The Influence of Formulation Components and Environmental Humidity on Spray-Dried Phage Powders for Treatment of Respiratory Infections Caused by Acinetobacter baumannii

Powder aerosol formulation of Pseudomonas aeruginosa bacteriophage for pulmonary delivery

The purpose of this study was to develop Pseudomonas aeruginosa bacteriophage 95 (ATCC 14211-B1) as a stable and aerosolizable dry powder formulation. We specifically investigated the effects of different excipients (e.g. trehalose, lactose, leucine, mannitol, gelatin and hydrolyzed gelatin) on the aerosol performance and stabilization of spray dried bacteriophage powder formulations. Our data demonstrated that hydrolyzed gelatin was the most effective bacteriophage stabilizer during spray drying, showing a titer reduction of only 0.6 log. When stored at 4 °C, hydrolyzed gelatin and gelatin showed the best stability with negligible bacteriophage titer reduction for 12 weeks. The in vitro aerosol performance of spray dried formulations was assessed using a multistage liquid impinger coupled with a low-resistance RS01 inhaler device.The hydrolyzed gelatin formulation showed an emitted dose (ED) of 60 % and fine particle fraction (FPF) of 77 %. The inclusion of leucine and trileucine at 5 % w/w significantly improved the aerosol performance of the hydrolyzed gelatin-bacteriophage formulation to an ED of 90 % and an FPF of 80-86 %; both were amorphous matrix that showed low bacteriophage titer reduction (0.7 log). This is the first study to report that a composite spray dried matrix of hydrolyzed gelatin (as a stabilizer) with leucine or trileucine (as dispersion enhancers) provides both high bacteriophage stability and excellent aerosol performance, making it a promising dry powder formulation for treating pulmonary bacterial infections.

The (re)emergence of aerosol delivery: Treatment of pulmonary diseases and its clinical challenges

Aerosol delivery represents a rapid and non-invasive way to directly reach the lungs while escaping the hepatic first-pass effect. The development of pulmonary drugs for respiratory diseases such as cystic fibrosis, lung infections, pulmonary fibrosis or lung cancer requires an enhanced understanding of the relationships between the natural physiology of the respiratory system and the pathophysiology of these conditions. This knowledge is crucial to better predict and thereby control drug deposition. Moreover, aerosol administration faces several challenges, including the pulmonary tract, immune system, mucociliary clearance, the presence of fluid on the airway surfaces, and, in some cases, bacterial colonisation. Each of them directly influences on the bioavailability of the active molecule. In addition to these challenges, particle size and the device used to administer the treatment are critical factors that can significantly impact the biodistribution of the drugs. Nanoparticles are very promising in the development of new formulations for aerosol drug delivery, as they can be fine-tuned to reach the entire pulmonary tract and overcome the difficulties encountered along the way. However, to properly assess drug delivery, preclinical studies need to be more thorough to efficiently enhance drug delivery.

Evaluation of Different Formulations on the Viability of Phages for Use in Agriculture

Bacteriophages have been proposed as biological controllers to protect plants against different bacterial pathogens. In this scenario, one of the main challenges is the low viability of phages in plants and under adverse environmental conditions. This work explores the use of 12 compounds and 14 different formulations to increase the viability of a phage mixture that demonstrated biocontrol capacity against Pseudomonas syringae pv. actinidiae (Psa) in kiwi plants. The results showed that the viability of the phage mixture decreases at 44 °C, at a pH lower than 4, and under UV radiation. However, using excipients such as skim milk, casein, and glutamic acid can prevent the viability loss of the phages under these conditions. Likewise, it was demonstrated that the use of these compounds prolongs the presence of phages in kiwi plants from 48 h to at least 96 h. In addition, it was observed that phages remained stable for seven weeks when stored in powder with skim milk, casein, or sucrose after lyophilization and at 4 °C. Finally, the phages with glutamic acid, sucrose, or skim milk maintained their antimicrobial activity against Psa on kiwi leaves and persisted within kiwi plants when added through roots. This study contributes to overcoming the challenges associated with the use of phages as biological controllers in agriculture.

