentations. Although C. difficile-associated mortality has reduced in recent years, expansion of lineages associated with increased severity could herald increases in future mortality. Enhanced surveillance for emerging lineages such as RT220 that are associated with more severe disease is required, with genomic approaches to dissect pathogenicity.

Journal article

Turner CE, Holden MTG, Blane B, Horner C, Peacock SJ, Sriskandan Set al., 2019, The emergence of successful streptococcus pyogenes lineages through convergent pathways of capsule loss and recombination directing high toxin expression, mBio, Vol: 10, Pages: 1-20, ISSN: 2150-7511

Gene transfer and homologous recombination in Streptococcus pyogenes has the potential to trigger the emergence of pandemic lineages, as exemplified by lineages of emm1 and emm89 that emerged in the 1980s and 2000s, respectively. Although near-identical replacement gene transfer events in the nga (NADase) and slo (streptolysin O) loci conferring high expression of these toxins underpinned the success of these lineages, extension to other emm genotype lineages is unreported. The emergent emm89 lineage was characterized by five regions of homologous recombination additional to nga-slo, including complete loss of the hyaluronic acid capsule synthesis locus hasABC, a genetic trait replicated in two other leading emm types and recapitulated by other emm types by inactivating mutations. We hypothesized that other leading genotypes may have undergone similar recombination events. We analyzed a longitudinal data set of genomes from 344 clinical invasive disease isolates representative of locations across England, dating from 2001 to 2011, and an international collection of S. pyogenes genomes representing 54 different genotypes and found frequent evidence of recombination events at the nga-slo locus predicted to confer higher toxin genotype. We identified multiple associations between recombination at this locus and inactivating mutations within hasAB, suggesting convergent evolutionary pathways in successful genotypes. This included common genotypes emm28 and emm87. The combination of no or low capsule and high expression of nga and slo may underpin the success of many emergent S. pyogenes lineages of different genotypes, triggering new pandemics, and could change the way S. pyogenes causes disease.IMPORTANCE Streptococcus pyogenes is a genetically diverse pathogen, with over 200 different genotypes defined by emm typing, but only a minority of these genotypes are responsible for the majority of human infection in high-income countries. Two prevalent genotypes associated w

Journal article

Lynskey NN, Jauneikaite E, Li H-K, Zhi X, Turner CE, Mosavie M, Pearson M, Asai M, Lobkowicz L, Chow JY, Parkhill J, Lamagni T, Chalker V, Sriskandan Set al., 2019, Emergence of dominant toxigenic M1T1 Streptococcus pyogenes clone during increased scarlet fever activity in England: a population-based molecular epidemiological study, Lancet Infectious Diseases, Vol: 19, Pages: 1209-1218, ISSN: 1473-3099

BackgroundEngland is experiencing scarlet fever activity unprecedented in modern times. In 2016, England’s scarlet fever seasonal rise coincided with an unexpected elevation in invasive Streptococcus pyogenes infections. We describe the molecular-epidemiological investigation of these events and emergence of a new emm1 lineage.Methods We analysed changes in S. pyogenes emm-genotypes, and notifications of scarlet fever and invasive disease 2014-2016 using regional (North-West London) and national (England and Wales) data. We analysed genomes of 135 non-invasive and 552 invasive emm1 isolates from 2009-2016, and compared 2800 global emm1 sequences. Expression of Streptococcal pyrogenic exotoxin (Spe)A by sequenced non-invasive emm1 isolates was quantified.FindingsCoincident with national increases in scarlet fever and invasive disease notifications, emm1 S. pyogenes increased significantly, from 19% (28/147) of upper respiratory tract isolates in MarchMay 2015, to 32·6% (47/144) in the same period 2016 in North-West London (χ2 (1df)=7·024, p=0·008), and from 31% (183/587) of invasive isolates in March-May 2015, to 41·9% (267/637)in the same period 2016 nationally (χ2 (1df)=15·16, p=0·0001). Sequences of emm1 isolates from 2009-2016 demonstrated emergence of a new emm1 lineage (M1UK), with overlap of pharyngitis, scarlet fever, and invasive M1UK strains, that could be genotypically distinguished from pandemic emm1 isolates (M1global). Compared with M1global, median expression of SpeA increased 9-fold in M1UK isolates (M1global, median=20·9 ng/ml, IQ range=21.3; (M1UK, median=190·2 ng/ml, IQ3 range 31.5; Mann-Whitney p<0·001). M1UK expanded nationally to represent 84% (252/299) of all emm1 genomes in 2016; phylogenetic analysis of published datasets identified single M1UK isolates in Denmark and USA.

