A one-year study of streptococcal infections and their complications among Ethiopian children

Harnessing AI for precision tonsillitis diagnosis: a revolutionary approach in endoscopic analysis

BACKGROUND

Diagnosing and treating tonsillitis pose no significant challenge for otolaryngologists; however, it can increase the infection risk for healthcare professionals amidst the coronavirus pandemic. In recent years, with the advancement of artificial intelligence (AI), its application in medical imaging has also thrived. This research is to identify the optimal convolutional neural network (CNN) algorithm for accurate diagnosis of tonsillitis and early precision treatment.

METHODS

Semi-supervised learning with pseudo-labels used for self-training was adopted to train our CNN, with the algorithm including UNet, PSPNet, and FPN. A total of 485 pharyngoscopic images from 485 participants were included, comprising healthy individuals (133 cases), patients with the common cold (295 cases), and patients with tonsillitis (57 cases). Both color and texture features from 485 images are extracted for analysis.

RESULTS

UNet outperformed PSPNet and FPN in accurately segmenting oropharyngeal anatomy automatically, with average Dice coefficient of 97.74% and a pixel accuracy of 98.12%, making it suitable for enhancing the diagnosis of tonsillitis. The normal tonsils generally have more uniform and smooth textures and have pinkish color, similar to the surrounding mucosal tissues, while tonsillitis, particularly the antibiotic-required type, shows white or yellowish pus-filled spots or patches, and shows more granular or lumpy texture in contrast, indicating inflammation and changes in tissue structure. After training with 485 cases, our algorithm with UNet achieved accuracy rates of 93.75%, 97.1%, and 91.67% in differentiating the three tonsil groups, demonstrating excellent results.

CONCLUSION

Our research highlights the potential of using UNet for fully automated semantic segmentation of oropharyngeal structures, which aids in subsequent feature extraction, machine learning, and enables accurate AI diagnosis of tonsillitis. This innovation shows promise for enhancing both the accuracy and speed of tonsillitis assessments.

Mechanisms that potentially contribute to the development of post-streptococcal glomerulonephritis

Post-streptococcal glomerulonephritis (PSGN) is primarily associated with preceding group A streptococcal skin or throat infections, now mainly observed in economically disadvantaged communities. This condition significantly predisposes individuals to later-life chronic kidney disease and concurrent renal complications, with the elderly experiencing increased severity and less favourable outcomes. Streptococcal pyrogenic exotoxin B and nephritis-associated plasmin receptor are identified nephritogenic antigens (nephritogens). Pathogenesis of PSGN is multifactorial. It can involve the formation of antigen-antibody immune complexes, causing inflammatory damage to renal glomeruli. Deposition of circulating immune complexes or in situ formation of immune complexes in glomeruli, or both, results in glomerulonephritis. Additionally, molecular mimicry is hypothesized as a mechanism, wherein cross-reactivity between anti-streptococcal antibodies and glomerular intrinsic matrix proteins leads to glomerulonephritis. Besides, as observed in clinical studies, streptococcal inhibitor of complement, a streptococcal-secreted protein, can also be associated with PSGN. However, the interplay between these streptococcal antigens in the pathogenesis of PSGN necessitates further investigation. Despite the clinical significance of PSGN, the lack of credible animal models poses challenges in understanding the association between streptococcal antigens and the disease process. This review outlines the postulated mechanisms implicated in the development of PSGN with possible therapeutic approaches.

Rheumatic Heart Disease in East Africa: A Systematic Review and Meta-Analysis

Background

Despite being a grave problem, there is little information on rheumatic heart disease's prevalence in East Africa. Therefore, the purpose of this systematic review and meta-analysis was to estimate the pooled prevalence of rheumatic heart disease in East Africa.

Materials and Methods

A computerized systematic search of using multiple database searching engines was performed in search of relevant English articles from the inception of the databases to December 2019. It was done in accordance with the preferred reporting items for systematic review and meta-analysis (PRISMA) standard. The funnel plot was used to assess publication bias. R and RStudio for Windows were used for all statistical analysis. The random-effect model was used for calculating the pooled estimate of the prevalence of rheumatic heart disease.

Results

The database search retrieved 1073 papers, and 80 articles (78 cross-sectional and two cohort study designs) with a total of 184575 individuals were found to be appropriate for the review. In East Africa, the overall prevalence of rheumatic heart disease was 14.67% (95% CI: 13.99% to 15.35%). In Ethiopia, Uganda, Tanzania, and Sudan, respectively, the subgroup analysis of rheumatic heart disease pooled prevalence was 22% (95% CI: 13% to 36%), 11% (95%t CI: 5% to 20%), 9% (95%t CI: 5% to 16%), and 3% (95%t CI: 1% to 10%), while the pooled prevalence of rheumatic heart disease in adults was 20% (95% CI: 12% to 30%), and in children, it was 4% (95% CI: 2% to 8%).

