Evolution of genotypes of Group A streptococci from colonization and infection

Dissertação para obtenção do Grau de Doutor em BiologiaStreptococcus pyogenes is one pathogenic bacterium of humans and is associated with a wide variety of infections and disease states, ranging from uncomplicated but highly prevalent pharyngitis to extremely severe infections, such as necrotizing fasciitis and streptococcal toxic shock syndrome. This work aimed to study important and unexplored aspects of the epidemiology, transmission and evolution of S. pyogenes causing colonization and a wide range of diseases. Our sample included 1,629 nonduplicated S. pyogenes isolates associated with colonization and infections. Out of the 1,629 isolates, 1,026 were recovered from 10,578 throat swabs of asymptomatic populations (children and adults) during 2000-2007 and 603 isolates were from patients diagnosed with clinical infections: 487 with tonsillitis/pharyngitis in 2000-2006, 72 with skin/soft tissue infections in 1999-2005, and 44 with invasive diseases in 1999-2005. This study demonstrated that a very heterogeneous population of S. pyogenes colonized healthy carriers. The mean carrier rate was higher among pre-school children (0-6 years) than among school-aged children (7-16 years) and colonization frequency was higher during Winter periods, which suggests that the crowding of children in day-care centers may possibly increase the carrier rate in healthy pre-school children. Moreover, it was also found that a high diversity of S. pyogenes strains was associated with long-term colonization, and it was detected co-colonization of the oropharynx by multiple S. pyogenes strains. In this work, it was reported the long term persistence among carriers of the low-level bacitracin-resistant emm28/ST52 lineage, which is prevalent in Europe. It was also reported for the first time a high-level bacitracin-resistant isolate of the emm74/ST120 lineage, which was not previously known to include bacitracin-resistant isolates. In this study were also reported for the first time temporal inversions of macrolide resistance phenotypes among colonization isolates, reinforcing the importance of surveillance of carriers, as they may be indicators of the pool of isolates circulating in the community that may cause infections. The high prevalence (>20%) of virulence genes speC, prtF1 and ssa was probably caused either by clonal dissemination (speC), or to horizontal gene transfer events (prtF1 and ssa). In this work it was observed that ciprofloxacin-nonsusceptibility rate was slightly lower among colonization isolates (4.3%) than among the clinical isolates (6.0%). All but one ciprofloxacin-nonsusceptible isolates had parC-QRDR mutations generating the aminoacid substitutions S79A (n=63) and D83G (n=2); the ParC-D83G substitution was found for the first time in this study and emm1 association with fluoroquinolone-nonsusceptibility was also first detected in this work. It was observed a higher frequency of virulence genes among isolates from disease, such as tonsillitis/pharyngitis, skin/soft tissue infections or invasive disease, than among colonization. In particular, this study contributed to a better knowledge of S. pyogenes virulence factors that circulate in this country. Among the 1,629 isolates, novel genotypes were discovered, such as emm-subtypes 6.63, 28.9, 53.10, st4040.0 and stMrp6.0, as well as sequence types ST380, ST397, ST398, ST401, ST402, ST427, ST428, ST429, ST430, ST431 and ST581. In conclusion, the results from this dissertation extend our knowledge about the carrier state, the susceptibility to antimicrobial agents, molecular epidemiology and virulence of S. pyogenes isolates from oropharyngeal colonization and symptomatic infections.Fundação para a Ciência e a Tecnologia (FCT)- (SFRH/BD/32374/2006

The Role of Lysogenic Bacteriophage in Virulence and Survival of Streptococcus Pyogenes

