Clinical and microbiologic characteristics of invasive Streptococcus pyogenes infections in north and south India

Global Streptococcus pyogenes strain diversity, disease associations, and implications for vaccine development: a systematic review

The high strain diversity of Streptococcus pyogenes serves as a major obstacle to vaccine development against this leading global pathogen. We did a systematic review of studies in PubMed, MEDLINE, and Embase that reported the global distribution of S pyogenes emm-types and emm-clusters from Jan 1, 1990, to Feb 23, 2023. 212 datasets were included from 55 countries, encompassing 74 468 bacterial isolates belonging to 211 emm-types. Globally, an inverse correlation was observed between strain diversity and the UNDP Human Development Index (HDI; r=-0·72; p<0·0001), which remained consistent upon subanalysis by global region and site of infection. Greater strain diversity was associated with a lower HDI, suggesting the role of social determinants in diseases caused by S pyogenes. We used a population-weighted analysis to adjust for the disproportionate number of epidemiological studies from high-income countries and identified 15 key representative isolates as vaccine targets. Strong strain type associations were observed between the site of infection (invasive, skin, and throat) and several streptococcal lineages. In conclusion, the development of a truly global vaccine to reduce the immense burden of diseases caused by S pyogenes should consider the multidimensional diversity of the pathogen, including its social and environmental context, and not merely its geographical distribution.

Group A Streptococcus Infections: Their Mechanisms, Epidemiology, and Current Scope of Vaccines

Group A streptococci (GAS) are gram-positive, cocci-shaped bacteria that cause a wide variety of infections and are a cause of significant health burden, particularly in lower- and middle-income nations. The GAS genome contains a number of virulence factors such as the M-protein, hyaluronic acid, C5a peptidase, etc. Despite its significant health burden across the globe, a proper vaccine against GAS infections is not yet available. Various candidates for an effective GAS vaccine are currently being researched. These are based on various parts of the streptococcal genome. These include candidates based on the N-terminal region of the M protein, the conserved C-terminal region of the M protein, and other parts of the streptococcal genome. The development of a vaccine against GAS infections is hampered by certain challenges, such as extensive genetic heterogeneity and high protein sequence variation. This review paper sheds light on the various virulence factors of GAS, their epidemiology, the different vaccine candidates currently being researched, and the challenges associated with M-protein and non-M-protein-based vaccines. This review also sheds light on the current scenario regarding the status of vaccine development against GAS-related infections.

Interspecies signaling affects virulence related morphological characteristics of Streptococcus pyogenes M3

Streptococcus pyogenes is a Gram-positive human-specific pathogen that asymptomatically colonizes the human respiratory tract. The factors affecting the colonization to the host is not clearly understood. Adherence of the pathogen to host epithelial cell is the initial step for a successful colonization process. In the host, bacteria live in a polymicrobial community; thus, the signaling mediated between the bacteria plays a significant role in the colonization of the pathogen to the host. Thus, the effect of acyl-homoserine lactone, secreted by Gram-negative bacteria on the adhesion properties of S. pyogenes M3 strain was examined. N-(3-Oxododecanoyl)-L-homoserine lactone (Oxo-C12) increased the cell size as well as hydrophobicity of S. pyogenes. qPCR data revealed that the expression of sagA and hasA was negatively affected by Oxo-C12. Moreover, Oxo-C12 leads to changes in the morphological characteristic of S. pyogenes, further promoting adherence to host epithelia and biofilm formation on abiotic surface. The study demonstrates the role of Oxo-C12 as a factor that can promote virulence in S. pyogenes M3.

Whole-Genome Sequence of an Indian Group A Streptococcus emm Type 1-2 Strain Isolated from a Blood Sample in North India

Group A Streptococcus emm type 1-2 is more prevalent than emm type 1 in India. Only partial information is available about the genetic characteristics of this type. Here, genome sequencing of emm type 1-2 strain 1085 (from blood) was conducted. A contig 2,010,300 bp long, with a total of 1,877 annotated proteins, was obtained (NCBI accession number CP047120, assembly accession number ASM983284v1).