Formulation of Bacteriophage for Inhalation to Treat Multidrug-Resistant Pulmonary Infections

Rapid development of antibiotic resistance in pathogenic bacteria and a decline in the pharmaceutical development of new antibiotics are pushing the research community to explore alternative antimicrobials that can replace or complement antibiotics. Bacteriophages (or, phages) are naturally occurring viruses that can kill bacteria with high specificity and can evolve to target resistant bacteria. Phages have been historically employed as antimicrobial agents, but they were overshadowed by the emergence of antibiotics. With a renewed focus on phages, it is important to study their clinical efficacy, safety, and formulation. Pulmonary infections have a large burden of global morbidity and frequently involve multidrug-resistant pathogens such as Acinetobacter baumannii, Klebsiella pneumoniae, Mycobacterium tuberculosis, and Pseudomonas aeruginosa. Therefore, this can be an important area of application of phages. Dry powder inhalers can be an effective strategy to deliver phages to the lungs because they are easy-to-use, portable, and capable of delivering a higher lung dose than oral or intravenous route. They also have longer shelf life and lower cold storage requirements than solutions. Therefore, the aim of the current review is to summarize recent findings on bacteriophage dry powder formulations, particularly focusing on the effect of various excipients and manufacturing factors on phage titer preservation.

Phage formulations and delivery strategies: Unleashing the potential against antibiotic-resistant bacteria

Bacterial control promoted by bacteriophages (phages) is an attractive tool in the face of the antibiotic crisis triggered by the exacerbated use of these drugs. Despite the growing interest in using these viruses, some gaps still need answers, such as the protection and delivery of phages. Some limitation points involve the degradation of phage proteins by enzymes or inactivation in low-pH environments. In this review, a literature search using keywords related to the field of virus delivery formulations was done to understand the current scenario of using delivery techniques and phage formulations. A total of 2096 raw results were obtained, which resulted in 140 publications after refinement. These studies were analyzed for main application techniques and areas, keywords, and countries. Of the total, 57% of the publications occurred in the last five years, and the encapsulation technique was the most used among the articles analyzed. As excipient agents, lactose, trehalose, mannitol, PEG, and Leucine stand out. The development of phage formulations, protection approaches, their delivery routes, and the knowledge about the best application strategy enables the use of these organisms in several sectors. It can act as a powerful tool against antibiotic-resistant bacteria.

Bacteriophages and their derived enzymes as promising alternatives for the treatment of Acinetobacter baumannii infections

Nosocomial infections with the opportunistic bacterium Acinetobacter baumannii pose a severe challenge to clinical treatment, which is aggravated by the increasing occurrence of multi-drug resistance, especially resistance to carbapenems. The use of phage therapy as an alternative and supplement to the current antibiotics has become an important research topic in the post-antibiotic era. This review summarizes in vivo and in vitro studies on phage therapy against multi-drug-resistant A. baumannii infection that have used different approaches, including treatment with a single phage, combination with other phages or non-phage agents, and administration of phage-derived enzymes. We also briefly discuss the current challenges of phage-based therapy as well as promising approaches for the treatment of A. baumannii infection in the future.

Bacteriophage endolysin powders for inhaled delivery against pulmonary infections

Endolysins are bacteriophage-encoded enzymatic proteins that have great potential to treat multidrug-resistant bacterial infections. Bacteriophage endolysins Cpl-1 and ClyJ-3 have shown promising antimicrobial activity against Streptococcus pneumoniae, which causes pneumonia in humans. This is the first study to investigate the feasibility of spray-dried endolysins Cpl-1 and ClyJ-3 with excipients to produce inhalable powders. The two endolysins were individually tested with leucine and sugar (lactose or trehalose) for spray drying method followed by characterization of biological and physico-chemical properties. A complete loss of ClyJ-3 bioactivity was observed after atomization of the liquid feed solution（before the drying process）, while Cpl-1 maintained its bioactivity in the spray-dried powders. Cpl-1 formulations containing leucine with lactose or trehalose showed promising physico-chemical properties (particle size, crystallinity, hygroscopicity, etc.) and aerosol performances (fine particle fraction values above 65%). The results indicated that endolysin Cpl-1 can be formulated as spray dried powders suitable for inhaled delivery to the lungs for the potential treatment of pulmonary infections.

Pulmonary delivery of spray-dried Nisin ZP antimicrobial peptide for non-small cell lung cancer (NSCLC) treatment

Nisin ZP is an antimicrobial peptide (AMP) produced by the bacterium Lactococcus lactis, and we have previously demonstrated anticancer activity in NSCLC (A549) cells. In this study, we formulated a nisin ZP dry powder (NZSD) using a spray dryer to facilitate inhaled delivery for the treatment of NSCLC. Nisin ZP was spray-dried with mannitol, l-leucine, and trehalose in a ratio of 75:15:10 using Büchi mini spray-dryer B-290 in different drug loadings (10, 20, and 30% w/w). NZSD powder revealed a good powder yield of >55% w/w with ≤3 % w/w moisture content and high nisin ZP drug loading for all the peptide ratios. The NZSD powder particles were irregularly shaped with corrugated morphology. The presence of an endothermic peak in DSC thermograms and attenuated crystalline peaks in PXRD diffractograms confirmed the semi-crystalline powder nature of NZSD. The anticancer activity of nisin ZP was maintained after fabricating it into NZSD powder and showed a similar inhibitory concentration to free nisin ZP. Stability studies indicated that NZSD powders were stable for three months at 4 and 25 ℃ with more than 90% drug content and semi-crystalline nature, as confirmed by DSC and PXRD. Aerosolization studies performed using NGI indicated an aerodynamic diameter (MMAD) within the desired range (1-5 µm) and a high fine particle fraction (FPF > 75%) for all peptide ratios, suggesting powder deposition in the lung's respiratory airways. In conclusion, a dry powder of nisin ZP was formulated using a spray dryer with enhanced storage stability and suitable for inhaled delivery.

