Characterization of a novel phage infecting the pathogenic multidrug-resistant Bacillus cereus and functional analysis of its endolysin

Abstract

Bacillus cereus is widely distributed food-borne pathogenic bacterium. Due to the harmness to human hearth and the generation of multidrug-resistant B. cereus, it is urgent to develop novel antimicrobial agents. Phage and phage endolysin were taken as novel antimicrobial substance for their specific lytic activity against pathogenic bacteria. In this study, a Myoviridae family phage, designated as vB_BceM-HSE3, infecting the pathogenic multidrug-resistant B. cereus strain was isolated and characterized along with its endolysin. Phage vB_BceM-HSE3 can specially infect the B. cereus group strains, including B. cereus, B. anthracis, and B. thuringiensis, and exhibits high temperature and pH tolerance, which endow it with high potential for been used in controlling pathogenic B. cereus group strains. Genomic analysis reveals that vB_BceM-HSE3 is a novel phage and only shows extremely low genome similarity with available phage genome. Functional analysis of endolysin PlyHSE3 encoding by vB_BceM-HSE3 shows that PlyHSE3 exhibits broader lytic spectrum than the phage and can lyse all the tested B. cereus group strains as well as the tested pathogenic strain of P. aeruginosa. PlyHSE3 also shows broad temperature and pH tolerance, and can efficiently lyse B. cereus strain at temperature at 4 °C and higher than 45 °C, which indicating that PlyHSE3 might can be used in controlling food-borne B. cereus during both the cold storage of food and the stage after the heat treatment of food. The findings of this study enrich our understanding of phage diversity as well as providing resources for developing phage therapy.

Characterization of PlyB221 and PlyP32, Two Novel Endolysins Encoded by Phages Preying on the Bacillus cereus Group

“…The thermal stability of endolysins is also important for their potential application in the food industry. Both endolysins retained high lytic activity (>50%) after treatments up to 45-50 • C which, although not as resistant as some Listeria specific endolysins (e.g., HPL511 70% activity after 30 min at 70 • C [50]) is consistent with other endolysins encoded by phages infecting B. cereus [35,51]. Overall, PlyB221 appeared to be active in a wider range of pH and NaCl conditions and withstood higher temperature treatments than PlyP32.…”

Isolation and Characterization of a Novel Phage for Controlling Multidrug-Resistant Klebsiella pneumoniae

“…The phage isolated in this study only targets specific strains of the bacterial pathogen, but not all the strains of the same bacterial species isolated from the same hospital. Several other phages were also isolated from hospital sewage by using pathogenic bacteria from the same hospital as indicators [34,47]. The findings of this study indicate that the hospital sewage provides a resource for isolating phages that can target the multidrug-resistant bacterial pathogens.…”

“…Then, the pellet was resuspended in 50 mL fresh LB broth, and the phage titers in the culture were determined at an interval of 15 min. The burst size of the phage was determined as previously described in a single experiment with technical triplicates [34].…”

Characterization of LysBC17, a Lytic Endopeptidase from Bacillus cereus

“…PlyP56, an endopeptidase, and PlyN76, an amidase, both had optimal activity between pH 7.0 and pH 9.0 [22]. Similarly, PlyHSE3, another B. cereus endolysin with amidase activity, had optimal activity at pH 8.0 with substantial activity at pH 7.0 and pH 9.0 [23].…”