Abstract
Antibiotic-resistant bacteria (ARB) have spread widely and rapidly, with their increased occurrence corresponding with the increased use of antibiotics. Infections caused by Staphylococcus aureus have a considerable negative impact on human and livestock health. Bacteriophages and their peptidoglycan hydrolytic enzymes (endolysins) have received significant attention as novel approaches against ARB, including S. aureus. In the present study, we purified an endolysin, Lys-phiSA012, which harbors a cysteine/histidine-dependent amidohydrolase/peptidase (CHAP) domain, an amidase domain, and a SH3b cell wall binding domain, derived from a polyvalent S. aureus bacteriophage which we reported previously. We demonstrate that Lys-phiSA012 exhibits high lytic activity towards staphylococcal strains, including methicillin-resistant S. aureus (MRSA). Analysis of deletion mutants showed that only mutants possessing the CHAP and SH3b domains could lyse S. aureus, indicating that lytic activity of the CHAP domain depended on the SH3b domain. The presence of at least 1 mM Ca2+ and 100 µM Zn2+ enhanced the lytic activity of Lys-phiSA012 in a turbidity reduction assay. Furthermore, a minimum inhibitory concentration (MIC) assay showed that the addition of Lys-phiSA012 decreased the MIC of oxacillin. Our results suggest that endolysins are a promising approach for replacing current antimicrobial agents and may contribute to the proper use of antibiotics, leading to the reduction of ARB.
Highlights
Antibiotic-resistant bacteria (ARB) have spread rapidly worldwide and are an important global health issue
Several reports have suggested that antibiotics are used more heavily in livestock than in humans and veterinary antibiotics (VA) may be the largest source of ARB [9,10,11]
We previously demonstrated that phage therapy is effective for treating equine keratitis caused by P. aeruginosa [26] and the lysis of antibiotic-resistant P. aeruginosa [27]
Summary
Antibiotic-resistant bacteria (ARB) have spread rapidly worldwide and are an important global health issue. Annual worldwide veterinary antibiotics (VA) use is 105–106 tones [7,8]. Several reports have suggested that antibiotics are used more heavily in livestock than in humans and VAs may be the largest source of ARB [9,10,11]. Transmission of ARB, such as methicillin-resistant Staphylococcus aureus (MRSA), by veterinary staff in contact with ARB carrier animals, and the potential role of the farm environment in the spread of ARB, have been reported [12,13,14,15,16], suggesting the environmental transfer of ARB from animals to humans
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