This thesis investigates the interactions of lysogenic bacteriophage with Streptococcus pyogenes. We were specifically interested in elucidating novel ways in which the prophage influence GrAS virulence and survival either within the host cell or within the bacterial population. In turn, we also hoped to determine how the bacteria (and possibly other integrated phage) might influence prophage activity or gene expression. Our studies focused on two polylysogenized GrAS strains, a M6 serotype (MGAS10394) and a M1 serotype (SF370). In our M6 studies, we chose a streptococcal strain lysogenized by a chimeric bacteriophage element (Φ10394.4), which contains the erythromycin resistance gene mefA, in order to elucidate why genomes of certain erythromycin-resistant isolates of group A streptococci are resistant to SmaI endonuclease cleavage. In the work presented here, we identified a restriction modification system contained on the bacteriophage chimeric-element and successfully characterized the first methyltransferase (M.SpyI) encoded in S. pyogenes. In the M1 strain, allelic recombination techniques were used to begin to analyze the role and regulation of a bacteriophage-encoded potential superantigen, SpeH. Next, we designed a novel system to specifically select for the loss of integrated phages entirely from the genome. This technique allowed us to study the novel role that two SF370 phage play in regulating GrAS chromosomal genes involved in bacterial metabolism, DNA repair and mutagenesis. We were also able to begin to elucidate the effects that individual and multiple phage loss have on SF370 virulence and survival, as we successfully constructed the first strain of GrAS that is completely devoid of bacteriophages. In the course of these studies, we also manipulated lytic bacteriophage genes from two different Staphylococcus phage genomes to genetically engineer a novel chimeric endolysin (ClyS). We demonstrated the antimicrobial lytic activity of ClyS against methicillin-resistant Staphylococcus aureus (MRSA) in both in vivo colonization and septicemia models, and were also able to show its synergistic activity with oxacillin in in vitro and in vivo models. This work highlights the potential of ClyS as a novel therapeutic agent for the treatment of MRSA and other staphylococcal infections

Streptococcus pyogenes -bakteerin aiheuttamien tautien molekyyliepidemiologiaa ja epidemiologiaa Suomessa : vakavat infektiot ja selluliitit

