Group A streptococcal puerperal sepsis: initial characterization of virulence factors in association with clinical parameters

Characterization of M-Type-Specific Pilus Expression in Group A Streptococcus

Our ability to characterize how a pathogen infects and causes disease, and consequently our ability to devise approaches to prevent or attenuate such infections, is inhibited by the finding that isolates of a given pathogen often show phenotypic variability, for example, in their ability to adhere to host cells through modulation of cell surface adhesins. Such variability is observed between isolates of group A Streptococcus (GAS), and this study investigates the molecular basis for why some GAS isolates produce pili, cell wall-anchored adhesins, in lower abundance than other isolates do.

The RD2 Pathogenicity Island Modifies the Disease Potential of the Group A Streptococcus

Serotype M28 isolates of the group A Streptococcus (GAS; Streptococcus pyogenes) are nonrandomly associated with cases of puerperal sepsis, a potentially life-threatening infection that can occur in women following childbirth. Previously, we discovered that the 36.3-kb RD2 pathogenicity island, which is present in serotype M28 isolates but lacking from most other isolates, promotes the ability of M28 GAS to colonize the female reproductive tract. Here, we performed a gain-of-function study in which we introduced RD2 into representative serotype M1, M49, and M59 isolates and assessed the phenotypic consequences of RD2 acquisition. All RD2-containing derivatives colonized a higher percentage of mice, and at higher CFU levels, than did the parental isolates in a mouse vaginal colonization model. However, for two additional phenotypes, survival in heparinized whole human blood and adherence to two human vaginal epithelial cell lines, there were serotype-specific differences from RD2 acquisition. Using transcriptomic comparisons, we identified that such differences may be a consequence of RD2 altering the abundance of transcripts from select core genome genes along serotype-specific lines. Our study is the first that interrogates RD2 function in GAS serotypes other than M28 isolates, shedding light on variability in the phenotypic consequences of RD2 acquisition and informing on why this mobile genetic element is not ubiquitous in the GAS population.

A Mobile Genetic Element Promotes the Association Between Serotype M28 Group A Streptococcus Isolates and Cases of Puerperal Sepsis

BACKGROUND

Bacterial infections following childbirth-so-called puerperal infections-cause morbidity in 5%-10% of all new mothers. At low frequency, the infection can spread to the blood, resulting in life-threatening sepsis known as puerperal sepsis. Pathogens causing puerperal sepsis include group A Streptococcus (GAS), and epidemiological analyses have identified isolates of a single serotype, M28, as being nonrandomly associated with cases of puerperal sepsis. The genomes of serotype M28 GAS isolates harbor a 36.3-kb mobile genetic element of apparent group B Streptococcus origin, termed region of difference 2 (RD2).

METHODS

The phenotypic (determined via tissue culture and a vaginal colonization model) and regulatory (determined via RNA sequencing analysis) contributions of RD2 were assessed by comparing parental, RD2 deletion mutant, and complemented mutant serotype M28 GAS strains.

RESULTS

RD2 affords serotype M28 isolates an enhanced ability to adhere to human vaginal epithelial cells and to colonize the female reproductive tract in a mouse model of infection. In addition, RD2 influences the abundance of messenger RNAs from >100 core chromosomal GAS genes.

CONCLUSIONS

The data are consistent with RD2 directly, via encoded virulence factors, and indirectly, via encoded regulatory proteins, modifying the virulence potential of GAS and contributing to the decades-old association of serotype M28 isolates with cases of puerperal sepsis.

Clinical Variables Associated With Adverse Maternal Outcomes in Puerperal Group A Streptococci Infection

OBJECTIVE

To identify clinical variables associated with increased risk of composite adverse outcome in a cohort of women with puerperal group A streptococci infection.

