Genome Analysis of Pseudomonas aeruginosa Bacteriophage KPP23, Belonging to the Family Siphoviridae

Current knowledge in the use of bacteriophages to combat infections caused by Pseudomonas aeruginosa in cystic fibrosis

Pseudomonas aeruginosa (PA) is considered the first causal agent of morbidity and mortality in people with cystic fibrosis (CF) disease. Multi-resistant strains have emerged due to prolonged treatment with specific antibiotics, so new alternatives have been sought for their control. In this context, there is a renewed interest in therapies based on bacteriophages (phages) supported by several studies suggesting that therapy based on lytic phages and biofilm degraders may be promising for the treatment of lung infections in CF patients. However, there is little clinical data about phage studies in CF and the effectiveness and safety in patients with this disease has not been clear. Therefore, studies regarding on phage characterization, selection, and evaluation in vitro and in vivo models will provide reliable information for designing effective cocktails, either using mixed phages or in combination with antibiotics, making a great progress in clinical research. Hence, this review focuses on the most relevant and recent findings on the activity of lytic phages against PA strains isolated from CF patients and hospital environments, and discusses perspectives on the use of phage therapy on the treatment of PA in CF patients.

Characterization of a novel bullet-shaped lytic bacteriophage against extensively drug-resistant Pseudomonas aeruginosa isolated from human and domestic sources

Global spread and emergence of the extensively drug-resistant (XDR) strains of P. aeruginosa have become a concern, thus, searching for new alternative treatment approaches are required. This study was aimed to isolate and characterize a novel lytic phage against P. aeruginosa. Seventy XDR isolates of P. aeruginosa were collected from May to September 2018. Wastewater samples were used for isolation of lytic phage against XDR P. aeruginosa isolates. Host range, thermal and pH stability, adsorption rate, latent period, burst size and morphology of phage were determined following the standard protocols. Morphological characteristics of the phage revealed that it belonged to Podoviridae family and it was named vB-PaeP-007. Although the phage had a narrow host range, 47 out of 70 XDR isolates were susceptible to it. The adsorption rate, latent period and burst size of vB-PaeP-007 were approximately 89.80% in 8 min, 10 min and 93 phages per cell, respectively. Its lysis activity remained at a wide range of pH (4 up to 12) and temperature (- 20.00 up to 70.00 ˚C). Regarding the physiological features and host range of the vB-PaeP-007 phage, it could be a promising candidate for phage therapy and bio-controlling of infections from XDR isolates of P. aeruginosa in human and livestock storage centers.

Characterization of Pseudomonas aeruginosa phage KPP21 belonging to family Podoviridae genus N4-like viruses isolated in Japan

Bacteriophages (phages) belonging to the family Podoviridae genus N4-like viruses have been used as therapeutic agent in phage therapy against Pseudomonas aeruginosa infections. P. aeruginosa phage KPP21 was isolated in Japan, and phylogenetically investigated the phages belonging to this viral genus. Morphological and genetic analyses confirmed that phage KPP21 belongs to the family Podoviridae genus N4-like viruses. Moreover, phylogenetic analyses based on putative DNA polymerase and major virion protein showed that P. aeruginosa phages belonging to the genus N4-like viruses are separated into two lineages and that phage KPP21 is in the same clade as phage LUZ7.

A virulent phage JHP against Pseudomonas aeruginosa showed infectivity against multiple genera

The resistance to antibiotics in clinically important bacteria is one of the major global health concerns. Phage therapy could be one reliable alternative therapeutic strategy to combat these superbugs. In this study, we assessed host range of a novel bacteriophage, JHP, and characterized for its potential use in phage therapy. The bacteriophage demonstrated infectivity over a broad range of genera including multidrug resistant clinical isolates of Pseudomonas aeruginosa, members of family Enterobacteracae, and other important human pathogens. The antibacterial activity was highest at pH 7, and at temperature of 37 °C. The phage lytic activity gradually decreased till 60 °C and showed no activity when temperature was further raised. The bacteriophage could safely be stored at 4 °C or -20 °C. The latent period of the bacteriophage was 25 min and showed a burst size of 433 virions per cell. The size of JHP genome was approximately 30 kb. Family, Siphoviridae was assigned to JHP based on its icosahedral head with non-contractile tail. The diameter of JHP head and tail length was found 115 and 152 nm, respectively. To sum up, the broad spectrum Siphoviridae phage JHP is an ingenious candidate for phage therapy.

Phylogenetic Distribution of CRISPR-Cas Systems in Antibiotic-Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is an antibiotic-refractory pathogen with a large genome and extensive genotypic diversity. Historically, P. aeruginosa has been a major model system for understanding the molecular mechanisms underlying type I clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR-associated protein (CRISPR-Cas)-based bacterial immune system function. However, little information on the phylogenetic distribution and potential role of these CRISPR-Cas systems in molding the P. aeruginosa accessory genome and antibiotic resistance elements is known. Computational approaches were used to identify and characterize CRISPR-Cas systems within 672 genomes, and in the process, we identified a previously unreported and putatively mobile type I-C P. aeruginosa CRISPR-Cas system. Furthermore, genomes harboring noninhibited type I-F and I-E CRISPR-Cas systems were on average ~300 kb smaller than those without a CRISPR-Cas system. In silico analysis demonstrated that the accessory genome (n = 22,036 genes) harbored the majority of identified CRISPR-Cas targets. We also assembled a global spacer library that aided the identification of difficult-to-characterize mobile genetic elements within next-generation sequencing (NGS) data and allowed CRISPR typing of a majority of P. aeruginosa strains. In summary, our analysis demonstrated that CRISPR-Cas systems play an important role in shaping the accessory genomes of globally distributed P. aeruginosa isolates.

IMPORTANCE

P. aeruginosa is both an antibiotic-refractory pathogen and an important model system for type I CRISPR-Cas bacterial immune systems. By combining the genome sequences of 672 newly and previously sequenced genomes, we were able to provide a global view of the phylogenetic distribution, conservation, and potential targets of these systems. This analysis identified a new and putatively mobile P. aeruginosa CRISPR-Cas subtype, characterized the diverse distribution of known CRISPR-inhibiting genes, and provided a potential new use for CRISPR spacer libraries in accessory genome analysis. Our data demonstrated the importance of CRISPR-Cas systems in modulating the accessory genomes of globally distributed strains while also providing substantial data for subsequent genomic and experimental studies in multiple fields. Understanding why certain genotypes of P. aeruginosa are clinically prevalent and adept at horizontally acquiring virulence and antibiotic resistance elements is of major clinical and economic importance.