Biofilm formation or internalization into epithelial cells enable Streptococcus pyogenes to evade antibiotic eradication in patients with pharyngitis

Molecular Aspects of the Functioning of Pathogenic Bacteria Biofilm Based on Quorum Sensing (QS) Signal-Response System and Innovative Non-Antibiotic Strategies for Their Elimination

One of the key mechanisms enabling bacterial cells to create biofilms and regulate crucial life functions in a global and highly synchronized way is a bacterial communication system called quorum sensing (QS). QS is a bacterial cell-to-cell communication process that depends on the bacterial population density and is mediated by small signalling molecules called autoinducers (AIs). In bacteria, QS controls the biofilm formation through the global regulation of gene expression involved in the extracellular polymeric matrix (EPS) synthesis, virulence factor production, stress tolerance and metabolic adaptation. Forming biofilm is one of the crucial mechanisms of bacterial antimicrobial resistance (AMR). A common feature of human pathogens is the ability to form biofilm, which poses a serious medical issue due to their high susceptibility to traditional antibiotics. Because QS is associated with virulence and biofilm formation, there is a belief that inhibition of QS activity called quorum quenching (QQ) may provide alternative therapeutic methods for treating microbial infections. This review summarises recent progress in biofilm research, focusing on the mechanisms by which biofilms, especially those formed by pathogenic bacteria, become resistant to antibiotic treatment. Subsequently, a potential alternative approach to QS inhibition highlighting innovative non-antibiotic strategies to control AMR and biofilm formation of pathogenic bacteria has been discussed.

Role of serotype and virulence determinants of Streptococcus pyogenes biofilm bacteria in internalization and persistence in epithelial cells in vitro

Streptococcus pyogenes causes a multitude of local and systemic infections, the most common being pharyngitis in children. Recurrent pharyngeal infections are common and are thought to be due to the re-emergence of intracellular GAS upon completion of antibiotic treatment. The role of colonizing biofilm bacteria in this process is not fully clear. Here, live respiratory epithelial cells were inoculated with broth-grown or biofilm bacteria of different M-types, as well as with isogenic mutants lacking common virulence factors. All M-types tested adhered to and were internalized into epithelial cells. Interestingly, internalization and persistence of planktonic bacteria varied significantly between strains, whereas biofilm bacteria were internalized in similar and higher numbers, and all strains persisted beyond 44 hours, showing a more homogenous phenotype. The M3 protein, but not the M1 or M5 proteins, was required for optimal uptake and persistence of both planktonic and biofilm bacteria inside cells. Moreover, the high expression of capsule and SLO inhibited cellular uptake and capsule expression was required for intracellular survival. Streptolysin S was required for optimal uptake and persistence of M3 planktonic bacteria, whereas SpeB improved intracellular survival of biofilm bacteria. Microscopy of internalized bacteria showed that planktonic bacteria were internalized in lower numbers as individual or small clumps of bacteria in the cytoplasm, whereas GAS biofilm bacteria displayed a pattern of perinuclear localization of bacterial aggregates that affected actin structure. Using inhibitors targeting cellular uptake pathways, we confirmed that planktonic GAS mainly uses a clathrin-mediated uptake pathway that also required actin and dynamin. Clathrin was not involved in biofilm internalization, but internalization required actin rearrangement and PI3 kinase activity, possibly suggesting macropinocytosis. Together these results provide a better understanding of the potential mechanisms of uptake and survival of various phenotypes of GAS bacteria relevant for colonization and recurrent infection.

Bactericidal effect of lascufloxacin on HEp-2 cell-internalized group A Streptococcus

INTRODUCTION

Although amoxicillin (AMPC) is recommended as first-line therapy for acute pharyngotonsillitis caused by group A streptococci (GAS), it often fails to eradicate infections. Internalization and subsequent intracellular survival of GAS are considered major mechanisms for penicillin therapeutic failure. It is, therefore, desirable to administer drugs that exert bactericidal effects on extracellular and intracellular GAS. In this study, we aim to investigate the bactericidal effects of lascufloxacin (LSFX) on internalized GAS in HEp-2 cells.

MATERIALS AND METHODS

The GAS strain M1 and clinical isolate strain #2 were used in this study. Following treatment of GAS-infected human pharyngeal carcinoma epithelial HEp-2 cells with LSFX or AMPC, internalized GAS cells were recovered. The concentrations of LSFX and AMPC were equivalent to 1 × and 2 × MIC for strain M1. Culture medium was used as a control. Time-lapse and fluorescence images of GAS invading HEp-2 cell were obtained. LIVE/DEAD fluorescence staining was used to confirm the viability of internalized GAS.

RESULTS

LSFX significantly reduced the number of cell-internalized M1 and #2 GAS strains compared to the control (p < 0.01) in a dose-dependent manner. However, AMPC did not reduce this in both strains. Both live and dead intracellular GAS were confirmed in HEp-2 cells exposed to LSFX. In contrast, intracellular GAS survived in HEp-2 cells exposed to AMPC and in the control.

CONCLUSION

LSFX elicits significant bactericidal effects on cell-internalized GAS, hence it may represent a potent therapeutic option for patients with acute pharyngotonsillitis in whom AMPC treatment has failed.

Antibiofilm properties of cathelicidin LL-37: an in-depth review

Notwithstanding ceaseless endeavors toward developing effective antibiofilm chemotherapeutics, biofilm-associated infections continue to be one of the most perplexing challenges confronting medicine today. Endogenous host defense peptides, such as the human cathelicidin LL-37, are being propounded as promising options for treating such infectious diseases. Over the past decennium, LL-37 has duly received tremendous research attention by virtue of its broad-spectrum antimicrobial activity and immunomodulatory properties. No attempt has hitherto been made, as far as we are aware, to comprehensively review the antibiofilm effects of LL-37. Accordingly, the intent in this paper is to provide a fairly all-embracing review of the literature available on the subject. Accumulating evidence suggests that LL-37 is able to prevent biofilm establishment by different bacterial pathogens such as Acinetobacter baumannii, Aggregatibacter actinomycetemcomitans, Bacteroides fragilis, Burkholderia thailandensis, Cutibacterium acnes, Escherichia coli, Francisella tularensis, Helicobacter pylori, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pyogenes. Inhibition of bacterial adhesion, downregulation of biofilm-associated genes, suppression of quorum-sensing pathways, degradation of biofilm matrix, and eradication of biofilm-residing cells are the major mechanisms responsible for antibiofilm properties of LL-37. In terms of its efficacy and safety in vivo, there are still many questions to be answered. Undoubtedly, LL-37 can open up new windows of opportunity to prevent and treat obstinate biofilm-mediated infections.

Impact of Phosphorylcholine Expression on the Adherence and Invasion of Streptococcus pyogenes to Epithelial Cells

Phosphorylcholine (PC) is a structural component of various pathogens and is involved in bacterial adhesion via the platelet-activating factor receptor (PAF-R). In this study, we investigated how PC expression affects cell adhesion and invasion of Streptococcus pyogenes (S. pyogenes). Eight clinical strains of S. pyogenes were cultured, and PC expression was measured using fluorescence-activated cell sorting. Bacterial adherence and invasion were examined using Detroit 562 cells. An anti-PC-specific monoclonal antibody (TEPC-15) was used to inhibit bacterial PC, and a PAF-R antagonist (ABT-491) was used to inhibit cellular PAF-R. The emm gene was amplified by the polymerase chain reaction with the standard primers. The level of PC expressed on the S. pyogenes surfaces differed in each strain and differed even in the same emm genotype. Adherence assay experiments showed a significant negative correlation between TEPC-15 and ABT-491 inhibitory effects and PC expression in S. pyogenes. Similarly, intracellular invasion assay experiments showed a significant negative correlation between TEPC-15 and ABT-491 inhibitory effects and PC expression in S. pyogenes. This study suggests that S. pyogenes is involved in cell adhesion and invasion by PC.

