Molecular characterization of group A Streptococcus strains isolated during a scarlet fever outbreak

Incidence of Scarlet Fever in Children in Jeju Province, Korea, 2002-2016: An Age-period-cohort Analysis

Objectives:

Outbreaks of scarlet fever in Mexico in 1999, Hong Kong and mainland China in 2011, and England in 2014-2016 have received global attention, and the number of notified cases in Korean children, including in Jeju Province, has also increased since 2010. To identify relevant hypotheses regarding this emerging outbreak, an age-period-cohort (APC) analysis of scarlet fever incidence was conducted among children in Jeju Province, Korea.

Methods:

This study analyzed data from the nationwide insurance claims database administered by the Korean National Health Insurance Service. The inclusion criteria were children aged ≤14 years residing in Jeju Province, Korea who received any form of healthcare for scarlet fever from 2002 to 2016. The age and year variables were categorized into 5 groups, respectively. After calculating the crude incidence rate (CIR) for age and calendar year groups, the intrinsic estimator (IE) method was applied to conduct the APC analysis.

Results:

In total, 2345 cases were identified from 2002 to 2016. Scarlet fever was most common in the 0-2 age group, and boys presented more cases than girls. Since the CIR decreased with age between 2002 and 2016, the age and period effect decreased in all observed years. The IE coefficients suggesting a cohort effect shifted from negative to positive in 2009.

Conclusions:

The results suggest that the recent outbreak of scarlet fever among children in Jeju Province might be explained through the cohort effect. As children born after 2009 showed a higher risk of scarlet fever, further descriptive epidemiological studies are needed.

The Group A Streptococcus serotype M2 pilus plays a role in host cell adhesion and immune evasion

Group A Streptococcus (GAS), or Streptococcus pyogenes, is a human pathogen that causes diseases ranging from skin and soft tissue infections to severe invasive diseases, such as toxic shock syndrome. Each GAS strain carries a particular pilus type encoded in the variable fibronectin-binding, collagen-binding, T antigen (FCT) genomic region. Here, we describe the functional analysis of the serotype M2 pilus encoded in the FCT-6 region. We found that, in contrast to other investigated GAS pili, the ancillary pilin 1 lacks adhesive properties. Instead, the backbone pilin is important for host cell adhesion and binds several host factors, including fibronectin and fibrinogen. Using a panel of recombinant pilus proteins, GAS gene deletion mutants and Lactococcus lactis gain-of-function mutants we show that, unlike other GAS pili, the FCT-6 pilus also contributes to immune evasion. This was demonstrated by a delay in blood clotting, increased intracellular survival of the bacteria in macrophages, higher bacterial survival rates in human whole blood and greater virulence in a Galleria mellonella infection model in the presence of fully assembled FCT-6 pili.

Scarlet fever is caused by a limited number of Streptococcus pyogenes lineages and is associated with the exotoxin genes ssa, speA and speC

BACKGROUND

Several outbreaks of scarlet fever caused by Streptococcus pyogenes were recently reported. Scarlet fever is historically considered a toxin-mediated disease, dependent on the production of the exotoxins SpeA and SpeC, but a strict association between scarlet fever and these exotoxins is not always detected. The aims of this study were to characterize the scarlet fever bacterial isolates recovered from patients in a Lisbon hospital and to identify any distinctive characteristics of such isolates.

METHODS

We characterized a collection of 303 pharyngeal S. pyogenes collected between 2002 and 2008. One-hundred and one were isolated from scarlet fever patients and 202 were associated to a diagnosis of tonsillo-pharyngitis. Isolates were characterized by T and emm typing, pulsed field gel electrophoresis profiling and superantigen gene profiling.

RESULTS

The diversity of the scarlet fever isolates was lower than that of the pharyngitis isolates. Specific lineages of emm87, emm4 and emm3 were overrepresented in scarlet fever isolates but only 1 pulsed field gel electrophoresis major lineage was significantly associated with scarlet fever. Multivariate analysis indicated associations of ssa, speA and speC with scarlet fever.

CONCLUSIONS

In nonoutbreak conditions, scarlet fever is caused by a number of distinct genetic lineages. The lower diversity of these isolates and the association with specific exotoxin genes indicates that some lineages are more prone to cause this presentation than others even in nonoutbreak conditions.