Clinical Description and Outcomes of Australian Children With Invasive Group A Streptococcal Disease

BACKGROUND

Invasive group A streptococcal disease is a severe infection with a high case fatality rate, estimated to cause more than 150,000 deaths per year worldwide. The clinical presentation of this infection is variable, and early diagnosis can be challenging. There are few data on its short- and longer-term outcomes, especially in children. The aim of this study was to assess the clinical presentation, management and short- and longer-term outcomes of invasive group A streptococcal disease in children in Australia.

METHODS

We undertook a prospective surveillance study of children with laboratory-confirmed invasive group A streptococcus disease admitted to 7 sentinel tertiary and quaternary pediatric hospitals in Australia between July 2016 and June 2018. We collected demographic and clinical data and contacted patients 6 months after discharge to assess longer-term outcomes.

RESULTS

We enrolled 181 children, 7 days to 16 years of age. The principal site of invasive infection was blood (126 children, 69.6%), and the most frequent clinical presentation was pneumonia in 46 children (25.4%). Twenty-six children developed streptococcal toxic shock syndrome (14.4%), and 74 had severe disease (40.9%), including 71 admitted to the intensive care unit. Five children died (2.8%). At discharge and 6 months, 29.3% and 15.2% of the children had persisting health problems, respectively.

CONCLUSIONS

Invasive group A streptococcal infection in Australian children is frequently severe and has a high long-term morbidity burden, highlighting the need for strengthened clinical care pathways, epidemiologic surveillance and prevention strategies.

Structure-based group A streptococcal vaccine design: Helical wheel homology predicts antibody cross-reactivity among streptococcal M protein-derived peptides

Group A streptococcus (Strep A) surface M protein, an α-helical coiled-coil dimer, is a vaccine target and a major determinant of streptococcal virulence. The sequence-variable N-terminal region of the M protein defines the M type and also contains epitopes that promote opsonophagocytic killing of streptococci. Recent reports have reported considerable cross-reactivity among different M types, suggesting the prospect of identifying cross-protective epitopes that would constitute a broadly protective multivalent vaccine against Strep A isolates. Here, we have used a combination of immunological assays, structural biology, and cheminformatics to construct a recombinant M protein-based vaccine that included six Strep A M peptides that were predicted to elicit antisera that would cross-react with an additional 15 nonvaccine M types of Strep A. Rabbit antisera against this recombinant vaccine cross-reacted with 10 of the 15 nonvaccine M peptides. Two of the five nonvaccine M peptides that did not cross-react shared high sequence identity (≥50%) with the vaccine peptides, implying that high sequence identity alone was insufficient for cross-reactivity among the M peptides. Additional structural analyses revealed that the sequence identity at corresponding polar helical-wheel heptad sites between vaccine and nonvaccine peptides accurately distinguishes cross-reactive from non-cross-reactive peptides. On the basis of these observations, we developed a scoring algorithm based on the sequence identity at polar heptad sites. When applied to all epidemiologically important M types, this algorithm should enable the selection of a minimal number of M peptide-based vaccine candidates that elicit broadly protective immunity against Strep A.

Decoding the molecular epidemiology of group A streptococcus - an Indian perspective

PURPOSE

Unlike western countries the knowledge of group A streptococcus (GAS) epidemiology in India remains patchy and incomplete. Typing is crucial for surveillance as well as in predicting the efficacy of multivalent M protein vaccine. The present study aimed to explore the emm types of 206 invasive and non-invasive GAS isolates from South India as well as reviewing all the published literature on GAS molecular epidemiology from India thereby generating a pan-Indian data to predict the conjectural coverage of the 30-valent M-protein vaccine in this population.

METHODOLOGY

emm typing and superantigen (SAg) profiling of GAS along with reviewing literatures on GAS molecular epidemiology from India.

