Investigation Of Chloramphenicol Pollution In The Freshwater Aquiculture And The Biodegradation Of Chloramphenicol

Chloramphenicol (CAP) is a broad spectrum antibiotic which is commonly used in aquaculture as a prophylactic or disinfectant to prevent diseases, or as a chemotherapeutic agent to control diseases. CAP has the potential to cause mutagenesis and carcinogenesis and also cause serious toxic effects to hematopoietic and digestive system in humans and animals when given by mouth or injection. CAP can also be accumulated and transferred throughout food chain and may be dangerous to environment and human health. Therefore, these are more and more concerned internationally in recent years.The current research focus for the CAP mostly concentrated in the food content analysis of CAP residues and radiation degradation of its content. Few researches are in the content analysis in the environment especially in the freshwater aquiculture environment. Although the content analysis in fish is the current research focus, much less research is in the content analysis of CAP in different species of fish from the same pond and the different organs from the fish. Microbial degradation of CAP, in particular, the use of environmental bacteria in the original source of domestication screening microbial degradation bacteria research work, is still not been reported. From these areas, this paper conducted a series of discussions and studies, and a number of innovations are obtained.Extraction, purification, elution methods and analytical conditions of high performance liquid chromatography (HPLC) for the determination of CAP in sediments were studied. The optimal condition for obtaining CAP from pond sediments was obtained. Through the use of ethyl acetate as extractant of CAP in water samples and liquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis of CAP on the water, this method can effectively detect trace amounts of CAP of water aquaculture ponds. Through the use of alkaline ethyl acetate as ultrasound extractant, purification by C18 SPE solid phase extraction cartridges, using LC-MS/MS as analytical tools, research has been proved feasibility in analyzing CAP residues in different organs of fish.Utilizing analytical methods of CAP in the aquiculture environment which have been developed, the contents of CAP were determined respectively in fish, water and sediment from the same freshwater aquiculture pond including pond A and pond B. The accumulation and migration of CAP in aquiculture environment were researched. The study found that CAP was detected in the water, sediment and fish of both pond A and B. These indicated that two ponds are subject to CAP contamination, and contamination of pond A was more serious than pond B. CAP content in different ponds was different. The more contamination of CAP in the environment, the more accumulation of CAP in fish. Different species and different organs were accumulated various levels of CAP. Studies show that the different accumulation of CAP in different species fish from the same environment was likely to be related to their living habits. The study also found that 3 species of fish including carp, chub and grass carp in pond A, only the content of CAP in grass carp fish is lower than the EU and the Untied States of FDA testing standards required (0.3μg·kg-1), grass carp fish was safe food. While in pond B, 4 species of fish including tilapia, herring, chub, and dace, only the CAP of tilapia fish were higher than those testing standards, the others were lower than testing standards and may be safe to eat.An aerobic bacterial strain CSFO-3 that degraded CAP was screened, enriched and isolated from the aquiculture pond sediments which utilized CAP as the sole carbon and energy source for growth. Strain CSFO-3 was identified as Pseudomonas Migula by its morphology, physiological characters, biochemical characters, and 16S rDNA sequence analysis. The strain CSFO-3 was possible Pseudomonas aeruginosa since they exhibited 99% similarity in partial 16S rDNA sequence. The strain CSFO-3 can produce resistance to some commonly used antibiotics such as amoxicillin, cefuroxime, erythromycin, and tetracycline. It also can produce bio-surfactants which was deduced as unsaturated glycolipid matter. The optimal CAP degradation condition of CSFO-3 was: pH=6.0, 35℃, 150 rpm with a CAP concentration of 100 mg·L-1, the CAP degradation was 37.5% under the cell density 9.5×107 (c.f.u·mL-1) after incubation 7 days, and its degradation was 46.1% if adding source of carbon and energy at 0.1‰sodium benzoate.Through the use of UV-visible spectrophotometers and LC-MS/MS analyzer for analysing microbial degradation products, a preliminary study was discussed about the metabolic pathway of degradating CAP of the CSFO-3 stain. The pssible ways are: the strain CSFO-3 under the effect of CAP degradation generates intermediate products 1-p-nitrophenyl-2-amino-1,3-propanediol and 2,2-dichloroacetamide, or generates intermediate products 1-p-nitrophenyl-1,2-ethanediol and 2,2-Dichloroacetamide and finally convertes to the products carbon dioxide, water, ammonium ion and chloride ion.