Characterization and Therapeutic Potential of Bacteriophage-Encoded Polysaccharide Depolymerases with β Galactosidase Activity against Klebsiella pneumoniae K57 Capsular Type.

Nikolay V Volozhantsev,Vladimir V Verevkin,Valentina M Krasilnikova,Alexander S Shashkov,Ekaterina V Komisarova,Yuriy A Knirel,Anna M Shpirt,Alexander I Borzilov

doi:10.3390/antibiotics9110732

Abstract

Bacteriophages and phage enzymes are considered as possible alternatives to antibiotics in the treatment of infections caused by antibiotic-resistant bacteria. Due to the ability to cleave the capsular polysaccharides (CPS), one of the main virulence factors of Klebsiella pneumoniae, phage depolymerases, has potential in the treatment of K. pneumoniae infections. Here, we characterized in vivo two novel phage-encoded polysaccharide depolymerases as therapeutics against clinical isolates of K. pneumoniae. The depolymerases Dep_kpv79 and Dep_kpv767 encoded by Klebsiella phages KpV79 (Myoviridae; Jedunavirus) and KpV767 (Autographiviridae, Studiervirinae, Przondovirus), respectively, were identified as specific β-galactosidases that cleave the K. pneumoniae K57 type CPS by the hydrolytic mechanism. They were found to be highly effective at combating sepsis and hip infection caused by K. pneumoniae in lethal mouse models. Here, 80–100% of animals were protected against death by a single dose (e.g., 50 μg/mouse) of the enzyme injected 0.5 h after infection by K. pneumoniae strains of the K57 capsular type. The therapeutic effect of the depolymerases is because they strip the capsule and expose the underlying bacterium to the immune attack such as complement-mediated killing. These data provide one more confirmation that phage polysaccharide depolymerases represent a promising tool for antimicrobial therapy.

Highlights

Antibiotic resistance of pathogenic bacteria has become an increasingly pressing clinical issue worldwide
We evaluated the lytic spectrum of KpV767 and KpV79 on a collection of K. pneumoniae clinical isolates (N = 250) including 21 strains of capsular type K57 (Table 1)
Both phages multiplied and lysed K. pneumoniae capsular type K57 to form plaques with a halo expanding during incubation, which we suspected is related to a putative phage-derived depolymerase (Figure 1A)

Summary

Introduction

Antibiotic resistance of pathogenic bacteria has become an increasingly pressing clinical issue worldwide. K. pneumoniae has been considered as an opportunistic pathogen, primarily causing different types of healthcare-associated infections in immunocompromised patients, including pneumonia, urinary and intestinal tract infections, and wound or surgical site infections [1,2]. In recent years, a new type of hypervirulent K. pneumoniae (hvKp) which causes community-acquired invasive life-threatening infections characterized by pyogenic liver abscesses complicated with meningitis and endophthalmitis, has emerged worldwide, especially in Southeast Asia [2,3,4]. K. pneumoniae cells produce a number of virulence factors including fimbrial adhesins, lipopolysaccharides (O antigen), siderophore iron acquisition systems, and a polysaccharide capsule (K antigen) [2]. An essential virulence factor and a defense barrier of K. pneumoniae are a polysaccharide capsule (CPS) that allows a bacterial cell to survive and spread inside the host overcoming the protective mechanisms of the immune system. The capsule impairs phagocytosis and opsonophagocytosis of the K. pneumoniae cells by immune cells hinders the bactericidal action of antimicrobial peptides and blocks complement components, such as C3, preventing complement-mediated killing [2,5,6]

Methods

Results

Conclusion