Natasa Kilibarda

Investigation of the possibility of detection of fluoroquinolones in carp kidney by microbiological diffusion method.

Fish is one of the most valuable food products used in human nutrition, due to the content of proteins, fat, minerals, vitamins, essential n -3 polyunsaturated fatty acids (PUFAs) and cholesterol. To meet the growing needs of the population for this kind of food, fish are increasingly grown in aquaculture. Intensive fish production, due to increased stock density, is favoring the occurrence of bacterial diseases. As a consequence, there is increased morbidity and mortality, reduced growth and reduced leasing sockets materials, which pose a serious problem for the aquaculture and lead to massive use of chemotherapeutics. Antibiotics are the common practice for the treatment of bacterial infections in fish ponds, and flurohinolones are used as antibiotics of choice. Fluoroquinolones are a group of antibiotics that have a broad spectrum of activity, low toxicity and only a few side effects in the treated fish. However, residues of antibiotic in fish tissues represent a real risk to human health. Consumption of fish containing residues of antibiotics can cause allergic, toxic, carcinogenic, mutagenic and teratogenic effects. Therefore, it is necessary to establish the residual amounts of antibiotics in fish tissues, that can be achieved by using reliable laboratory methods and techniques. Because of this, the goal of the work was set to investigate the possibility of identification and quantification of fluoroquinolones in the kidneys of carp by microbiological diffusion method, using the test organism E. coli ATCC 11303. The investigations revealed that microbiological diffusion method enables detection of all five fluoroquinolones (oxolinic acid, enrofloxacin, sarafloxacin, difloxacin and flumequine) in kidney of carp at different maximum residue levels, MRL (100 mg/kg, 100 mg/kg, 30 mg/kg, 300 mg/kg and 600mg/kg, respectively). Identification and quantification of fluoroquinolones at MRL levels was only achieved for enrofloxacin, flumequine and difloksacin. These fluoroquinolones can be detected and quantified at the level below the MRL, i.e. at the level of 1/4 MRL. Contrary to these fluoroquinolones, sarafloxacin can be detected only at the level of 2MRL and oxolinic acid can be detected at the level of 4MRL, as well. EU regulations provide that a screening method can be applicable only if a compound can be detected in the amount of at least at the MRL, and the ½ MRL is recommended. This means that the microbiological diffusion method can be used in routine analytical practice for the identification and quantification of enrofloxacin, flumequine and difloxacin in kidney tissues of carp.