Novel Bacteriophages Show Activity against Selected Australian Clinical Strains of Pseudomonas aeruginosa

Phage Therapy: An Alternative Approach to Combating Multidrug-Resistant Bacterial Infections in Cystic Fibrosis

Patients with cystic fibrosis (CF) are prone to developing life-threatening lung infections with a variety of pathogens that are difficult to eradicate, such as Burkholderia cepacia complex (Bcc), Hemophilus influenzae, Mycobacterium abscessus (Mab), Pseudomonas aeruginosa, and Staphylococcus aureus. These infections still remain an important issue, despite the therapy for CF having considerably improved in recent years. Moreover, prolonged exposure to antibiotics in combination favors the development and spread of multi-resistant bacteria; thus, the development of alternative strategies is crucial to counter antimicrobial resistance. In this context, phage therapy, i.e., the use of phages, viruses that specifically infect bacteria, has become a promising strategy. In this review, we aim to address the current status of phage therapy in the management of multidrug-resistant infections, from compassionate use cases to ongoing clinical trials, as well as the challenges this approach presents in the particular context of CF patients.

A Novel Bacteriophage Infecting Multi-Drug- and Extended-Drug-Resistant Pseudomonas aeruginosa Strains

The prevalence of carbapenem-resistant P. aeruginosa has dramatically increased over the last decade, and antibiotics alone are not enough to eradicate infections caused by this opportunistic pathogen. Phage therapy is a fresh treatment that can be administered under compassionate use, particularly against chronic cases. However, it is necessary to thoroughly characterize the virus before therapeutic application. Our work describes the discovery of the novel sequenced bacteriophage, vB_PaeP-F1Pa, containing an integrase, performs a phylogenetical analysis, describes its stability at a physiological pH and temperature, latent period (40 min), and burst size (394 ± 166 particles per bacterial cell), and demonstrates its ability to infect MDR and XDR P. aeruginosa strains. Moreover, this novel bacteriophage was able to inhibit the growth of bacteria inside preformed biofilms. The present study offers a road map to analyze essential areas for successful phage therapy against MDR and XDR P. aeruginosa infections, and shows that a phage containing an integrase is also able to show good in vitro results, indicating that it is very important to perform a genomic analysis before any clinical use, in order to prevent adverse effects in patients.

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

Biofilms of P. aeruginosa are known to be resilient forms of survival of this opportunistic pathogen, both within the host and in natural or engineered environments. This study investigated the role of phages in the disruption and inactivation of clinical P. aeruginosa biofilms by previously isolated phages. All seven tested clinical strains formed biofilms in 56-80 h. Four previously isolated phages were effective in disrupting the formed biofilms when applied at multiplicity of infection (MOI) of 10, where phage cocktails had equivalent or worse performance than single phages. Phage treatments reduced the biofilms' biomass (cells and extracellular matrix) by 57.6-88.5% after 72 h of incubation. Biofilm disruption led to the detachment of 74.5-80.4% of the cells. The phages were also able to kill the cells from the biofilms, reducing the living cell counts by approximately 40.5-62.0% after a single treatment. A fraction of 24-80% of these killed cells were also lysed due to phage action. This study showed that phages can have a relevant role in disrupting, inactivating, and destroying P. aeruginosa biofilms, which can be used in the development of treatment processes to complement or replace antibiotics and/or disinfectants.

Peptidoglycan Endopeptidase from Novel Adaiavirus Bacteriophage Lyses Pseudomonas aeruginosa Strains as Well as Arthrobacter globiformis and A. pascens Bacteria

A novel virus lytic for Pseudomonas aeruginosa has been purified. Its viral particles have a siphoviral morphology with a head 60 nm in diameter and a noncontractile tail 184 nm long. The dsDNA genome consists of 16,449 bp, has cohesive 3' termini, and encodes 28 putative proteins in a single strain. The peptidoglycan endopeptidase encoded by ORF 16 was found to be the lytic enzyme of this virus. The recombinant, purified enzyme was active up to 55 °C in the pH range 6-9 against all tested isolates of P. aeruginosa, but, surprisingly, also against the distant Gram-positive micrococci Arthrobacter globiformis and A. pascens. Both this virus and its endolysin are further candidates for possible treatment against P. aeruginosa and probably also other bacteria.