Conclusions

From this report, the prevalence of rheumatic heart disease in East Africa is very high, affecting about one in seven people. Therefore, future strategies should emphasize preventive measures at appropriate times to minimize the burden of this type of preventable heart disease.

Predictors of rheumatic fever in sore throat patients: a systematic review and meta-analysis

Background

Concerns about rheumatic fever (RF) drive antibiotic prescriptions for sore throat (ST) in endemic areas. Better guidance is needed on which patients are likely to develop RF in order to avoid misuse and overuse of antibiotics. Our aim was to identify predictive factors for RF in ST patients.

Methods

Multiple databases were searched to identify cohort, case–control, cross-sectional or randomised controlled trials that measured RF incidence in ST patients. An inverse variance random effects model was used to pool the data and calculate odds ratios (ORs).

Results

Seven studies with a total of 6890 participants were included: three RCTs and four observational studies. Factors significantly associated with RF development following ST were positive group A streptococcal (GAS) swab (OR 1.74 [95% confidence interval {CI} 1.13 to 2.69]), previous RF history (OR 13.22 [95% CI 4.86 to 35.93]) and a cardiac murmur (OR 3.55 [95% CI 1.81 to 6.94]). Many potential risk factors were not reported in any of the included studies, highlighting important evidence gaps.

Conclusions

ST patients in endemic areas with a positive GAS swab, previous RF history and a cardiac murmur are at increased risk of developing RF. This review identifies vital gaps in our knowledge of factors predicting RF development in ST patients. Further research is needed to develop better clinical prediction tools and rationalise antibiotic use for ST.

The incidence of sore throat and group A streptococcal pharyngitis in children at high risk of developing acute rheumatic fever: A systematic review and meta-analysis

BACKGROUND

Group A streptococcal (GAS) pharyngitis has traditionally been considered the sole precursor of acute rheumatic fever (ARF). Evidence from Australia, however, suggests that GAS skin infections may contribute to the pathogenesis of ARF. A missing piece of evidence is the incidence of sore throat and GAS pharyngitis in this setting. We conducted a systematic review and meta-analysis of the incidence of sore throat and GAS pharyngitis in all children at risk of developing ARF.

METHODS

Databases were systematically searched for studies reporting on the incidence of pharyngitis among children from low to upper-middle income countries, and Indigenous children living in high-income countries. Studies were subjected to data extraction by two independent reviewers. Following an assessment of the methodological quality of the studies, we extracted incidence rates (IRs) and conducted a meta-analysis. This systematic review is registered on PROSPERO (CRD42019113019).

RESULTS

From 607 titles identified by the search, 11 articles met the predetermined inclusion criteria; ten studies reported IRs while for the remaining study, the incidence was calculated. The pooled incidence estimated for sore throat was 82.5 per 100 child-years (95% confidence interval [CI], 6.5 to 1044.4 per 100 child-years, I2 = 100%) and GAS pharyngitis was 10.8 per 100 child-years (95% CI, 2.3 to 50.0 per 100 child-years, I2 = 99.9%).

CONCLUSIONS

The pooled IRs for sore throat in children at risk of developing ARF were higher than rates reported in developed nations (32.70-40 per 100 child-years) and similar for GAS pharyngitis (12.8-14 per 100 years). The limited Australian data lend support to the need for further studies to inform the role of GAS pharyngitis in the development of ARF in Australian Indigenous children, so as to inform local primary prevention strategies for ARF and Rheumatic Heart Disease (RHD).

Prevalence, Clinical Features and Antibiotic Susceptibility of Group A Streptococcal Skin Infections in School Children in Urban Western and Northern Uganda

BACKGROUND

Group A Streptococcus (GAS) skin infections can lead to invasive sepsis, poststreptococcal glomerulonephritis, and potentially rheumatic heart disease (RHD). Within a study to identify predisposing factors of RHD in Ugandan schoolchildren, we determined the prevalence of skin infections and assessed the clinical features and antibiotic susceptibility of GAS skin infection.

METHODS

Cross-sectional study conducted at 3 urban primary schools in Western and Northern Uganda in March 2017. A dermatologist rendered clinical diagnoses and obtained a skin swab specimen from lesions with signs of bacterial infection. Beta-hemolytic colonies underwent Lancefield grouping, species identification by polymerase chain reaction and antimicrobial susceptibility testing.

