The effectiveness and role of phages in the disruption and inactivation of clinical P. aeruginosa biofilms

Screening and Identification of Vibrio cholerae Bacteriophages VC3 and Its Role in the Inhibition and Removal of Biofilms in Seafood

As biological control agents, bacteriophages can both inhibit the pathogenic bacteria and remove the bacterial biofilms from the seafood. Vibrio cholerae is the pathogen of cholera and the severe infection could lead watery diarrhea and even death. The double-layer agar plate method was used to isolate and screen the V. cholerae bacteriophages from the samples of aquaculture water and sewage. Purified bacteriophages were examined through genome sequencing, as well as morphological and biological characterizations. Among the isolated bacteriophages, bacteriophage VC3 was found to be a long-tailed bacteriophage. Whole-genome sequencing showed that the full length of VC3 genome was 27,645 bp. It was a circular dsDNA, with 40.37% G + C content. The optimal multiplicity of infection was 1, the incubation period was 20 min, the burst period was 40 min, and the lysis volume was 73 PFU/cell. Bacteriophage VC3 exhibited good activity under low temperatures and neutral pH conditions. Bacteriophage VC3 could effectively inhibit and eliminate the biofilm of V. cholerae. In addition, bacteriophage VC3 significantly inhibited V. cholerae in fish fillets and shrimp meat. At the same time, it also showed lytic activity against 9 pathogenic bacteria, indicating that it has the potential to inhibit a variety of pathogenic bacteria.

Correlation between the development of phage resistance and the original antibiotic resistance of host bacteria under the co-exposure of antibiotic and bacteriophage

Bacteriophages (phages) are viruses capable of regulating the proliferation of antibiotic resistant bacteria (ARB). However, phages that directly cause host lethality may quickly select for phage resistant bacteria, and the co-evolutionary trade-offs under varying environmental conditions, including the presence of antibiotics, remains unclear as to their impact on phage and antibiotic resistance. Here, we report the emergence of phage resistance in three distinct E. coli strains with varying resistance to β-lactam antibiotics, treated with different ampicillin (AMP) concentrations. Hosts exhibiting stronger antibiotic resistance demonstrated a higher propensity to develop and maintain stable phage resistance. When exposed to polyvalent phage KNT-1, the growth of AMP-sensitive E. coli K12 was nearly suppressed within 18 h, while the exponential growth of AMP-resistant E. coli TEM and super-resistant E. coli NDM-1 was delayed by 12 h and 8 h, respectively. The mutation frequency and mutated colony count of E. coli NDM-1 were almost unaffected by co-existing AMP, whereas for E. coli TEM and K12, these metrics significantly decreased with increasing AMP concentration from 8 to 50 μg/mL, becoming unquantifiable at 100 μg/mL. Furthermore, the fitness costs of phage resistance mutation and its impact on initial antibiotic resistance in bacteria were further examined, through analyzing AMP susceptibility, biofilm formation and EPS secretion of the isolated phage resistant mutants. The results indicated that acquiring phage resistance could decrease antibiotic resistance, particularly for hosts lacking strong antibiotic resistance. The ability of mutants to form biofilm contributes to antibiotic resistance, but the correlation is not entirely positive, while the secretion of extracellular polymeric substance (EPS), especially the protein content, plays a crucial role in protecting the bacteria from both antibiotic and phage exposure. This study explores phage resistance development in hosts with different antibiotic resistance and helps to understand the limitations and possible solutions of phage-based technologies.

Nanocomposites against Pseudomonas aeruginosa biofilms: Recent advances, challenges, and future prospects

Pseudomonas aeruginosa is an opportunistic bacterial pathogen that causes life-threatening and persistent infections in immunocompromised patients. It is the culprit behind a variety of hospital-acquired infections owing to its multiple tolerance mechanisms against antibiotics and disinfectants. Biofilms are sessile microbial aggregates that are formed as a result of the cooperation and competition between microbial cells encased in a self-produced matrix comprised of extracellular polymeric constituents that trigger surface adhesion and microbial aggregation. Bacteria in biofilms exhibit unique features that are quite different from planktonic bacteria, such as high resistance to antibacterial agents and host immunity. Biofilms of P. aeruginosa are difficult to eradicate due to intrinsic, acquired, and adaptive resistance mechanisms. Consequently, innovative approaches to combat biofilms are the focus of the current research. Nanocomposites, composed of two or more different types of nanoparticles, have diverse therapeutic applications owing to their unique physicochemical properties. They are emerging multifunctional nanoformulations that combine the desired features of the different elements to obtain the highest functionality. This review assesses the recent advances of nanocomposites, including metal-, metal oxide-, polymer-, carbon-, hydrogel/cryogel-, and metal organic framework-based nanocomposites for the eradication of P. aeruginosa biofilms. The characteristics and virulence mechanisms of P. aeruginosa biofilms, as well as their devastating impact and economic burden are discussed. Future research addressing the potential use of nanocomposites as innovative anti-biofilm agents is emphasized. Utilization of nanocomposites safely and effectively should be further strengthened to confirm the safety aspects of their application.

Bacteriophages for bronchiectasis: treatment of the future?

PURPOSE OF REVIEW

Bronchiectasis is a chronic respiratory disease characterized by dilated airways, persistent sputum production and recurrent infective exacerbations. The microbiology of bronchiectasis includes various potentially pathogenic microorganisms including Pseudomonas aeruginosa which is commonly cultured from patients' sputum. P. aeruginosa is difficult to eradicate and frequently exhibits antimicrobial resistance. Bacteriophage therapy offers a novel and alternative method to treating bronchiectasis and can be used in conjunction with antibiotics to improve patient outcome.

RECENT FINDINGS

Thirteen case reports/series to date have successfully used phages to treat infections in bronchiectasis patients, however these studies were constrained to few patients ( n  = 32) and utilized personalized phage preparations and adjunct antibiotics. In these studies, phage therapy was delivered by inhalation, intravenously or orally and was well tolerated in most patients without any unfavourable effects. Favourable clinical or microbiological outcomes were seen following phage therapy in many patients. Longitudinal patient follow-up reported regrowth of bacteria and phage neutralization in some studies. There are five randomized clinical controlled trials ongoing aiming to use phage therapy to treat P. aeruginosa associated respiratory conditions, with limited results available to date.

SUMMARY

More research, particularly robust clinical trials, into how phages can clear respiratory infections, interact with resident microbiota, and how bacteria might develop resistance will be important to establish to ensure the success of this promising therapeutic alternative.

Exploiting phage-antibiotic synergies to disrupt Pseudomonas aeruginosa PAO1 biofilms in the context of orthopedic infections

IMPORTANCE

Biofilm-related infections are among the most difficult-to-treat infections in all fields of medicine due to their antibiotic tolerance and persistent character. In the field of orthopedics, these biofilms often lead to therapeutic failure of medical implantable devices and urgently need novel treatment strategies. This forthcoming article aims to explore the dynamic interplay between newly isolated bacteriophages and routinely used antibiotics and clearly indicates synergetic patterns when used as a dual treatment modality. Biofilms were drastically more reduced when both active agents were combined, thereby providing additional evidence that phage-antibiotic combinations lead to synergism and could potentially improve clinical outcome for affected patients.