Streptococcus pyogenes (group A streptococcus) is an important human pathogen, causing a wide array of infections ranging in severity. The majority of S. pyogenes infections are mild upper respiratory tract or skin infections. Severe, invasive infections, such as bacteraemia, are relatively rare, but constitute a major global burden with a high mortality. Certain streptococcal types are associated with a more severe disease and higher mortality. Bacterial, non-necrotizing cellulitis and erysipelas are localised infections of the skin, and although they are usually not life-threatening, they have a tendency to recur and therefore cause substantial morbidity. Despite several efforts aimed at developing an effective and safe vaccine against S. pyogenes infections, no vaccine is yet available. In this study, the epidemiology of invasive S. pyogenes infections in Finland was described over a decade of national, population-based surveillance. Recent trends in incidence, outcome and bacterial types were investigated. The beta-haemolytic streptococci causing cellulitis and erysipelas infections in Finland were studied in a case-control study. Bacterial isolates were characterised using both conventional and molecular typing methods, such as the emm typing, which is the most widely used typing method for beta-haemolytic streptococci. The incidence of invasive S. pyogenes disease has had an increasing trend during the past ten years in Finland, especially from 2006 onwards. Age- and sex-specific differences in the incidence rate were identified, with men having a higher incidence than women, especially among persons aged 45-64 years. In contrast, more infections occurred in women aged 25-34 years than men. Seasonal patterns with occasional peaks during the midsummer and midwinter were observed. Differences in the predisposing factors and underlying conditions of patients may contribute to these distinctions. Case fatality associated with invasive S. pyogenes infections peaked in 2005 (12%) but remained at a reasonably low level (8% overall during 2004-2007) compared to that of other developed countries (mostly exceeding 10%). Changes in the prevalent emm types were associated with the observed increases in incidence and case fatality. In the case-control study, acute bacterial non-necrotizing cellulitis was caused predominantly by Streptococcus dysgalactiae subsp. equisimilis, instead of S. pyogenes. The recurrent nature of cellulitis became evident. This study adds to our understanding of S. pyogenes infections in Finland and provides a basis for comparison to other countries and future trends. emm type surveillance and outcome analyses remain important for detecting such changes in type distribution that might lead to increases in incidence and case fatality. Bacterial characterisation serves as a basis for disease pathogenesis studies and vaccine development.Streptococcus pyogenes (A-ryhmän streptokokki) on tärkeä ihmisen taudinaiheuttaja, joka aiheuttaa vakavuusasteeltaan erilaisia infektioita. Suurin osa tämän bakteerin aiheuttamista taudeista on lieviä ylähengitystie- tai ihoinfektioita. Vakavat streptokokki-infektiot, kuten bakteremia eli verenmyrkytys, taas ovat suhteellisen harvinaisia, mutta niihin liittyy korkea kuolleisuus ja ne aiheuttavat maailmanlaajuisesti suuria kansantaloudellisia menetyksiä. Tietyt streptokokkityypit liittyvät vakavampaan taudinkuvaan ja tavallista korkeampaan kuolleisuuteen. Streptokokin aiheuttamat selluliitti ja erysipelas (eli ruusutulehdus) ovat paikallisia ihon ja ihonalaiskudoksen infektioita. Ne eivät yleensä ole hengenvaarallisia infektioita, mutta niillä on taipumus uusiutua, ja siksi ne huonontavat oleellisesti potilaan elämänlaatua ja aiheuttavat merkittäviä kustannuksia. Vaikka tutkimustyöhön on panostettu tavoitteena kehittää tehokas ja turvallinen rokote S. pyogenes tauteja vastaan, rokotetta ei ole vielä saatavilla. Tutkimus pohjautuu kansalliseen ja väestöpohjaiseen streptokokkitautien seurantaan ja siinä kuvataan vakavien S. pyogenes infektioiden (bakteremioiden) epidemiologiaa Suomessa viimeisen kymmenen vuoden aikana. Työssä tutkittiin vakavien S. pyogenes -infektioiden ilmaantuvuutta, tapauskuolleisuutta ja vallitsevia bakteerityyppejä. Erillisessä tapaus-verrokkitutkimuksessa tutkittiin selluliitti- ja erysipelasinfektioita aiheuttavia streptokokkeja Suomessa. Näistä tutkimuksista eristettyjä streptokokkibakteerikantoja tutkittiin erilaisilla perinteisillä ja moderneilla menetelmillä, kuten emm-tyypityksellä, joka on yleisimmin käytössä oleva streptokokkibakteerien tyypitysmenetelmä. Vakavien S. pyogenes infektioiden ilmaantuvuudessa on ollut nouseva suuntaus viimeisten kymmenen vuoden aikana Suomessa, etenkin vuodesta 2006 lähtien. Ilmaantuvuudessa havaittiin ikä- ja sukupuolispesifisiä eroja siten, että miehillä oli korkeampi taudin ilmaantuvuus kuin naisilla, etenkin 45 64-vuotiaiden ikäryhmässä. Naisilla taas 25 34-vuotiailla oli korkeampi ilmaantuvuus kuin miehillä. Tapausmäärissä havaittiin satunnaisia huippuja keskikesällä ja keskitalvella. Erot potilaiden altistavissa tekijöissä ja perussairauksissa olivat todennäköisesti vaikuttavina tekijöinä näihin havaittuihin eroihin. Keskimääräinen tapauskuolleisuus 7 päivän kohdalla nousi huippuunsa vuonna 2005 (12%), mutta pysytteli silti suhteellisen matalalla tasolla (8 % vuosina 2004 2007) verrattuna muihin kehittyneisiin maihin (yleensä yli 10%). Muutokset bakteerien vallitsevissa emm-tyypeissä liittyivät havaittuihin ilmaantuvuuden ja tapauskuolleisuuden nousuun. Tapaus-verrokki-tutkimuksessa havaittiin, että selluliitti- ja erysipelasinfektiot olivat etupäässä Streptococcus dysgalactiae subsp. equisimilis-bakteerin aiheuttamia, S. pyogenes -bakteerin sijaan. Tutkimus vahvisti käsitystä selluliitti-infektioiden toistuvasta luonteesta. Tutkimus lisää tietoutta S. pyogenes bakteerin aiheuttamista infektioista Suomessa ja luo pohjan vertailulle muiden maiden tilanteeseen ja tuleviin suuntauksiin. Vallitsevien bakteerityyppien seuranta ja kuolleisuustutkimukset ovat tärkeitä, jotta voidaan havaita sellaisia muutoksia tyyppijakaumassa, jotka voivat johtaa ilmaantuvuuden ja kuolleisuuden kasvuun. Tutkimuksen tuloksena saadaan myös tietoa streptokokkibakteerin taudinaiheutuskyvystä ja sen tuloksena voidaan arvioida tulevien rokotteiden kattavuutta Suomessa