RESULTS

From 3265 schoolchildren, we observed 32% with ≥1 fungal, 1.8% with ≥1 bacterial, 0.9% with ≥1 viral, and 0.2% with ≥1 ectoparasitic infection. Of 79, 25 (32%) specimens were GAS-positive, of which one-third demonstrated tetracycline resistance. Of 17 impetigo cases, 13 (76%) were located on the leg/foot and 3 (18%) on the head/neck. Prevalence of GAS skin infection was 0.8% (25 of 3265). In Northern Uganda, where subclinical definite RHD prevalence is 1.1%, GAS skin infection prevalence was 1.2% (4 of 343) and 0.9% (3 of 352).

CONCLUSION

This study identifies tetracycline-resistant GAS in Ugandan communities, suggests modified skin examination of exposed anatomic locations may be appropriate for population-based GAS skin infection studies, and underscores need for clear case definitions of GAS skin infection. Future studies are needed to evaluate the role of GAS skin infection in development of RHD in Ugandan communities.

Prevalence of group A Streptococcal infection in Africa to inform GAS vaccines for rheumatic heart disease: A systematic review and meta-analysis

BACKGROUND

The prevalence of group A streptococcal (GAS) disease is estimated at >18.1 million cases with an incidence of >1.78 million cases per year. While a significant cause of mortality and morbidity on the global scale, the burden of GAS disease in Africa is unknown. We conducted a systematic review on the prevalence of GAS disease among children and adults in Africa and the frequency and distribution of emm types among isolates.

METHODS

We performed a comprehensive literature search in a number of databases, using an African search filter. Two reviewers independently selected articles meeting pre-specified criteria and extracted relevant data as per a data extraction form. We applied the random-effects meta-analysis model to aggregate GAS prevalence estimates with 95% CI for GAS prevalence, incorporating the Freeman-Tukey transformation to account for between-study variability.

RESULTS

Twenty-five studies were included. Invasive GAS disease prevalence ranged from 0.6% to 10.8% in samples from normally-sterile sites including blood, CSF and soft tissue. A single study reported a prevalence of 74% in skin infections. Prevalence of emm types varied with up to 88 different strains reported, corresponding to a vaccine coverage of 28% to 65%. The pooled prevalence of GAS in persons presenting with pharyngitis was 21% (95% CI, 17% to 26%).

CONCLUSIONS

The prevalence of GAS remains high among symptomatic individuals residing in Africa. Data on molecular strain characterisation of GAS in Africa is largely non-existent, thus the need for further studies is warranted to inform current prevention efforts including vaccine development.

Asymptomatic pharyngeal carriage rate of Streptococcus pyogenes, its associated factors and antibiotic susceptibility pattern among school children in Hawassa town, southern Ethiopia

Objectives

The aim of this study was to determine the asymptomatic pharyngeal carriage rate of S. pyogenes, antimicrobial pattern and related risk factors among school children in Hawassa, southern Ethiopia.

Results

Out of 287 school children’s screened, 35 (12.2%) were colonized with S. pyogenes. The carriage rate was significantly associated with factors such as sex (female p = 0.013) occupational status of mother (p = 0.002), lower income source (500–900 ETB, 1000–1500 ETB) (p = 0.001, and p = 0.042), history of hospitalization (p = 0.00) and residence of the children (p = 0.002). High level resistant to tetracycline and low level to vancomycin were observed, while penicillin, amoxicillin, erythromycin, chloramphenicol, and ceftriaxone were found to be effective.

Outbreak of Glomerulonephritis Caused by Streptococcus zooepidemicus SzPHV5 Type in Monte Santo de Minas, Minas Gerais, Brazil

Streptococcus zooepidemicus is an emerging and opportunistic zoonotic pathogen which plays an important role in the development of severe and life-threatening diseases and is potentially capable of triggering large glomerulonephritis outbreaks. Between December 2012 and February 2013, 175 cases of glomerulonephritis were confirmed in the town of Monte Santo de Minas, MG, Brazil. During the outbreak, 19 isolates of S. zooepidemicus were recovered, 1 from ice cream, 2 from the oropharynx of food handlers, and 16 from patients affected by acute poststreptococcal glomerulonephritis (APSGN). All S. zooepidemicus isolates involved in the outbreak amplified the same sequence of the hypervariable region of the SzP protein (SzPHV5) and presented indistinguishable banding patterns with high similarity (>99%) to each other by the repetitive element sequence-based PCR (rep-PCR) technique. Inspection programs on the milk supply chain should be strengthened and continuously encouraged so that the health of consumers is preserved.