RESULTS

This study revealed a high diversity of emm types with emm 63, 82, 183, 85, 92, 169, 42, 44, 106, 74, 12 being frequently encountered, belonging to twenty emm clusters. The pan-Indian data on prevalent emm types further supports our study findings with 135 emm different types. Six clusters dominated accounting for 80 % of the GAS isolates: E3(26 %), E6(20 %), E2(11 %), E4(10 %), D4(7 %), E1(6 %). No significant association was noted between emm types and the nature of infection (P≥0.05) while a few SAg profiles were significantly associated with certain emm types. Pan Indian data revealed that only 16 % of the emm types encountered were included in proposed 30-valent M protein based vaccine.

CONCLUSION

The coverage among the South Indian GAS isolates was 28.2 % which increased to only 46.6 % with the cross-opsonic effect, thus highlighting the importance of developing a specific multivalent vaccine including the prevalent emm types in India or considering the use of conserved C-repeat vaccines and non-M protein based vaccines.

Canada-Wide Epidemic of emm74 Group A Streptococcus Invasive Disease

Background

The number of invasive group A Streptococcus (iGAS) infections due to hitherto extremely rare type emm74 strains has increased in several Canadian provinces since late 2015. We hypothesized that the cases recorded in the different provinces are linked and caused by strains of an emm74 clone that recently emerged and expanded explosively.

Methods

We analyzed both active and passive surveillance data for iGAS infections and used whole-genome sequencing to investigate the phylogenetic relationships of the emm74 strains responsible for these invasive infections country-wide.

Results

Genome analysis showed that highly clonal emm74 strains, genetically different from emm74 organisms previously circulating in Canada, were responsible for a country-wide epidemic of >160 invasive disease cases. The emerging clone belonged to multilocus sequence typing ST120. The analysis also revealed dissemination patterns of emm74 subclonal lineages across Canadian provinces. Clinical data analysis indicated that the emm74 epidemic disproportionally affected middle-aged or older male individuals. Homelessness, alcohol abuse, and intravenous drug usage were significantly associated with invasive emm74 infections.

Conclusions

In a period of 20 months, an emm74 GAS clone emerged and rapidly spread across several Canadian provinces located more than 4500 km apart, causing invasive infections primarily among disadvantaged persons.

Factors that cause trimethoprim resistance in Streptococcus pyogenes

The use of trimethoprim in treatment of Streptococcus pyogenes infections has long been discouraged because it has been widely believed that this pathogen is resistant to this antibiotic. To gain more insight into the extent and molecular basis of trimethoprim resistance in S. pyogenes, we tested isolates from India and Germany and sought the factors that conferred the resistance. Resistant isolates were identified in tests for trimethoprim or trimethoprim-sulfamethoxazole (SXT) susceptibility. Resistant isolates were screened for the known horizontally transferable trimethoprim-insensitive dihydrofolate reductase (dfr) genes dfrG, dfrF, dfrA, dfrD, and dfrK. The nucleotide sequence of the intrinsic dfr gene was determined for resistant isolates lacking the horizontally transferable genes. Based on tentative criteria, 69 out of 268 isolates (25.7%) from India were resistant to trimethoprim. Occurring in 42 of the 69 resistant isolates (60.9%), dfrF appeared more frequently than dfrG (23 isolates; 33.3%) in India. The dfrF gene was also present in a collection of SXT-resistant isolates from Germany, in which it was the only detected trimethoprim resistance factor. The dfrF gene caused resistance in 4 out of 5 trimethoprim-resistant isolates from the German collection. An amino acid substitution in the intrinsic dihydrofolate reductase known from trimethoprim-resistant Streptococcus pneumoniae conferred resistance to S. pyogenes isolates of emm type 102.2, which lacked other aforementioned dfr genes. Trimethoprim may be more useful in treatment of S. pyogenes infections than previously thought. However, the factors described herein may lead to the rapid development and spread of resistance of S. pyogenes to this antibiotic agent.

