Enzyme-based targeted decontamination of bacterial pathogens

Abstract

The emergence of resistance to antibacterial agents is a pressing concern for human health. There continues to be a need for developing efficient and environmentally friendly treatments for several deadly bacterial pathogens. One emerging approach for inactivation of gram-positive bacteria is the use of bacteriolytic enzymes with highly evolved specificity toward bacterium-specific peptidoglycan cell walls. In this work, we have targeted selective decontamination of B. anthracis, used as a biological weapon and the causative agent of anthrax. Specifically, we performed in silico analysis of the genome of B. anthracis strain Ames using a consensus binding domain amino acid sequence as a probe, and identified a novel bacteriolytic enzyme (AmiBA2446). We characterized its amidase activity on isolated cell wall peptidoglycan, demonstrated its potent and selective bactericidal activity against B. anthracis amongst various Bacillus species tested, and its excellent storage and thermal stability. We also studied the influence of bacterial growth stage on bactericidal activity of lytic enzymes.

The bioinformatics approach discussed in this work provides a way to expand repertoire of bacteriolytic enzymes against a variety of gram positive bacterial pathogens. The development of enzymes that recognize different targets in the cell wall peptidoglycan can possibly minimize the emergence of resistance, thereby, providing a very attractive approach towards the development of next-generation antibiotics - enzyme-based antibiotics or enzybiotics.

Using the approach discussed above, we identified (a) a lytic enzyme, PlyBeta and demonstrated the minimal dependence of its bactericidal activity on the bacterial culture age, (b) lytic enzymes CD11 and CDG, and demonstrated its operational activity in simulated gastrointestinal fluids to develop them as potential treatment against Clostridium difficile infections (major hospital acquired and antibiotic-associated infections), and (c) lytic enzymes against Staphylococcus aureus (a major nosocomial pathogen) that recognize different targets in the cell wall, and rationally designed a mutant of SA1 with improved bactericidal activity.