Treatment Challenges of Group A Beta-hemolytic Streptococcal Pharyngo-Tonsillitis

[Research progress on the mechanism of -lactam resistance in group A Streptococci in vivo]

-lactams, including penicillin, have been used for over 80 years in the treatment of group A Streptococcus (GAS) infections. Although -lactam-resistant GAS strains have not been identified in vitro tests, clinical treatment failures have been reported since the 1950s. The mechanism underlying the clinical failure of -lactam treatment in GAS infections remains unclear. Previous research has suggested that -lactam resistance in GAS in vivo is associated with reduced drug susceptibility of strains, bacterial inoculation effects, biofilm formation, the effect of coexisting bacteria, bacterial persistence, and bacterial internalization into host cells. This article reviews the main reports on -lactam treatment failure in GAS infections and analyzes the possible mechanisms of -lactam resistance in vivo. The findings aim to contribute to future research and clinical approaches in the field.

Antibiotic Use for Common Infections in Pediatric Emergency Departments: A Narrative Review

Antibiotics are one of the most prescribed medications in pediatric emergency departments. Antimicrobial stewardship programs assist in the reduction of antibiotic use in pediatric patients. However, the establishment of antimicrobial stewardship programs in pediatric EDs remains challenging. Recent studies provide evidence that common infectious diseases treated in the pediatric ED, including acute otitis media, tonsillitis, community-acquired pneumonia, preseptal cellulitis, and urinary-tract infections, can be treated with shorter antibiotic courses. Moreover, there is still controversy regarding the actual need for antibiotic treatment and the optimal dosing scheme for each 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.

Carvacrol inhibits Streptococcus pyogenes biofilms by suppressing the expression of genes associated with quorum-sensing and reducing cell surface hydrophobicity

Streptococcus pyogenes is a leading cause of chronic and acute infections, including streptococcus pharyngitis. Biofilm formation by S. pyogenes can cause tolerance against antibiotics. Although penicillin remains the first choice of antibiotic for S. pyogenes, alternative approaches have gained interest due to treatment failures and hypersensitive individuals. Carvacrol is a monoterpenoid from herbal plants with selective biocidal activity on S. pyogenes. Therefore, the present study reveals the efficacy of carvacrol in inhibiting and eradicating S. pyogenes biofilm. The antibiofilm activities were investigated using colorimetric assays, microscopy, cell surface hydrophobicity, gene expression analysis, and in-silico analysis. Carvacrol also showed a minimum biofilm inhibitory concentration (MBIC) against S. pyogenes of 125 μg/mL. The electron microscopic and confocal microscopic analyses revealed a dose-dependent suppression of biofilm formation and a reduction in the biofilm thickness by carvacrol. Carvacrol also inhibited the biofilm-associated virulence factors such as cell surface hydrophobicity. Quantitative real-time polymerase chain reaction analysis showed the downregulation of speB, srtB, luxS, covS, dltA, ciaH, and hasA genes involved in biofilm formation. The results suggested the therapeutic potential of carvacrol against biofilm-associated streptococcal infections.

Cellular Growth Arrest and Efflux Pumps Are Associated With Antibiotic Persisters in Streptococcus pyogenes Induced in Biofilm-Like Environments

Streptococcus pyogenes (group A Streptococcus-GAS) is an important pathogen for humans. GAS has been associated with severe and invasive diseases. Despite the fact that these bacteria remain universally susceptible to penicillin, therapeutic failures have been reported in some GAS infections. Many hypotheses have been proposed to explain these antibiotic-unresponsive infections; however, none of them have fully elucidated this phenomenon. In this study, we show that GAS strains have the ability to form antimicrobial persisters when inoculated on abiotic surfaces to form a film of bacterial agglomerates (biofilm-like environment). Our data suggest that efflux pumps were possibly involved in this phenomenon. In fact, gene expression assays by real-time qRT-PCR showed upregulation of some genes associated with efflux pumps in persisters arising in the presence of penicillin. Phenotypic reversion assay and whole-genome sequencing indicated that this event was due to non-inherited resistance mechanisms. The persister cells showed downregulation of genes associated with protein biosynthesis and cell growth, as demonstrated by gene expression assays. Moreover, the proteomic analysis revealed that susceptible cells express higher levels of ribosome proteins. It is remarkable that previous studies have reported the recovery of S. pyogenes viable cells from tissue biopsies of patients presented with GAS invasive infections and submitted to therapy with antibiotics. The persistence phenomenon described herein brings new insights into the origin of therapeutic failures in S. pyogenes infections. Multifactorial mechanisms involving protein synthesis inhibition, cell growth impairment and efflux pumps seem to play roles in the formation of antimicrobial persisters in S. pyogenes.

