A PK/PD study in trachemis turtles after single intracoelomic injection of Marbofloxacin at different doses

INTRODUCTION/OBJECTIVE Marbofloxacin (M) belongs to the fluoroquinolone class of antibiotics. It is commonly used in a variety of animal species, mostly in pets. M and other fluoroquinolones resistance is an emerging problem [1]. Thus, there is a need to select dosage regimens based on approaches such as PK/PD integration and modelling to minimize the selection of resistant mutants of bacteria and extend the useful life of antimicrobial agents. The aim of this study was to evaluate its pharmacokinetics and in vivo efficacy after a single intracoelomic injection at different dose rates. MATERIALS AND METHODS 3 groups of 6 healthy adult turtles each (Trachemysscripta) were housed in controlled conditions of temperature and humidity. Randomly, M was administered at 0.4, 2 and 10 mg kg respectively with a single intracoelomic injection. Blood samples were collected from sub-carapacial site and rectal swabs were collected at scheduled times. M concentrations in serum were assayed using an HPLCFL validated method. Bacteria isolation was performed using blood agar and Hektoen Enteric Agar; in vitro antimicrobial susceptibility test of M was developed with disc diffusion test (Kirby-Bauer Method) RESULTS The PK profiles of M, fit by a bi-compartmental model. The PK were dose dependent. The Tmax and half life ranged between 2.82–4.64 and 16.14–30.68 h, respectively. Bacteria isolation showed the presence of both E. coli and Salmonella spp. All E. coli strains isolates were susceptible to M (diffu sion > 18 mm) and were all eliminated within 48 h after administration of any dosage. Salmonella spp. have been isolated only after 48 h and all strains were resistant to M (diffusion < 14 mm). Two turtles in the highest dose group died 2 days after the treatment. CONCLUSIONS The Cmax at the clinical dosing (2 mg kg 1) was slightly higher and drastically lower than those reported in mammals [2] and in CarettaCarettaturles [3] after IM administrations. Interestingly, Salmonella spp. was isolated after 48 h from the administration, probably because, E.coli had a such high concentration as to hide his presence. Moreover, Salmonella spp. shown an unequivocal resistance of M that even at the lowest dose was able to select resistant strains. The results of the present study seem to suggest that even if M is able to reach considerable plasma concentrations, it is also useless to a pathogen for humans.