Isolation of a bacteriophage targeting Pseudomonas aeruginosa and exhibits a promising in vivo efficacy

Pseudomonas aeruginosa is an important pathogen that causes serious infections. Bacterial biofilms are highly resistant and render bacterial treatment very difficult, therefore necessitates alternative antibacterial strategies. Phage therapy has been recently regarded as a potential therapeutic option for treatment of bacterial infections. In the current study, a novel podovirus vB_PaeP_PS28 has been isolated from sewage with higher lytic activity against P. aeruginosa. Isolated phage exhibits a short latent period, large burst size and higher stability over a wide range of temperatures and pH. The genome of vB_PaeP_PS28 consists of 72,283 bp circular double-stranded DNA, with G + C content of 54.75%. The phage genome contains 94 open reading frames (ORFs); 32 for known functional proteins and 62 for hypothetical proteins and no tRNA genes. The phage vB_PaeP_PS28 effectively inhibited the growth of P. aeruginosa planktonic cells and displayed a higher biofilm degrading capability. Moreover, therapeutic efficacy of isolated phage was evaluated in vivo using mice infection model. Interestingly, survival of mice infected with P. aeruginosa was significantly enhanced upon treatment with vB_PaeP_PS28. Furthermore, the bacterial load in liver and kidney isolated from mice infected with P. aeruginosa and treated with phage markedly decreased as compared with phage-untreated P. aeruginosa-infected mice. These findings support the efficacy of isolated phage vB_PaeP_PS28 in reducing P. aeruginosa colonization and pathogenesis in host. Importantly, the isolated phage vB_PaeP_PS28 could be applied alone or as combination therapy with other lytic phages as phage cocktail therapy or with antibiotics to limit infections caused by P. aeruginosa.

Isolation and phenotypic characterization of bacteriophage SA14 with lytic- and anti-biofilm activity against multidrug-resistant Enterococcus faecalis

Background

Antimicrobial resistance is a growing global health concern demanding more attention and action at the international-, national- and regional levels. In the present study, bacteriophage was sought as a potential alternative to traditional antibiotics.

Results

Vancomycin-resistant Enterococcus faecalis was isolated from a urine sample. Partial 16S rRNA-gene sequencing and VITEK®2 system were employed for its identification, biochemical characterization, and antibiotic susceptibility testing. The isolate was resistant to eight antibiotics (out of 11): vancomycin, gentamicin (high-level synergy), streptomycin (high-level synergy), ciprofloxacin, levofloxacin, erythromycin, quinupristin/dalfopristin, and tetracycline. Bacteriophage SA14 was isolated from sewage water using the multidrug-resistant isolate as a host. Transmission electron micrographs revealed that phage SA14 is a member of the Siphoviridae family displaying the typical circular head and long non-contractile tail. The phage showed characteristic stability to a wide range of solution pH and temperatures, with optimal stability at pH 7.4 and 4 °C, while showing high specificity toward their host. Based on the one-step growth curve, the phage's latent period was 25 min, and the burst size was 20 PFU/ml. The lytic activity of phage SA14 was evaluated at various multiplicities of infection (MOI), all considerably suppressed the growth of the host organism. Moreover, phage SA14 displayed a characteristic anti-biofilm activity as observed by the reduction in adhered biomass and -viable cells in the pre-formed biofilm by 19.1-fold and 2.5-fold, respectively.

Conclusion

Phage therapy can be a valuable alternative to antibiotics against multi-drug resistant microorganisms.

Phascinating Phages

Treatment of infections caused by bacteria has become more complex due to the increasing number of bacterial strains that are resistant to conventional antimicrobial therapy. A highly promising alternative appears to be bacteriophage (phage) therapy, in which natural predators of bacteria, bacteriophages, play a role. Although these viruses were first discovered in 1917, the development of phage therapy was impacted by the discovery of antibiotics, which spread more quickly and effectively in medical practice. Despite this, phage therapy has a long history in Eastern Europe; however, Western countries are currently striving to reintroduce phage therapy as a tool in the fight against diseases caused by drug-resistant bacteria. This review describes phage biology, bacterial and phage competition mechanisms, and the benefits and drawbacks of phage therapy. The results of various laboratory experiments, and clinical cases where phage therapy was administered, are described.