Streptococcus pyogenes ("Group A Streptococcus"), a Highly Adapted Human Pathogen-Potential Implications of Its Virulence Regulation for Epidemiology and Disease Management

Streptococcus pyogenes (group A streptococci; GAS) is an exclusively human pathogen. It causes a variety of suppurative and non-suppurative diseases in people of all ages worldwide. Not all can be successfully treated with antibiotics. A licensed vaccine, in spite of its global importance, is not yet available. GAS express an arsenal of virulence factors responsible for pathological immune reactions. The transcription of all these virulence factors is under the control of three types of virulence-related regulators: (i) two-component systems (TCS), (ii) stand-alone regulators, and (iii) non-coding RNAs. This review summarizes major TCS and stand-alone transcriptional regulatory systems, which are directly associated with virulence control. It is suggested that this treasure of knowledge on the genetics of virulence regulation should be better harnessed for new therapies and prevention methods for GAS infections, thereby changing its global epidemiology for the better.

The clinical path to deliver encapsulated phages and lysins

The global emergence of multidrug-resistant pathogens is shaping the current dogma regarding the use of antibiotherapy. Many bacteria have evolved to become resistant to conventional antibiotherapy, representing a health and economic burden for those afflicted. The search for alternative and complementary therapeutic approaches has intensified and revived phage therapy. In recent decades, the exogenous use of lysins, encoded in phage genomes, has shown encouraging effectiveness. These two antimicrobial agents reduce bacterial populations; however, many barriers challenge their prompt delivery at the infection site. Encapsulation in delivery vehicles provides targeted therapy with a controlled compound delivery, surpassing chemical, physical and immunological barriers that can inactivate and eliminate them. This review explores phages and lysins' current use to resolve bacterial infections in the respiratory, digestive, and integumentary systems. We also highlight the different challenges they face in each of the three systems and discuss the advances towards a more expansive use of delivery vehicles.

[How to reduce the antibacterial load in the treatment of acute tonsillitis and pharyngitis? Possible tactics and practical approaches]

Acute tonsillopharyngitis is one of the most frequent reasons for visiting a doctor and prescribing inappropriate antibiotic therapy (ABT). There are several reasons for this - from the difficulties of etiological diagnosis and the development of relapses and possible severe complications to the personal attitude of doctors and patients to the choice of treatment. At the same time, the issue of antibiotic resistance and other aspects associated with the prescription of ABT is one of the most important problems of modern healthcare worldwide. The purpose of this review is to demonstrate the best practical approaches to the choice of treatment tactics for acute tonsillitis (AT) in the treatment of children and adults, with an emphasis on reducing the load of ABT. The review examines the indications and disadvantages of clinical and laboratory diagnosis of AT. There are no highly sensitive clinical and laboratory instruments that differentiate viral and bacterial AT. Exudativeis AT in children is not an underlying symptom of streptococcal etiology. Despite the limitations, the modified Centor/McIsaac score ≥3 (taking into account age and the presence of respiratory symptoms) should be used as an indication for ABT in conjunction with a rapid streptotest and subsequent bacteriological culture for S. pyogenes if the screening test is negative. Additional examinations (determination of leukocytosis, CRP and procalcitonin test) are not required for most patients. ABT should not be given to low-risk patients for the treatment and prevention of rheumatic fever and acute glomerulonephritis. Prevention of purulent complications (paratonsillitis and retropharyngeal abscess, acute otitis media, cervical lymphadenitis, mastoiditis, or acute sinusitis) is not a specific indication for ABT in AT and is not required in most patients. The strategy of «delayed antibiotic prescriptions» with monitoring the patient's condition for 2-3 days is appropriate and highly effective in doubtful cases. The drugs of choice for treatment of AT are amoxicillin and oral forms of I and II generation cephalosporins. Macrolides are not indicated as first-line treatment for AT. The course of ABT for streptococcal AT is 10 days, which reduces the risk of recurrent episode. Topical drugs can be the only means of etiopathogenetic treatment with viral AT, or additional for bacterial AT. Their use not only relieves sore throat, but also shortens the duration of the disease, and also improves the patients prognosis. Benzalkonium chloride + tyrothricin + benzocaine (Dorithyrcin) may be a rational drug of choice for topical therapy due to the available clinical evidence. There is a significant reserve for reducing the load of ABT during AT. Further clinical trials are needed to assess the efficacy of short courses of ABT in the treatment of AT in high-income countries and provide a basis for strong recommendations for topical drug use. This can reduce the frequency of ABT prescribing and increase the level of interaction between specialists and patients.

