Exploring the antimicrobial potentials of bacteriophage endolysin against methicillin-resistant Staphylococcus pseudintermedius strains: A novel biotherapeutic strategy

• Grant number: 25/07535-4
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: July 01, 2025
• End date: June 30, 2026
• Field of knowledge: Health Sciences - Medicine
• Principal Investigator: Ana Cristina Gales
• Grantee: Ikechukwu Benjamin Moses
• Supervisor: Roderick Slavcev
• Host Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil
• Institution abroad: University of Waterloo, Canada
• Associated to the scholarship: 24/01488-1 - Combating the emergence and spread of multidrug-resistant Staphylococcus pseudintermedius in companion animals and its zoonotic transmission by phage therapy: An alternative therapeutic approach, BP.PD

Abstract

Staphylococcus pseudintermedius, a normal microbiota and an opportunistic pathogen of companion dogs, is increasingly becoming a challenging and underestimated zoonotic pathogen. In companion dogs, S. pseudintermedius, especially multidrug-resistant strains, have been recognized to be causative agents of skin infections like canine pyoderma, surgical site infections, and urinary tract infections. The epidemiological situation is further exacerbated with reports of its zoonotic transmission and human infections which have been mostly attributed to the increasing frequency of dog ownership and close contacts between dogs and humans. Most reports on human infections due to S. pseudintermedius are skin and soft tissue infections (SSTIs), dog bite wounds, lung infections, prosthetic joint infections, device-associated infections, bloodstream infections, and invasive infections, especially among hospitalized patients who have or had prior contact with companion animals. Importantly, methicillin-resistant S. pseudintermedius (MRSP) which is usually multidrug-resistant has emerged with serious public health consequences. MRSP are known to be intrinsically resistant to most beta-lactams (penicillins and their derivatives) as they possess the staphylococci cassette chromosome mec (SCCmec) gene, a mobile genetic element, which harbours the mecA gene that codes for an alternative penicillin binding protein, PBP2a. The multidrug-resistant traits of MRSP to important non-beta-lactam antimicrobials such as aminoglycosides, sulfonamides, fluoroquinolones, lincosamides, macrolides, phenicols, and tetracyclines have also been well-documented; thus, further limiting and complicating treatment options for MRSP infections. Due to the increasing global menace of antimicrobial resistance in the face of dwindling development of newer antimicrobials, there is urgent need for the development of alternative therapeutic strategies to combat "difficult-to-treat" bacterial infections. One of such therapeutic strategies is the use of endolysin, a bacteriophage-encoded protein. Endolysin has a selective capacity to degrade bacterial peptidoglycan layer and disrupt bacterial cell; thus, making it a promising biotherapeutic agent. In our ongoing study, an open reading frame that is homologous to endolysin-encoding genes on the genomes of S. pseudintermedius bacteriophages was identified. The open reading frame encoding the putative endolysin cell-wall hydrolyzing enzymes will be amplified by polymerase chain reaction and cloned into an expression vector pET-21a. The cloned gene product will then be overexpressed in E. coli, purified, and characterized for temperature, pH, and salinity stability. The antibacterial activity of the characterized endolysin against pathogenic strains of methicillin-resistant S. pseudintermedius (MRSP) recovered from dogs and humans will then be evaluated to confirm their lytic activity spectrum. (AU)