METHODS

Our prospective case registry enrolled patients between 1991 and 2017. Chart abstraction was conducted for admission demographic and clinical data in patients with culture-proven puerperal group A streptococci infection. We created a composite variable of signs of capillary leakage including pulmonary edema, pleural effusion, ascites, and abdominal distention. The composite adverse outcome included death, hysterectomy, intensive care unit admission, mechanical ventilation, and blood transfusion. Clinical characteristics were compared between those with a composite adverse outcome and those without. We fit unadjusted log-linear models with robust error variance to measure the relative risk of a composite adverse outcome associated with clinical and demographic variables among patients with group A streptococci.

RESULTS

Thirty-five of 71 (49%) patients had an adverse outcome. Women who had adverse outcomes had higher admission heart rates (126±19 vs 112±22 beats per minute, P=.008) and respiratory rates (26±10 vs 20±5 breaths per minute, P=.01), lower systolic blood pressure (98±24 vs 114±19 mm Hg, P=.004), and were more likely to have signs of capillary leakage (77% vs 20%, P<.001) and symptoms of capillary leakage (dyspnea, cough, shoulder pain, abdominal bloating, and chest pain) (40% vs 17%, P=.03) compared with those without adverse outcomes. Log-linear models indicated that these clinical variables were individually associated with increased risk of a composite adverse outcome. The relative risk of an adverse outcome was 3.5 times higher among women with signs of capillary leakage (relative risk 3.67, 95% CI 1.94-6.94, P<.001).

CONCLUSION

Vital sign parameters consistent with severe infection correlate with adverse outcomes in women with puerperal group A streptococci infection. Signs of capillary leakage are most strongly associated with a composite adverse outcome. These clinical characteristics, particularly signs of capillary leakage, are potentially useful to guide clinical care.

Characterisation of clinically isolated Streptococcus pyogenes from balanoposthitis patients, with special emphasis on emm89 isolates

PURPOSE

Streptococcus pyogenes causes a variety of diseases, such as pharyngitis and toxic shock syndrome. In addition, this bacterium is a causative agent of balanoposthitis. To reveal the bacteriological characteristics of the isolates from balanoposthitis patients, we analysed 47 isolates. In addition, novel clade genotype emm89 S. pyogenes isolates have been reported to be spreading worldwide recently. Hence, we further analysed eight emm89 isolates.

METHODOLOGY

A drug susceptibility experiment was performed and emm types were determined. More detailed experiments, such as PCR analysis for the presence of virulence-associated genes and MLST analysis, were performed especially using emm89 isolates.

RESULTS

All isolates were sensitive to ampicillin, but 34 % of the isolates were resistant to at least one antibiotic. The emm types of the isolates varied, with emm89 and emm11 being the most prevalent, but the emm1 type was not detected. The analysis of emm89 isolates revealed that drug susceptibilities varied. All isolates were negative for the hasABC gene and produced active NADase that are characteristics of novel clade genotype emm89 S. pyogenes. MLST analysis demonstrated that six isolates were of the ST101 type, the most predominant type reported thus far, but two isolates were of the ST646 type. According to the PCR analysis used to determine the presence of streptococcal pyrogenic exotoxin-related genes, the six ST101 isolates were further classified into four groups.

CONCLUSION

These results suggest that balanoposthitis is caused by a variety of types of S. pyogenes, with novel clade genotype emm89 isolates playing a role in balanoposthitis infections in Japan.

Streptococcal Toxic Shock Syndrome: Life Saving Role of Peritoneal Lavage and Drainage

PURPOSE

We encountered a case where an infection with group A streptococcus (GAS; ie, Streptococcus pyogenes) initially caused primary peritonitis and then subsequently caused streptococcal toxic shock syndrome. The patient’s life was likely saved by an emergency laparotomy followed by extensive peritoneal lavage and drainage.

CASE PRESENTATION

A 40-year-old woman was admitted to the Emergency Department for lower abdominal pain and numbness in the extremities. She presented with systemic inflammatory response syndrome. An emergency laparotomy was performed, and ascites that resembled pus and general peritonitis were noted. Peritoneal lavage and drainage were performed, and GAS was isolated from peritoneal fluid. Gram staining of cervical polyp specimens revealed Gram-positive bacteria.