Consistent Biofilm Formation by Streptococcus pyogenes emm 1 Isolated From Patients With Necrotizing Soft Tissue Infections

Objectives

Biofilm formation has been demonstrated in muscle and soft tissue samples from patients with necrotizing soft tissue infection (NSTI) caused by Streptococcus pyogenes, but the clinical importance of this observation is not clear. Although M-protein has been shown to be important for in vitro biofilm formation in S. pyogenes, the evidence for an association between emm type and biofilm forming capacity is conflicting. Here we characterize the biofilm forming capacity in a collection of S. pyogenes isolates causing NSTI, and relate this to emm type of the isolates and clinical characteristics of the patients.

Methods

Bacterial isolates and clinical data were obtained from NSTI patients enrolled in a multicenter prospective observational study. Biofilm forming capacity was determined using a microtiter plate assay.

Results

Among 57 cases, the three most frequently encountered emm types were emm1 (n = 22), emm3 (n = 13), and emm28 (n = 7). The distribution of biofilm forming capacity in emm1 was qualitatively (narrow-ranged normal distribution) and quantitatively (21/22 isolates in the intermediate range) different from other emm types (wide ranged, multimodal distribution with 5/35 isolates in the same range as emm1). There were no significant associations between biofilm forming capacity and clinical characteristics of the patients.

Conclusions

The biofilm forming capacity of emm1 isolates was uniform and differed significantly from other emm types. The impact of biofilm formation in NSTI caused by S. pyogenes on clinical outcomes remains uncertain.

Emerging Fatal Ib/CC12 Hypervirulent Multiresistant Streptococcus agalactiae in Young Infants With Bloodstream Infection in China

Streptococcus agalactiae [also known as group B Streptococcus (GBS)] is a tremendous threat to young infants. Eighty pediatric GBS infection cases were enrolled from a teaching hospital in Shanghai between 2009 and 2020; among them, 72.5% (58/80) were diagnosed with bloodstream infection (BSI). Sequence types (STs) and serotypes of associated GBS strains were identified, and most of the Ib/clonal complex (CC)12 (86.7%, 13/15) strains caused BSIs, which was significantly higher than that of the genetically related clone Ib/CC10 (20%, 2/10; p < 0.05). Ib/CC12 BSI (30.8%) mortality was significantly higher than that of non-Ib/CC12 BSI (2.2%; p < 0.05). Virulence genes associated with adhesion, invasion, and immune evasion were detected using polymerase chain reaction. The fbsA and gbsPC1 positive rates of Ib/CC12 strains was higher than that of non-Ib/CC12 strains, whereas cpsIaJ, cpsJ, cpsI, and cpsG positive rates were lower than those of non-Ib/CC12 (p < 0.05). In in vitro studies, the Ib/CC12 strains had strong invasiveness in RAW264.7 cells, but less invasiveness in human umbilical vein endothelial cells, human brain microvascular endothelial cells, and human mammary epithelial cells when compared to other two clones. In the in vivo model, the Ib/CC12 GBS invaded the circulation system more rapidly after intraperitoneal injection, was more difficult to eradicate by phagocytes, and caused significantly higher mortality than Ib/CC10 and III/ST17 (p < 0.05). Genome analysis showed that the Ib/CC12 strains had two clustered regularly interspaced short palindromic repeat-Cas systems and carried more antibiotic resistant genes, which conferred resistance to macrolides, clindamycin, aminoglycosides, and tetracycline. The Ib/CC12 strains had 45 unique annotated genes compared to that of Ib/CC10, including the pathogen-related toxin/antitoxin system, PezA/T. In conclusion, Ib/CC12 is an emerging hypervirulent multiresistant GBS clone that causes invasive and fatal infections in pediatric patients. The prevention and control of Ib/CC12 GBS infection should be emphasized.

Adjunctive Rifampicin Increases Antibiotic Efficacy in Group A Streptococcal Tissue Infection Models

Biofilm has recently been highlighted as a complicating feature of necrotizing soft tissue infections (NSTI) caused by Streptococcus pyogenes (i.e., group A Streptococcus [GAS]) contributing to a persistence of bacteria in tissue despite prolonged antibiotic therapy. Here, we assessed the standard treatment of benzylpenicillin and clindamycin with or without rifampin in a tissue-like setting. Antibiotic efficacy was evaluated by CFU determination in a human organotypic skin model infected for 24 or 48 h with GAS strains isolated from NSTI patients. Antibiotic effect was also evaluated by microcalorimetric metabolic assessment in in vitro infections of cellular monolayers providing continuous measurements over time. Adjunctive rifampin resulted in enhanced antibiotic efficacy of bacterial clearance in an organotypic skin tissue model, 97.5% versus 93.9% (P = 0.006). Through microcalorimetric measurements, adjunctive rifampin resulted in decreased metabolic activity and extended lag phase for all clinical GAS strains tested (P < 0.05). In addition, a case report is presented of adjunctive rifampin treatment in an NSTI case with persistent GAS tissue infection. The findings of this study demonstrate that adjunctive rifampin enhances clearance of GAS biofilm in an in vitro tissue infection model.

Antimicrobial and Antibiofilm Activities of Weissella cibaria against Pathogens of Upper Respiratory Tract Infections

Recently discovered preventive effects of probiotics on oral health have attracted interest to their use for the prevention and treatment of various diseases. This study aimed to evaluate the antimicrobial and antibiofilm properties of Weissella cibaria against Streptococcus pyogenes, Staphylococcus aureus, S. pneumoniae, and Moraxella catarrhalis, the major pathogens of upper respiratory tract infections (URTIs). The antimicrobial activities of W. cibaria were compared with those of other oral probiotics using a competitive inhibition assay and the determination of the minimum inhibitory concentrations (MICs). In addition, a time-kill assay, spectrophotometry, and confocal laser scanning microscopy were used to confirm the antimicrobial and antibiofilm abilities of W. cibaria CMU (oraCMU) and CMS1 (oraCMS1). Both live cells and cell-free supernatants of all tested probiotics, except Streptococcus salivarius, showed excellent antimicrobial activities. All target pathogens were killed within 4 to 24 h at twice the MIC of oraCMU and oraCMS1, which showed the highest antimicrobial activities against M. catarrhalis. The antimicrobial substances that affected different target pathogens were different. Both oraCMU and oraCMS1 showed excellent abilities to inhibit biofilm formation and remove preformed biofilms. Our results suggest that the W. cibaria probiotics offer new possibilities for the prevention and treatment of bacterial URTIs.

Effectiveness of antibacterial agents against cell-invading bacteria such as Streptococcus pyogenes and Haemophilus influenzae

BACKGROUND

Recurrent tonsillitis is one of the most common otolaryngological disorders caused by cell-invading bacteria, such as Streptococcus pyogenes (S. pyogenes) and Haemophilus influenzae. The aim of this study was to investigate the effect of antibacterial agents against cell-invading bacteria.