Respiratory tract infections in primary care - aspects of diagnosis and treatment

Background Primary health care is accountable for most of the antibiotic prescriptions in humans. In Sweden, most of these antibiotics are used for respiratory tract infections, and pharyngotonsillitis (acute sore throat) is the single respiratory tract infection that leads to most antibiotic prescriptions. The first line treatment for pharyngotonsillitis with presence of group A streptococci is penicillin V 1000 mg three times daily for 10 days. Though, effectiveness of shorter penicillin V treatment for pharyngotonsillitis is unknown. Antibiotic treatment can induce ecological changes in the intestinal microbiota, including emergence of antimicrobial resistance. Previous studies on side-effects from penicillin V therapy, including antimicrobial resistance in the intestinal microbiota, are lacking. To restrict the use of antibiotics, two point-of-care tests have become very popular in Swedish primary care: the C reactive protein (CRP) and rapid antigen detection test for group A streptococci (GAS). They have capacity to restrict unnecessary use of antibiotics in primary care, when used according to the guidelines. However, concentration of CRP in primary care patients with influenza-like illness has not been investigated earlier, and the reliability of rapid tests for GAS after recent penicillin V treatment for pharyngotonsillitis has been questioned. Aim The overall aim of the thesis was to contribute to a safe reduction in antibiotic use and to investigate the benefit of two popular near-patient tests in patients with common RTIs. We set out to: i) determine if a shorter but more intense penicillin V treatment could give a clinical cure rate of GAS pharyngotonsillitis comparable to the currently recommended treatment; ii) compare the presence of GAS in rapid antigen detection test (RADT) and throat culture among patients recently treated with penicillin V for pharyngotonsillitis; iii) evaluate penicillin V effects on the microbiota with a focus on the emergence of β-lactam resistance; iv) examine if CRP can predict presence of influenza A in primary care patients presenting with influenza-like symptoms. Methods The first paper was a randomised controlled non-inferiority trial, comparing penicillin V 800 mg x 4 for 5 days to 1000 mg x 3 for 10 days. The second paper was an observational study comparing the results from RADT and culture for GAS at a follow-up visit within 21 days from inclusion. In the third paper we explored some clinically relevant changes in cultures of faecal swab samples from patients, before and after pencillin V treatment for pharyngotonsillitis. The fourth paper was a cross-sectional study in patients with an influenza-like illness for less than 72 h. The main outcome measures were capillary blood CRP and PCR test for detection of influenza A or B in the upper respiratory tract. Results and conclusions We found penicillin V for 5 days to be non-inferior to the 10-day treatment regarding clinical cure. Hence, it is possible to maintain the clinical effectiveness with a shorter penicillin V treatment for GAS pharyngotonsillitis. The most reported side-effects from treatment were diarrhoea and vulvovaginal symptoms. With the 10-day treatment 35% of patients reported gastrointestinal side-effects and 25% of female patients reported vulvovaginal symptoms. The incidence of these side-effects was lower with the 5-day treatment. We found penicillin V treatment to induce several alterations in the faecal microbiota that are generally considered signs of ecological disturbance, including a significant increase of resistance towards ampicillin and third generation cephalosporins. These findings emphasise the importance to restrict the use of penicillin V. Further, we found no significant difference between the results of RADT and throat culture for GAS after recent penicillin V treatment for pharyngotonsillitis. Thus, we conclude that RADT for GAS is reliable also after recent penicillin V treatment. Finally, we found that the CRP concentrations in patients with influenza-like illness of different confirmed aetiology had a great overlap. We found no association between CRP and confirmed influenza A. We conclude that the CRP concentration cannot predict influenza A in patients with influenza-like illness. The results of this thesis is relevant in other primary care settings. It may influence the future treatment recommendation for pharyngotonsillitis and the clinical use of two popular rapid tests. The demonstrated ecological disturbances in the microbiota from penicillin V treatment ought to raise awareness of the risks from treatment and may guide the design of future studies in the field