Using preceding hospital admissions to identify children at risk of developing acute rheumatic fever

AIMS

New Zealand (NZ) Māori and Pacific children have high rates of acute rheumatic fever (ARF). Around 150 new cases arise each year. As part of the national ARF prevention programme, funding is available to improve housing. To obtain maximum benefit from interventions, an effective tool is needed for targeting high-risk children. This study aimed to assess the effectiveness of using hospitalisations for identifying children at risk of subsequent ARF.

METHODS

Three potentially avoidable hospitalisation (PAH) groups were investigated, including diseases thought to be influenced by housing. All were developed using expert opinion or systematic reviews. These were: (i) the PAH conditions associated with the housing environment (PAHHE) group; (ii) the Crowding group; and (iii) the Ministry of Health (MoH) group. We analysed NZ public hospital discharge data (2000-2014). The prevalence of ARF among patients hospitalised in each group was calculated to estimate sensitivity and potential effectiveness. The number needed to screen (NNS) to identify one ARF case was estimated as a measure of efficiency.

RESULTS

Nearly one-third of ARF patients experienced a PAH as children (before developing ARF). Sensitivity for detecting future ARF ranged from <5% (MoH group) to 27% (PAHHE group). NNS ranged from 502.4 (PAHHE) to 707.5 (MoH).

CONCLUSIONS

Because ARF is relatively rare, observing hospitalisations is not particularly efficient for targeting prevention activities for this condition alone. However, housing interventions are likely to improve multiple outcomes; thus, the hospital setting is still useful for identifying at-risk children who could benefit from such programmes.

Throat culture positivity rate and antibiotic susceptibility pattern of beta-hemolytic streptococci in children on secondary prophylaxis for rheumatic heart disease

Background

Among children diagnosed to have chronic rheumatic valvular heart disease (RHD) in Ethiopia, many have been observed to develop recurrence of rheumatic fever (RF) despite secondary prophylaxis. This study determined the throat culture positivity rate and drug susceptibility pattern of beta hemolytic streptococci (BHS) isolated from children attending a specialized cardiac clinic in Ethiopia.

Methods

Throat swabs were collected from 233 children receiving benzathine penicillin injection as secondary prophylaxis for RHD and cultured. The bacterial isolates were characterized using Matrix Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) mass spectrometry. Drug susceptibility was tested with the Kirby Bauer disc diffusion method. Anti-streptolysin O (ASO) titers were determined using ASO latex reagents.

Results

The throat culture positivity rate for BHS was 24 % (56/233). Among the BHS bacterial strains isolated, four were characterized as S. pyogenes and another four as S. dysgalactiae subsp. equisimilis (Lancefield group A, C and G). All BHS were susceptible to penicillin except one isolate of S. agalactiae. Among 233 children enrolled, 46(19.7 %) showed increased ASO titer. Children who received antibiotic prophylaxis within 2-weeks of last injection had significantly lower BHS throat culture positivity rate than those injected every 4-weeks (p = 0.02). Children who missed at least one prophylaxis within the last 6 months had a higher BHS culture positivity rate than those who did not miss any (p = 0.0003).

Conclusions

The presence of groups A, C and G streptococci in the throat of children under secondary prophylaxis for RHD and increased ASO titer suggests failure of the regimen. This calls for further investigation into the causes of inadequate prophylaxis (including bioavailability of drugs used, optimal duration and patient compliance) and intervention.

Post-vaccine glomerulonephritis in an infant with hereditary C2 complement deficiency: case study

We describe a case of a post vaccine immune complex-mediated glomerulonephritis in an infant with compound heterozygous mutations of C2 complement component gene, which is the first such case in the literature. The three and a half months old boy presented with clinical and laboratory signs of nephritic syndrome and was successfully treated with methylprednisolone. An explanation of such a clinical picture may lie in the interaction between C2 deficiency and vaccination.

Group A streptococcal genotypes from throat and skin isolates in the United Arab Emirates

Background

The bacterium Streptococcus pyogenes causes a variety of human diseases that range from relatively mild skin infections to severe invasive diseases, such as acute rheumatic fever, glomerulonephritis, puerperal sepsis, necrotizing fasciitis, meningitis, and streptococcal toxic shock syndrome. Accurate identification and typing of group A hemolytic streptococci (GAS) is essential for epidemiological and pathogenetic studies of streptococcal diseases. For this reason, The genetic diversity of group A streptococcal (GAS) isolates from subjects in the United Arab Emirates with streptococcal disease was studied using emm gene sequence analysis. The emm typing system which is based on sequence analysis of PCR products of the N-terminal hypervariable region of the M protein gene, concurs with M serotyping almost 1:1.