Distribution of small native plasmids in Streptococcus pyogenes in India

Complete characterization of a Streptococcus pyogenes population from a defined geographic region comprises information on the plasmids that circulate in these bacteria. Therefore, we determined the distribution of small plasmids (<5kb) in a collection of 279 S. pyogenes isolates from India, where diversity of strains and incidence rates of S. pyogenes infections are high. The collection comprised 77 emm-types. For plasmid detection and discrimination, we developed PCRs for different plasmid replication initiation protein genes, the putative repressor gene copG and bacteriocin genes dysA and scnM57. Plasmid distribution was limited to 13 emm-types. Co-detection analysis using aforementioned PCRs revealed four distinct plasmid sub-types, two of which were previously unknown. Representative plasmids pA852 and pA996 of the two uncharacterized plasmid sub-types were sequenced. These two plasmids could be assigned to the pMV158 and the pC194/pUB110 family of rolling-circle plasmids, respectively. The majority of small plasmids found in India belonged to the two newly characterized sub-types, with pA852- and pA996-like plasmids amounting to 42% and 22% of all detected plasmids, respectively. None of the detected plasmids coded for a known antibiotic resistance gene. Instead, all of the four plasmid sub-types carried known or potential bacteriocin genes. These genes may have influence on the evolutionary success of certain S. pyogenes genotypes. Notably, pA852-like plasmids were found in all isolates of the most prevalent emm-type 11.0. Together, a priori fitness of this genotype and increased fitness due to the acquired plasmids may have rendered type emm11.0 successful and caused the prevalence of pA852-like plasmids in India.

Septic Arthritis caused by Group A Streptococcus in Newborn: An Unusual Presentation

Streptococcal sepsis in neonates is a potentially lethal condition. A wide spectrum of clinical presentations has been often reported in Group B Streptococcal infections in neonates. Bone and joint infections which are caused by Group B Streptococcus are also encountered frequently, but they have not yet been reported in case of Group A Streptococcal infection in neonates. Here, we are reporting a case of septic arthritis and late onset neonatal sepsis which were caused by Group A Streptococcus in a full term, healthy baby.

Pediatric bloodstream infections in Cambodia, 2007 to 2011

BACKGROUND

Pediatric bacterial bloodstream infections (BSIs) are a major cause of morbidity and mortality worldwide. Epidemiological data from resource-limited settings in southeast Asia, such as Cambodia, are sparse but have important implications for treatment and public health strategies.

METHODS

We retrospectively investigated BSI in children at a pediatric hospital and its satellite clinic in Siem Reap, Cambodia, from January 1, 2007, to July 31, 2011. The range of bacterial pathogens and their antimicrobial susceptibility patterns were analyzed in conjunction with demographic, clinical and outcome data.

RESULTS

Of 7682 blood cultures with results (99.9% of cultures taken), 606 (7.9%) episodes of BSI were identified in 588 children. The incidence of BSI increased from 14 to 50/1000 admissions (P < 0.001); this was associated with an increased sampling rate. Most BSI were community acquired (89.1%). Common pathogens included Salmonella Typhi (22.8% of all isolates), Staphylococcus aureus (12.2%), Streptococcus pneumoniae (10.0%), Klebsiella pneumoniae (6.4%) and Escherichia coli (6.3%). 21.5% of BSI were caused by a diverse group of uncommon organisms, the majority of which were environmental Gram-negative species. No Listeria monocytogenes or Group B streptococcal BSI were identified. Antimicrobial resistance, particularly among the Enterobacteriaceae, was common. Overall mortality was substantial (19.0%), higher in neonates (36.9%) and independently associated with meningitis/meningoencephalitis and K. pneumoniae infection.

CONCLUSIONS

BSI is a common problem in Cambodian children attending hospital and associated with significant mortality. Further studies are needed to clarify the epidemiology of neonatal sepsis, the contribution of atypical organisms and the epidemiology of pneumococcal disease before the introduction of vaccine.