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.

Reduced In Vitro Susceptibility of Streptococcus pyogenes to β-Lactam Antibiotics Associated with Mutations in the pbp2x Gene Is Geographically Widespread

Recently, two related Streptococcus pyogenes strains with reduced susceptibility to ampicillin, amoxicillin, and cefotaxime, antibiotics commonly used to treat S. pyogenes infections, were reported. The two strains had the same nonsynonymous (amino acid-substituting) mutation in the pbp2x gene, encoding penicillin-binding protein 2X (PBP2X). This concerning report led us to investigate our library of 7,025 genome sequences of type emm1, emm28, and emm89 S. pyogenes clinical strains recovered from intercontinental sources for mutations in pbp2x We identified 137 strains that, combined, had 37 nonsynonymous mutations in 36 codons in pbp2x Although to a lesser magnitude than the two previously published isolates, many of our strains had decreased susceptibility in vitro to multiple beta-lactam antibiotics. Many pbp2x mutations were found only in single strains, but 16 groups of two or more isolates of the same emm type had an identical amino acid replacement. Phylogenetic analysis showed that, with one exception, strains of the same emm type with the same amino acid replacement were clonally related by descent. This finding indicates that strains with some amino acid changes in PBP2X can successfully spread to new human hosts and cause invasive infections. Mapping of the amino acid changes onto a three-dimensional structure of the related Streptococcus pneumoniae PBP2X suggests that some substitutions are located in regions functionally important in related pathogenic bacterial species. Decreased beta-lactam susceptibility is geographically widespread in strains of numerically common emm gene subtypes. Enhanced surveillance and further epidemiological and molecular genetic study of this potential emergent antimicrobial problem are warranted.

Four-Weekly Benzathine Penicillin G Provides Inadequate Protection against Acute Rheumatic Fever in Some Children

This study aimed to identify recurrent acute rheumatic fever (ARF) episodes which occurred despite adherence to prophylactic benzathine penicillin G (BPG). Data from Australia's Northern Territory were analyzed; ARF recurrences between 2012 and 2017 diagnosed while the person was prescribed BPG were identified. Days at risk (DAR)-median and interquartile range-preceding ARF onset were calculated. The timing of BPG doses was examined for individuals with no DAR. One hundred sixty-nine ARF recurrences were analyzed; median DAR in the previous 8 weeks before ARF onset was 29. Most recurrences occurred following > 7 DAR (87%). Eight recurrences (5%) occurred despite no DAR; all were aged less than 16 years at the time of their recurrence/s. Recurrent ARF most commonly occurs after delayed BPG doses, but in some cases, receiving every prescribed BPG dose on time did not prevent recurrent ARF. A method to identify high-risk individuals before recurrent ARF is needed.

Simvastatin and ML141 Decrease Intracellular Streptococcus pyogenes Infection

BACKGROUND

Recurrent pharyngotonsillitis due to Streptococcus pyogenes develops regardless of whether infecting strains are resistant or susceptible to first-line antimicrobials. Causation for recurrent infection is associated with the use of first-line antimicrobials that fail to penetrate deep tissue and host cell membranes, enabling intracellular S. pyogenes to survive throughout repeated rounds of antimicrobial therapy.

OBJECTIVE

To determine whether simvastatin, a therapeutic approved for use in the treatment of hypercholesterolemia, and ML141, a first-in-class small molecule inhibitor with specificity for human CDC42, limit host cell invasion by S. pyogenes.

METHODS

Assays to assess host cell invasion, bactericidal activity, host cell viability, actin depolymerization, and fibronectin binding were performed using the RAW 267.4 macrophage cell line and Human Umbilical Vein Endothelial Cells (HUVEC) infected with S. pyogenes (90-226) and treated with simvastatin, ML141, structural analogs of ML141, or vehicle control.

RESULTS

Simvastatin and ML141 decreased intracellular infection by S. pyogenes in a dose-dependent manner. Inhibition by simvastatin persisted following 1 h washout whereas inhibition by ML141 was reversed. During S. pyogenes infection, actin stress fibers depolymerized in vehicle control treated cells, yet remained intact in simvastatin and in ML141 treated cells. Consistent with the previous characterization of ML141, simvastatin decreased host cell binding to fibronectin. Structural analogs of ML141, designated as the RSM series, decreased intracellular infection through non-cytotoxic, nonbactericidal mechanisms.

CONCLUSION

Our findings demonstrate the potential of repurposing simvastatin and of developing CDC42-targeted therapeutics for eradicating intracellular S. pyogenes infection to break the cycle of recurrent infection through a host-directed approach.

