engleski

Fluoroquinolone susceptibility in Pseudomonas aeruginosa isolates from dogs - comparing disk diffusion and microdilution methods

Pseudomonas aeruginosa has been determined to be the distinct cause of a number of different infections in both humans and animals. Apart from its high intrinsic resistance, which makes it difficult to treat, it also has a great capacity to acquire further resistance mechanisms. These mechanisms can be present simultaneously in one cell, conferring a multiresistant phenotype. Taking into account that the known risk factor for selection of resistant strains is excessive and inappropriate drug use, especially fluoroquinolones, the aim of this study was to determine the susceptibility of P. aeruginosa isolates to these antibacterial agents. The susceptibility of 90 canine isolates was determined by disk diffusion susceptibility test and the broth microdilution method. Both methods showed that isolates were significantly more sensitive to ciprofloxacin than to marbofloxacin or enrofloxacin, and more sensitive to marbofloxacin than to enrofloxacin. The results of microdilution and disk diffusion testing were in 98.9% agreement for ciprofloxacin and in 91.1% agreement for marbofloxacin, with no statistically significant difference between the two methods (P>0.05) for these two antibiotics. For enrofloxacin, the results of microdilution and disk diffusion testing were in 76.6% agreement, with a statistically significant disagreement between the two methods (P<0.05). In 16 cases, the disk diffusion test overestimated the number of strains susceptible to enrofloxacin compared with the microdilution test. These results suggest that for P. aeruginosa infections in dogs, therapy using enrofloxacin, based on the results of disk diffusion testing, may lead to ineffective treatment and could contribute to selection of resistant and multiresistant strains.

Pseudomonas aeruginosa ; dog ; fluoroquinolones ; antimicrobial susceptibility ; disk diffusion ; broth microdilution

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