Evaluation of potential factors contributing to microbiological treatment failure in Streptococcus pyogenes pharyngitis

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.

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.

Group A Streptococcus infections in children: from virulence to clinical management

PURPOSE OF REVIEW

Recent findings have open new perspectives on group A Streptococcus (GAS) virulence understanding with special focus on the carrier stage and new hopes for an efficient vaccine against this important pathogen.

RECENT FINDINGS

Understanding of carriage state, transmission and role of virulence factors in invasive infections have been recently active research fields questioning the link between carriage and infections and highlighting the potential to prevent invasive diseases. New roles for already well known virulence factors, such as Streptolysin O, M protein or NAD(+)-glycohydrolase have been discovered. Immunological studies have also shown diversity in both clinical and immunological responses toward various GAS antigens raising questions, and hopes, for the development of an efficient global vaccine candidate.

SUMMARY

A greater understanding of GAS virulence strategies, and their associated clinical manifestations, may be obtained by shifting our research scope toward virulence determinant interactions and cooperation rather than focusing on individual virulence factor or specific strain characterization only.

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.

In Vitro Antibacterial Activity of Essential Oils against Streptococcus pyogenes

Streptococcus pyogenes plays an important role in the pathogenesis of tonsillitis. The present study was conducted to evaluate the in vitro antibacterial activities of 18 essential oils chemotypes from aromatic medicinal plants against S. pyogenes. Antibacterial activity of essential oils was investigated using disc diffusion method. Minimum Inhibitory Concentration of essential oils showing an important antibacterial activity was measured using broth dilution method. Out of 18 essential oils tested, 14 showed antibacterial activity against S. pyogenes. Among them Cinnamomum verum, Cymbopogon citratus, Thymus vulgaris CT thymol, Origanum compactum, and Satureja montana essential oils exhibited significant antibacterial activity. The in vitro results reported here suggest that, for patients suffering from bacterial throat infections, if aromatherapy is used, these essential oils, considered as potential antimicrobial agents, should be preferred.

Boesenbergia pandurata (Roxb.) Schltr., Eleutherine americana Merr. and Rhodomyrtus tomentosa (Aiton) Hassk. as antibiofilm producing and antiquorum sensing in Streptococcus pyogenes

Biofilm formation has been demonstrated as a potentially important mechanism contributing to antibiotic treatment failure on Streptococcus pyogenes. It could play a significant role in recurrent and chronic infections. Boesenbergia pandurata (Roxb.) Schltr., Eleutherine americana Merr. and Rhodomyrtus tomentosa (Aiton) Hassk. have been previously reported from our laboratory as effective agents against S. pyogenes. Therefore, in the present study, we observed the effect of these plants on biofilm formation. The bacterial biofilms were quantified by safranin staining and absorbance at 492 nm. The results clearly demonstrated that all subinhibitory concentrations [1/32-1/2 minimal inhibitory concentration (MIC)] of E. americana (7.81-125 microg mL(-1)) and R. tomentosa (0.24-7.81 microg mL(-1)) extracts significantly prevented biofilm formation while 1/2MIC (7.81 microg mL(-1)) of B. pandurata extract produced this effect. The issue of antiquorum sensing of this pathogenic bacterium has been further explored. A correlation between antiquorum-sensing and antibiofilm-producing activities was demonstrated. Strong inhibition on quorum sensing was displayed with the extract of R. tomentosa. Eleutherine americana extract showed partial inhibition, while B. pandurata did not show this activity. By contrast, an assay of microbial adhesion to hydrocarbon revealed no changes in the cell-surface hydrophobicity of the treated organisms. Active organisms with the ability to inhibit quorum sensing and biofilm formation are worth studying as they may provide complimentary medicine for biofilm-associated infections.

Biofilm formation by group a streptococci: is there a relationship with treatment failure?

Group A streptococcus (GAS) is the primary cause of bacterial pharyngitis in children and adults. Up to one-third of patients treated for GAS pharyngitis fail to respond to antibiotic therapy. The objective of this cohort study was to evaluate GAS biofilm formation as a mechanism for antibiotic treatment failure using previously collected GAS isolates and penicillin treatment outcome data. The minimum biofilm eradication concentration (MBEC) assay device was used to determine the biofilm-forming capabilities, efficiencies, and antibiotic susceptibilities of GAS isolates. The MBECs and MICs of several antibiotics for GAS were determined. All 99 GAS isolates available for this study formed biofilms, with various efficiencies. Antibiotic MBECs were consistently higher than MICs for all of the GAS isolates. MBECs indicated penicillin insensitivity in 60% of GAS isolates, producing the first report of in vitro GAS insensitivity to penicillin. Using MBECs to predict penicillin treatment failure had better sensitivity (56%) but lower specificity (36%) than the sensitivity (0%) and specificity (100%) when MICs were used. However, the positive predictive value of the MBEC was superior to that of the MIC (56 versus 0%), while the negative predictive values (42 and 47%) were similar. More studies are needed to understand the roles of biofilms and the MBEC assay in predicting GAS treatment failure. In addition, further investigations are necessary to determine if non-biofilm-forming strains of GAS exist and the roles of in vivo monospecies and multispecies biofilms in streptococcal pharyngitis treatment failure.