A study of determinants and prevalence of Rheumatic Heart Disease in Cape Town

Includes abstract.Includes bibliographical references.Rheumatic Heart Disease (RHD) is a post-infectious immune disease ascribed to an interaction between a rheumatogenic strain of group A streptococcus, a susceptible host who lives in poor social conditions with limited access to medical facilities. The disease process begins with repeated group A streptococcal (GAS) infections, which, subsequently result in acute rheumatic fever (ARF). In the absence of intervention, repeated bouts of ARF in turn, may result in progression to RHD, particularly in those ARF patients with cardiac involvement. The prevalence of ARF and RHD in developed countries has shown considerable decline during the last century, largely attributed to improved living conditions and access to healthcare. Epidemiological data from developing countries, while scant, indicate a continued high prevalence of GAS-positive pharyngitis and RHD. Furthermore, while much is known about the social factors and the microbial agent that predispose individuals to ARF, little progress has been made in elucidating genetic susceptibility factors that are reproducible in different populations. This thesis aimed to establish determinants of RHD as well as to document the prevalence of RHD in South African school children. The specific objectives of each study component were as follows: To derive quantitative estimates of the size of the genetic contribution to the risk of developing ARF/RHD. To determine the prevalence of GAS carriage and emm strains of GAS isolates among asymptomatic children enrolled in primary and secondary school. To describe the epidemiology of GAS among 3- to 15-year old children with pharyngitis attending primary health care facilities. To develop a clinical prediction rule for diagnosis of GAS throat infection that is valid for children aged 5-15 years in the primary care setting within the South African context. To determine the prevalence of echocardiographically-proven rheumatic heart disease in school children

Virulence factors of Streptococcus anginosus – a molecular perspective

Streptococcus anginosus together with S. constellatus and S. intermedius constitute the Streptococcus anginosus group (SAG), until recently considered to be benign commensals of the human mucosa isolated predominantly from oral cavity, but also from upper respiratory, intestinal, and urogenital tracts. For years the virulence potential of SAG was underestimated, mainly due to complications in correct species identification and their assignment to the physiological microbiota. Still, SAG representatives have been associated with purulent infections at oral and non-oral sites resulting in abscesses formation and empyema. Also, life threatening blood infections caused by SAG have been reported. However, the understanding of SAG as potential pathogen is only fragmentary, albeit certain aspects of SAG infection seem sufficiently well described to deserve a systematic overview. In this review we summarize the current state of knowledge of the S. anginosus pathogenicity factors and their mechanisms of action

Systematic Assessment of the Contribution of Superantigens to Nasopharyngeal Colonization in a Mouse Model of Streptococcal Infection

