Corynebacterium accolens is the predominant species of the healthy human nasal microbiota, and its relative abundance is decreased in the context of chronic rhinosinusitis (CRS). This study aimed to evaluate the antimicrobial potential of C. accolens isolated from a healthy human nasal cavity against planktonic and biofilm growth of Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA) clinical isolates (CIs) from CRS patients. Nasal swabs from twenty non-CRS control subjects were screened for the presence of C. accolens using microbiological and molecular techniques. C. accolens CIs and their culture supernatants were tested for their antimicrobial activity against eight S. aureus and eight MRSA 4CIs and S. aureus ATCC25923. The anti-biofilm potential of C. accolens cell-free culture supernatants (CFCSs) on S. aureus biofilms was also assessed. Of the 20 nasal swabs, 10 C. accolens CIs were identified and confirmed with rpoB gene sequencing. All isolates showed variable antimicrobial activity against eight out of 8 S. aureus and seven out of eight MRSA CIs. Culture supernatants from all C. accolens CIs exhibited a significant dose-dependent antibacterial activity (p < 0.05) against five out of five representative S. aureus and MRSA CIs. This inhibition was abolished after proteinase K treatment. C. accolens supernatants induced a significant reduction in metabolic activity and biofilm biomass of S. aureus and MRSA CIs compared to untreated growth control (p < 0.05). C. accolens exhibited antimicrobial activity against S. aureus and MRSA CIs in both planktonic and biofilm forms and holds promise for the development of innovative probiotic therapies to promote sinus health.

The high infection and mortality rate of methicillin-resistant Staphylococcus aureus (MRSA) necessitates the urgent development of new treatment strategies. Bacteriophages (phages) have several advantages compared to antibiotics for the treatment of multi-drug-resistant bacterial infections, and thus provide a promising alternative to antibiotics. Here, S. aureus phages were isolated from patients and environmental sources. Phages were characterized for stability, morphology and genomic sequence and their bactericidal activity against the biofilm form of methicillin-susceptible Staphylococcus aureus (MSSA) and MRSA was investigated. Four S. aureus phages were isolated and tested against 51 MSSA and MRSA clinical isolates and reference strains. The phages had a broad host range of 82–94% individually and of >98% when combined and could significantly reduce the viability of S. aureus biofilms. The phages had a latent period of ≤20 min and burst size of >11 plaque forming units (PFU)/infected cell. Transmission electron microscopy (TEM) identified phages belonging to the family of Myoviridae. Genomic sequencing indicated the lytic nature of all four phages, with no identified resistance or virulence genes. The 4 phages showed a high complementarity with 49/51 strains (96%) sensitive to at least 2/4 phages tested. Furthermore, the frequency of bacteriophage insensitive mutant (BIM) generation was lower when the phages were combined into the phage cocktail APTC-C-SA01 than for bacteria exposed to each of the phages alone. In conclusion, APTC-C-SA01, containing four lytic S. aureus phages has the potential for further development as a treatment against MSSA and MRSA infections.

Background: Corynebacterium accolens (C. accolens) is a common nasal colonizer, whereas Staphylococcus aureus (S. aureus) is typically regarded a pathogenic organism in patients with chronic rhinosinusitis (CRS). This study aims to evaluate the interaction of the two bacteria in vitro.Methods: Clinical isolates of C. accolens and S. aureus from sinonasal swabs, as well as primary human nasal epithelial cells (HNECs) cultured from cellular brushings of both healthy and CRS patients were used for this study. The cell-free culture supernatants of all isolates grown alone and in co-cultures were tested for their effects on transepithelial electrical resistance (TER), FITC-Dextran permeability, lactate dehydrogenase (LDH), and IL-6 and IL-8 secretion of HNECs. Confocal scanning laser microscopy and immunofluorescence were also used to visualize the apical junctional complexes. C. accolens cell-free culture supernatants were also tested for antimicrobial activity and growth on planktonic and biofilm S. aureus growth.Results: The cell-free culture supernatants of 3\C. accolens strains (at 60% for S. aureus reference strain and 30% concentration for S. aureus clinical strains) inhibited the growth of both the planktonic S. aureus reference and clinical strains significantly. The C. accolens cell-free culture supernatants caused no change in the TER or FITC-Dextran permeability of the HNEC-ALI cultures, while the cell-free culture supernatants of S. aureus strains had a detrimental effect. Cell-free culture supernatants of C. accolens co-cultured with both the clinical and reference strains of S. aureus delayed the S. aureus-dependent mucosal barrier damage in a dose-dependent manner.Conclusion: Corynebacterium accolens cell-free culture supernatants appear to inhibit the growth of the S. aureus planktonic bacteria, and may reduce the mucosal barrier damage caused by S. aureus.