Findings

A total of 38 GAS isolates were analyzed, including 35 isolates from throat and 3 from skin. Among the 38 isolates, a total of 25 different emm/st types were detected: 20 isolates (53%) belonged to 16 validated standard reference emm types and 18 isolates (47%) belonged to 9 recognized sequence types.

Conclusions

This is the first emm typing study in the United Arab Emirates to demonstrate the heterogeneity of the GAS population.

High burden of impetigo and scabies in a tropical country

Background

Impetigo and scabies are endemic diseases in many tropical countries; however the epidemiology of these diseases is poorly understood in many areas, particularly in the Pacific.

Methodology/Principal Findings

We conducted three epidemiological studies in 2006 and 2007 to determine the burden of disease due to impetigo and scabies in children in Fiji using simple and easily reproducible methodology. Two studies were performed in primary school children (one study was a cross-sectional study and the other a prospective cohort study over ten months) and one study was performed in infants (cross-sectional). The prevalence of active impetigo was 25.6% (95% CI 24.1–27.1) in primary school children and 12.2% (95% CI 9.3–15.6) in infants. The prevalence of scabies was 18.5% (95% CI 17.2–19.8) in primary school children and 14.0% (95% CI 10.8–17.2) in infants. The incidence density of active impetigo, group A streptococcal (GAS) impetigo, Staphylococcus aureus impetigo and scabies was 122, 80, 64 and 51 cases per 100 child-years respectively. Impetigo was strongly associated with scabies infestation (odds ratio, OR, 2.4, 95% CI 1.6–3.7) and was more common in Indigenous Fijian children when compared with children of other ethnicities (OR 3.6, 95% CI 2.7–4.7). The majority of cases of active impetigo in the children in our study were caused by GAS. S. aureus was also a common cause (57.4% in school aged children and 69% in infants).

Conclusions/Significance

These data suggest that the impetigo and scabies disease burden in children in Fiji has been underestimated, and possibly other tropical developing countries in the Pacific. These diseases are more than benign nuisance diseases and consideration needs to be given to expanded public health initiatives to improve their control.

Scabies and impetigo are often thought of as nuisance diseases, but have the potential to cause a great deal of morbidity and even mortality if infection becomes complicated. Accurate assessments of these diseases are lacking, particularly in tropical developing countries. We performed a series of studies in infants and primary school children in Fiji, a tropical developing country in the South Pacific. Impetigo was very common: more than a quarter of school-aged children and 12% of infants had active impetigo. Scabies was also very common affecting 18% of school children and 14% of infants. The group A streptococcus was the most common infective organism followed by Staphylococcus aureus. The size of the problem has been underestimated, particularly in the Pacific. It is time for more concerted public health efforts in controlling impetigo and scabies.

Streptococcal emm types in Hawaii: a region with high incidence of acute rheumatic fever

BACKGROUND

The clinical epidemiology of group A streptococcal (GAS) infections in Hawaii seems different from that in the continental United States with frequent skin infections and endemically high rates of acute rheumatic fever (ARF).

METHODS

GAS emm types in Hawaii were determined to identify any possible association between the emm types and specific clinical manifestations. A convenience sample of 1482 Hawaii GAS isolates collected between February 2000 and December 2005 was used. All isolates were characterized by emm sequence typing. The distribution of emm types in Hawaii was compared with the published continental US data for pharyngeal and invasive GAS strains, the CDC database from similar time periods, as well as with emm types present in a candidate GAS vaccine.

RESULTS

Ninety-three distinct emm types were recognized among the 1482 GAS isolates. The most frequently identified emm types in order of decreasing frequency were 12, 1, 28, 4, 22, 77, 81, 58, 65/69, 49, 74, 85, 92, 75, 101 and 2. Of this study sample, 27 of the 50 invasive GAS isolates belonged to uncommon continental US emm types (54% in Hawaii cultures vs. 10% reported from the continental US). Of the 1179 pharyngeal isolates, 509 belonged uncommon continental US emm types (43% in Hawaii cultures vs. 27% reported from the continental US).

CONCLUSIONS

The prevalent emm types in Hawaii differ from those in the continental US. The prevalence of these unusual emm types might limit the effectiveness of any proposed multivalent type-specific GAS vaccine in Hawaii.

