A multi-center clinical investigation on invasive Streptococcus pyogenes infection in China, 2010-2017

Functional and Transcriptome Analysis of Streptococcus pyogenes Virulence on Loss of Its Secreted Esterase

Esterases are broadly expressed in bacteria, but much remains unknown about their pathogenic effect. In previous studies, we focused on an esterase secreted by Streptococcus pyogenes (group A Streptococcus, GAS). Streptococcal secreted esterase (Sse) can hydrolyze the sn−2 ester bonds of platelet−activating factor (PAF), converting it to an inactive form that inhibits neutrophil chemotaxis to the infection sites. However, as a virulent protein, Sse probably participates in GAS pathogenesis far beyond chemotaxis inhibition. In this study, we generated the sse gene knockout strain (Δsse) from the parent strain MGAS5005 (hypervirulent M1T1 serotype) and compared the difference in phenotypes. Absence of Sse was related to weakened skin invasion in a murine infection model, and significantly reduced GAS epithelial adherence, invasion, and intracellular survival. Reduced virulence of the Δsse mutant strain was explored through transcriptome analysis, revealing a striking reduction in the abundance of invasive virulence factors including M protein, SIC, ScpA, and SclA. Besides the influence on the virulence, Sse also affected carbohydrate, amino acid, pyrimidine, and purine metabolism pathways. By elucidating Sse−mediated pathogenic process, the study will contribute to the development of new therapeutic agents that target bacterial esterases to control clinical GAS infections.

Renal Interstitial Invasion by Group A Streptococcus: A Rare Presentation

We report the case of a 5-year-old who had interstitial invasion of his kidneys with group A Streptococcus (GAS). Glomeruli and tubules were relatively preserved. He recovered from this event and was admitted a couple of months later with dilated cardiomyopathy needing a heart transplant. To our knowledge, this is the first reported case of direct invasion of renal interstitium by GAS.

Characteristics of Streptococcus pyogenes Versus Streptococcus pneumoniae Pleural Empyema and Pneumonia With Pleural Effusion in Children

BACKGROUND

Streptococcus pneumoniae is the most common cause of complicated pneumonia in children, but its incidence is decreasing since the introduction of the antipneumococcal conjugated vaccines. Streptococcus pyogenes is an uncommon cause of community-acquired pleuropneumonia/empyema in children, but its relative incidence is rising.

METHODS

The medical records of all children 0-18 years of age from 2004 to 2019, with discharge diagnoses of pleuropneumonia or empyema, and a positive blood and/or pleural effusion culture for group A streptococcus (GAS) (S. pyogenes), or S. pneumonia (SP) were reviewed. A comparison of clinical and laboratory characteristics for the 2 etiologies was performed.

RESULTS

Ninety cases of community-acquired pleuropneumonia/empyema caused by these organisms were included: 20 GAS and 70 SP. Compared with children with SP, those with GAS were more likely to have larger pleural effusion requiring drainage and longer hospitalization, and less likely to have a positive blood culture. The relative portion of GAS empyema increased over the study period.

CONCLUSIONS

Compared with patients with SP empyema, GAS appears to cause more morbidity and a longer hospital stay. This organism is more frequently recovered from pleural fluid without bacteremia, and thus necessitates pleural fluid tap for accurate diagnosis.

Epidemiological analysis of Group A Streptococcus infections in a hospital in Beijing, China

Our study aimed to investigate the epidemiological and molecular characteristics of isolates collected from Group A Streptococcus (GAS) infections in children in Beijing China during the year 2019. Emm typing, superantigens, and erythromycin resistance genotypes were determined by PCR. Antimicrobial susceptibility testing was performed as recommended by Clinical Laboratory Standards Institute (CLSI). A total of 271 GAS isolates were collected. Thirteen different emm types, including 31 subtypes, were identified. The most prevalent emm types were emm12 (52.77%), emm1 (36.9%), emm3.1 (2.95%), and emm75.0 (2.95%). Two variant subtypes, STC36.0 and STG840.2, were identified. There was no difference in the portion of emm12 and emm1 isolates in scarlet fever, impetigo, and psoriasis. The majority of superantigens detected were smeZ (94.46%), speC (91.14%), and ssa (74.91%), followed by speH (56.46%), speI (45.76%), speJ (36.9%), and speA (34.32%). More scarlet fever isolates harbored speA (35.6%) and speJ (38.4%), more psoriasis isolates harbored speI (57.9%), and more impetigo isolates harbored ssa (89.7%). Isolates were universally susceptible to penicillin and resistant to erythromycin (94.83%). Moreover, 89.67% erythromycin resistance isolates harbored the ermB gene. The erythromycin resistance rate of the isolates from the three diseases was different. Scarlet fever is the common streptococcal infectious disease in dermatology. Emm12 and emm1 were the most prevalent emm types. The most prevalent superantigens detected were smeZ, spec, and ssa. There is association between diversity of superantigens and disease manifestation. Hence, continuous surveillance of GAS molecular epidemiological characterizations in different diseases is needed.

Immunization With a Secreted Esterase Protects Mice Against Multiple Serotypes (M1, M3, and M28) of Group A Streptococcus

Streptococcal secreted esterase (Sse) is a platelet-activating factor acetylhydrolase that is critical for Group A Streptococcus (GAS) skin invasion and innate immune evasion. There are two Sse variant complexes that share >98% identity within each complex but display about 37% variation between the complexes in amino acid sequences. Sse immunization protects mice against lethal infection and skin invasion in subcutaneous infection with the hypervirulent CovRS mutant strain, MGAS5005. However, it is not known whether Sse immunization provides significant protection against infection of GAS with functional CovRS and whether immunization with Sse of one variant complex provides protection against infection of GAS that produces Sse of another variant complex. This study was designed to address these questions. Mice were immunized with recombinant Sse of M1 GAS (Sse^M1) and challenged with MGAS5005 (serotype M1, CovS mutant, and Sse of variant complex I), MGAS315 (M3, CovS mutant, and Sse of variant complex I), MGAS2221 (M1, wild-type CovRS, and Sse of variant complex I), and MGAS6180 (M28, wild-type CovRS, and Sse of variant complex II). Sse^M1 immunization significantly increased survival rates of mice in subcutaneous MGAS5005 and intraperitoneal MGAS6180 challenges and showed consistently higher or longer survival in the other challenges. Immunized mice had smaller skin lesion and higher neutrophil responses in subcutaneous infections and lower GAS burdens in spleen, liver, and kidney in most of the challenge experiments than control mice. Sse^M1 immunization enhanced proinflammatory responses. These data suggest that Sse immunization has a broad benefit against GAS infections that can vary in extent from strain to strain and that the benefit may be due to the immunization-enhanced proinflammatory responses. In particular, immunization with Sse^M1 can provide protection against M28 GAS infection even though its Sse and Sse^M1 have significant variations.