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 beta-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 ?g/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.

Klebsiella pneumoniae, bacteriophage, antimicrobial therapy, polysaccharide depolymerase

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,2,4	aDManp	101.5	71.4	71.6	68.0	74.0	62.2
3,2	aDGalpA	102.1	69.5	78.4	79.0	72.2	174.7
3	aDManp	96.2	81.2	71.6	68.4	74.1	62.3
	bDGalp	105.7	71	78	65.9	76.3	62.5


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,2,4	aDManp	4.99	3.87	3.82	3.69	4.02	3.80-3.89
3,2	aDGalpA	5.21	4.07	4.16	4.63	4.57	-
3	aDManp	5.21	4.05	4.02	3.77	4.01	3.75-3.84
	bDGalp	4.66	3.64	3.72	4.01	3.63	3.77-3.83


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,2,4	aDManp	101.5/4.99	71.4/3.87	71.6/3.82	68.0/3.69	74.0/4.02	62.2/3.80-3.89
3,2	aDGalpA	102.1/5.21	69.5/4.07	78.4/4.16	79.0/4.63	72.2/4.57	
3	aDManp	96.2/5.21	81.2/4.05	71.6/4.02	68.4/3.77	74.1/4.01	62.3/3.75-3.84
	bDGalp	105.7/4.66	71/3.64	78/3.72	65.9/4.01	76.3/3.63	62.5/3.77-3.83

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*O[C@@H]1[C@@H](O)[C@@H](O[C@H]2[C@@H](O)[C@H](O)[C@@H](CO)O[C@@H]2O[C@@H]2[C@@H](O)[C@H](*)O[C@H](CO)[C@@H]2O)O[C@H](C(=O)O)[C@@H]1O[C@H]1O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]1O

662.547 g/mol (C₂₄H₃₈R₂O₂₁, R = next and previous repeats, not counted in mol weight)