M protein gene (emm type) analysis of group A beta-hemolytic streptococci from Ethiopia reveals unique patterns

The genetic diversity of group A streptococcal (GAS) isolates obtained in 1990 from Ethiopian children with various streptococcal diseases was studied by using emm gene sequence analysis. A total of 217 GAS isolates were included: 155 and 62 isolates from throat and skin, respectively. A total of 78 different emm/st types were detected among the 217 isolates. Of these, 166 (76.5%) belonged to 52 validated reference emm types, 26 (11.9%) belonged to 16 already recognized sequence types (st types) and 25 (11.5%) belonged to 10 undocumented new sequence types. Resistance to tetracycline (148 of 217) was not correlated to emm type. Isolation rate of the classical rheumatogenic and nephritogenic strains was low from cases of acute rheumatic fever (ARF) and acute glomerulonephritis (AGN), respectively. Instead, the recently discovered st types were overrepresented among isolates from patients with ARF (3 of 7) and AGN (9 of 16) (P < 0.01) compared to isolates from subjects with tonsillitis and from healthy carriers (10 of 57 and 16 of 90, respectively). In contrast to rheumatogenic strains from the temperate regions, more than half of the isolates from ARF (four of seven) carried the genetic marker for skin preference, emm pattern D, although most of them (six of seven) were isolated from throat. Of 57 tonsillitis-associated isolates, 16 (28%) belonged to emm pattern D compared to <1% in temperate regions. As in other reports emm patterns A to C were strongly associated with throat, whereas emm pattern D did not correlate to skin. This first large-scale emm typing report from Africa has demonstrated a heterogeneous GAS population and contrasting nature of GAS epidemiology in the region.

Seasonal occurrence of impetigo: a retrospective 8-year review (1996-2003)

Impetigo, a common skin infection, has shown seasonal variation in African, Australian and Indian studies. We investigated seasonal variation of impetigo in a UK paediatric population. A total of 1552 children with impetigo were seen in the Accident and Emergency (A&E) department between 1996 and 2003. The number of impetigo cases was always higher in late summer than in winter, and furthermore, increased year on year. These changes could not be accounted for by variation in total patient numbers seen in A&E, and suggest a correlation between impetigo frequency and climatic temperature. Possible reasons for these findings include exposed skin due to loose clothing in the summer leading to more skin-to-skin contact and minor trauma.

Overview: end-stage renal disease in the developing world

Although the vast majority of patients with end-stage renal disease (ESRD) worldwide live in what is called the developing world, little is known about its epidemiology and management. With the current paucity of credible and adequately representative registries, it is justified to resort to innovative means of obtaining information. In this attempt, world-renowned leading nephrologists in 10 developing countries collaborated in filling a 103-item questionnaire addressing epidemiology, etiology, and management of ESRD in their respective countries on the basis of integrating available data from different sources. Through this joint effort, it was possible to identify a number of important trends. These include the expected high prevalence of ESRD, despite the limited access to renal replacement therapy, and the dependence of prevalence on wealth. Glomerulonephritis, rather than diabetes, remains as the main cause of ESRD with significant geographical variations in the prevailing histopathological types. The implementation of different modalities of renal replacement therapy (RRT) is inhibited by the lack of funding, although governments, insurance companies, and donations usually constitute the major sponsors. Hemodialysis is the preferred modality in most countries with the exception of Mexico where chronic ambulatory peritoneal dialysis (CAPD) takes the lead. In several other countries, dialysis is available only for those on the transplant waiting list. Dialysis is associated with a high frequency of complications particularly HBV and HCV infections. Data on HIV are lacking. Aluminum intoxication remains as a major problem in a number of countries. Treatment withdrawal is common for socioeconomic reasons. Transplantation is offered to an average of 4 per million population (pmp). Recipient exclusion criteria are minimal. Donor selection criteria are generally loose regarding tissue typing, remote viral infection, and, in some countries, blood-relation to the recipient in live-donor transplants. Cadaver donors are accepted in many countries participating in this survey. Treatment outcomes with different RRT modalities are, on the average, inferior to the internationally acknowledged standards largely due to infective and cardiovascular complications.

Allele substitution of the streptokinase gene reduces the nephritogenic capacity of group A streptococcal strain NZ131

To investigate the role of allelic variants of streptokinase in the pathogenesis of acute poststreptococcal glomerulonephritis (APSGN), site-specific integration plasmids were constructed, which contained either the non-nephritis-associated streptokinase gene (skc5) from the group C streptococcal strain Streptococcus equisimilis H46A or the nephritis-associated streptokinase gene (ska1) from the group A streptococcal nephritogenic strain NZ131. The plasmids were introduced by electroporation and homologous recombination into the chromosome of an isogenic derivative of strain NZ131, in which the streptokinase gene had been deleted and which had thereby lost its nephritogenic capacity in a mouse model of APSGN. The introduction of a non-nephritis-associated allelic variant of streptokinase did not rescue the nephritogenic capacity of the strain. The mutant and the wild-type strains produced equivalent amounts of streptokinase. Complementation of the ska deletion derivative with the original ska allele reconstituted the nephritogenicity of wild-type NZ131. The findings support the hypothesis that the role of streptokinase in the pathogenesis of APSGN is related to the allelic variant of the protein.