METHODS

The intracellular invasion of Detroit 562 cells by five strains of nontypeable Haemophilus influenzae (NTHi) and four strains of S. pyogenes was investigated. The antibacterial agents used were garenoxacin (GRNX), clarithromycin (CAM), amoxicillin (AMPC), cefditoren pivoxil (CDTR-PI), and levofloxacin (LVFX).

RESULTS

Both NTHi and S. pyogenes fully invaded Detroit 562 cells in 6 h and were less sensitive to CAM. GRNX, CAM, and LVFX were effective against bacteria invading the cells, but AMPC and CDTR-PI were not effective. GRNX was the most effective.

CONCLUSION

GRNX was the most effective agent against bacteria invading cells.

Genital Tract GAS Infection ISIDOG Guidelines

There has been an increasing worldwide incidence of invasive group A streptococcal (GAS) disease in pregnancy and in the puerperal period over the past 30 years. Postpartum Group A streptococci infection, and in particular streptococcal toxic shock syndrome (TSS) and necrotizing fasciitis, can be life threatening and difficult to treat. Despite antibiotics and supportive therapy, and in some cases advanced extensive surgery, mortality associated with invasive group A streptococcal postpartum endometritis, necrotizing fasciitis, and toxic shock syndrome remains high, up to 40% of postpartum septic deaths. It now accounts for more than 75,000 deaths worldwide every year. Postpartum women have a 20-fold increased incidence of GAS disease compared to non-pregnant women. Despite the high incidence, many invasive GAS infections are not diagnosed in a timely manner, resulting in potentially preventable maternal and neonatal deaths. In this paper the specific characteristics of GAS infection in the field of Ob/Gyn are brought to our attention, resulting in guidelines to improve our awareness, early recognition and timely treatment of the disease. New European prevalence data of vaginal GAS colonization are presented, alongside two original case histories. Additionally, aerobic vaginitis is proposed as a supplementary risk factor for invasive GAS diseases.

Prevalence and antibiotics susceptibility profiles of Streptococcus pyogenes among pediatric patients with acute pharyngitis at Felege Hiwot Comprehensive Specialized Hospital, Northwest Ethiopia

BACKGROUND

Streptococcus pyogenes (S. pyogenes) is a Gram positive bacterium which is a leading cause of pharyngitis, skin and soft tissue infection and post streptococcal syndromes. Due to lack of β-lactamase enzyme production, it was considered universally susceptible to penicillin group and later generation of β-lactam antibiotics. As such, empirical treatment was common which might leads to development of antibiotics resistance. Therefore, the aims of this study were to determine the prevalence, antibiotics susceptibility profile; and associated factors of S. pyogenes among pediatric patients with acute pharyngitis in Felege Hiwot Comprehensive Specialized Hospital (FHCSH), Northwest Ethiopia.

METHODS

Hospital based cross-sectional study was carried out on 154 pediatric patients, whose age ranged from 0 to 18 years old using consecutive convenient sampling technique from 1st February to 19th June 2020 at FHCSH. S. pyogenes were identified by throat swab culture on 5% sheep blood agar with an overnight incubation at 37 °C in candle jar containing 5% CO2. Gram stain, catalase test and bacitracin test were used to identify S. pyogenes. Then,the data were entered into EpiData version 3.1 and analyzed by SPSS version 20 software. Finally, stepwise, bivariable and multivariable logistic regressions were carried out for identifyying factors having significant ssociation (p<0.05) with  acute pharyngitis.  RESULTS: From the total throat swabs, 14 (9.1%) with (95% CI; 4.5-14.3) were culture positive for S. pyogenes. From these, all isolates were sensitive to penicillin and ampicillin. On the otherhand, 4 (35.7%), 4 (35.5%), 3 (21.4%), 2 (14.3%), 1 (7.1%), 7 (50.0%) and 1 (7.1%) isolates were resistant for ceftriaxone, vancomycin, erythromycin, tetracycline, chloramphenicol, clindamycin and levofloxacin, respectively. The presence of any smoker in home showed significant association with S. pyogenes acute pharyngitis. Furthermore, having tender lymphadenopathy and recurrence were clinical predictors for S. pyogenes acute pharyngitis (P < 0.05).

CONCLUSION

The prevalence of S. pyogenes was guaged at 9.1% which is considered as low prevalence. All S. pyogenes isolats remain sensitive to penicillin. However, resistance was reported to clindamycin 7 (50.0%), ceftriaxone 5 (35.7%) and erythromycin 3 (21.4%). The current practice of giving erythromycin, clindamycin instead of penicillin and ampicillin is againest the microbiology result. Therefore, current empirical treatment of acute pharyngitis shall take in to account the current evidences. Continuous surveillance of antibiotics resistance pattern of S. pyogenes for acute pharyngitis must be strengthen to improve the use of antibiotics in hospitals.

Pathogenic Mechanisms of Streptococcal Necrotizing Soft Tissue Infections

Necrotizing skin and soft tissue infections (NSTIs) are severe life-threatening and rapidly progressing infections. Beta-hemolytic streptococci, particularly S. pyogenes (group A streptococci (GAS)) but also S. dysgalactiae subsp. equisimilis (SDSE, most group G and C streptococcus), are the main causative agents of monomicrobial NSTIs and certain types, such as emm1 and emm3, are over-represented in NSTI cases. An arsenal of bacterial virulence factors contribute to disease pathogenesis, which is a complex and multifactorial process. In this chapter, we summarize data that have provided mechanistic and immuno-pathologic insight into host-pathogens interactions that contribute to tissue pathology in streptococcal NSTIs. The role of streptococcal surface associated and secreted factors contributing to the hyper-inflammatory state and immune evasion, bacterial load in the tissue and persistence strategies, including intracellular survival and biofilm formation, as well as strategies to mimic NSTIs in vitro are discussed.

Singularities of Pyogenic Streptococcal Biofilms - From Formation to Health Implication

Biofilms are generally defined as communities of cells involved in a self-produced extracellular matrix adhered to a surface. In biofilms, the bacteria are less sensitive to host defense mechanisms and antimicrobial agents, due to multiple strategies, that involve modulation of gene expression, controlled metabolic rate, intercellular communication, composition, and 3D architecture of the extracellular matrix. These factors play a key role in streptococci pathogenesis, contributing to therapy failure and promoting persistent infections. The species of the pyogenic group together with Streptococcus pneumoniae are the major pathogens belonging the genus Streptococcus, and its biofilm growth has been investigated, but insights in the genetic origin of biofilm formation are limited. This review summarizes pyogenic streptococci biofilms with details on constitution, formation, and virulence factors associated with formation.

Rheumatic heart disease: A review of the current status of global research activity

Rheumatic heart disease (RHD) is a serious and long-term consequence of acute rheumatic fever (ARF), an autoimmune sequela of a mucosal infection by Streptococcus pyogenes (Group A Streptococcus, Strep A). The pathogenesis of ARF and RHD is complex and not fully understood but involves host and bacterial factors, molecular mimicry, and aberrant host innate and adaptive immune responses that result in loss of self-tolerance and subsequent cross-reactivity with host tissues. RHD is entirely preventable yet claims an estimated 320 000 lives annually. The major burden of disease is carried by developing nations and Indigenous populations within developed nations, including Australia. This review will focus on the epidemiology, pathogenesis and treatment of ARF and RHD in Australia, where: streptococcal pyoderma, rather than streptococcal pharyngitis, and Group C and Group G Streptococcus, have been implicated as antecedents to ARF; the rates of RHD in remote Indigenous communities are persistently among the highest in the world; government register-based programs coordinate disease screening and delivery of prophylaxis with variable success; and researchers are making significant progress in the development of a broad-spectrum vaccine against Strep A.

