Research On The Drug-resistant Bacteria Isolated From Net-cage Areas In The South China Sea

Drug-resistant bacteria has been a world-wide healthy problem. Thedrug-resisitan bacteria in the ocean pose threats not only to mariculture but also tohuman health. In this study, we investigate the drug-resisitant bacteria isolated fromnet-cage areas located in the South China Sea by using the medium containing anantibiotic. The antibiotics’ concentrations mixed in the medium were confirmed bytesting the bacteria shows different susceptibilities. The samples were taken in Hainan,Beibu Gulf and othe net-cage areas from April to September in2012.Differences between the resistance rate to different antibiotics of the bacteria canbe seen directly by calculating the number of colonies after spreding the watersamples on the plate that containing an antibiotic for24hours.The colony number inoxytertracycline HCL or amoxicillin is significantly more than the number inEnrofloxacin HCL and florfenicol.It’s mean that there are much more bacteria showtolerance to oxytertracyclin and amoxicillin in sea water.The isolates after screening were identified and tested for it’s drugsusceptibility.The result of identification shows that decades of genuses wereseperated by this method and the dominant strains are vibrios.28and60isolates wereclassfied as vibrios in Hainan and Beibu Gulf respectively,while the total number ofisolates in these two places are104and126.The drug susceptibility test shows that thetotal tolerance rate to gentamicin,furazolidone,amoxicillin and tetracycline are over50%in both places,while it’s below50%to rifampicin,erythrocin andchloramphenicol and the isolates show the lowest tolerance rate tochloramphenicol,it’s10%and16%, respectively.The tolerance rates of the vibriosisolated from Hainan and Beibu Gulf are over50%to gentamicin, furazolidone,amoxicillin, tetracycline and norfloxacin,and the tolerance rates to rifampicin,erythrocin and chloramphenicol are below50%,the vibrios show the lowesttolerance rate to chloramphenicol,it’s0%and12%,respectively. Except for investigating the drug resistance of all bacteria by using specialplates,we also specially investigate the drug resistance of the vibrios.The vibrios wereisolated by TCBS medium and88isolates were classfied to13kinds of vibrio speciesafter sampling in July,August and September in2012.Among them,12kinds can causediseases in mariculture.The susceptibility tests shows that all the isolates wereresisitant to amoxicillin and tetracycline,and the tolerance rates togentamicin,furazolidone,enrofloxacin and norfloxacin were over50%,while it’s below50%to rifampicin and chloramphenicol,the lowest tolerance rate to chloramphenicolis5%.Except for the high tolerance rate,all the isolates show multi-drug profile.