Streptococcus pyogenes (group A Streptococcus; GAS) is always of clinical significance in wounds where it can initiate infection, destroy skin grafts and persist as a biofilm. Manuka honey has broad spectrum antimicrobial activity and its use in the clinical setting is beginning to gain acceptance with the continuing emergence of antibiotic resistance and the inadequacy of established systemic therapies; novel inhibitors may affect clinical practice. In this study, the effect of manuka honey on S. pyogenes (M28) was investigated in vitro with planktonic and biofilm cultures using MIC, MBC, microscopy and aggregation efficiency. Bactericidal effects were found in both planktonic cultures and biofilms, although higher concentrations of manuka honey were needed to inhibit biofilms. Abrogation of adherence and intercellular aggregation was observed. Manuka honey permeated 24 h established biofilms of S. pyogenes, resulting in significant cell death and dissociation of cells from the biofilm. Sublethal concentrations of manuka honey effectively prevented the binding of S. pyogenes to the human tissue protein fibronectin, but did not inhibit binding to fibrinogen. The observed inhibition of fibronectin binding was confirmed by a reduction in the expression of genes encoding two major fibronectin-binding streptococcal surface proteins, Sof and SfbI. These findings indicate that manuka honey has potential in the topical treatment of wounds containing S. pyogenes. INTRODUCTIONStreptococcus pyogenes (group A Streptococcus) colonizes the nasopharynx and skin of healthy individuals, forming part of the commensal microbiota. Under appropriate conditions, S. pyogenes can be transmitted to wounds and is especially problematic after surgery, following skin grafting and for military personal with traumatic or puncture wounds. Wounds provide a route of entry to the host and damaged tissues display a matrix of proteins including collagen, albumin, fibronectin and fibrinogen, which collectively provide a plethora of ligands to which opportunistic pathogens, including streptococci, adhere (Kubo et al., 2001). Surgical site infection accounts for approximately 25 % of all hospital-acquired infections and may result in the development of a non-healing or chronic wound (Werdin et al., 2009). Non-healing wounds are defined as wounds that have failed to proceed through the normal, orderly and timely reparative process that results in restoration of anatomical and functional integrity, within 3 months (Cooper, 2005;Guo & Dipietro, 2010). In the developed world, approximately 1-1.5 % of populations have non-healing wounds, and these account for 2-4 % of all health care expenses (Gottrup, 2008).Biofilms have been associated with persistent or chronic wound infections and are a major obstacle to healing (James et al., 2008;Rhoads et al., 2008). Streptococcus species readily form biofilms, by a process in which numerous cell-wall-anchored adhesins specifically attach to human tissue protein ligands and promote bacterial aggregation (Nobbs et ...
Manuka honey can directly affect bacterial cells embedded in a biofilm and exhibits antiadhesive properties against three common wound pathogens.
Several models exist for the study of chronic wound infection, but few combine all of the necessary elements to allow high throughput, reproducible biofilm culture with the possibility of applying topical antimicrobial treatments. Furthermore, few take into account the appropriate means of providing nutrients combined with biofilm growth at the air-liquid interface. In this manuscript, a new biofilm flow device for study of wound biofilms is reported. The device is 3D printed, straightforward to operate, and can be used to investigate single and mixed species biofilms, as well as the efficacy of antimicrobial dressings. Single species biofilms of Staphylococcus aureus or Pseudomonas aeruginosa were reproducibly cultured over 72 h giving consistent log counts of 8-10 colony forming units (CFU). There was a 3-4 log reduction in recoverable bacteria when antimicrobial dressings were applied to biofilms cultured for 48 h, and left in situ for a further 24 h. Two-species biofilms of S. aureus and P. aeruginosa inoculated at a 1:1 ratio, were also reproducibly cultured at both 20 °C and 37 °C; of particular note was a definitive Gram-negative shift within the population that occurred only at 37 °C.
Aims To determine the antimicrobial activity of enacyloxin IIa and gladiolin against Neisseria gonorrhoeae and Ureaplasma spp. Methods and Results The Burkholderia polyketide antibiotics enacyloxin IIa and gladiolin were tested against 14 N. gonorrhoeae and 10 Ureaplasma spp. isolates including multidrug‐resistant N. gonorrhoeae isolates WHO V, WHO X and WHO Z as well as macrolide, tetracycline and ciprofloxacin‐resistant ureaplasmas. Susceptibility testing of N. gonorrhoeae was carried out by agar dilution, whereas broth micro‐dilution and growth kinetic assays were used for Ureaplasma spp. The MIC range for enacyloxin IIa and gladiolin against N. gonorrhoeae was 0·015–0·06 mg l−1 and 1–2 mg l−1 respectively. The presence of resistance to front line antibiotics had no effect on MIC values. The MIC range for enacyloxin IIa against Ureaplasma spp. was 4–32 mg l−1 with a clear dose‐dependent effect when observed using a growth kinetic assay. Gladiolin had no antimicrobial activity on Ureaplasma spp. at 32 mg l−1 and limited impact on growth kinetics. Conclusions Enacyloxin IIa and gladiolin antibiotics have antimicrobial activity against a range of antibiotic susceptible and resistant N. gonorrhoeae and Ureaplasma isolates. Significance and Impact of the Study This study highlights the potential for a new class of antimicrobial against pathogens in which limited antibiotics are available. Development of these compounds warrants further investigation in the face of emerging extensively drug‐resistant strains.
The effect of the flavonol morin on Streptococcus pyogenes biofilm growth was determined using a static biofilm model, in which reduced biofilm biomass was observed in the presence of morin, suggesting that morin inhibited biofilm development. Morin at concentrations exceeding 225 μM had the greatest impact on biofilm biomass causing reductions of up to 65%, which was found to be statistically significant. Morin was also shown to induce rapid bacterial aggregation. Approximately 55% of S. pyogenes in liquid suspension aggregated when incubated with morin at concentrations of 275 and 300 μM for 120 min, compared to the control group in which only 10% of the cells aggregated, this was also shown to be statistically significant.
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