Diversity of lytic bacteriophages against XDR Klebsiella pneumoniae sequence type 16 recovered from sewage samples in different parts of the world

Characterization and therapeutic potential of MRABP9, a novel lytic bacteriophage infecting multidrug-resistant Acinetobacter baumannii clinical strains

Acinetobacter baumannii is one of the most important pathogens of healthcare-associated infections. The rising prevalence of multidrug-resistant A. baumannii (MRAB) strains and biofilm formation impact the outcome of conventional treatment. Phage-related therapy is a promising strategy to tame troublesome multidrug-resistant bacteria. Here, we isolated and evaluated a highly efficient lytic phage called MRABP9 from hospital sewage. The phage was a novel species within the genus Friunavirus and exhibited lytic activity against 2 other identified MRAB strains. Genomic analysis revealed it was a safe virulent phage and a pectate lyase domain was identified within its tail spike protein. MRABP9 showed potent bactericidal and anti-biofilm activity against MRAB, significantly delaying the time point of bacterial regrowth in vitro. Phage administration could rescue the mice from acute lethal MRAB infection. Considering its features, MRABP9 has the potential as an efficient candidate for prophylactic and therapeutic use against acute infections caused by MRAB strains.

Characterization of a novel genus of jumbo phages and their application in wastewater treatment

Phages widely exist in numerous environments from wastewater to deep ocean, representing a huge virus diversity, yet remain poorly characterized. Among them, jumbo phages are of particular interests due to their large genome (>200 kb) and unusual biology. To date, only six strains of jumbo phages infecting Klebsiella pneumoniae have been described. Here, we report the isolation and characterization of two jumbo phages from hospital wastewater representing the sixth genus: φKp5130 and φKp9438. Both phages showed lytic activity against broad range of clinical antibiotic-resistant K. pneumoniae strains and distinct physiology including long latent period, small burst size, and high resistance to thermal and pH stress. The treatment of sewage water with the phages cocktail resulted in dramatic decline in K. pneumoniae population. Overall, this study provides detailed molecular and genomics characterization of two novel jumbo phages, expands viral diversity, and provides novel candidate phages to facilitate environmental wastewater treatment.

New Bacteriophages Members of the Ackermannviridae Family Specific for Klebsiella pneumoniae ST258

Background

Carbapenem-resistant Klebsiella pneumoniae, particularly isolates classified as sequence-type 258 (ST258), are multidrug-resistant strains that are strongly associated with poor-prognosis nosocomial infections, as current therapeutic options are limited and ineffective. In recent years, phage therapy has emerged as a promising treatment option for these scenarios.

Methodology and Results

We report the isolation and characterization of three new phages against Klebsiella pneumoniae ST258 strains recovered from Machángara river wastewater. These new members of the Ackermannviridae family showed stability over a wide temperature and pH range and burst sizes ranging from 6 to 44 plaque-forming units per bacteria. Their genomes were about 157 kilobases, with an average guanine-cytosine content of 46.4% and showed presence of several transfer RNAs, which also allowed us to predict in silico a lytic replicative cycle due to the presence of endolysins and lysozymes.

Conclusion

Three lytic phages of Ackermannviridae family were recovered against Klebsiella pneumoniae ST258 strains from sewage; however, further characterization is needed for future consideration as therapeutic alternatives.

Characterization and genomic analysis of novel bacteriophage NK20 to revert colistin resistance and combat pandrug-resistant Klebsiella pneumoniae in a rat respiratory infection model

AIM

We investigated the therapeutic capacity of the isolated Klebsiella bacteriophage NK20 against pandrug-resistant strains. Moreover, we assessed the impact of resistance development on the overall therapeutic outcome both in vitro and in vivo.

MAIN METHODS

The pandrug-resistant K. pneumoniae Kp20 is used as a host strain for the isolation of bacteriophages using sewage samples. Spot assay was then used to compare the spectra of the isolated phages, while kinetic and genomic analysis of the phage with the broadest spectrum was assessed. Antibacterial potential of the phage was assessed using turbidimetric assay and MIC with and without colistin. Finally, the therapeutic efficacy was evaluated in vivo using a rat respiratory infection model.

KEY FINDINGS

The isolated lytic bacteriophage (NK20) showed a relatively broad spectrum and an acceptable genomic profile. In vitro antibacterial assay revealed bacterial resistance development after 12 h. Colistin inhibited bacterial regrowth and reduced pandrug-resistant strains' colistin MICs. Despite the isolation of resistant clones, intranasal administration of NK20 significantly (p < 0.05) reduced the bacterial load in both the pulmonary and blood compartments and rescued 100 % of challenged rats. Histological and immunological analysis of treated animals' lung tissue revealed less inflammation and lower TNF-α and caspase-3 expression.

SIGNIFICANCE

NK20 is a promising candidate that rescued rats from untreatable, pan-drug-resistant K. pneumoniae Kp20. Moreover, it steers the evolution of resistant mutants with higher sensitivity to colistin and less virulence, opening the door for using phages as sensitizing and anti-virulence entities rather than direct killer.

Phages for treatment of Klebsiella pneumoniae infections

Klebsiella pneumoniae is an opportunistic pathogen involved in both hospital- and community-acquired infections. K. pneumoniae is associated with various infections, including pneumonia, septicemia, meningitis, urinary tract infection, and surgical wound infection. K. pneumoniae possesses serious virulence, biofilm formation ability, and severe resistance to many antibiotics especially hospital-acquired strains, due to excessive use in healthcare systems. This limits the available effective antibiotics that can be used for patients suffering from K. pneumoniae infections; therefore, alternative treatments are urgently needed. Bacteriophages (for short, phages) are prokaryotic viruses capable of infecting, replicating, and then lysing (lytic phages) the bacterial host. Phage therapy exhibited great potential for treating multidrug-resistant bacterial infections comprising K. pneumoniae. Hence, this chapter emphasizes and summarizes the research articles in the PubMed database from 1948 until the 15th of December 2022, addressing phage therapy against K. pneumoniae. The chapter provides an overview of K. pneumoniae phages covering different aspects, including phage isolation, different morphotypes of isolated phages, in vitro characterization, anti-biofilm activity, various therapeutic forms, in vivo research and clinical studies.