Streptococcus pyogenes is adapted for persistence in humans. It typically colonizes the tonsils and skin, and humans are the only known reservoir. S. pyogenes can cause a wide range of mild to serious infections. Most streptococci-related deaths are due to complications of rheumatic fever and invasive infections. S. pyogenes produces virulence factors that contribute to the pathogen’s ability to colonize and cause disease, including streptococcal superantigens (SAgs), also known as streptococcal pyrogenic exotoxins (Spes). SAgs function by cross-linking T cells and antigen presenting cells (APC) which may cause a massive inflammatory response, and as such have been found to contribute to streptococcal toxic shock syndrome (STSS). The role of SAgs in adaptation of S. pyogenes to its target niche has not been investigated. S. pyogenes experimentally colonizes mouse complete nasal turbinates (cNT). Murine models of streptococcal infection are imperfect systems due to inherent host-specific tropism. In this thesis, the colonization potential of S. pyogenes MGAS8232, associated with rheumatic heart disease, and S. pyogenes MGAS5005, associated with invasive infections, were assessed to explore the contribution of SAgs to nasal colonization in a mouse model. Colonization was tested in multiple mouse strains expressing human or mouse major histocompatibility complex (MHC) class II. C57BL/6 (B6) mice expressing human leukocyte antigen (HLA) transgenes showed enhanced colonization, up to ~100,000-fold at 48 hours post-inoculation. Individual and combined SAg deletions were assessed for nasal colonization. S. pyogenes MGAS8232 deletion colonization in mice expressing HLA-DR4 and HLA-DQ8 (DR4/DQ8) determined that SpeA was the major contributing SAg to the establishment of colonization, with minor contributions from SpeL and streptococcal mitogenic exotoxin Z (SmeZ). Colonization of S. pyogenes MGAS5005 was assessed in FVB mice, which express murine MHC class II q (H-2q), and SpeJ and SmeZ were the main contributing SAgs to the establishment of nasal colonization. SAgs contribute to 48-hour streptococcal recovery, but do not change the kinetics of bacterial clearance from cNT. These findings support the hypothesis that SAgs play an important role in niche adaptation and the establishment of colonization in mild or asymptomatic streptococcal infections in a murine model of nasal infection

Severe orofacial and neck infections – predisposing factors, changing characteristics, and advanced diagnostics

Deep neck infections are most commonly caused by spreading of odontogenic or tonsillopharyngeal infections. They are often purulent inflammations or abscesses of the floor of the mouth or fascial planes of the neck. Intravenous antimicrobial therapy and even surgery is often warranted to manage these infections. Cross-sectional imaging using computed tomography or magnetic resonance imaging is crucial when planning surgery and assessing the extent of the infection. This clinical study of 277 patients retrospectively reviewed aggravating factors, complications, and microbiological etiology between 2004 and 2015. It also evaluated the feasibility of using magnetic resonance imaging as a primary imaging modality in cases of acute neck infection. The results showed that deep neck infections are a growing problem and that the proportion of odontogenic infections has increased significantly. The mortality rate was 1.4% and complications were observed in one in five patients. Magnetic resonance imaging was found to be a feasible and accurate diagnostic tool when neck infection was suspected. Pediatric deep neck infections are more rarely encountered and are more often caused by pharyngeal or lymph node infections than dental infections. The study showed that faster surgical treatment significantly shortened the length of hospital stay among children. In addition, to ensure adequate diagnostics, the importance and of obtaining cross-sectional imaging instead of ultrasound was emphasized in cases of suspected deep neck infection. In the prospective part of the study, preventive and predisposing factors and causes of severity were analyzed. The study confirmed that poor oral hygiene and limited access to dental care were background factors of infections requiring hospital treatment. Patients who frequently used acute dental care services were a particular risk group. In this study, dental infections, especially manifestations of advanced caries, were the main origin of adult deep neck infections that require hospital treatment, although these are often preventable. Thus, investments in good oral health, education, and adequate access to basic dental care could help reduce the economic burden, complications, and mortality caused by these infections.Pään ja kaulan syvät infektio – altistavat tekijät, muuttuvat piirteet ja kehittynyt diagnostiikka Kaulan syvä infektio on usein hammas- tai nieluperäisen tulehduksen edetessä ilmenevä jopa henkeä uhkaava bakteeri-infektio. Se on märkäinen infektio, joka etenee tyypillisesti suunpohjan tai kaulan sidekudoksen välitiloissa. Hoitona käytetään suoneen annettavia antibiootteja sekä suun, leukojen ja kaulan alueen kirurgiaa ja tarvittaessa tehohoitoa. Kuvantaminen ohjaa erityisesti kirurgista hoitoa ja leikekuvantaminen diagnostiikan alkuvaiheessa tehdään tietokonetomografialla tai magneettikuvantamisella. Tässä potilastutkimuksessa selvitettiin retrospektiivisesti taudin kulkuun vaikuttavia tekijöitä, komplikaatiota ja mikrobiologiaa 277 potilaalla sekä magneettikuvantamisen käyttöä päivystyksellisessä kaulan kuvantamisessa. Tuloksena todettiin kaulainfektioiden olevan lisääntyvä ongelma ja hammasperäisten tulehdusten osuus oli lisääntynyt. Kuolleisuutta esiintyi vaikeasti sairastuneilla (1,4 %) ja komplikaatioita noin viidenneksellä. Kaulan magneettikuvauksen todettiin olevan käyttökelpoinen ja tarkka diagnostinen menetelmä kuvantamiseen myös päivystys¬aikana. Lapsilla syvät kaulainfektiot ovat harvinaisempia ja yleisemmin nielu- ja imusolmuketulehdusten aiheuttamia kuin hammasperäisiä. Tutkimus osoitti, että nopeammin toteutettu leikkaushoito lyhensi merkittävästi sairaalahoidon kestoa. Riittävän tarkan diagnostiikan varmistamiseksi viiveetön leikekuvantaminen on usein tarpeen ultraäänen sijaan, kun epäillään syvää kaulainfektiota. Tutkimuksen etenevässä osuudessa selvitettiin mahdollisia pahentavia ja ennaltaehkäistävissä olevia tekijöitä. Tutkimuksessa vahvistui huonon suuhygienian ja hammashoidon saatavuuden merkitys taustatekijöinä sairaalahoitoa vaativille infektioille. Erityisesti akuuttihammashoidon palveluita toistuvasti käyttävät potilaat ovat riskiryhmä. Koska karies ja sen eteneminen ovat ehkäistävissä, panostukset hyvään suun terveyteen, valistukseen ja riittävään hammashoidon saatavuuteen voivat auttaa vähentämään näistä infektioista johtuvia merkittäviä kustannuksia sekä komplikaatiota ja myös kuolleisuutta