A Presumed Etiology of Kawasaki Disease Based on Epidemiological Comparison With Infectious or Immune-Mediated Diseases

Background: Kawasaki disease (KD) may be associated with infection of unknown pathogen(s). For predicting of the etiology of KD, we evaluated epidemiological characteristics in KD, common infectious diseases and immune-mediated diseases in childhood. Methods: We respectively, reviewed the data of patients with KD, influenza, aseptic meningitis, exanthem subitum (ES), Mycoplasma pneumoniae (MP) pneumonia, acute pyelonephritis (APN), Henoch-Schönlein purpura (HSP), acute poststreptococcal glomerulonephritis (APSGN), and childhood asthma. We compared and interpreted epidemiological data across the groups. Results: In age distribution, KD, APN, and ES showed a similar pattern in that majority of patients were infants or young children, and other diseases showed a relatively even age-distribution which had a peak age, mainly 5-6 years, with bell-shape patterns. In annual-case pattern, there were epidemic years in aseptic meningitis and MP pneumonia, and the fluctuated annual cases were seen in other diseases. The trends of decreasing cases were seen in APSGN, HSP, and childhood asthma in recent years. In seasonal frequency, influenza or aseptic meningitis occurred in mainly winter or summer season, respectively. HSP and APSGN cases had less in summer, and KD, APN, and ES showed relatively even occurrence throughout a year without significant seasonal variations. Conclusions: Our results suggest that KD agents may be associated with normal flora that are influenced by environmental changes, since pathogens of APN and ES could be regarded as normal flora that originate from the host itself or ubiquitously existing human reservoirs.

Revisiting cefditoren for the treatment of community-acquired infections caused by human-adapted respiratory pathogens in adults

Fifteen years after its licensure, this revision assesses the role of cefditoren facing the current pharmacoepidemiology of resistances in respiratory human-adapted pathogens (Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae and Moraxella catarrhalis). In the era of post- pneumococcal conjugate vaccines and in an environment of increasing diffusion of the ftsI gene among H. influenzae isolates, published studies on the cefditoren in vitro microbiological activity, pharmacokinetic/pharmcodynamic (PK/PD) activity and clinical efficacy are reviewed. Based on published data, an overall analysis is performed for PK/PD susceptibility interpretation. Further translation of PK/PD data into clinical/microbiological outcomes obtained in clinical trials carried out in the respiratory indications approved for cefditoren in adults (tonsillitis, sinusitis, acute exacerbation of chronic bronchitis and community-acquired pneumonia) is commented. Finally, the role of cefditoren within the current antibiotic armamentarium for the treatment of community respiratory tract infections in adults is discussed based on the revised information on its intrinsic activity, pharmacodynamic adequacy and clinical/bacteriological efficacy. Cefditoren remains an option to be taken into account when selecting an oral antibiotic for the empirical treatment of respiratory infections in the community caused by human-adapted pathogens, even when considering changes in the pharmacoepidemiology of resistances over the last two decades.

Antibiotics for recurrent acute pharyngo-tonsillitis: systematic review

The purpose was to determine the current evidence for preferable antibiotic treatment in three common clinical situations with insufficient consensus: Q1: Can antibiotic treatment prevent future attacks of acute pharyngo-tonsillitis (APT) in patients with recurrent APT (RAPT)? Q2: Which antibiotic regimen is preferable in the treatment of APT in patients with RAPT? Q3: Which antibiotic regimen is preferable in the treatment of relapsing APT? Five databases were searched systematically for randomized clinical trials on patients with RAPT with or without current APT or with relapse of APT. Of the unique publications, 643 were found. Five studies addressing Q1 (n = 3) and Q2 (n = 2) met the eligibility criteria. No studies reporting on Q3 were included. Q1: Two studies found that clindamycin and cefpodoxime, respectively, were effective in preventing future APT episodes and in eradicating group A streptococci from the tonsils of RAPT patients. One study found that long-term azithromycin had no effect on the number of APT episodes. Q2: Two studies reported superior clinical and microbiological effects of clindamycin and amoxicillin with clavulanate, respectively, compared to penicillin. The four studies showing superior effects of clindamycin and amoxicillin with clavulanate were assessed to have high risk of bias. Hence, the level of evidence was moderate. There is considerable evidence to suggest that clindamycin and amoxicillin with clavulanate are superior to penicillin with preferable effects on the microbiological flora and the number of future attacks of APT in patients with RAPT. Antibiotic treatment is an option in patients with RAPT, who has contraindications for tonsillectomy.