Journal article

Greer O, Shah NM, Sriskandan S, Johnson MRet al., 2019, Sepsis: precision-based medicine for pregnancy and the puerperium, International Journal of Molecular Sciences, Vol: 20, Pages: 1-18, ISSN: 1422-0067

Sepsis contributes significantly to global morbidity and mortality, particularly in vulnerable populations. Pregnant and recently pregnant women are particularly prone to rapid progression to sepsis and septic shock, with 11% of maternal deaths worldwide being attributed to sepsis. The impact on the neonate is considerable, with 1 million neonatal deaths annually attributed to maternal infection or sepsis. Pregnancy specific physiological and immunological adaptations are likely to contribute to a greater impact of infection, but current approaches to the management of sepsis are based on those developed for the non-pregnant population. Pregnancy-specific strategies are required to optimise recognition and management of these patients. We review current knowledge of the physiology and immunology of pregnancy and propose areas of research, which may advance the development of pregnancy-specific diagnostic and therapeutic approaches to optimise the care of pregnant women and their babies.

Journal article

Sharma H, Turner CE, Siggins MK, El-Bahrawy M, Pichon B, Kearns A, Sriskandan Set al., 2019, Toxic shock syndrome toxin-1 evaluation and antibiotic impact in a transgenic model of staphylococcal soft tissue infection, mSphere, Vol: 4, ISSN: 2379-5042

Nonmenstrual toxic shock syndrome (nmTSS), linked to TSST-1-producing CC30 Staphylococcus aureus, is the leading manifestation of toxic shock syndrome (TSS). Due to case rarity and a lack of tractable animal models, TSS pathogenesis is poorly understood. We developed an S. aureus abscess model in HLA class II transgenic mice to investigate pathogenesis and treatment. TSST-1 sensitivity was established using murine spleen cell proliferation assays and cytokine assays following TSST-1 injection in vivo. HLA-DQ8 mice were infected subcutaneously with a tst-positive CC30 methicillin-sensitive S. aureus clinical TSS-associated isolate. Mice received intraperitoneal flucloxacillin, clindamycin, flucloxacillin and clindamycin, or a control reagent. Abscess size, bacterial counts, TSST-1 expression, and TSST-1 bioactivity were measured in tissues. Antibiotic effects were compared with the effects of control reagent. Purified TSST-1 expanded HLA-DQ8 T-cell Vβ subsets 3 and 13 in vitro and instigated cytokine release in vivo, confirming TSST-1 sensitivity. TSST-1 was detected in abscesses (0 to 8.0 μg/ml) and draining lymph nodes (0 to 0.2 μg/ml) of infected mice. Interleukin 6 (IL-6), gamma interferon (IFN-γ), KC (CXCL1), and MCP-1 were consistent markers of inflammation during infection. Clindamycin-containing antibiotic regimens reduced abscess size and TSST-1 production. Infection led to detectable TSST-1 in soft tissues, and TSST-1 was detected in draining lymph nodes, events which may be pivotal to TSS pathogenesis. The reduction in TSST-1 production and lesion size after a single dose of clindamycin underscores a potential role for adjunctive clindamycin at the start of treatment of patients suspected of having TSS to alter disease progression.

Journal article

Parks T, Auckland K, Lamagni TL, Mentzer A, Elliott K, Guy R, Cartledge D, Strakova L, OConnor D, Pollard AJ, Chapman SJ, Thomas M, Brodlie M, Colot J, DOrtenzio E, Baroux N, Mirabel M, Gilchrist JJ, Scott JAG, Williams TN, Knight J, Steer AC, Hill AVS, Sriskandan Set al., 2019, Host genetic variants near the PAX5 gene locus associate with susceptibility to invasive group A streptococcal disease