Lipid core peptide technology and group A streptococcal vaccine delivery

The antiphagocytic surface M protein of group A streptococcus has been widely studied as the major candidate antigen for a vaccine to prevent group A streptococcus infection. Approaches that have proven to be effective in animal models include the use of multi-epitope vaccines incorporating highly variable amino terminal serotypic determinants, those based on the carboxy terminal conserved region and combination vaccines incorporating both serotypic and conserved region determinants of the M protein. The use of lipid core peptide technology is at the forefront of this research in the quest to develop a broad-strain protective vaccine that can be delivered via the mucosal route, stimulating mucosal and systemic immunity. This review aims to cover the various strategies and technologies that have been investigated with regard to group A streptococcus vaccine design and development.

Outbreak of scarlet fever associated with emm12 type group A Streptococcus in 2011 in Shanghai, China

BACKGROUND

An unprecedented, large outbreak of childhood scarlet fever occurred in Shanghai between April and July 2011. Investigation of the epidemiology could enhance our understanding of the factors related to the outbreak.

METHODS

We retrospectively analyzed the demographic and seasonal characteristics of children with scarlet fever and the outcome. During the peak month of the 2011 outbreak, 45 GAS isolates recovered from pediatric patients and 13 (43.3%) GAS isolates recovered from 30 asymptomatic student contacts were characterized by emm typing, superantigen profiles, pulsed-field gel electrophoresis genotypes, mutilocus sequence typing and antimicrobial susceptibility.

RESULTS

The 2011 outbreak of scarlet fever started in April and peaked in May and June. Boys outnumbered girls (65.1% versus 34.9%). Preschool and primary school children accounted for 96% of cases. No severe outcome was found. emm1, emm12 and emm75 were identified among 58 GAS isolates, and 53 (91.4%) isolates belonged to emm12, st36. Ten pulsed-field gel electrophoresis genotypes were identified among emm12 GAS isolates, 43 (81.1%) shared SPYS16.001 genotype and the remaining 7 genotypes detected were related to SPYS16.001 closely or possibly. No streptococcal pyrogenic exotoxin A and streptococcal pyrogenic exotoxin M were detected in 58 isolates. All emm12 GAS isolates were resistant to azithromycin and clindamycin.

CONCLUSIONS

emm12 GAS strain caused the large 2011 outbreak of scarlet fever in Shanghai. Antibiotic resistance to macrolides and clindamycin in GAS is prevalent in Shanghai.

Changing epidemiology of Streptococcus pyogenes emm types and associated invasive and noninvasive infections in Southern Taiwan

A total of 242 isolates were recovered from 76 patients with invasive diseases, 89 with scarlet fever, and 77 with pharyngitis. The most frequent emm types were types 12 (43.4%), 4 (18.2%), and 1 (16.9%). emm12 reemerged in 2005 and peaked in 2007. emm11 was recovered only from patients with invasive disease.

Report and analysis of a scarlet fever outbreak among adults through food-borne transmission in China

BACKGROUND

Scarlet fever is caused by group A beta-hemolytic streptococci (GAS). The clinical syndrome has receded in recent years, but occasionally explosive outbreaks do occur likely due to the emergence of GAS with virulence factors peculiar to this syndrome.

METHODS

Following the notification of an unexpectedly large number of scarlet fever cases amongst adults associated with a school in Ningbo, China, in June 2006, the epidemiological and clinical features of the outbreak were investigated. Logistic regression was conducted to investigate the risk factors of the outbreak and its transmission route.

RESULTS

Forty five individuals suffered scarlet fever with an attack rate of 4.98% (45/904). There was a single peak in the epidemic curve, with the majority of the cases occurring during the first two days of the outbreak. The median age of cases was 35.5 years (range 17-65). Most patients had fever (43/45), sore throat (40/45), scarlatinoid rash (39/45) and strawberry-like tongue (30/45). In laboratory detection, 45 cases' throat swabs samples were collected and GAS were isolated from 8 throat swabs samples. All of the cases, except for 2, had eaten the Plain Boiled Chicken (PBC) for lunch on June 6th, and teaching staff and students who had not eaten the PBC were not affected by the epidemic. Logistic regression analysis indicated that PBC was a key risk factor (OR=21.0, P<0.05). The chef of the school refectory was responsible for washing, braising, cutting, and distributing the PBC, and was identified as the likely source.