An Evaluation of the Antibacterial Properties of Tormentic Acid Congener and Extracts From Callistemon viminalis on Selected ESKAPE Pathogens and Effects on Biofilm Formation

ESKAPE pathogens, namely, Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species, are responsible for a majority of all healthcare-acquired infections (HAI). The bacteria cause nosocomial infections in immunocompromised patients. Extracts from Callistemon viminalis have been shown to have antibacterial, antifungal, and anti-inflammatory activities. Tormentic acid congener, a pentacyclic triterpene saponin, was isolated from C. viminalis leaves. This study aimed to investigate the antibacterial effects of tormentic acid congener and leaf extracts on biofilm formation by A. baumannii, S. aureus, S. pyogenes, and P. aeruginosa. The antibacterial effects were determined by the microbroth dilution method, and ciprofloxacin was used as the standard antibacterial drug. Biofilm formation and detachment assays were performed using crystal violet staining. Production of extracellular polymeric DNA and polysaccharides from biofilms was also determined. Tormentic acid congener showed time-dependent antibacterial activity against P. aeruginosa with a MIC of 100 µg/ml and caused significant protein leakage. Antibacterial activity was found when tormentic acid congener was tested against both S. aureus and P. aeruginosa. The MICs were found to be 25 µg/ml and 12.5 µg/ml for P. aeruginosa and S. aureus cells, respectively. S. pyogenes was found to be susceptible to tormentic acid congener and the hydroethanolic extract with an MIC of 100 µg/ml and 25 µg/ml, respectively. A. baumannii was found not to be susceptible to the compound or the extracts. The compound and the extracts caused a significant decrease in the biofilm extracellular polysaccharide content of S. pyogenes. The extracts and tormentic acid congener caused detachment of biofilms and decreased the release of extracellular DNA and capsular polysaccharides from biofilms of P. aeruginosa and S. aureus. Tormentic acid congener and extracts, thus, have significant antibacterial and antibiofilm activities on these selected ESKAPE bacteria and can act as source lead compounds for the development of antibacterial triterpenoids.

Deciphering Streptococcal Biofilms

Streptococci are a diverse group of bacteria, which are mostly commensals but also cause a considerable proportion of life-threatening infections. They colonize many different host niches such as the oral cavity, the respiratory, gastrointestinal, and urogenital tract. While these host compartments impose different environmental conditions, many streptococci form biofilms on mucosal membranes facilitating their prolonged survival. In response to environmental conditions or stimuli, bacteria experience profound physiologic and metabolic changes during biofilm formation. While investigating bacterial cells under planktonic and biofilm conditions, various genes have been identified that are important for the initial step of biofilm formation. Expression patterns of these genes during the transition from planktonic to biofilm growth suggest a highly regulated and complex process. Biofilms as a bacterial survival strategy allow evasion of host immunity and protection against antibiotic therapy. However, the exact mechanisms by which biofilm-associated bacteria cause disease are poorly understood. Therefore, advanced molecular techniques are employed to identify gene(s) or protein(s) as targets for the development of antibiofilm therapeutic approaches. We review our current understanding of biofilm formation in different streptococci and how biofilm production may alter virulence-associated characteristics of these species. In addition, we have summarized the role of surface proteins especially pili proteins in biofilm formation. This review will provide an overview of strategies which may be exploited for developing novel approaches against biofilm-related streptococcal infections.

Assessing the Role of Pharyngeal Cell Surface Glycans in Group A Streptococcus Biofilm Formation

Group A Streptococcus (GAS) causes 700 million infections and accounts for half a million deaths per year. Antibiotic treatment failure rates of 20–40% have been observed. The role host cell glycans play in GAS biofilm formation in the context of GAS pharyngitis and subsequent antibiotic treatment failure has not been previously investigated. GAS serotype M12 GAS biofilms were assessed for biofilm formation on Detroit 562 pharyngeal cell monolayers following enzymatic removal of all N-linked glycans from pharyngeal cells with PNGase F. Removal of N-linked glycans resulted in an increase in biofilm biomass compared to untreated controls. Further investigation into the removal of terminal mannose and sialic acid residues with α1-6 mannosidase and the broad specificity sialidase (Sialidase A) also found that biofilm biomass increased significantly when compared to untreated controls. Increases in biofilm biomass were associated with increased production of extracellular polymeric substances (EPS). Furthermore, it was found that M12 GAS biofilms grown on untreated pharyngeal monolayers exhibited a 2500-fold increase in penicillin tolerance compared to planktonic GAS. Pre-treatment of monolayers with exoglycosidases resulted in a further doubling of penicillin tolerance in resultant biofilms. Lastly, an additional eight GAS emm-types were assessed for biofilm formation in response to terminal mannose and sialic acid residue removal. As seen for M12, biofilm biomass on monolayers increased following removal of terminal mannose and sialic acid residues. Collectively, these data demonstrate that pharyngeal cell surface glycan structures directly impact GAS biofilm formation in a strain and glycan specific fashion.

Current Understanding of Group A Streptococcal Biofilms

Background:

It has been proposed that GAS may form biofilms. Biofilms are microbial communities that aggregate on a surface, and exist within a self-produced matrix of extracellular polymeric substances. Biofilms offer bacteria an increased survival advantage, in which bacteria persist, and resist host immunity and antimicrobial treatment. The biofilm phenotype has long been recognized as a virulence mechanism for many Gram-positive and Gram-negative bacteria, however very little is known about the role of biofilms in GAS pathogenesis.

Objective:

This review provides an overview of the current knowledge of biofilms in GAS pathogenesis. This review assesses the evidence of GAS biofilm formation, the role of GAS virulence factors in GAS biofilm formation, modelling GAS biofilms, and discusses the polymicrobial nature of biofilms in the oropharynx in relation to GAS.

Conclusion:

Further study is needed to improve the current understanding of GAS as both a mono-species biofilm, and as a member of a polymicrobial biofilm. Improved modelling of GAS biofilm formation in settings closely mimicking in vivo conditions will ensure that biofilms generated in the lab closely reflect those occurring during clinical infection.

Survival of Group A Streptococcus (GAS) is Enhanced Under Desiccated Culture Conditions

Streptococcus pyogenes or Group A Streptococcus (GAS) infections are the leading cause of bacterial tonsillopharyngitis. The bacterium can survive and persist within the human host for a long time as it is observed in up to 40% of the population who are considered as carriers. Recurrent tonsillopharyngitis is a particular problem in children which is caused either by relapses due to failed bacterial clearance or by reinfection. A prolonged survival in tonsillar crypts or on inanimate surfaces might be sources for reinfection. We therefore examined 64 clinical GAS isolates from children with tonsillopharyngitis for their long-term survival under either liquid or desiccated culture conditions. After 6 weeks, the overall GAS survival rate was 400-fold increased under desiccated culture conditions compared to liquid culture conditions, but varied depending on the emm-type between 20-fold (emm4) and 14000-fold (emm3). The survival rates of isolates from emm75 were significantly lower which is probably due to their production of hydrogen peroxide up to fatal doses. No hydrogen peroxide production could be detected for other emm-types. Furthermore, 11 isolates from patients with recurrent tonsillopharyngitis were compared to isolates of the same emm-type from patients with single episodes of tonsillopharyngitis. A significant elevated pH value and an increased survival rate for isolates from patients with recurrent infections were observed. In conclusion, significant differences in long-term survival of different GAS isolates as well as survival under desiccated culture conditions might contribute to both failed bacterial clearance and reinfection in patients with recurrent tonsillopharyngitis.