<jats:title>Abstract</jats:title><jats:p>We undertook a genome-wide association study of susceptibility to invasive group A streptococcal (GAS) disease combining data from distinct clinical manifestations and ancestral populations. Amongst other signals, we identified a susceptibility locus located 18kb from <jats:italic>PAX5</jats:italic>, an essential B-cell gene, which conferred a nearly two-fold increased risk of disease (rs1176842, odds ratio 1.8, 95% confidence intervals 1.5-2.3, P=3.2×10<jats:sup>−7</jats:sup>). While further studies are needed, this locus could plausibly explain some inter-individual differences in antibody-mediated immunity to GAS, perhaps providing insight into the effects of intravenous immunoglobulin in streptococcal toxic shock.</jats:p>

Journal article

Davies F, Olme C, Lynskey N, Turner CE, Sriskandan Set al., 2019, Streptococcal superantigen‐induced expansion of human tonsil T cells leads to altered T follicular helper cell phenotype, B cell death and reduced immunoglobulin release, Clinical and Experimental Immunology, Vol: 197, Pages: 83-94, ISSN: 1365-2249

Streptococcal pyrogenic exotoxin (Spe) A expression is epidemiologically linked to streptococcal tonsillo‐pharyngitis and outbreaks of scarlet fever, although the mechanisms by which superantigens confer advantage to Streptococcus pyogenes are unclear. S. pyogenes is an exclusively human pathogen. As the leucocyte profile of tonsil is unique, the impact of SpeA production on human tonsil cell function was investigated. Human tonsil cells from routine tonsillectomy were co‐incubated with purified streptococcal superantigens or culture supernatants from isogenic streptococcal isolates, differing only in superantigen production. Tonsil cell proliferation was quantified by tritiated thymidine incorporation, and cell surface characteristics assessed by flow cytometry. Soluble mediators including immunoglobulin were measured using enzyme‐linked immunosorbent assay. Tonsil T cells proliferated in response to SpeA and demonstrated typical release of proinflammatory cytokines. When cultured in the absence of superantigen, tonsil preparations released large quantities of immunoglobulin over 7 days. In contrast, marked B cell apoptosis and abrogation of total immunoglobulin (Ig)A, IgM, and IgG production occurred in the presence of SpeA and other superantigens. In SpeA‐stimulated cultures, T follicular helper (Tfh) cells showed a reduction in C‐X‐C chemokine receptor (CXCR)5 (CD185) expression, but up‐regulation of OX40 (CD134) and inducible T cell co‐stimulator (ICOS) (CD278) expression. The phenotypical change in the Tfh population was associated with impaired chemotactic response to CXCL13. SpeA and other superantigens cause dysregulated tonsil immune function, driving T cells from Tfh to a proliferating phenotype, with resultant loss of B cells and immunoglobulin production, providing superantigen‐producing bacteria with a probable survival advantage.

Journal article

Mosavie M, Blandy O, Jauneikaite E, Caldas I, Ellington MJ, Woodford N, Sriskandan Set al., 2019, Sampling and diversity of Escherichia coli from the enteric microbiota in patients with Escherichia coli bacteraemia, BMC Research Notes, Vol: 12, ISSN: 1756-0500

ObjectiveThe increase in Escherichia coli bloodstream infections mandates better characterisation of the relationship between commensal and invasive isolates. This study adopted a simple approach to characterize E. coli in the gut reservoir from patients with either E. coli or other Gram-negative bacteraemia, or those without bacteraemia, establishing strain collections suitable for genomic investigation. Enteric samples from patients in the three groups were cultured on selective chromogenic agar. Genetic diversity of prevailing E. coli strains in gut microbiota was estimated by RAPD-PCR.ResultsEnteric samples from E. coli bacteraemia patients yielded a median of one E. coli RAPD pattern (range 1–4) compared with two (range 1–5) from groups without E. coli bacteraemia. Of relevance to large-scale clinical studies, observed diversity of E. coli among hospitalised patients was not altered by sample type (rectal swab or stool), nor by increasing the colonies tested from 10 to 20. Hospitalised patients demonstrated an apparently limited diversity of E. coli in the enteric microbiota and this was further reduced in those with E. coli bacteraemia. The reduced diversity of E. coli within the gut during E. coli bacteraemia raises the possibility that dominant strains may outcompete other lineages in patients with bloodstream infection.

Journal article

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