Pulmonary Delivery of Emerging Antibacterials for Bacterial Lung Infections Treatment

Bacterial infections in the respiratory tract are considered as one of the major challenges to the public health worldwide. Pulmonary delivery is an attractive approach in the management of bacterial respiratory infections with a few inhaled antibiotics approved. However, with the rapid emergence of antibiotic-resistant bacteria, it is necessary to develop new/alternative inhaled antibacterial agents in the post-antibiotic era. A pipeline of novel biological antibacterial agents, including antimicrobial peptides, RNAi therapeutics, and bacteriophages, has emerged to combat bacterial infections with excellent performance. In this review, the causal effects of bacterial infections on the related pulmonary infectious diseases will be firstly introduced. This is followed by an overview on the development of emerging antibacterial therapeutics for managing lung bacterial infections through nebulization/inhalation of dried powders. The obstacles and underlying proposals regarding their clinical transformation are also discussed to seek insights for further development. Research on inhaled therapy of these emerging antibacterials are still in the infancy, but the promising progress warrants further attention.

Enhancing the Stability of Bacteriophages Using Physical, Chemical, and Nano-Based Approaches: A Review

Phages are efficient in diagnosing, treating, and preventing various diseases, and as sensing elements in biosensors. Phage display alone has gained attention over the past decade, especially in pharmaceuticals. Bacteriophages have also found importance in research aiming to fight viruses and in the consequent formulation of antiviral agents and vaccines. All these applications require control over the stability of virions. Phages are considered resistant to various harsh conditions. However, stability-determining parameters are usually the only additional factors in phage-related applications. Phages face instability and activity loss when preserved for extended periods. Sudden environmental changes, including exposure to UV light, temperature, pH, and salt concentration, also lead to a phage titer fall. This review describes various formulations that impart stability to phage stocks, mainly focusing on polymer-based stabilization, encapsulation, lyophilization, and nano-assisted solutions.

Prophylactic Delivery of a Bacteriophage Cocktail in Feed Significantly Reduces Salmonella Colonization in Pigs

Nontyphoidal Salmonella spp. are a leading cause of human food poisoning and can be transmitted to humans via consuming contaminated pork. To reduce Salmonella spread to the human food chain, bacteriophage (phage) therapy could be used to reduce bacteria from animals' preslaughter. We aimed to determine if adding a two-phage cocktail to feed reduces Salmonella colonization in piglets. This first required spray drying phages to allow them to be added as a powder to feed, and phages were spray dried in different excipients to establish maximum recovery. Although laboratory phage yields were not maintained during scale up in a commercial spray dryer (titers fell from 3 × 108 to 2.4 × 106 PFU/g respectively), the phage titers were high enough to progress. Spray dried phages survived mixing and pelleting in a commercial feed mill, and sustained no further loss in titer when stored at 4°C or barn conditions over 6 months. Salmonella-challenged piglets that were prophylactically fed the phage-feed diet had significantly reduced Salmonella colonization in different gut compartments (P < 0.01). 16S rRNA gene sequencing of fecal and gut samples showed phages did not negatively impact microbial communities as they were similar between healthy control piglets and those treated with phage. Our study shows delivering dried phages via feed effectively reduces Salmonella colonization in pigs. IMPORTANCE Infections caused by Salmonella spp. cause 93.8 million cases of human food poisoning worldwide, each year of which 11.7% are due to consumption of contaminated pork products. An increasing number of swine infections are caused by multidrug-resistant (MDR) Salmonella strains, many of which have entered, and continue to enter the human food chain. Antibiotics are losing their efficacy against these MDR strains, and thus antimicrobial alternatives are needed. Phages could be developed as an alternative approach, but research is required to determine the optimal method to deliver phages to pigs and to determine if phage treatment is effective at reducing Salmonella colonization in pigs. The results presented in this study address these two aspects of phage development and show that phages delivered via feed prophylactically to pigs reduces Salmonella colonization in challenged pigs.