Identification of VIM-2 metallo-ß-lactamase-producing Pseudomonas aeruginosa isolated from dogs with pyoderma and otitis in Korea.

BACKGROUND: Pseudomonas aeruginosa is a challenging pathogen cultured from cases of acute and chronic canine otitis and sometimes in cases of deep pyoderma. The spread of antimicrobial resistance, especially carbapenem resistance, is a serious therapeutic challenge worldwide. HYPOTHESIS/OBJECTIVES: To investigate the identification and characterization of resistant P. aeruginosa clinical canine isolates. MATERIALS: Clinical isolates (n = 80) were collected from dogs with pyoderma (n = 18) and otitis (n = 62) in Korea. METHODS: Antimicrobial susceptibility was determined using agar dilution and using Clinical and Laboratory Standards Institute guidelines for recording susceptibility for human Pseudomonas isolates; genetic relatedness of isolates was investigated by multilocus sequence typing (MLST) and SpeI macrorestriction analysis. The class 1 integrons were amplified and sequenced using primer walking. RESULTS: Most isolates were susceptible to colistin (97.5%), polymyxin B (96.3%), ciprofloxacin (81.3%) and meropenem (80.0%); whereas resistance to aztreonam (80%), piperacillin (52.5%), piperacillin/tazobactam (41.3%) and cefepime (37.5%) was high; 12 carbapenem-nonsusceptible isolates (15%) were detected. MLST revealed 45 different sequence types (STs) and macrorestriction analysis detected 55 distinct pulsotypes (PTs), which were divided into 25 clonal groups. Among carbapenem-nonsusceptible isolates, 10 (83.3%) were VIM-2-producing strains. Nine VIM-2-producing isolates were identified as ST1047 and harboured the same 2.8 kb class 1 integron. One remaining isolate was ST1203 with 2.1 kb class 1 integron. CONCLUSIONS AND CLINICAL IMPORTANCE: This study demonstrated the diversity of the phenotype and genotype of clinical P. aeruginosa isolates from dogs with pyoderma and otitis. The identification of VIM-2-producing P. aeruginosa in dogs is alarming and warrants further surveillance.

In vitro efficacy of the essential oil from Leptospermum scoparium (manuka) on antimicrobial susceptibility and biofilm formation in Staphylococcus pseudintermedius isolates from dogs.

BACKGROUND: Staphylococcus pseudintermedius is a common pathogen of skin and ear infections in dogs. The widespread and rapid emergence of meticillin-resistant S. pseudintermedius (MRSP) has created therapeutic challenges in veterinary medicine and the need for alternative treatments. HYPOTHESIS/OBJECTIVES: We aimed to evaluate the in vitro antimicrobial activity of the essential oil manuka (Leptospermum scoparium) against S. pseudintermedius. METHODS: This study was performed using S. pseudintermedius strains isolated from dogs with skin and ear infections collected throughout Korea between 2009 and 2011. The in vitro antimicrobial activity of manuka oil against 39 MRSP and 11 meticillin-susceptible S. pseudintermedius (MSSP) strains was analysed by measuring minimal inhibitory concentrations (MICs) using the agar dilution method and biofilm inhibition activity as assessed by the colorimetric microtitre plate assay. RESULTS: Our results indicated that manuka oil had excellent activity against all bacterial isolates. The MICs for MRSP and MSSP to manuka oil were in the range of 2(-9) to 2(-6) and 2(-9) to 2(-7) % (v/v), respectively. Manuka oil was a potent inhibitor of S. pseudintermedius biofilm formation, and the majority of bacteria decreased by >50%. No significant differences were observed in the MICs or biofilm formation between the MRSP and MSSP strains. CONCLUSIONS AND CLINICAL IMPORTANCE: These results suggest that manuka oil has the potential to be a useful therapeutic option for treating superficial infections caused by MRSP and MSSP; further clinical investigations are required.

Antimicrobial effects of silver nanoparticles.

The antimicrobial effects of silver (Ag) ion or salts are well known, but the effects of Ag nanoparticles on microorganisms and antimicrobial mechanism have not been revealed clearly. Stable Ag nanoparticles were prepared and their shape and size distribution characterized by particle characterizer and transmission electron microscopic study. The antimicrobial activity of Ag nanoparticles was investigated against yeast, Escherichia coli, and Staphylococcus aureus. In these tests, Muller Hinton agar plates were used and Ag nanoparticles of various concentrations were supplemented in liquid systems. As results, yeast and E. coli were inhibited at the low concentration of Ag nanoparticles, whereas the growth-inhibitory effects on S. aureus were mild. The free-radical generation effect of Ag nanoparticles on microbial growth inhibition was investigated by electron spin resonance spectroscopy. These results suggest that Ag nanoparticles can be used as effective growth inhibitors in various microorganisms, making them applicable to diverse medical devices and antimicrobial control systems.