|HYMAN, PAUL - Ashland-Us|
Submitted to: Evergreen International Phage Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2015
Publication Date: N/A
Technical Abstract: Enterococcus faecalis is an intestinal bacteria species that can become an opportunistic pathogen in humans and farm animals with antibiotic resistant strains becoming increasingly common. In farm animals, strong antimicrobials, such as Vancomycin, should not be used due to the risk of propagation and spread of resistance genes that may passed to human pathogens. The overuse of avoparcin in farm animals has lead to an increased cross-resistance to Vancomycin in E. faecalis that is still seen today. On the advent of a predicted FDA ban on antibiotic growth promotants in animal feeds is a strong incentive to identify alternatives to antibiotics for use in animal feeds. One alternative currently being researched is the use of bacteriophage (viruses that infect bacteria) lytic enzymes. Bacteriophage endolysins are peptidoglycan hydrolases that when produced by bacteriophages, degrade the peptidoglycan of bacterial cell walls and allow the phage to escape from the cell and infect new hosts. Purified endolysin can be used externally to lyse Gram-positive bacteria. There have been no reports of a bacterial host that can develop resistance to its phage endolysin, despite efforts to find them. Lysin A was originally isolated from a bacteriophage that targeted E. faecalis. It has a CHAP (cysteine- and histidine-dependent amidohydrolase/peptidase) domain, which corresponds to either an amidase or endopeptidase peptidoglycan degradation function. In this study, the optimum buffer conditions for Lysin A activity, stability and lytic activity on several strains of E. faecalis, E. faecum, and other gut bacteria were tested. Optimal Lysin A activity occurred at pH 5, calcium ion had a stimulatory effect that peaked at 1mM, and increasing NaCl resulted in reduced activity. In a plate lysis assay, six out of eleven E. faecalis strains tested were growth-inhibited and/or lysed in the presence of Lysin A. Other species of bacteria tested were not affected by Lysin A, demonstrating the specificity of Lysin A. Lysin A was effective against drug-resistant E. faecalis. Most importantly, Lysin A did not lose lytic activity after being heated up to 65°C, suggesting that it is highly thermostable and thus a potential alternative antimicrobial for addition to animal feed.