CONCLUSIONS

The patient was diagnosed with streptococcal toxic shock syndrome due to an ascending GAS infection originating from vagina.

Interleukin-17A Contributes to the Control of Streptococcus pyogenes Colonization and Inflammation of the Female Genital Tract

Postpartum women are at increased risk of developing puerperal sepsis caused by group A Streptococcus (GAS). Specific GAS serotypes, including M1 and M28, are more commonly associated with puerperal sepsis. However, the mechanisms of GAS genital tract infection are not well understood. We utilized a murine genital tract carriage model to demonstrate that M1 and M28 GAS colonization triggers TNF-α, IL-1β, and IL-17A production in the female genital tract. GAS-induced IL-17A significantly influences streptococcal carriage and alters local inflammatory responses in two genetically distinct inbred strains of mice. An absence of IL-17A or the IL-1 receptor was associated with reduced neutrophil recruitment to the site of infection; and clearance of GAS was significantly attenuated in IL-17A(-/-) mice and Rag1(-/-) mice (that lack mature lymphocytes) but not in mice deficient for the IL-1 receptor. Together, these findings support a role for IL-17A in contributing to the control of streptococcal mucosal colonization and provide new insight into the inflammatory mediators regulating host-pathogen interactions in the female genital tract.

Virulence factors of Streptococcus pyogenes strains from women in peri-labor with invasive infections

Invasive group A streptococcal (GAS) infections constitute an important epidemiological problem. Many cases occur in women during the postnatal period. The objective of this study was to evaluate the presence of the genes responsible for production of iron-chelating protein (perR) and superantigens (speA, speB, speC, speF, speG, speH, speI, speJ, speK, speL, speM, smeZ, and ssa) in S. pyogenes strains isolated from invasive infections in women after delivery. Furthermore, this study sought to verify whether S. pyogenes strains show special phenotypic and genotypic (sla, spy1325) characteristics that may play a decisive role in adherence to the genital tract epithelium. Moreover, the emm-types and antibiotic susceptibility were determined. We tested 30 invasive S. pyogenes strains isolated from postpartum invasive infection and 37 GAS control strains isolated from the genital tracts of asymptomatic multiparous women. The majority of the tested strains were shown to express two types of emm genes (1 and 28), though emm -12, -28, -75 and -89 were uniquely expressed in the group of strains isolated from invasive infections. A significantly higher prevalence of perR in the strains from puerperal fever was shown. Significant differences were also found between the two groups with respect to the incidence of the genes related to adherence; GAS strains originating from women with sepsis/puerperal fever showed presence of these genes less frequently than those of the control group. Although differences in frequencies of the gene coding for various superantigens were noted between the compared groups of GAS strains, they were not significant.

Group A Streptococcal Infection in Pregnancy and the Puerperium

There has been an increasing incidence worldwide of invasive group A streptococcal disease in pregnancy and the puerperal period over the past 30 years. Group A Streptococcus (GAS) was identified as the major cause of maternal morbidity and mortality from sepsis before the identification that hand washing techniques could prevent the transmission of the bacteria. Hand washing remains the cornerstone of prevention as transmission can occur directly from an asymptomatic colonized healthcare provider, other patients, or a community-acquired source. Pregnancy and the puerperal period are associated with significant maternal physiologic changes that must be identified and clarified to identify signs and symptoms of GAS so that treatment can be initiated at the earliest moment. Treatment of group A streptococcal sepsis follows the guidelines developed under the Surviving Sepsis Campaign model. Maternal outcomes are improved by identifying risk factors and working with the perinatal team to implement rapid intervention. Even with prompt treatment of invasive group A Streptococcus, it remains the most common cause of infection that results in severe maternal morbidity and death in the world.