The Arginine Deiminase Pathway Impacts Antibiotic Tolerance during Biofilm-Mediated Streptococcus pyogenes Infections

Bacterial biofilms are responsible for a variety of serious human infections and are notoriously difficult to treat due to their recalcitrance to antibiotics. Further work is necessary to elicit a full understanding of the mechanism of this antibiotic tolerance. The arginine deiminase (ADI) pathway is responsible for bacterial pH maintenance and is highly expressed during biofilm growth in multiple bacterial species. Using the group A Streptococcus (GAS) as a model human pathogen, the ADI pathway was demonstrated to contribute to biofilm growth. The inability of antibiotics to reduce GAS populations when in a biofilm was demonstrated by in vitro studies and a novel animal model of nasopharyngeal infection. However, disruption of the ADI pathway returned GAS biofilms to planktonic levels of antibiotic sensitivity, suggesting the ADI pathway is influential in biofilm-related antibiotic treatment failure and provides a new strategic target for the treatment of biofilm infections in GAS and potentially numerous other bacterial species.IMPORTANCE Biofilm-mediated bacterial infections are a major threat to human health because of their recalcitrance to antibiotic treatment. Through the study of Streptococcus pyogenes, a significant human pathogen that is known to form antibiotic-tolerant biofilms, we demonstrated the role that a bacterial pathway known for responding to acid stress plays in biofilm growth and antibiotic tolerance. This not only provides some insight into antibiotic treatment failure in S. pyogenes infections but also, given the widespread nature of this pathway, provides a potentially broad target for antibiofilm therapies. This discovery has the potential to impact the treatment of many different types of recalcitrant biofilm infections.

Herbal Tea for the Management of Pharyngitis: Inhibition of Streptococcus pyogenes Growth and Biofilm Formation by Herbal Infusions

Herbal teas are becoming popular as functional beverages due to their various health promotional properties. This study aimed at assessing 13 hot water infusions (HWIs) from different herbs against streptococcal pharyngitis (strep throat). Licorice root exhibited the lowest minimum inhibitory concentrations (MIC) of 1.56 mg/mL, followed by barberry root, thyme, and oregano flowering shoots, with a MIC of 3.13 mg/mL. At their respective minimum bactericidal concentrations (MBC), licorice showed the bactericidal effect on S. pyogenes within 12 h after exposure while others need 24 h for a similar outcome. The HWIs exhibited inhibitory activity on biofilm formation, ranging from 1.56 to 6.25 mg/mL, which confirmed by ruptured cells or clusters of dead cell debris observed in scanning electron microscope (SEM). Overall, non-toxic concentrations of efficacious HWIs from licorice root, barberry root, thyme, and oregano flowering shoots may provide potential sources for developing herbal teas or biomedicine for the management of S. pyogenes infections.

Diagnosis and treatment of biofilm infections in children

PURPOSE OF REVIEW

Biofilm-associated infections cause difficulties in the management of childhood chronic infections and other diseases, due to the invasive nature of interventions which are often necessary for definitive management. Despite their importance, there are challenges in diagnosing biofilm infections and gaps in clinicians' understanding regarding the significance of biofilms.

RECENT FINDINGS

Many chronic infections associated with biofilms remain difficult or impossible to eradicate with conventional therapy. Surgical intervention, implant removal or long-term intermittent or suppressive antimicrobial therapy may be required. There are still significant challenges in detecting biofilms which presents a barrier in clinical practice and research. Novel therapies to disrupt biofilms are currently under investigation, which may help reduce the impact of antimicrobial resistance.

SUMMARY

Biofilm-associated infection should be considered wherever there is clinical concern for an infection affecting prosthetic material, where there is a predisposing condition such as suppurative lung disease; or in the setting of chronic or relapsing infections which may be culture negative. New diagnostic methods for detecting biofilms are a research priority for both clinical diagnosis and the ability to conduct high quality clinical trials of novel antibiofilm interventions.

Bactericidal and Anti-Biofilm Activity of Ethanol Extracts Derived from Selected Medicinal Plants against Streptococcus pyogenes

Background: There is a growing interest in medicinal plants which have been traditionally used for the treatment of human infections. This study assessed 14 ethanol extracts (EEs) on bacterial growth and biofilm formation of Streptococcus pyogenes. Methods: Constituent major phytochemicals in the extracts were identified using ultra performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS). Micro-broth dilution and time-kill assays were used to determine antibacterial activities. Anti-biofilm activities were studied using MTT assay, and morphology of biofilms was observed by scanning electron microscopy (SEM). Transmission electron microscopy (TEM) was employed to visualize the ultra-cross section structure of bacteria treated with efficacious extracts. Results: Licorice root, purple coneflower flower, purple coneflower stem, sage leaves and slippery elm inner bark EEs were the most effective, with minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of 62.5 μg/mL and 125 μg/mL, respectively. The minimum biofilm inhibitory concentration (MBIC) of extracts ranged from 31.5–250 μg/mL. Morphological changes were observed in treated biofilms compared to the untreated. The four most effective extracts exhibited the ability to induce degradation of bacterial cell wall and disintegration of the plasma membrane. Conclusion: We suggest that EEs of sage leaf and purple coneflower flower are promising candidates to be further investigated for developing alternative natural therapies for the management of streptococcal pharyngitis.

Human Streptococcal Necrotizing Fasciitis Histopathology Mirrored in a Murine Model

Streptococcal necrotizing fasciitis (NF) causes high morbidity and mortality despite state-of-the-art therapy. Low incidence and rapid disease progression, necessitating immediate initiation of therapy, have proven challenging aspects for setting up prospective randomized trials. This has resulted in little therapeutic progress over the past decade. The validation of reliable murine NF models to study both pathogenesis and optimized therapeutic regimens of streptococcal NF are thus essential. In this study, we characterized a murine NF model and compared the pathology with an in-depth tissue analysis of streptococcal NF in patients. We found that the streptococcal murine NF model closely reflected all histologic characteristics encountered in human streptococcal NF. This murine NF model helps understanding of human NF pathology better in a time-dependent manner and will allow studying novel therapeutic options in the future.