Rheumatic chorea in northern Australia: a clinical and epidemiological study

To describe the epidemiology and clinical features of Sydenham's chorea in the Aboriginal population of northern Australia a review was conducted of 158 episodes in 108 people: 106 were Aborigines, 79 were female, and the mean age was 10.9 years at first episode. Chorea occurred in 28% of cases of acute rheumatic fever, carditis occurred in 25% of episodes of chorea, and arthritis in 8%. Patients with carditis or arthritis tended to have raised acute phase reactants and streptococcal serology. Two episodes lasted at least 30 months. Mean time to first recurrence of chorea was 2.1 years compared with 1.2 years to second recurrence. Established rheumatic heart disease developed in 58% of cases and was more likely in those presenting with acute carditis, although most people who developed rheumatic heart disease did not have evidence of acute carditis with chorea. Differences in the patterns of chorea and other manifestations of acute rheumatic fever in different populations may hold clues to its pathogenesis. Long term adherence to secondary prophylaxis is crucial following all episodes of acute rheumatic fever, including chorea, to prevent recurrence.

Streptokinase as a mediator of acute post-streptococcal glomerulonephritis in an experimental mouse model

Group A streptococcal infections are sometimes followed by the inflammatory kidney disease acute post-streptococcal glomerulonephritis (APSGN). To test the importance of streptokinase in the pathogenesis of this disease, isogenic strains of the nephritis isolate NZ131, differing only in the ability to produce streptokinase of the nephritis-associated ska1 genotype, were used for infection in a mouse tissue cage model for APSGN. Streptokinase production was found to be a prerequisite for the capacity of the strain to induce APSGN in mice. In addition, streptokinase was demonstrated in the kidneys of mice infected with the nephritogenic NZ131 and EF514 strains. After infection with the nonnephritogenic strain S84, neither streptokinase nor C3 deposition were observed. Deposition of streptokinase in the glomeruli was detected as soon as 4 days after infection. These findings provide support for the hypothesis that streptokinase initiates the nephritis process by glomerular deposition, which leads to local activation of the complement cascade. Detection of streptokinase in kidney tissue increased with the degree of glomerular hypercellularity. Thus, the severity of the pathological process may be a reflection of the degree of streptokinase deposition.

Acute rheumatic fever. Still a challenge

At the end of the 20th century, after an apparent decline, acute rheumatic fever (ARF) now constitutes a great challenge for developed and developing countries. It is caused by a group A beta-hemolytic Streptococcus upper airways infection, but the exact pathogenetic mechanisms are not yet clear. The role of the immune system in the pathogenesis of ARF is understood better than genetic host factors. ARF can mimic many other diseases, and the diagnosis is based on clinical criteria. It is still overdiagnosed and underdiagnosed in different settings. Penicillin has greatly contributed to the reduction in the incidence and recurrence of this disease. Current schemes of prophylaxis, however, present many problems, and failures are common. Future efforts to reduce the burden of this disease should induce public health measures the vaccine strategies.

Outbreak of acute glomerulonephritis in children: observed association with the T1 subtype of group A streptococcal infection in northern Kyushu, Japan

Group A streptococcal infection is associated with the occurrence of acute glomerulonephritis (AGN) and rheumatic fever (RF). A surveillance study in the Saga area, in northern Kyushu, Japan, showed a small variation in the reported number of group A streptococcal infections in the period 1988-94. However, of the AGN cases reported in this period, more than half were observed in 1992. In order to examine whether some change had occurred in the serotype distribution of Streptococcus pyogenes during the period, patients in the Saga area diagnosed as having group A streptococcal infection and patients with AGN or RF were analyzed. Serological T-typing of S. pyogenes was carried out for patients with group A streptococcal infections, and the association between the occurrence of AGN or RF and the distribution of each different T subtype was analyzed. M-typing of S. pyogenes was also carried out and the correlation between T and M types was examined. From 1988 to 1994, the annual number of patients with group A streptococcal infections in the Saga area showed a small variation, range 65-100 patients/year. Of the 42 patients with AGN and three with RF observed in this period, 27 with AGN (64%) and one with RF (33.3%) were detected in 1992. Only the T1 subtype increased in 1992; the other T subtypes showed little variation in incidence. The number of patients with the T1 subtype was significantly correlated with the occurrence of AGN by regression analysis (P < 0.01). Of the 170 subjects tested for both T and M subtypes, 44 of the 45 T1-typed subjects had the M1 protein. Our epidemiological study suggested that the T1 subtype of streptococcal infection was associated with an outbreak of AGN in 1992 in the Saga area.