Background: Chronic rhinosinusitis (CRS) is defined as a chronic inflammation of the nose and paranasal sinus mucosa associated with relapsing infections—particularly with S. aureus. Long-term treatments with protein synthesis inhibitor antibiotics have been proposed to reduce inflammation in the context chronic severe inflammatory airway pathologies, including CRS. This study assessed the effect of subinhibitory clindamycin and azithromycin on S. aureus exoprotein induced inflammation, toxicity and invasiveness. Methods: S. aureus ATCC51650 and two clinical isolates grown in planktonic and biofilm form were treated with subinhibitory clindamycin and azithromycin. Exoproteins were collected and applied to primary human nasal epithelial cells (HNECs) in monolayers and at air-liquid interface. This was followed by lactate dehydrogenase (LDH), enzyme-linked immunosorbent assay (ELISA), Transepithelial Electrical Resistance (TEER) and paracellular permeability assays to assess the effect on cell toxicity, inflammatory cytokine production and mucosal barrier structure and function, respectively. The effect of these treatments was tested as well on the S. aureus invasiveness of HNECs. Results: Subinhibitory clindamycin reduced S. aureus exoprotein production in planktonic and biofilm form, thereby blocking exoprotein-induced toxicity, reversing its detrimental effects on mucosal barrier structure and function and modulating its inflammatory properties. Sub-inhibitory azithromycin had similar effects—albeit to a lesser extent. Furthermore, clindamycin—but not azithromycin—treated S. aureus lost its invasive capacity of HNECs. Conclusion: Subinhibitory clindamycin and azithromycin reduce S. aureus exoprotein production, thereby modulating the inflammatory cascade by reducing exoprotein-induced toxicity, inflammation, mucosal barrier disruption and invasiveness.

A Pseudomonas aeruginosa (P. aeruginosa) airway infection is one of the predominant causes contributing to the high morbidity and mortality rates in cystic fibrosis (CF) patients. The emergence of antibiotic resistant P. aeruginosa strains has led to an urgent need for new therapeutic approaches. Bacteriophages (phages) are viruses that can infect and lyse specific bacteria, providing a potential alternative approach in targeting antibiotic-resistant strains. We aim to isolate and characterise novel P. aeruginosa phages for combination in a cocktail to kill P. aeruginosa. One particular phage, PA4, could lyse 14/20 clinical isolates as observed through spot assays. This phage could significantly reduce the growth of bacteria in vitro, as determined through planktonic adsorption and inhibition assays as well as crystal violet- and LIVE/DEAD-stained biofilm assays. A morphological and genomic analysis revealed that PA4 belongs to the Myoviridae family and contained 66,450 bp. The broad infectivity profile, good stability in various pH and temperature conditions, lytic ability and the absence of the absences of antibiotic resistance, toxic and lysogenic genes suggest that PA4 is a good candidate for clinical grade use. Overall, phage therapy represents a promising alternative treatment option to antibiotics when treating a P. aeruginosa infection.

Escherichia coli (E. coli) are common bacteria that colonize the human and animal gastrointestinal tract, where they help maintain a balanced microbiome. However, some E. coli strains are pathogenic and can cause serious infectious diseases and life-threatening complications. Due to the overuse of antibiotics and limited development of novel antibiotics, the emergence of antibiotic-resistant strains has threatened modern medicine, whereby common infections can become lethal. Phage therapy has once again attracted interest in recent years as an alternative treatment option to antibiotics for severe infections with antibiotic-resistant strains. The aim of this study was to isolate and characterize phage against multi-drug resistant E. coli isolated from clinical samples and hospital wastewater. For phage isolation, wastewater samples were collected from The Queen Elizabeth Hospital (Adelaide, SA, Australia) followed by phage enrichment as required. Microbiological assays, electron microscopy and genomic sequencing were carried out to characterize the phage. From the 10 isolated E. coli phages, E. coli phage APTC-EC-2A was the most promising and could lyse 6/7 E. coli clinical isolates. APTC-EC-2A was stable at a broad pH range (3–11) and could lyse the host E. coli at temperatures ranging between 30–50 °C. Furthermore, APTC-EC-2A could kill E. coli in planktonic and biofilm form. Electron microscopy and genomic sequencing indicated the phage to be from the Myoviridae family and of lytic nature. In conclusion, the newly isolated phage APTC-EC-2A has the desired properties that support its potential for development as a therapeutic agent against therapy refractory E. coli infections.