Essential oils from Origanum vulgare and Salvia officinalis exhibit antibacterial and anti-biofilm activities against Streptococcus pyogenes

In the present study, essential oils (EOs) extracted from oregano, sage, cloves, and ginger were evaluated for the phytochemical profile, antibacterial, and anti-biofilm activities against Streptococcus pyogenes. The broth microdilution method was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of EOs. The minimum biofilm inhibitory concentrations (MBICs) were determined using MTT assay and fixed biofilms were observed through scan electron microscopy. The oregano and sage EOs showed the lowest MIC as well as MBC of 0.25-0.5 mg/mL. Time kill assay results showed that oregano and sage EOs exhibited bactericidal effects within 5 min and 4 h, respectively. Both oregano and sage extracts acts as a potent anti-biofilm agent with dual actions, preventing and eradicating the biofilm. The microscopic visualization of biofilms treated with EOs have shown morphological and density changes compared to the untreated control. Oregano EO was constituted predominantly carvacrol (91.6%) and in sage EO, higher levels of α-thujone (28.5%) and camphor (16.6%) were revealed. EOs of oregano and sage inhibit the growth and biofilm formation of S. pyogenes. Effective concentrations of oregano and sage EOs and their phytochemicals can be used in developing potential plant-derived antimicrobial agents in the management of streptococcal pharyngitis.

The Regulatory Small RNA MarS Supports Virulence of Streptococcus pyogenes

Small regulatory RNAs (sRNAs) play a role in the control of bacterial virulence gene expression. In this study, we investigated an sRNA that was identified in Streptococcus pyogenes (group A Streptococcus, GAS) but is conserved throughout various streptococci. In a deletion strain, expression of mga, the gene encoding the multiple virulence gene regulator, was reduced. Accordingly, transcript and proteome analyses revealed decreased expression of several Mga-activated genes. Therefore, and because the sRNA was shown to interact with the 5′ UTR of the mga transcript in a gel-shift assay, we designated it MarS for mga-activating regulatory sRNA. Down-regulation of important virulence factors, including the antiphagocytic M-protein, led to increased susceptibility of the deletion strain to phagocytosis and reduced adherence to human keratinocytes. In a mouse infection model, the marS deletion mutant showed reduced dissemination to the liver, kidney, and spleen. Additionally, deletion of marS led to increased tolerance towards oxidative stress. Our in vitro and in vivo results indicate a modulating effect of MarS on virulence gene expression and on the pathogenic potential of GAS.

Microbiological assessment of effects of clinical mouth rinses on common oral microbes

Dry mouth occurs frequently in aged individuals, as well as in patients who are hospitalized, receiving multiple drugs, undergoing radiation treatment to the head and neck, or wearing a removable denture prosthesis, use of mouth rinse being often an option for relief. In the present study, we performed microbiological assessments of subjects given three different commercially available mouth rinses commonly employed in clinical practice (Peptisal, Biotène, ConCool) to determine their effects. For bacterial clearance in vitro, Peptisal showed the highest level of suppression of oral indigenous bacteria found in both planktonic formations and biofilm. Furthermore, the inhibitory effects of these agents on biofilm formation on acrylic resin plates were examined using scanning electron microscopy. Again, Peptisal proved superior, because acquisition of resistance to antimicrobial peptides by a sensitive microbial strain was rarely observed. We conclude that Peptisal is an effective mouth rinse for clearance of planktonic and biofilm microorganisms present in the oral cavity.

Biofilm formation of beta-hemolytic group G Streptococcus dysgalactiae subspecies equisimilis isolates and its association with emm polymorphism

Biofilm formation has been well known as a determinant of bacterial virulence. Group G Streptococcus dysgalactiae subspecies equisimilis (SDSE), a relevant pathogen with increasing medical importance, was evaluated for the biofilm-forming potential. Microtiter plate assay was used to assess the most feasible medium for group G SDSE to form a biofilm. Among 246 SDSE isolates examined, 46.7%, 43.5%, 33.3%, and 26.4% of isolates showed moderate or strong biofilm-forming abilities using tryptic soy broth (TSB), brain heart infusion broth (BHI), Todd-Hewitt broth (THB), and C medium with 30 mM glucose (CMG), respectively. The addition of glucose significantly increased the biofilm-forming ability of group G SDSE. FCT (fibronectin-collagen-T-antigen) typing of SDSE was first undertaken and 11 FCT types were found. Positive associations of stG10.0 or negative associations of stG245.0, stG840.0, and stG6.1 with biofilm-forming ability of SDSE were, respectively, found. This was the first investigation demonstrating biofilm-forming potential in clinical group G SDSE isolates; also, some significant associations of biofilm-forming ability with certain emm types were presented.

Management of children with persistent group A streptococcal carriage

INTRODUCTION

Chronic GAS carrier state is best defined as the prolonged presence of group A β-haemolytic Streptococcus (GAS) in the pharynx without evidence of infection or inflammation. Chronic GAS carriers have a low risk of immune mediated complications. Persistent pharyngeal carriage often raises management issues. In this study, we review the evidence on the management of persistent GAS carriage in children and propose a management algorithm. Areas covered: Chronic GAS pharyngeal carriage is quite common affecting 10-20% of school-aged children. Pathogenesis of carriage has been related to the pharynx microflora and to special properties of GAS, but several aspects are yet to be elucidated. Management greatly depends on whether the individual child belongs to a 'high-risk' group and might benefit from eradication regimens or not, when observation-only and reassurance are enough. Penicillin plus rifampin and clindamycin monotherapy have been recommended for eradication; limited evidence of effectiveness of azithromycin has been reported. Surgical intervention is not indicated. Expert commentary: GAS infection is a common reason for antibiotic use and abuse in children and asymptomatic carriers constitute the major reservoir of GAS in the community. Several aspects are yet to be elucidated and well-designed studies are needed for firm conclusions to be drawn.

YvqE and CovRS of Group A Streptococcus Play a Pivotal Role in Viability and Phenotypic Adaptations to Multiple Environmental Stresses

Streptococcus pyogenes (group A Streptococcus, or GAS) is a human pathogen that causes a wide range of diseases. For successful colonization within a variety of host niches, GAS utilizes TCSs to sense and respond to environmental changes and adapts its pathogenic traits accordingly; however, many GAS TCSs and their interactions remain uncharacterized. Here, we elucidated the roles of a poorly characterized TCS, YvqEC, and a well-studied TCS, CovRS, in 2 different GAS strain SSI-1 and JRS4, respectively. Deletion of yvqE and yvqC in JRS4 resulted in lower cell viability and abnormality of cell division when compared to the wild-type strain under standard culture conditions, demonstrating an important role for YvqEC. Furthermore, a double-deletion of yvqEC and covRS in SSI-1 and JRS4 resulted in a significantly impaired ability to survive under various stress conditions, as well as an increased sensitivity to cell wall-targeting antibiotics compared to that observed in either single mutant or wild-type strains suggesting synergistic interactions. Our findings provide new insights into the impact of poorly characterized TCS (YvqEC) and potential synergistic interactions between YvqEC and CovRS and reveal their potential role as novel therapeutic targets against GAS infection.

DNA-based culture-independent analysis detects the presence of group a streptococcus in throat samples from healthy adults in Japan

Background

Group A Streptococcus (GAS; Streptococcus pyogenes) causes a range of mild to severe infections in humans. It can also colonize healthy persons asymptomatically. Therefore, it is important to study GAS carriage in healthy populations, as carriage of it might lead to subsequent disease manifestation, clonal spread in the community, and/or diversification of the organism. Throat swab culture is the gold standard method for GAS detection. Advanced culture-independent methods provide rapid and efficient detection of microorganisms directly from clinical samples. We investigated the presence of GAS in throat swab samples from healthy adults in Japan using culture-dependent and culture-independent methods.

