Abstract
The spread of antibiotic-resistant bacteria (ARB) in human and veterinary medicine is of global concern. Notably, the emergence of methicillin-resistant Staphylococcus pseudintermedius has become a serious problem. In this context, bacteriophages and their lytic enzymes, endolysins, have received considerable attention as therapeutics for infectious diseases in place of antibiotics. The aim of the present study was to investigate the antibiotic-resistance patterns of staphylococcal species isolated from canine skin at a primary care animal hospital in Tokyo, Japan and evaluate the lytic activity of the staphylococcal bacteriophage phiSA012 and its endolysin Lys-phiSA012 against isolated antibiotic-resistant staphylococcal strains. Forty clinical staphylococcal samples were isolated from infection sites of dogs (20 from skin and 20 from the external ear canal). Susceptibility to antimicrobial agents was determined by a disk diffusion method. The host range of phiSA012 was determined by using a spot test against staphylococcal isolates. Against staphylococcal isolates that showed resistance toward five classes or more of antimicrobials, the lytic activity of phiSA012 and Lys-phiSA012 was evaluated using a turbidity reduction assay. Twenty-three S. pseudintermedius, 16 Staphylococcus schleiferi, and 1 Staphylococcus intermedius were detected from canine skin and ear infections, and results revealed 43.5% methicillin resistance in S. pseudintermedius and 31.3% in S. schleiferi. In addition, the prevalence multidrug resistance (MDR) S. pseudintermedius was 65.2%. PhiSA012 could infect all staphylococcal isolates by spot testing, but showed little lytic activity by turbidity reduction assay against MDR S. pseudintermedius isolates. On the other hand, Lys-phiSA012 showed lytic activity and reduced significantly the number of staphylococcal colony-forming units. These results demonstrated that ARB issues underlying in small animal hospital and proposed substitutes for antibiotics. Lys-phiSA012 has broader lytic activity than phiSA012 against staphylococcal isolates; therefore, Lys-phiSA012 is a more potential candidate therapeutic agent for several staphylococcal infections including that of canine skin.
Highlights
Administration of systemic and/or topical antimicrobial agents is the most common therapeutic treatment for bacterial infectious diseases
We focused on antibiotic-resistant staphylococci isolated from canine skin infectious diseases and evaluated the lytic activity of the bacteriophage phiSA012 and its endolysin Lys-phiSA012
Our investigation indicated that the emergence of multi-drug resistance (MDR) S. pseudintermedius is becoming a serious problem in primary care animal hospitals as observed for methicillin-resistant S. pseudintermedius (MRSP)
Summary
Administration of systemic and/or topical antimicrobial agents is the most common therapeutic treatment for bacterial infectious diseases. It has been previously reported that antibiotics are used in livestock more so than in humans [2,3,4]. In this context, the overuse and misuse of antibiotics in humans and animals have resulted in the global wide-spread emergence of antibiotic-resistant bacteria (ARB) [5]. Methicillin-resistant S. aureus (MRSA) is one of the most frequently isolated ARB and can cause nosocomial infections [11]. Staphylococcus pseudintermedius is most frequently isolated as part of the normal canine skin flora and as a pathogen of pyoderma, bacterial otitis, wounds, and abscess. As with MRSA in humans, methicillin-resistant S. pseudintermedius (MRSP) is frequently isolated from canine skin infections. It is imperative that alternative therapeutic agents against staphylococci including MRSP are identified in the field of companion animal medicine
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