Allelic variation of the streptokinase gene in beta-hemolytic streptococci group C and G isolates of human origin

Genetic diversity of the streptokinase gene (sk) from 36 strains of S. equisimilis and 54 strains of group G streptococci was examined. The strains were isolated from patients with various streptococcal disease manifestations and healthy carriers. The region of the gene that corresponds to amino acid residues 174-244, was PCR amplified. The amplified product was subjected to MluI, PvuII, DraI and DdeI digestion. Based on the restriction enzyme digestion patterns nine sk alleles were recognized. There was no correlation between the various sk gene alleles and streptococcal disease manifestations. Three of the nine sk gene alleles, sk4, sk7, and sk8, were detected earlier among group A streptococci. The other six alleles were unique to S. equisimilis and group G streptococci. The most common alleles were sk5, found in 21/90 (23%) and sk10 detected in 43/90 (47%) of the strains. Alleles sk1 and sk2, the most frequent among group A streptococci, were not found among the strains in the present investigation. Thus, it appears that the sk gene has been evolving in line with other species distinguishing features of the streptococci.

Streptokinase activity among group A streptococci in relation to streptokinase genotype, plasminogen binding, and disease manifestations

Certain genotypic variants of streptokinase (ska) of beta-hemolytic streptococci group A have been associated with acute post-streptococcal glomerulonephritis (APSGN). In our earlier studies on strains isolated from Ethiopian children with various streptococcal disease manifestation, we reported an even distribution of streptokinase genotypes with no association to disease patterns. Considering the possibility that strains could differ in their ability to secrete the protein, levels of streptokinase activity in culture supernatants of these strains were determined by a plasminogen activation assay using a synthetic tripeptide, H-D-valyl-leucyl-lysin-p-nitroaniline, as a substrate. Of the 53 streptococcal group A strains, ten (19%), which belonged to genotype ska4 and ska8, did not activate human plasminogen. These strains did not activate bovine, sheep, horse, rabbit or porcine plasminogens either. They represented at least five M protein and non-typeable serotypes, and were characterized by high human plasminogen binding activity. Six of the 53 strains (11%) harbouring genotype ska3 and ska7 showed low levels of human plasminogen activation. Strains of ska1 and ska2, 37/53, activated human plasminogen at a higher level (p < 0.005). Levels of plasminogen activation were not significantly different among the ska1 and ska2 strains associated with various streptococcal disease manifestations. Antibody levels against streptokinase were higher (p < 0.05) in convalescent sera from acute rheumatic fever and APSGN patients in comparison with sera from other patient categories and healthy controls. Streptokinase genotype and in vitro streptokinase production do not correlate directly to streptococcal disease manifestation, indicating a probable significance of additional streptococcal and/or host factors in the initiation of APSGN.

Distribution of presumptive pathogenicity factors among beta-hemolytic streptococci isolated from Ethiopia

Beta-hemolytic streptococci are known to bind several mammalian proteins, which are presumed to be important in pathogenicity. The distribution of such binding structures was examined for mouse albumin, human serum IgA, human IgG, human fibrinogen, and human plasminogen. A total of 218 group A beta-hemolytic streptococci (GAS) were studied: 5 isolates from children with acute rheumatic fever (ARF), 18 from acute post-streptococcal glomerulonephritis (APSGN), 57 from tonsillitis, 52 from skin infections, and 86 from healthy carriers. Sixty-eight Streptococcus equisimilis and 20 group G streptococci were also included. Most of the S. equisimilis (60/68) and group G (14/20) were obtained from apparently healthy carriers. The results were evaluated with respect to T type, serum opacity reaction (SOR), site of isolation, and disease type. No direct correlation was detected between the protein-binding structures studied. There was no apparent correlation between any particular protein-binding structure and specific T type. Albumin-binding and IgA-binding activities were inversely correlated among skin and nephritis GAS isolates. A strong correlation was demonstrated between IgA-binding activity and SOR production, while albumin-binding activity correlated with SOR-negative strains. Albumin-binding levels in isolates from ARF, APSGN and tonsillitis were significantly higher than in isolates from healthy carriers (P < 0.001). A higher albumin-binding capacity was shown in skin isolates from APSGN than in isolates from impetigo (P < 0.001).