Results

Two throat swab samples were collected from 148 healthy volunteers. One was cultured on selective medium, while total DNA extracted from the other was polymerase chain reaction (PCR) amplified with two GAS-specific primer pairs: one was a newly designed 16S rRNA-specific primer pair, the other a previously described V-Na⁺-ATPase primer pair. Although only 5 (3.4 %) of the 148 samples were GAS-positive by the culture-dependent method, 146 (98.6 %) were positive for the presence of GAS DNA by the culture-independent method. To obtain serotype information by emm typing, we performed nested PCR using newly designed emm primers. We detected the four different emm types in 25 (16.9 %) samples, and these differed from the common emm types associated with GAS associated diseases in Japan. The different emm types detected in the healthy volunteers indicate that the presence of unique emm types might be associated with GAS carriage.

Conclusions

Our results suggest that culture-independent methods should be considered for profiling GAS in the healthy hosts, with a view to obtaining better understanding of these organisms. The GAS-specific primers (16S rRNA and V-Na⁺-ATPase) used in this study can be used to estimate the maximum potential GAS carriage in people.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0858-5) contains supplementary material, which is available to authorized users.

A bacteriophage endolysin that eliminates intracellular streptococci

PlyC, a bacteriophage-encoded endolysin, lyses Streptococcus pyogenes (Spy) on contact. Here, we demonstrate that PlyC is a potent agent for controlling intracellular Spy that often underlies refractory infections. We show that the PlyC holoenzyme, mediated by its PlyCB subunit, crosses epithelial cell membranes and clears intracellular Spy in a dose-dependent manner. Quantitative studies using model membranes establish that PlyCB interacts strongly with phosphatidylserine (PS), whereas its interaction with other lipids is weak, suggesting specificity for PS as its cellular receptor. Neutron reflection further substantiates that PlyC penetrates bilayers above a PS threshold concentration. Crystallography and docking studies identify key residues that mediate PlyCB–PS interactions, which are validated by site-directed mutagenesis. This is the first report that a native endolysin can traverse epithelial membranes, thus substantiating the potential of PlyC as an antimicrobial for Spy in the extracellular and intracellular milieu and as a scaffold for engineering other functionalities.

DOI:http://dx.doi.org/10.7554/eLife.13152.001

Streptococcus pyogenes is the bacterium that causes throat infections and other serious infections in humans. Antibiotics such as penicillin are used to treat active infections, but so-called “strep throat infections” often return after treatment. This is because S. pyogenes can enter the cells that line the throat and hide from the antibiotics, which cannot enter the throat cells.

Endolysins are enzymes produced by viruses that attack bacteria, and these enzymes target and destroy the bacterial cell wall. A previous study revealed that an endolysin known as PlyC could destroy S. pyogenes bacteria on contact. PlyC and other endolysins have the potential to act as alternatives to common antibiotics, but before these enzymes can be developed as therapeutics, it is important to understand how they interact with human host cells.

Like antibiotics, the PlyC endolysin was not expected to enter throat cells. However, Shen, Barros et al. have now discovered that not only can PlyC enter throat cells, it can essentially chase down and kill S. pyogenes that are hiding inside. Other similar enzymes could not act in this way, and further studies confirmed that PlyC could move around inside a throat cell without causing it damage. Shen, Barros et al. also determined that PlyC has a pocket on its surface that binds with a specific component of the throat cell membrane, a molecule called phosphatidylserine. This interaction – which is a bit like a lock and key – grants PlyC access into the cell.

While it is clear that PlyC eventually kills S. pyogenes hiding inside throat cells, future experiments will aim to determine how PlyC moves around once inside an infected throat cell. Together, an understanding of how an endolysin enters cells and destroys hiding S. pyogenes will contribute to the development of endolysins with broader activity, which can be used as alternatives to common antibiotics.

DOI:http://dx.doi.org/10.7554/eLife.13152.002

Auranofin-loaded nanoparticles as a new therapeutic tool to fight streptococcal infections

Drug-loaded nanoparticles (NPs) can improve infection treatment by ensuring drug concentration at the right place within the therapeutic window. Poly(lactic-co-glycolic acid) (PLGA) NPs are able to enhance drug localization in target site and to sustainably release the entrapped molecule, reducing the secondary effects caused by systemic antibiotic administration. We have loaded auranofin, a gold compound traditionally used for treatment of rheumatoid arthritis, into PLGA NPs and their efficiency as antibacterial agent against two Gram-positive pathogens, Streptococcus pneumoniae and Streptococcus pyogenes was evaluated. Auranofin-PLGA NPs showed a strong bactericidal effect as cultures of multiresistant pneumococcal strains were practically sterilized after 6 h of treatment with such auranofin-NPs at 0.25 μM. Moreover, this potent bactericidal effect was also observed in S. pneumoniae and S. pyogenes biofilms, where the same concentration of auranofin-NPs was capable of decreasing the bacterial population about 4 logs more than free auranofin. These results were validated using a zebrafish embryo model demonstrating that treatment with auranofin loaded into NPs achieved a noticeable survival against pneumococcal infections. All these approaches displayed a clear superiority of loaded auranofin PLGA nanocarriers compared to free administration of the drug, which supports their potential application for the treatment of streptococcal infections.

Streptococcus pyogenes biofilms-formation, biology, and clinical relevance

Streptococcus pyogenes (group A streptococci, GAS) is an exclusive human bacterial pathogen. The virulence potential of this species is tremendous. Interactions with humans range from asymptomatic carriage over mild and superficial infections of skin and mucosal membranes up to systemic purulent toxic-invasive disease manifestations. Particularly the latter are a severe threat for predisposed patients and lead to significant death tolls worldwide. This places GAS among the most important Gram-positive bacterial pathogens. Many recent reviews have highlighted the GAS repertoire of virulence factors, regulators and regulatory circuits/networks that enable GAS to colonize the host and to deal with all levels of the host immune defense. This covers in vitro and in vivo studies, including animal infection studies based on mice and more relevant, macaque monkeys. It is now appreciated that GAS, like many other bacterial species, do not necessarily exclusively live in a planktonic lifestyle. GAS is capable of microcolony and biofilm formation on host cells and tissues. We are now beginning to understand that this feature significantly contributes to GAS pathogenesis. In this review we will discuss the current knowledge on GAS biofilm formation, the biofilm-phenotype associated virulence factors, regulatory aspects of biofilm formation, the clinical relevance, and finally contemporary treatment regimens and future treatment options.

The Group A Streptococcal Carrier State Reviewed: Still an Enigma

Despite the common nature of group A streptococcal (GAS) infections, the carrier state of this organism is not well understood. In this article, we review the historical and recent research on the definition, epidemiology, and pathogenesis of the GAS carrier state. In addition, we outline trials of antimicrobial agents in the eradication of the carrier state and discuss indications for providing treatment to patients in the clinical setting.