Prevalence and disease associations of superantigens szeF, szeN and szeP in the S. zooepidemicus population and possible functional redundancy of szeF

Streptococcus equi subspecies zooepidemicus (S. zooepidemicus) causes a variety of infections in a broad range of species. This study broadens prevalence data for three recently identified novel superantigens (szeF, szeN, and szeP) to define links between their presence and disease type. Screening of 437 strains across 190 sequence types (STs) revealed that 50% of strains contained superantigen genes. Results confirmed that the presence of S. zooepidemicus superantigen genes is significantly associated with non-Strangles lymph node abscessation in the horse (p-value = 0.003) and their absence is associated with uterine infection/abortion (p-value = 0.006). This study also investigated the lack of mitogenicity observed in szeF only. Results show that szeF is polymorphic, with 23 different alleles, and mutations altering the protein sequence. Gene expression differences are not responsible for lack of mitogenic activity in these strains. Taken together, these findings suggest that superantigens are important for S. zooepidemicus pathogenesis but SzeF probably has little involvement.

Puerperal group a streptococcal infections: a case series and discussion

Puerperal group A streptococcal infections, a major postpartum killer during the late 19th and early 20th centuries, have become (fortunately) rare. We describe a cluster of 4 serious peripartum group A streptococcal infections occurring within the past five years at a single medical center. These cases were not epidemiologically linked and serve to illustrate the continuing risk of these potentially fulminant infections.

Pregnancy-related group a streptococcal infections: temporal relationships between bacterial acquisition, infection onset, clinical findings, and outcome

Puerperal sepsis caused by group A Streptococcus (GAS) remains an important cause of maternal and infant mortality worldwide, including countries with modern antibiotic regimens, intensive care measures and infection control practices. To provide insights into the genesis of modern GAS puerperal sepsis, we reviewed the published cases and case series from 1974 to 2009, specifically seeking relationships between the likely source of pathogen acquisition, clinical signs, and symptoms at infection onset and patient outcomes that could provide clues for early diagnosis. Results suggest that the pathogenesis of pregnancy-related GAS infections in modern times is complex and not simply the result of exposure to GAS in the hospital setting. Additional research is needed to further explore the source of GAS, the specific M types involved, and the pathogenesis of these pregnancy-related infections to generate novel preventative and therapeutic strategies.

Creatine kinase as an indicator for hysterectomy in postpartum endomyometritis due to group A streptococci: a hypothesis illustrated by a case report

BACKGROUND

Puerperal group A streptococcus (GAS) infection, once the leading cause of postpartum sepsis, has been increasing again since the 1980s. Streptococcal toxic shock syndrome (STSS) is a serious complication characterized by rapidly spreading GAS infection, shock, and multiple organ failure. Immediate recognition and implementation of therapy is crucial for survival. Making informed decisions regarding surgical debridement, namely hysterectomy, based on clinical indicators is difficult for practitioners.

OBJECTIVES

This article discusses the potential role of creatine kinase in the decision-making process for treatment of STSS, particularly with regard to hysterectomy.

MATERIAL AND METHODS

A case report is presented. The literature was searched using the key words 'group A streptococcus', 'postpartum hysterectomy', 'creatine kinase', 'endomyometritis', and 'streptococcal toxic shock syndrome' in PubMed and the UptoDate database. Relevant articles published between 1991 and 2011 were evaluated.

CONCLUSION

Decisions regarding hysterectomy in STSS management are difficult. A rise in CK levels in the serum may indicate involvement of the myometrium and may be an important parameter in the difficult decision of hysterectomy when treating STSS.

[Late-onset postpartum sepsis with septic shock and heart dysfunction]

We report a case of late-onset postpartum sepsis from endometritis due to group A streptococci (GAS) in a 37-year-old white woman. The patient developed septic shock, with mitral regurgitation and cardiac dysfunction. Early treatment with broad-spectrum antibiotics and hemodynamic support was essential for a favorable outcome. Because of the resurgence of virulent strains of GAS that can cause fatal infections, these pathogens should be included in the differential diagnosis of postpartum infections in the mother. Although cardiac dysfunction is rare in association with GAS infection, it should be ruled out by echocardiography when the condition of a patient with sepsis does not improve.