Effect of Domain Manipulation in the Staphylococcal Phage Endolysin, Endo88, on Lytic Efficiency and Host Range.

The bacteriophage endolysin Endo88 targeting Staphylococcus aureus PS88 consists of the CHAP and Amidase-2 enzymatic domains and one SH3b targeting domain. In this study, the effects of domain manipulations on Endo88 functionality were determined. Three truncated mutants of Endo88 (CHAP, CHAPAmidase and CHAPSH3) and two chimeras (CHAPAmidase-Cpl7Cpl7 and Endo88-Cpl7Cpl7) containing the Cpl7Cpl7 targeting domains of the streptococcal LambdaSa2-ECC endolysin were cloned in E. coli (pET28a), expressed, and then purified. Lytic efficiency and host range were assessed through plate lysis assays and turbidity reduction assays. Endo88 required all domains for maximum functionality, with activity detected against Staphylococcus aureus PS88 (host strain), S. aureus Mu50 (VISA), CoNS (Staphylococcus epidermidis and Staphylococcus hominis), and Enterococcus faecalis. The truncated constructs maintained the original host range but with reduced lytic efficiency. The Amidase-2 and SH3b domains are interdependent in maximizing functionality. The chimera constructs demonstrated reduced functionality, without activity against Streptococcus agalactiae in both assays. This study provides insights into domain function in a staphylococcal endolysin, which could enable the development of prospective engineered antimicrobials against multidrug-resistant pathogens.

Lactococcus lactis secreting phage lysins as a potential antimicrobial against multi-drug resistant Staphylococcus aureus.

BACKGROUND: Staphylococcus aureus is an opportunistic Gram-positive bacterium that can form biofilm and become resistant to many types of antibiotics. The treatment of multi-drug resistant Staphylococcus aureus (MDRSA) infection is difficult since it possesses multiple antibiotic-resistant mechanisms. Endolysin and virion-associated peptidoglycan hydrolases (VAPGH) enzymes from bacteriophage have been identified as potential alternative antimicrobial agents. This study aimed to assess the ability of Lactococcus lactis NZ9000 secreting endolysin and VAPGH from S. aureus bacteriophage 88 to inhibit the growth of S. aureus PS 88, a MDRSA. METHOD: Endolysin and VAPGH genes were cloned and expressed in L. lactis NZ9000 after fusion with the SPK1 signal peptide for secretion. The recombinant proteins were expressed and purified, then analyzed for antimicrobial activity using plate assay and turbidity reduction assay. In addition, the spent media of the recombinant lactococcal culture was analyzed for its ability to inhibit the growth of the S. aureus PS 88. RESULTS: Extracellular recombinant endolysin (Endo88) and VAPGH (VAH88) was successfully expressed and secreted from L. lactis which was able to inhibit S. aureus PS 88, as shown by halozone formation on plate assays as well as inhibition of growth in the turbidity reduction assay. Moreover, it was observed that the spent media from L. lactis NZ9000 expressing Endo88 and VAH88 reduced the viability of PS 88 by up to 3.5-log reduction with Endo88 being more efficacious than VAH88. In addition, Endo88 was able to lyse all MRSA strains tested and Staphylococcus epidermidis but not the other bacteria while VAH88 could only lyse S. aureus PS 88. CONCLUSION: Recombinant L. lactisNZ9000 expressing phage 88 endolysin may be potentially developed into a new antimicrobial agent for the treatment of MDRSA infection.