Role of biofilm in children with recurrent upper respiratory tract infections

Recurrent respiratory tract infections (RRTIs) are very common in children and a major challenge for pediatricians. In the last few years, bacterial biofilms have been linked to RRTIs and antibiotic resistance, and have raised serious concerns regarding the therapeutic management of recurrent middle ear diseases, chronic rhinosinusitis, and recurrent pharyngotonsillitis. This paper aims to review the new insights into biofilm-related upper respiratory tract infections in children and possible therapeutic strategies. It focuses on the clinical implications for recurrent disease and on studies in pediatric patients. Analysis of the literature showed that the involvement of bacterial biofilm in recurrent upper airway tract infections is an emerging problem that may lead to serious concerns about infection control. Despite the large amount of research within this field, detailed insight into the complex structure of bacterial biofilms and the ultrastructural and biochemical mechanisms responsible for its evasion of the immune system and resistance to treatments is currently lacking. In the future, additional emphasis should be placed on biofilm management as a component of therapeutic strategies. This goal can be attained by finding feasible methods for detecting biofilms in vivo and identifying effective methods for administering treatments that eradicate preexisting bacterial biofilms or hinder bacterial adhesion to respiratory cells.

The IL-8 protease SpyCEP is detrimental for Group A Streptococcus host-cells interaction and biofilm formation

SpyCEP-mediated chemokine degradation translates into more efficient spreading and increased severity of invasive Group A Streptococcus (GAS) infections, due to impaired neutrophil recruitment to the site of infection. SpyCEP is markedly up-regulated in invasive as compared to colonizing GAS isolates raising the question whether SpyCEP expression hinders bacterial attachment and thus colonization of the host. To address this question we used a molecular approach involving the use of homologous GAS strains either expressing or not SpyCEP or expressing an enzymatically inactive variant of SpyCEP. We found that expression of enzymatically functional SpyCEP lowered GAS adherence and invasion potential toward various epithelial and endothelial cells. SpyCEP also blunted biofilm formation capacity. Our data indicate that expression of SpyCEP decreases colonization and thus might be detrimental for the spreading of GAS.

Disease manifestations and pathogenic mechanisms of Group A Streptococcus

Streptococcus pyogenes, also known as group A Streptococcus (GAS), causes mild human infections such as pharyngitis and impetigo and serious infections such as necrotizing fasciitis and streptococcal toxic shock syndrome. Furthermore, repeated GAS infections may trigger autoimmune diseases, including acute poststreptococcal glomerulonephritis, acute rheumatic fever, and rheumatic heart disease. Combined, these diseases account for over half a million deaths per year globally. Genomic and molecular analyses have now characterized a large number of GAS virulence determinants, many of which exhibit overlap and redundancy in the processes of adhesion and colonization, innate immune resistance, and the capacity to facilitate tissue barrier degradation and spread within the human host. This improved understanding of the contribution of individual virulence determinants to the disease process has led to the formulation of models of GAS disease progression, which may lead to better treatment and intervention strategies. While GAS remains sensitive to all penicillins and cephalosporins, rising resistance to other antibiotics used in disease treatment is an increasing worldwide concern. Several GAS vaccine formulations that elicit protective immunity in animal models have shown promise in nonhuman primate and early-stage human trials. The development of a safe and efficacious commercial human vaccine for the prophylaxis of GAS disease remains a high priority.

Disease manifestations and pathogenic mechanisms of Group A Streptococcus

Streptococcus pyogenes, also known as group A Streptococcus (GAS), causes mild human infections such as pharyngitis and impetigo and serious infections such as necrotizing fasciitis and streptococcal toxic shock syndrome. Furthermore, repeated GAS infections may trigger autoimmune diseases, including acute poststreptococcal glomerulonephritis, acute rheumatic fever, and rheumatic heart disease. Combined, these diseases account for over half a million deaths per year globally. Genomic and molecular analyses have now characterized a large number of GAS virulence determinants, many of which exhibit overlap and redundancy in the processes of adhesion and colonization, innate immune resistance, and the capacity to facilitate tissue barrier degradation and spread within the human host. This improved understanding of the contribution of individual virulence determinants to the disease process has led to the formulation of models of GAS disease progression, which may lead to better treatment and intervention strategies. While GAS remains sensitive to all penicillins and cephalosporins, rising resistance to other antibiotics used in disease treatment is an increasing worldwide concern. Several GAS vaccine formulations that elicit protective immunity in animal models have shown promise in nonhuman primate and early-stage human trials. The development of a safe and efficacious commercial human vaccine for the prophylaxis of GAS disease remains a high priority.

Inhibition of Growth and Gene Expression by PNA-peptide Conjugates in Streptococcus pyogenes

While Streptococcus pyogenes is consistently susceptible toward penicillin, therapeutic failure of penicillin treatment has been reported repeatedly and a considerable number of patients exhibit allergic reactions to this substance. At the same time, streptococcal resistance to alternative antibiotics, e.g., macrolides, has increased. Taken together, these facts demand the development of novel therapeutic strategies. In this study, S. pyogenes growth was inhibited by application of peptide-conjugated antisense-peptide nucleic acids (PNAs) specific for the essential gyrase A gene (gyrA). Thereby, HIV-1 Tat peptide-coupled PNAs were more efficient inhibitors of streptococcal growth as compared with (KFF)3K-coupled PNAs. Peptide-anti-gyrA PNAs decreased the abundance of gyrA transcripts in S. pyogenes. Growth inhibition by antisense interference was enhanced by combination of peptide-coupled PNAs with protein-level inhibitors. Antimicrobial synergy could be detected with levofloxacin and novobiocin, targeting the gyrase enzyme, and with spectinomycin, impeding ribosomal function. The prospective application of carrier peptide-coupled antisense PNAs in S. pyogenes covers the use as an antimicrobial agent and the employment as a knock-down strategy for the investigation of virulence factor function.

Neonatal pleural empyema caused by emm type 6 group A streptococcus

Since the mid-1980s, there have been increasing reports of severe invasive group A streptococcal (GAS) disease in children and adults. There are few reports, however, of neonatal invasive disease, particularly neonatal pleural empyema caused by GAS. Although many mechanisms have been reported for the pathophysiology of invasive GAS infections, similar reports for neonates were unable to be located. Reported herein is the case of a 3-day-old girl with pleural empyema caused by GAS that demonstrated a high invasive capacity for human epithelial cells.

Cysteine proteinase from Streptococcus pyogenes enables evasion of innate immunity via degradation of complement factors

Streptococcus pyogenes is an important human pathogen that causes invasive diseases such as necrotizing fasciitis, sepsis, and streptococcal toxic shock syndrome. We investigated the function of a major cysteine protease from S. pyogenes that affects the amount of C1-esterase inhibitor (C1-INH) and other complement factors and aimed to elucidate the mechanism involved in occurrence of streptococcal toxic shock syndrome from the aspect of the complement system. First, we revealed that culture supernatant of a given S. pyogenes strain and recombinant SpeB degraded the C1-INH. Then, we determined the N-terminal sequence of the C1-INH fragment degraded by recombinant SpeB. Interestingly, the region containing one of the identified cleavage sites is not present in patients with C1-INH deficiency. Scanning electron microscopy of the speB mutant incubated in human serum showed the abnormal superficial architecture and irregular oval structure. Furthermore, unlike the wild-type strain, that mutant strain showed lower survival capacity than normal as compared with heat-inactivated serum, whereas it had a significantly higher survival rate in serum without the C1-INH than in normal serum. Also, SpeB degraded multiple complement factors and the membrane attack complex. Flow cytometric analyses revealed deposition of C9, one of the components of membrane the attack complex, in greater amounts on the surface of the speB mutant, whereas lower amounts of C9 were bound to the wild-type strain surface. These results suggest that SpeB can interrupt the human complement system via degrading the C1-INH, thus enabling S. pyogenes to evade eradication in a hostile environment.