Streptococcus pyogenes carriage acquisition, persistence and transmission dynamics within households in The Gambia (SpyCATS): protocol for a longitudinal household cohort study

Background: Streptococcus pyogenes (StrepA) causes a significant burden of disease globally from superficial infections to invasive disease. It is responsible for over 500,000 deaths each year, predominantly in low- and middle-income countries (LMIC). Superficial StrepA infections of the skin and pharynx can lead to rheumatic heart disease, the largest cause of StrepA-related deaths in LMIC. StrepA can also asymptomatically colonise normal skin and the pharynx (carriage), potentially increasing infection risk. Streptococcus dysgalactiae subsp. equisimilis (SDSE) carriage is also common in LMIC and may interact with StrepA. This study aims to investigate StrepA and SDSE carriage and infection epidemiology, transmission dynamics and naturally acquired immunity within households in The Gambia. Methods: A longitudinal household observational cohort study will be conducted over one year. 45 households will be recruited from the urban area of Sukuta, The Gambia, resulting in approximately 450 participants. Households will be visited monthly, and available participants will undergo oropharyngeal and normal skin swabbing. Incident cases of pharyngitis and pyoderma will be captured via active case reporting, with swabs taken from disease sites. Swabs will be cultured for the presence of group A, C and G beta-haemolytic streptococci. Isolates will undergo whole genome sequencing. At each visit, clinical, socio-demographic and social mixing data will be collected. Blood serum will be collected at baseline and final visit. Oral fluid and dried blood spot samples will be collected at each visit. Mucosal and serum anti-StrepA antibody responses will be measured. Outcome: This study will report StrepA and SDSE clinical epidemiology, risk factors, transmission dynamics, and serological responses to carriage and infection. Detailed social mixing behaviour will be combined with phylogenetic relatedness to model the extent of transmission occurring withing and between households. The study will provide data to help meet global strategic StrepA research goals