CONCLUSIONS

We describe an outbreak of scarlet fever caused by GAS-contaminated food.

M protein typing of Thai group A streptococcal isolates by PCR-Restriction fragment length polymorphism analysis

BACKGROUND

Group A streptococcal (GAS) infections can lead to the development of severe post-infectious sequelae, such as rheumatic fever (RF) and rheumatic heart disease (RHD). RF and RHD are a major health concern in developing countries, and in indigenous populations of developed nations. The majority of GAS isolates are M protein-nontypeable (MNT) by standard serotyping. However, GAS typing is a necessary tool in the epidemiologically analysis of GAS and provides useful information for vaccine development. Although DNA sequencing is the most conclusive method for M protein typing, this is not a feasible approach especially in developing countries. To overcome this problem, we have developed a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)-based assay for molecular typing the M protein gene (emm) of GAS.

RESULTS

Using one pair of primers, 13 known GAS M types showed one to four bands of PCR products and after digestion with Alu I, they gave different RFLP patterns. Of 106 GAS isolates examined from the normal Thai population and from patients with GAS-associated complications including RHD, 95 isolates gave RFLP patterns that corresponded to the 13 known M types. Only 11 isolates gave RFLP patterns that differed from the 13 known M types. These were then analyzed by DNA sequencing and six additional M types were identified. In addition, we found that M93 GAS was the most common M type in the population studied, and is consistent with a previous study of Thai GAS isolates.

CONCLUSION

PCR-RFLP analysis has the potential for the rapid screening of different GAS M types and is therefore considerably advantageous as an alternative M typing approach in developing countries in which GAS is endemic.

Epidemiology and molecular characterization of Streptococcus pyogenes recovered from scarlet fever patients in central Taiwan from 1996 to 1999

One hundred seventy-nine Streptococcus pyogenes isolates recovered from scarlet fever patients from 1996 to 1999 in central Taiwan were characterized by emm, Vir, and pulsed-field gel electrophoresis (PFGE) typing methods. The protocols for Vir and PFGE typing were standardized. A database of the DNA fingerprints for the isolates was established. Nine emm or emm-like genes, 19 Vir patterns, and 26 SmaI PFGE patterns were detected among the isolates. Among the three typing methods, PFGE was the most discriminatory. However, it could not completely replace Vir typing because some isolates with identical PFGE patterns could be further differentiated into several Vir patterns. The prevalent emm types were emm4 (n = 81 isolates [45%]), emm12 (n = 64 [36%]), emm1 (n = 14 [8%]), and emm22 (n = 13 [7%]). Some emm type isolates could be further differentiated into several emm-Vir-PFGE genotypes; however, only one genotype in each emm group was usually predominant. DNA from nine isolates was resistant to SmaI digestion. Further PFGE analysis with SgrAI showed that the SmaI digestion-resistant strains could be derived from indigenous strains by horizontal transfer of exogenous genetic material. The emergence of the new strains could have resulted in an increase in scarlet fever cases in central Taiwan since 2000. The emm sequences, Vir, and PFGE pattern database will serve as a basis for information for the long-term evolutionary study of local S. pyogenes strains.

Molecular characterization of a strain of group a streptococcus isolated from a patient with a psoas abscess

We report the first case of a primary group A streptococcus (GAS) psoas abscess in a 31-year-old woman. The psoas abscess was preceded by an episode of acute pharyngitis. The M-protein gene (emm) and streptolysin S structural gene (sagA) were present in the isolate, with no significant amino acid differences from previously described sequences of M1 GAS isolates. Multilocus sequence typing (MLST) showed that the isolate belonged to MLST sequence type (MLST-ST) 28, the predominant MLST-ST associated with invasive disease caused by M1 isolates.

Molecular analysis of group A streptococcal isolates associated with scarlet fever in southern Taiwan between 1993 and 2002

Collected between 1993 and 2002 at a Taiwanese university hospital, 77 group A streptococcus isolates associated with scarlet fever were grouped by emm typing and pulsed-field gel electrophoresis. The predominance of an emm1 clone before 1996 and the presence of genetically diverse emm1 and emm4 strains thereafter were found.